texas commission on environmental quality section 319 … · 2007-06-30 · final 08/06/08 the city...

Submitted by

Texas Commission on Environmental QualitySection 319 nonpoint Source Grant

for

report for task 2, Watershed protection plan,

of the Grant entitled control of nonpoint Source Loads in the Hickory creek

Sub-basin of the Lake Lewisville Watershed as a component of a Watershed-based Water Quality trading program

FINAL 08/06/08

the city of denton in cooperation with cH2m HiLL, texas a&m university, and the university of north texas

WB022008002DFW

Submitted by

Texas Commission on Environmental Quality

Section 319 nonpoint Source Grant

for

report for task 2, Watershed protection plan, of the Grant entitled

control of nonpoint Source Loads in the Hickory creek Sub-basin of the Lake Lewisville Watershed

as a component of a Watershed-based Water Quality trading program

FINAL 08/06/08

the city of denton in cooperation with cH2m HiLL, texas a&m university, and the university of north texas

Kenneth banks, ph.d., principal investigator manager, division of environmental Quality

city of denton 901-a texas Street denton, tX 76209,

phone: (940)349-7165 fax: (940)349-7134

email: [email protected]

prepared in cooperation WitH tHe texas commission on environmental Quality and

U.S. Environmental Protection Agency.

The preparation of this report was financed through grants from the U.S. Environmental Protection Agency through thetexas commission on environmental Quality

WB022008002DFW


Section 319 Nonpoint Source Grant

Report for Task 2, Watershed Protection Plan, of the Grant Entitled

Control of Nonpoint Source Loads in the Hickory Creek Sub-basin of the Lake Lewisville Watershed as a Component

of a Watershed-Based Water Quality Trading Program

By

The City of Denton in cooperation with CH2M HILL, Texas A&M University, and the University of North Texas

Kenneth Banks, Ph.D., Principal Investigator

Manager, Division of Environmental Quality City of Denton

901-A Texas Street Denton, TX 76209, Phone: (940)349-7165 Fax: (940)349-7134

Email: [email protected]

Final: 08/06/08

PREPARED IN COOPERATION WITH THE


The preparation of this report was financed through grants from the


[This Page Intentionally Left Blank]

Contents

Chapter Page

Contents ................................................................................................................................ i Acronyms .............................................................................................................................. vi Executive Summary......................................................................................................................1

ES.1 Overview...............................................................................................................ES-1 ES.2 Population Growth Will Lead to Increased Nutrient Loadings without

Management Actions...........................................................................................ES-2 ES.2.1 Urbanization in the Lewisville Lake and Hickory Creek Watersheds ..............................................................................................ES-2 ES.2.2 Causes, Sources, and Projected Trends of Pollutant Loading to the

Hickory Creek Watershed .....................................................................ES-3 ES.2.3 Areas of Heaviest Pollutant Loading in 2007-2008 ............................ES-5 ES.2.4 Land Use Change Predictions for the Hickory Creek Watershed ...ES-7

ES.3 This Watershed Protection Plan is Designed to Ensure No Net Increase in Sediment and Nutrient Loads ............................................................................ES-7

ES.4 Optimizing BMPs by Location and Cost-Effectiveness is Key to Ensuring No Net Increase....................................................................................................ES-8

ES.4.1 Watershed-Wide BMP Portfolio ...........................................................ES-9 ES.4.2 Static and Dynamic BMP Portfolios for the 282 Priority Sites........ES-10 ES.4.3 BMP Portfolios for the Master Planned Communities (MPCs)......ES-12 ES 4.4 Demonstration BMPs ...........................................................................ES-13

ES.5 Market-Based Approaches Will Help Incentivize Private Investment and Leverage Public Resources ...............................................................................ES-14 ES.5.1 Opportunity for a Storm Water Credit Market ................................ES-14 ES.5.2 Recommended Storm Water Credit Market .....................................ES-15 ES.5.3 Phased Implementation for a Storm Water Credit Market.............ES-16

ES.6 The Watershed Protection Plan Establishes an Adaptive Blueprint for Water Quality Protection ..................................................................................ES-16

ES.6.1 The WPP’s Four Management Objectives and Highlighted Milestones ..............................................................................................ES-16 ES.6.2 Measuring Progress and Success in the Longer Term.....................ES-18 ES 6.3. Education and Outreach ......................................................................ES-19 ES 6.4 Summary WPP Implementation Schedule........................................ES-20

1 Introduction 1.1 Problem Definition ................................................................................................ 1-1

1.1.1 Denton and Lewisville Lake.................................................................... 1-1 1.1.2 Hickory Creek ........................................................................................... 1-2

1.2 Purpose of the Watershed Protection Plan......................................................... 1-4 1.3 Watershed Protection Plan Requirements.......................................................... 1-4

1.3.1 Unique Aspects of the Hickory Creek Watershed Protection Plan ... 1-5 2 Stakeholder Involvement..................................................................................................... 2-1

2.1 Formation of the Stakeholder Advisory Group................................................. 2-1

HICKORY CREEK WATERSHED PROTECTION PLAN__FINAL_2008.DOC i

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2.2 Stakeholder Meetings ............................................................................................ 2-1 3 Causes, Sources, and Projected Trends of Pollutant Loading to the Hickory Creek Watershed............................................................................................. 3-1

3.1 Background............................................................................................................. 3-1 3.2 Point Source Loads ................................................................................................ 3-3 3.3 Non-Point Source Loads ....................................................................................... 3-4 3.4 Areas of Heaviest Pollutant Loading in 2007-2008 ........................................... 3-7

3.4.1 Methodology ............................................................................................. 3-7 3.4.2 Results of Modeling Effort....................................................................... 3-9

3.5 Land Use Change Predictions for the Hickory Creek Watershed ................ 3-12 4 Methodology to Determine Load Reductions and Associated Costs for BMP Portfolios in Three Spatial Scales................................................................................ 4-1

4.1 Microsoft-Excel Based Analysis ........................................................................... 4-1 4.1.1 Available BMPs and Associated Costs .................................................. 4-1 4.1.2 Special Features......................................................................................... 4-5 4.1.3 Strengths and Weaknesses....................................................................... 4-5

4.2 Summary Results of the BMP Portfolios in Three Scales ................................. 4-6 4.2.1 Watershed-Wide ....................................................................................... 4-6 4.2.2 282 Priority Sites........................................................................................ 4-6 4.2.3 MPCs........................................................................................................... 4-6 4.2.4 Cross-Portfolio Summary ........................................................................ 4-7

5 Watershed-Wide BMP Portfolio ......................................................................................... 5-1 5.1 BMP Portfolios........................................................................................................ 5-1 5.2 Summary of Watershed-Wide BMP Portfolio Results...................................... 5-6

6 BMP Portfolios for the 282 Priority Sites .......................................................................... 6-1 6.1 Summary Characteristics of the 282 Priority Sites ............................................ 6-1 6.2 Static Portfolios for the 282 Priority Site Collective Acreage........................... 6-2 6.3 Dynamic Portfolio Incorporating Individual 282 Priority Sites ...................... 6-5 6.4 Summary of BMP Portfolio Results for the 282 Priority Sites ......................... 6-8

7 BMP Portfolios for the Master Planned Communities (MPCs).................................... 7-1 7.1 Current & Assumed Future Land Use Distributions for the MPCs ............... 7-1 7.2 MPC BMP Portfolios.............................................................................................. 7-2

7.2.1 Cole Ranch ................................................................................................. 7-2 7.2.2 Inspiration.................................................................................................. 7-3 7.2.3 Rayzor Ranch............................................................................................. 7-5 7.2.4 Summary Comparison Among MPCs ................................................... 7-6

8 Market-Based Approaches to Incentivize BMP Implementation ................................ 8-1 8.1 Assessment of Denton’s Current Storm Water Control Requirements.......... 8-1

8.1.1 Market Objectives ..................................................................................... 8-1 8.1.2 Current Requirements.............................................................................. 8-2 8.1.3 Assessment Conclusion ........................................................................... 8-3

8.2 Market-Based Approach Recommended............................................................ 8-3 8.3 Implementation Mechanisms and Process ......................................................... 8-6

8.3.1 Pilot Testing under the Drainage Code ................................................. 8-7 8.3.2 Pilot Testing under the ESA Code.......................................................... 8-8 8.3.3 Implementation Testing for Master Planned Communities ............... 8-9

8.4 Suggested Path Forward..................................................................................... 8-10

ii HICKORY CREEK WATERSHED PROTECTION PLAN_FINAL_2008.DOC

CONTENTS

9 Information/Education Component................................................................................... 9-1 9.1 Public Outreach Approaches................................................................................ 9-1

9.1.1 The Role of Demonstration Best Management Practices in the Public Outreach Approach .................................................................................. 9-2

9.1.2 Public Outreach: From the Demonstration projects to the Hickory Creek Watershed .................................................................................................. 9-3

9.1.3 BMP Implementation in the Development Process ............................. 9-4 9.2 Building on Existing Public Information and Participation Activities........... 9-4

10 Watershed Protection Plan Implementation................................................................. 10-1 10.1 Overview of Management Objectives Addressed By This Plan.................... 10-1 10.2 Interim Measurable Milestones.......................................................................... 10-2 10.3 Measuring Progress and Success in the Longer Term.................................... 10-6

10.3.1 Project-Specific ........................................................................................ 10-6 10.3.2 Project-Specific and Cumulative BMP Results ................................... 10-6 10.3.3 Comparing Cumulative BMP Results against Predictions ............... 10-7 10.3.4 Instream Conditions ............................................................................... 10-7

10.4 Funding Sources................................................................................................... 10-8 10.5 Summary Schedule .............................................................................................. 10-8

11 Chapter References ........................................................................................................... 11-1 Exhibits

Exhibit ES-1 How Urbanization Affects Water Quality .................................................ES-2 Exhibit ES-2 Map of Lake Lewisville Area.......................................................................ES-3 Exhibit ES-3 Detail of Hickory ...........................................................................................ES-3 Exhibit ES-4 Land Use Distribution in the Hickory Creek Watershed ........................ES-4 Exhibit ES-5 Constituent Concentrations (mg/L) for each Land Use Category.........ES-5 Exhibit ES-6 Estimated Annual Loads Per Acre and for the Watershed .....................ES-5 Exhibit ES-7 Mapping Priority Locations for BMP Installation ....................................ES-6 Exhibit ES-8 Projected Future Land Use Changes ..........................................................ES-7 Exhibit ES-9 EPA’s 9 Watershed Protection Plan Elements...........................................ES-7 Exhibit ES-10 Watershed Wide BMP Portfolio Results ..................................................ES-10

Cost of Each Watershed Wide Portfolio and TSS Reduction ............... ES-10 Cost of Each Watershed Wide Portfolio and TP Reduction ................. ES-10

Exhibit ES-11 Highlighted Results for the Three 282 Priority Site Portfolios..............ES-11 Exhibit ES-12 Cumulative BMP Cost Per Year and Cumulative Pounds of Pollutant

Reduced Per Year: Dynamic 282 Priority Site Portfolio.........................ES-12 Exhibit ES-13 Comparison of Pollutant Reduction and BMP Cost for MPC Portfolio 2 .....................................................................................................ES-13 Exhibit ES-14 Storm Water Credit Market Structure Recommended for Consideration...............................................................................................ES-15 Exhibit ES-15 WPP Interim Milestones and Longer-Term Progress Measures...........ES-21 Exhibit 1-1 Hickory Creek Watershed.............................................................................. 1-3 Exhibit 1-2 EPA’s Nine WPP Elements and Location Within this WPP...................... 1-5 Exhibit 3-1 Land Use Distribution in the Hickory Creek Watershed .......................... 3-3 Exhibit 3-2 Relative Annual Sediment (left) and Phosphorus (right) Loading to the Hickory Creek Watershed................................................................... 3-4

HICKORY CREEK WATERSHED PROTECTION PLAN_FINAL_2008.DOC iii

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Exhibit 3-3 Constituent Concentrations (mg/L) for Each Land Use Category .......... 3-5 Exhibit 3-4 Runoff Depths (inches) for Various Land Use/Rainfall Depth Combinations ................................................................................................... 3-5 Exhibit 3-5 Annual Loads per Unit Area from Each Land Use (pounds/acre).......... 3-6 Exhibit 3-6 Annual Loads in the Hickory Creek Watershed by Land Use (tons) ...... 3-6 Exhibit 3-7 Current Land Uses within the Hickory Creek Watershed ........................ 3-7 Exhibit 3-8 Current Aggregate Land Use Distribution of 282 Priority Sites............... 3-8 Exhibit 3-9 Land Use Distribution for Select Sites .......................................................... 3-9 Exhibit 3-10 Potential BMP Locations According to the Annual Sediment Load...... 3-10 Exhibit 3-11 Potential BMP Locations According to the Annual Phosphorus Load................................................................................................................. 3-11 Exhibit 3-12 Potential BMP Locations According to the Annual Nitrogen Load....... 3-12 Exhibit 3-13 Projected Population Densities for Denton’s Urbanizing Area .............. 3-13 Exhibit 3-14 Projected Increases in Urban Land Area.................................................... 3-13 Exhibit 3-15 Projected Future Land Use Changes .......................................................... 3-14 Exhibit 3-16 Cumulative Percent Land Use Change Assumed..................................... 3-15 Exhibit 4-1 BMP Options, Associated Removal Efficiencies, and Maximum Land Usage....................................................................................................... 4-2 Exhibit 4-2 Unit Removal Costs......................................................................................... 4-4 Exhibit 5-1 Percent Increase in TSS Loading Compared to 2008 Baseline .................. 5-2 Exhibit 5-2 Cost of Each Watershed Wide Portfolio and TSS Reduction .................... 5-3 Exhibit 5-3 Percent Increase in TP Loading Compared to 2008 Baseline .................... 5-4 Exhibit 5-4 Cost of Each Watershed Wide Portfolio and TP Reduction ...................... 5-4 Exhibit 5-5 Cost per Year Per Percent Reduction of TSS ............................................... 5-5 Exhibit 5-6 Cost per Year Per Percent Reduction of TP ................................................. 5-6 Exhibit 6-1 Current Aggregate Land Use Distribution For the 282 Priority Sites ...... 6-1 Exhibit 6-2 Land Use Distribution For Selected 282 Priority Sites ............................... 6-2 Exhibit 6-3 Percent Acres Managed with BMPs, by BMP (in blue) and by Land Use Category (in black) ........................................................................ 6-3 Exhibit 6-4 Amount of Contaminant Reduced Per Year in Tons.................................. 6-3 Exhibit 6-5 Additional Detail, Including Estimated Implementation Costs for the Three 282 Priority Site Portfolios ...................................................... 6-4 Exhibit 6-6 Land Use Distribution Changes Over Time in the 282 Dynamic Portfolio as Each Set of 22 Sites is Added to the Portfolio......................... 6-6 Exhibit 6-7 Cumulative BMP Cost Per Year and Cumulative Pounds of Pollutant

Reduced Per Year: Dynamic 282 Priority Site Portfolio............................. 6-7 Exhibit 6-8 Incremental BMP Cost Per Year and Incremental Pounds of Pollutant

Reduced Per Year: Dynamic 282 Priority Site Portfolio............................. 6-7 Exhibit 7-1 Existing and Future Land Uses for the Three Master Planned

Communities.................................................................................................... 7-1 Exhibit 7-2 Existing and Predicted Future Land Use Distributions in the Cole

Ranch MPC....................................................................................................... 7-2 Exhibit 7-3 Estimated Load Reductions in Cole Ranch Compared to Estimated Future Loadings at Build out with No BMPs.............................................. 7-3 Exhibit 7-4 Annual Costs for BMP Implementation in the Cole Ranch MPC............. 7-3 Exhibit 7-5 Existing and Predicted Future Land Use Distributions in the

Inspiration MPC .............................................................................................. 7-4

iv HICKORY CREEK WATERSHED PROTECTION PLAN_FINAL_2008.DOC

CONTENTS

HICKORY CREEK WATERSHED PROTECTION PLAN_FINAL_2008.DOC v

Exhibit 7-6 Estimated Load Reductions in Inspiration Compared to Estimated Future Loadings at Build Out with No BMPs ............................................. 7-4 Exhibit 7-7 Annual Costs for BMP Implementation in the Inspiration MPC ............. 7-5 Exhibit 7-8 Existing and Predicted Future Land Use Distributions in the Rayzor

Ranch MPC....................................................................................................... 7-5 Exhibit 7-9 Estimated Load Reductions in Rayzor Ranch Compared to Estimated Future

Loadings at Build Out with No BMPs.......................................................... 7-6 Exhibit 7-10 Annual Costs for BMP Implementation in the Rayzor Ranch MPC ........ 7-6 Exhibit 7-11 Comparison of Pollutant Reduction and BMP Cost, MPCs ...................... 7-7 Exhibit 8-1 Estimated Pollutant Removal Rates of Current Practices.......................... 8-2 Exhibit 8-2 Feasible Pollutant Removal Rates of BMPs ................................................. 8-2 Exhibit 8-3 Market Structure Recommended for Consideration .................................. 8-4 Exhibit 8-4 Two Implementation Schemes, Credit Purchase Options, and

Resulting Credit Awards................................................................................ 8-5 Exhibit 10-1 Interim Milestones and Longer-Term Progress Measures ...................... 10-9 Appendices

Appendix A Parcel Summary Worksheet

Appendix B Storm Water Credit Market Background

Appendix C-1 Best Management Practice Monitoring

Appendix C-2 Watershed Assessment Monitoring

Appendix C-3 Anticipated Pollutant Loading, Demonstration BMP Sites

Appendix C-4 Monitoring Results to Date, Demonstration BMP Sites Appendix D-1 2016-06-01 Addendum to Hickory Creek WPP

Acronyms

BMPs best management practices CWA Clean Water Act DEM Digital Elevation Model EPA U.S. Environmental Protection Agency EQIP Environmental Quality Incentives Program ESA environmentally sensitive areas ETJ Extraterritorial Jurisdiction FY Fiscal Year ISD Independent School District ISWM Integrated Storm Water Management LEED Leadership in Energy and Environmental Design mg/L milligrams per liter MPCs Master Planned Communities MS4 Municipal Separate Storm Sewer System NCTCOG North Central Texas Council on Governments NPS non-point source pollution SWAT Soil and Water Assessment Tool TCEQ Texas Commission on Environmental Quality TMDL total maximum daily load TN total nitrogen TP total phosphorus TPDES Texas Pollution Discharge Elimination System TSI Trophic Status Index TSS total suspended solids TxDOT Texas Department of Transportation USGBC United States Green Building Council WPP Watershed Protection Plan

vi HICKORY CREEK WATERSHED PROTECTION PLAN__FINAL_2008.DOC

Executive Summary

ES.1 Overview The primary objective of this Watershed Protection Plan (WPP or “Plan”) was to identify actions that could reduce pollutant loads to the Hickory Creek arm of Lewisville Lake and improve water quality in advance of continued urbanization and the development of numerical nutrient criteria, as either of these scenarios may result in the addition of Lewisville Lake to the Texas CWA 303(d) list of impaired waters. In a larger context, the goal of this WPP was to develop an approach for the cost-effective implementation of best management practices for pollutant control that may be applied throughout the Lewisville Lake watershed.

The technical analysis underpinning this Plan was organized around documenting and evaluating the following scientific assumptions and strategic objectives:

Population growth in the Hickory Creek watershed will lead to increased sediment and nutrient loadings without concerted management actions on the part of private and public parties;

Without an existing requirement to reduce pollutant loadings stemming from a Total Maximum Daily Load implementation plan, the watershed protection plan was structured to ensure no net increase in pollutant loading during the planning period pending scientific findings or regulatory developments that would suggest a need to reduce loadings below current levels;

The key to ensuring no net loading increases is prioritizing public and private investment in best management practices (BMPs) based on location and cost-effectiveness to secure the best possible return on financial investments (in the form of reduced or avoided pollutant loads);

Market-based approaches, specifically water quality credit banking and trading, should be used to incentivize private actions and leverage public resources and could readily be implemented by integrating such options into the local development code and land use planning process;

The resulting WPP should be based on stakeholder input, informed by demonstration BMPs designed and installed specifically in support of this project and phased for maximum flexibility and success.

This Executive Summary highlights the methodologies and the results of the Hickory Creek Watershed Protection Plan. The Plan was prepared with significant local stakeholder participation through a diverse advisory group created specifically for this project. The advisory group met formally in six workshops over the project’s two and a half year period to review technical work and provide input, and received additional periodic updates and had other opportunities for input via email and web communications. In addition to providing input on the formation of the WPP itself, they provided guidance on locating the three demonstration BMPs that were also part of project.

HICKORY CREEK WATERSHED PROTECTION PLAN_FINAL_2008.DOC ES-1

EXECUTIVE SUMMARY

ES.2 Population Growth Will Lead to Increased Nutrient Loadings without Management Actions

ES.2.1 Urbanization in the Lewisville Lake and Hickory Creek Watersheds

Lewisville Lake is a large, multipurpose reservoir that provides drinking water for several major cities in the area, including Denton, Denton County’s seat, and the City of Dallas; twenty-five cities are located in the Lewisville Lake watershed. This water body also serves as a receiving water for numerous utility wastewater treatment plant effluent streams and as a recreational and ecological amenity. Denton County is one of the fastest growing areas in the Dallas Metropolitan Statistical Area.

Hickory Creek is a tributary to Lewisville Lake, and the Hickory Creek watershed is located entirely in Denton County, with a large portion in the City of Denton. Through the City’s monitoring program, staff members determined the Hickory Creek subwatershed encompassed six of the ten “worst” sub-watersheds in the City’s three watersheds.. Hickory Creek has historically been associated with concerns relating to ammonia nitrogen. The ammonia loads may possibly be associated with increased residential fertilizer use, leakage from on-site wastewater systems, or agricultural operations. As population growth and land development increases within the Hickory Creek watershed, urban-related pollutant loads will become a proportionately larger source of water quality impacts.

The watershed has few permitted discharges, and the majority of the City’s water quality concerns within the Hickory Creek watershed reflect the extent of Storm Water runoff impacts within this watershed, the general dynamics of which are described in Exhibit ES-1. These impacts are expected to increase as development increases within the Hickory Creek watershed. The Hickory Creek watershed within the larger Lewisville Lake watershed and in isolation are shown in Exhibits ES-2 and ES-3.

EXHIBIT ES-1 How Urbanization Affects Water Quality Increased urbanization has a significant impact on water quality. Much of the rainfall occurring in more natural settings is absorbed into porous soils, stored as groundwater and enters surface water bodies via seeps and springs, which provides a natural treatment affect in the form of vegetation uptake and infiltration through the soil. When an area is urbanized, soil and vegetation are replaced with parking lots, roads, and other impervious surfaces. This eliminates the possibility of natural treatment and increases the velocity of the runoff traveling to a surface water body, enabling the runoff to carry more pollutants.

Development and construction not only adds impervious area, it also includes land clearing and grading. If a rainfall event occurs while these areas are unprotected, erosion occurs and sediment is transported to nearby water bodies. Excess sediment, measured via total suspended solids (TSS) causes increased turbidity, which harms aquatic life, increases water treatment costs, and decreases a water body’s recreational benefit. Sediment also clogs drainage infrastructure, stream channels, water intakes, and reservoirs and destroys aquatic habitats.

In addition, nutrients (e.g., nitrogen and phosphorus) are introduced to our surface water bodies through increased wastewater treatment plant effluent and increased use of fertilizers, although the latter is found in rural applications as well. Excess nutrients, measured via total nitrogen (TN) and total phosphorus (TP), can cause an overstimulation of growth of aquatic plants, especially algae. Excessive algae growth can clog water intakes and other structures, deplete the ecosystem of dissolved oxygen as the plants decompose, and block light to deeper waters. This affects the respiration of fish and aquatic invertebrates, leads to a decrease in plant and animal diversity, affects our use of the water for recreational purposes, and increases water treatment costs.

ES-2 HICKORY CREEK WATERSHED PROTECTION PLAN_FINAL_2008.DOC

EXECUTIVE SUMMARY

EXHIBIT ES-2 Map of Lake Lewisville Area

Denton’s Location in Denton County

Lake RayRoberts

Lake Lewisville

DentonCity Limits

Lake Grapevine

Sanger

Pilot Point

Krum

Ponder

Corinth

Denton

I-35W

I-35E

Intake

North

Waste water

EXHIBIT ES-3 Detail of Hickory

In the face of concerns about future development threatening state-designated beneficial uses in Hickory Creek and Lewisville Lake and a possible 303(d) listing1, the City of Denton has taken steps to enhance its existing Watershed Protection Program, including additional stakeholder outreach, revisions to the local development code, and increased monitoring. Previous studies2 indicated that even those enhancements might not be aggressive enough and more robust watershed management approaches are required to overcome the declining water quality trend. A first step toward identifying more robust strategies was an updated analysis of the causes, sources, and loads of nitrogen, phosphorous and total suspended solids in the Hickory Creek watershed, building on the previous analyses performed for Lewisville Lake (ibid).

ES.2.2 Causes, Sources, and Projected Trends of Pollutant Loading to the Hickory Creek Watershed

From the outset, the focus of the analysis was on non-point sources, based on the results of previous watershed studies and a 2007 review of point source discharge data provided by

1 According to the Clean Water Act, Section 305(b), the Texas Commission on Environmental Quality (TCEQ) must conduct a water quality assessment of its classified water bodies every two years. Each water body is assigned a “designated use”, and actual water quality information is compared to the standards set for that use and, potentially, that specific water body. If the TCEQ determines the water body is not meeting its standards, that water body is then placed on a Clean Water Act, Section 303(d) list (Impaired Waters List). Once on this list, the State must conduct a Total Maximum Daily Load (TMDL) analysis and prepare an implementation plan within a designated time period. As of August 2008, neither Lake Lewisville nor Hickory Creek were on the state’s 303(d) list. 2 Trading Options for Watershed Improvement: The Lake Lewisville Pilot Project Year 1. TX A&M. CH2M HILL , City of Denton. 2003. Trading Options for Watershed Improvement: The Lake Lewisville Pilot Project Year 2. TX A&M. CH2M HILL ,City of Denton. 2004.


EXECUTIVE SUMMARY

Texas Commission on Environmental Quality. This review re-confirmed that even at maximum permitted discharge flows, solids, phosphorus and nitrogen loads delivered from point source discharges are negligible relative to non-point source contributions.

To assess causes, sources and projected trends of non-point source pollutant loads to the Hickory Creek arm, the project team developed a model that combined the Soil and Water Assessment Tool (SWAT) and QUAL-TX models. ArcGISTM was used to delineate sub-watersheds, soil classifications, and land uses in the watershed from existing data, while precipitation, flow, and water quality measurements were obtained from a monitoring site that has been in place since 2001, near the downstream end of Hickory Creek.

Using this information, analysts were able to estimate annual loads of target pollutants contributed by runoff from four Hickory Creek land use categories:3

Urban— representing residential, commercial, industrial, transportation, utilities, and similar uses;

Agricultural— predominantly hay and wheat production;

Rangeland — predominantly low density cattle and horse grazing, and lightly grazed native prairies (rangelands are often grazed at low densities, and tend to be vegetated with coastal Bermuda, shrubs and brush, and native prairie grasses such as big bluestem, little bluestem, Indian grass and switch grass); and

Forest land —tends to be remnants of the Eastern Crosstimbers forest, are generally comprised of post oak and blackjack oak, and are interspersed with mesquite trees and prairie grasses such as little bluestem.

Exhibit ES-4 presents the current land use distribution in the Hickory Creek watershed.

EXHIBIT ES-4 Land Use Distribution in the Hickory Creek Watershed

Land Use Drainage Area (acres)

Urban 29,447

Agriculture 38,998

Rangeland 45,734

Forest 9,182

Water 1,109

Total 124,470

3 Because of the relative uniformity within forested, agricultural, and rangelands in the Hickory Creek watershed, the results of initial loadings analyses (prior to this project), and the fact that impacts to water quality in Hickory Creek are anticipated to be caused by future land use changes (i.e., urbanization), the project team determined that it was not necessary to evaluate more detailed subcategories of land uses in the loading analyses other than these four as defined.


EXECUTIVE SUMMARY

Exhibits ES-5 and ES-6 present the estimated expected pollutant concentrations in Storm Water runoff, or non-point source loads, from each of the land use categories as projected by the SWAT/QUAL-TX model, as well as the resulting estimated load per acre and the annual estimated load for the watershed based on the acreage assumptions presented in Exhibit ES-4.

EXHIBIT ES-5

Constituent Concentrations (mg/L) for each Land Use Category The model predicted higher runoff concentrations for agricultural land than for other land uses. However, because impervious land uses usually generate more runoff than pervious land, urban areas tend to generate greater loads per unit area than rural land, even though urban areas have lower constituent concentrations per unit runoff volume, as seen in Exhibit ES-6 below.

Land Use Rainfall Depth Sediment (mg/L) Phosphorus (mg/L) Nitrogen (mg/L)

Urban All 65 0.55 1.48

0.79 inches 80 1.29

1.57 inches 80 1.29

Agriculture

3.15 inches 80 1.29

3.04

2.39

2.26

Rangeland All 39 0.19 1.30

Forest All 29 0.11 0.90

EXHIBIT ES-6

Estimated Annual Loads Per Acre and for the Watershed On a relative basis, among the four land uses, urban areas generate more sediment load per unit area, urban and agricultural areas generate more nitrogen, and agricultural areas contribute more phosphorus. However, as Hickory Creek has a much greater amount of agricultural land than urban land, one can see in Exhibit ES-5 that agricultural areas are the main source of the three constituents in Hickory Creek by sheer mass.

Annual Loads per Unit Area from each Land Use (pounds/acre/yr)

Total Annual Loads in the Hickory Creek Watershed by Land Use

(tons/yr) Land Use

Sediment Phosphorus Nitrogen Sediment Phosphorus Nitrogen

Urban 161.49 1.34 3.66 1,305.14 10.80 29.54

Agriculture 123.12 1.96 3.75 2,030.46 32.41 61.84

Rangeland 55.32 0.27 1.87 1,050.50 5.07 35.60

Forest 21.41 0.09 0.71

71.65 0.33 2.43

ES.2.3 Areas of Heaviest Pollutant Loading in 2007-2008 In addition to the general spatial loading analysis presented above, a more detailed analysis was conducted to identify potential priority sites for future BMP implementation. Ideal BMP locations are defined as those associated with high annual loads of each of the three constituents (to take most advantage of the BMP’s removal efficiency percentage) and a relatively small drainage area (large enough to capture economies of scale for cost-effectiveness purposes). A total of 282 priority sites were identified with drainage areas between 80 and 125 acres. The drainage area, annual runoff volume, annual sediment load,


EXECUTIVE SUMMARY

annual phosphorus load, and annual nitrogen load were identified for each of these headwater areas.

The results, shown in Exhibit ES-7, illustrated high sediment load areas just north of the Hickory Creek watershed outlet, indicating the City of Denton’s urbanized areas are contributing significantly to the loadings. High nitrogen load areas are distributed somewhat evenly throughout the watershed, and high phosphorus load areas are located predominantly in the northwest, more rural, part of the watershed.

EXHIBIT ES-7 Mapping Priority Locations for BMP Installation


EXECUTIVE SUMMARY

ES.2.4 Land Use Change Predictions for the Hickory Creek Watershed To predict future loading rates, land use changes due to continued urbanization must be predicted. To estimate the land use changes that are occurring and will continue to occur as the Denton area continues to grow, the project team used planning studies previously conducted by the City of Denton. Exhibit ES-8 presents projected future land use changes for 2008, 2012, 2017 and 2020. Clearly, control of urban storm water runoff will be a major environmental challenge for the Hickory Creek watershed in the foreseeable future.

EXHIBIT ES-8 Projected Future Land Use Changes

CurrentWater

1%

Range37%

Forest7%

Agricultural31%

Urban24%

2012Water

1%

Agricultural27%

Forest6%

Range31%

Urban35%

2017

Forest5%

Water1%

Agricultural22%

Urban46%

Range26%

2020

Forest5%

Water1%

Agricultural20%

Range23%

Urban51%

ES.3 This Watershed Protection Plan is Designed to Ensure No Net Increase in Sediment and Nutrient Loads

The Hickory Creek WPP follows the nine EPA elements for such plans (Exhibit ES-9) and builds upon the technical work conducted concurrently with WPP development and previous efforts to evaluate water quality challenges and possible incentive-based solutions.

Notably, many WPPs are developed as an implementation guide for a total maximum

EXHIBIT ES-9 EPA’s 9 Watershed Protection Plan Elements In addition to the these nine elements, a unique aspect of the Hickory Creek WPP is the concurrent selection, design and construction of demonstration structural best management practices (BMPs) at three separate sites in the City. BMPs are techniques used to control Storm Water runoff and sediment and provide soil stabilization. BMPs can be intended to address water quality, water volume, or both.5


EXECUTIVE SUMMARY

daily load (TMDL) implementation plan. In this case, the Hickory Creek watershed is currently meeting designated uses, though the very real potential exists for this not to be the case in the future. As a result, there are no allocation targets or regulatory requirements to reduce pollutant loading. Therefore, pollutant control options will be largely voluntary and proactive or, possibly, implemented in response to local code requirements rather than Clean Water Act (CWA) regulation.

Against this regulatory backdrop, the goal of this WPP is to identify actions that will collectively protect against any net increases in sediment and nutrient loading. This WPP is a proactive plan that is benchmarked against current conditions, designed to minimize or prevent net increases in pollutant loadings and provide the information needed to optimize the choice of investments in pollutant management practices.4

(1) Identification of the causes and sources (or groups of similar sources) that must be controlled to achieve the load reductions described in (2).

(2) Estimates of the load reductions expected for the management measures described in (3).

(3) Descriptions of the non-point source management measures that will need to be implemented to achieve the load reductions described in (2).

(4) Estimates of the amounts of technical and financial assistance needed to implement this plan.

(5) Descriptions of the information/education component that will be used to enhance public understanding of this plan.

(6) A schedule for implementing the non-point source management measures described in (3).

(7) Descriptions of interim, measurable milestones for determining whether the non-point source management measures described in (3) are being implemented.

(8) Development of a set of criteria that can be used to determine whether the load reductions described in (2) are being achieved.

(9) Descriptions of the water quality monitoring activities that can be employed to evaluate the effectiveness of the implementation efforts over time, measured against the established criteria described in (8).

ES.4 Optimizing BMPs by Location and Cost-Effectiveness is Key to Ensuring No Net Increase

To determine what management measures could achieve desired and/or possible pollutant load reductions and where the City of Denton would implement these measures, the project team chose to evaluate BMP implementation at three spatial scales:

1. Watershed-wide;

2. The 282 optimal drainage areas identified in the SWAT/QUAL-TX model; and

3. Three Master Planned Communities (MPCs) currently proposed for development within the City of Denton.

For each scale, a set of BMP “portfolios” was simulated and evaluated with the goal of investigating how pollutant load reductions could be achieved most cost-effectively. To conduct the analyses, the project team employed a Microsoft Excel-based tool developed by

4 Section 2.4.3 of the Handbook for Developing Watershed Plans (EPA 2008) states, “Watershed project sponsors can use the tools presented in this handbook to develop watershed plans for waters that are not impaired by non-point source pollution to ensure that they remain unimpaired.” 5 The EPA defines a BMP as a "technique, measure or structural control that is used for a given set of conditions to manage the quantity and improve the quality of storm water runoff in the most cost-effective manner."


EXECUTIVE SUMMARY

CH2M HILL that allows the user to construct a BMP “portfolio” for a defined area and calculates key portfolio metrics, including total cost, load reduction, and unit costs (an indicator of cost effectiveness).

As detailed in this section, the analyses produced the following key findings:

Watershed-wide, sufficient acreage exists for cost-effective BMP installation;

Some BMP-land use combinations are not very cost-effective at all;

Limitations exist as to the practical number/level of BMPs that would realistically be placed on any given parcel;

Data, tools, and simple analyses can help point us to the best opportunities available;

Many land-owners with the best opportunities for BMP implementation will not necessarily have to act, and many with limited or poor opportunities for BMP implementation may have to act; and

Opportunities may exist to influence and incentivize which BMPs are placed where.

ES.4.1 Watershed-Wide BMP Portfolio Four alternative BMP portfolios were analyzed at the watershed-wide scale, as follows:

Portfolio 1. No additional BMPs are added within the watershed through 2020;

Portfolio 2. BMPs are added so that total sediment and phosphorus loading does not increase above current (2008) levels;

Portfolio 3. BMPs are added so that total sediment, phosphorus and nitrogen loading does not increase above current (2008) levels;

Portfolio 4. Annual investment in additional BMPs is capped at a specified monetary benchmark to approximate a consistently funded capital improvement program.

Note that, with regard to Portfolio 4, the benchmark chosen for these purposes is $465,000 per year, which equates to the estimated annual debt payment plus annual operations and maintenance costs for nutrient removal upgrades to Denton’s Pecan Creek Water Reclamation Plant.

Exhibit ES-10 presents the graphic results for TSS and TP with accompanying narrative.


EXECUTIVE SUMMARY

EXHIBIT ES-10 Watershed Wide BMP Portfolio Results The estimated average annual cost of the portfolio holding TSS and TP to the 2008 level is $439,000; to keep TSS and TP loading increases to only 7% and 5%, respectively, is $151,000 annually. Note the cost to control sediment is less than the cost to control phosphorus, and Portfolio 4 (the “Benchmark”), under which investments are capped at an average level of $465,000, provides the most cost-effective control.

Cost of Each Watershed Wide Portfolio and TSS Reduction Cost of Each Watershed Wide Portfolio and TP Reduction

All Hickory Portfolios: TSS

12%

23%

29%

-2%-1% 0%

-4%

-8% -9%

6%7% 7%

$281,800

$647,800

$850,000

$394,100

$932,800

$1,188,800

$75,600

$221,000

$397,700

-15%

-10%

-5%

0%

5%

10%

15%

20%

25%

30%

35%

2012 2017 2020

Year

TS

S T

on

s/yr

Per

cen

t +

/- v

200

8 B

asel

ine

$(500,000)

$(400,000)

$(300,000)

$(200,000)

$(100,000)

$-

$100,000

$200,000

$300,000

$400,000

$500,000

$600,000

$700,000

$800,000

$900,000

$1,000,000

$1,100,000

$1,200,000

An

nu

al C

os

t o

f B

MP

Po

rtfo

lio

No BMPs

Hold TSS & TP

Hold All

Benchmark

Hold TSS & TP $/yr

Hold All $/yr

Benchmark $/yr

All Hickory Portfolios: TP

5%

10%

13%

0% 0% 0%

-1%

-3%-4%

3%

5%5%

$281,800

$647,800

$850,000

$394,100

$932,800

$1,188,800

$75,600

$221,000

$397,700

-5%

-4%

-3%

-2%

-1%

0%

1%

2%

3%

4%

5%

6%

7%

8%

9%

10%

11%

12%

13%

14%

15%

2012 2017 2020

Year

TP

To

ns/

yr +

/- v

. 200

8 B

asel

ine

$(400,000)

$(300,000)

$(200,000)

$(100,000)

$-

$100,000

$200,000

$300,000

$400,000

$500,000

$600,000

$700,000

$800,000

$900,000

$1,000,000

$1,100,000

$1,200,000

An

nu

al C

os

t o

f B

MP

Po

rtfo

lio

No BMPs

Hold TSS & TP

Hold All

Benchmark

Hold TSS & TP $/yr

Hold All $/yr

Benchmark $/yr

Portfolio Details

Portfolio 1. No action will result in an ultimate sediment loading increase of 29% by 2020 and an TP loading increase of 13%.

Portfolio 2. When sediment is prioritized, sediment and phosphorus are held at loads slightly less than the 2008 baseline. Prioritizing phosphorus, sediment and phosphorus loads are held at the 2008 level target.

Portfolio 3. When sediment is prioritized, attempting to hold all constituents of concern at current levels results in an ultimate decrease in sediment loading of 9% below 2008 loadings. When phosphorus is prioritized, attempting to hold all constituents of concern at current levels results in an ultimate decrease in TP loading of 4% below 2008 loadings.

Portfolio 4. Managing BMP additions within a $465,000/year budget resulted in an ultimate 7% increase in sediment loading when sediment was prioritized, and an ultimate 5% increase in TP loading when phosphorus was prioritized, as compared to 2008 levels.

ES.4.2 Static and Dynamic BMP Portfolios for the 282 Priority Sites Three alternative “static” BMP portfolios were developed and analyzed for the 282 collective priority sites based on specified maximum, medium and minimum amounts of land treated by BMPs: 50%, 33%, and 19%, respectively. Unlike the watershed-wide analyses, which incorporated a temporal element examining changing loads and changing BMP portfolios over a 2008-2020 planning period, this Maximum-Medium-Minimum analysis for the 282 collective priority sites is static—a snapshot in time. Exhibit 11 presents the results of these static portfolios.


EXECUTIVE SUMMARY

EXHIBIT ES-11 Highlighted Results for the Three 282 Priority Site Portfolios The results are driven entirely by the BMPs selected for each portfolio, the BMP efficiencies and imposed coverage limits, and the relative unit costs. There are stark differences among the three portfolios with respect to key metrics such as cost per year, per acre of watershed, and per pound of pollutant removed.

282 Collective Portfolio BMP Max-All 282 BMP Med-All 282 BMP Min-All 282

TOTAL ACRES 24,749 24,749 24,749

Agricultural 9476 9476 9476

Range 9590 9590 9590

Forest 1118 1118 1118

Urban 4565 4565 4565

Acres Managed 12,289 8,246 4,680

Acres Managed % 50% 33% 19%

TSS Tons Reduced/yr 382.54 308.19 178.50

P Tons Reduced/yr 1.90 1.55 0.84

N Tons Reduced/yr 4.83 3.85 2.14

Total Cost/yr $3,008,550 $1,102,216 $122,739

$ total Pounds $3.86 $1.76 $0.34

$ per Acre $121.56 $44.54 $4.96

TSS $/Ton $7,865 $3,576 $688

P $/Ton $1,583,825 $709,716 $146,009

N $/Ton $622,985 $286,598 $57,292

TSS % Reduction 31% 25% 15%

P % Reduction 14% 11% 6%

N % Reduction 14% 11% 6%

Drawing on the results of the static portfolios, a “capital improvement program” approach was taken to simulate investments in BMPs on the 282 sites over a temporal period from 2008 to 2020, as shown in Exhibit ES-12. For mathematical convenience, it was assumed that BMPs would be installed on 22 sites in the first year of the program; on another 22 sites the second year of the program, and so on until all 282 sites had BMPs. Further, a priority ranking system was used to select the first best 22 for the program’s first year (ranking 1-22), the second best 22 for the program’s second year (ranking 23-44), and etcetera. The financial benchmark of $465,000 established for the watershed-wide portfolio was used as a target for the dynamic portfolio such that the average annual cost over the 2008-2020 period would approximate that benchmark. The BMP acreage results from the static portfolios were used to guide BMP selection for the dynamic portfolios.


EXECUTIVE SUMMARY

The results of the static and dynamic portfolios involving the 282 priority sites illustrate how a prioritization scheme can be used to select a list of specific sites to target for BMP implementation, and how investments could be prioritized among those sites to produce the most cost-effective load reductions as soon as possible. As with the watershed-wide scale, the higher levels of investment produce more reduction than appears necessary now, while a modest investment of $122,700 annually reduced TSS, TP, and TN loadings by 15%, 6%, and 6% respectively, compared to the estimated loadings from the sites with no BMPs.

EXHIBIT ES-12 Cumulative BMP Cost Per Year and Cumulative Pounds of Pollutant Reduced Per Year: Dynamic 282 Priority Site Portfolio

(700,000)

(600,000)

(500,000)

(400,000)

(300,000)

(200,000)

(100,000)

-

100,000

200,000

300,000

400,000

500,000

600,000

700,000

800,000

900,000

2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

Total Cost/yr

TSS Lbs Reduced

P Lbs Reduced

N Lbs Reduced

Cu

mu

lati

ve

BM

P $

/yr

Cum

ulat

ive

Poun

ds R

educ

ed/y

r

Without additional BMPs beyond those simulated in this analysis—either on the 282 sites or other locations, even if the dynamic BMP portfolio for the 282 sites was implemented at 100% immediately, it would only offset future loads from population growth and development for a few years: sometime between 2010 and 2011 TSS, TP, and TN loads would increase beyond the offsets provided by the “282” BMPs. So the 282 sites are a good place to start prioritizing BMP investments, but by themselves they will not be sufficient to ensure no net increases in pollutant loading through the planning period. If these were the only BMPs implemented between now and 2020, projected loads for TSS, TP, and TN would still increase 24%, 10%, and 15%, respectively, compared to the 29%, 13%, and 18% projected with no BMPs.

ES.4.3 BMP Portfolios for the Master Planned Communities (MPCs) Three Master Planned Communities (MPCs) are currently in the planning and design stages and the associated developers have agreed to work jointly with the City of Denton to incorporate BMPs in the respective site plans. These MPCs are called Cole Ranch, Inspiration, and Rayzor Ranch. Note the analysis assumed all MPCs will be built out to a distribution of approximately 80% urban and 20% range land use.

Three alternate BMP portfolios were employed for each of the MPCs of interest:

Portfolio 1. A maximum amount of BMPs possible;

Portfolio 2. BMPs are added such that total sediment loading does not increase above current (2008) levels; and

Portfolio 3. BMPs are added such that total phosphorus loading does not increase above current (2008) levels.

There are some similarities as well as some readily observable differences across the MPC portfolio results, as illustrated for Portfolio 2 shown in Exhibit ES-13. Pollutant load reduction percentages are similar for Cole Ranch and Inspiration, and significantly less for Rayzor. The very similar before and after land use distributions for Cole Ranch and


EXECUTIVE SUMMARY

Inspiration, along with their similar size, explain the consistency in their estimates. Because Rayzor is much smaller in size, fewer load reduction opportunities existed.

The significant differences in the cost metrics are the result of a few factors. Despite their similar before and after land use distributions, Cole Ranch and Inspiration were different enough that, to achieve the desired control target, the BMP portfolio for Inspiration had to rely on relatively more acreage being managed with detention ponds, which are more expensive, compared to Cole Ranch, which needed less acreage managed by detention ponds to achieve the target. By comparison, due to its smaller size overall, the Rayzor BMP portfolio did not exhaust the limits of lesser cost BMPs, and so requires no detention ponds to meet the target. With more case studies of MPCs, it might be possible to determine certain acreage thresholds that would foretell BMP costs; however, it is just as possible that, at this scale, the site-specific nature of each MPC would result in a broad range of costs without any predictive features.

EXHIBIT ES-13 Comparison of Pollutant Reduction and BMP Cost for MPC Portfolio 2

MPC Comparison: Hold TSS to PreDevelopment Levels Scenario

$84

$177

$18

$49

$125

$6

0%

10%

20%

30%

40%

50%

60%

Cole Ranch Inspiration Rayzor Ranch

Master Planned Community

Pe

rce

nt

Re

du

cti

on

v.

No

BM

P

$-

$20

$40

$60

$80

$100

$120

$140

$160

$180

$200

Un

it C

os

t S

cal

e TSS Reduction v. No BMP

TP Reduction v. No BMP

TN Reduction v. No BMP

$/100lb/yr TSS

$/Ac/yr

ES 4.4 Demonstration BMPs For this component of the project, three demonstration structural BMPs were installed with the purpose of providing a baseline for estimating the removal efficiencies of structural BMPs within the watershed for sediment, nitrogen and phosphorus in the future. Of an initial list of 11 candidate sites, the following three were selected: Denton Airport; Denton Public Safety Training Facility; Lake Forest Park Wiggly Fields Dog Park. The candidate list and final selection was developed based on criteria selected by stakeholders for selecting and installing BMPs.

Land Ownership/Access—First priority was given to City-owned property. Second priority was given to land owned by a jurisdiction other than the City, but was otherwise readily accessible. Subsequent priorities were allotted based on ease of access.


EXECUTIVE SUMMARY

Current Site Condition—Priority was given to undeveloped sites expected to undergo development and developed sites that could be retrofitted with one or more BMPs.

BMP Alternatives—Preference was given to natural-looking BMPs that match their surroundings and provide have multiple uses such as wildlife habitat.

BMP Effectiveness—Selection was based primarily on reduction in sediment and phosphorus loads, with secondary consideration for control of nitrogen.

The North Central Texas Council of Government’s (NCTCOG) Integrated Storm Water Management (iSWM™) Design Manual for Site Development was used as the basis for design. Selection of the individual BMPs themselves was based on land availability, characteristics of the drainage area, estimated removal efficiencies related to each BMP, ease of implementation, and site-specific challenges. Detailed designs for each BMP incorporated existing utility and easement data, survey data, and standard details from the City, NCTCOG and the Texas Department of Transportation. Additionally, knowledge of native soils and appropriate plantings was provided by local stakeholders. Monitoring methods were established to demonstrate the treatment efficiencies of each management practice.

Key conclusions based on this design effort included: BMP implementation can provide significant loading reductions; structural BMPs can effectively be integrated into new developments, as well as retrofitted into existing open spaces and drainage systems; and it is best to integrate BMPs into site planning at an early stage, especially in conjunction with other gravity utilities, e.g. storm and sanitary sewer.

ES.5 Market-Based Approaches Will Help Incentivize Private Investment and Leverage Public Resources

ES.5.1 Opportunity for a Storm Water Credit Market It appears that cost-effective opportunities exist to install BMPs throughout the watershed, in priority locations, and in planned communities and these installations could significantly reduce future loadings compared to levels estimated with no BMPs. However, under current regulations, policies, and site plan review and approval processes, it is quite likely that many land owners with the best opportunities for BMP implementation may have little or no need for BMPs, and some land owners with limited or poor opportunities for BMP implementation may in fact be required to act due to any number of factors.

One purpose of market-based approaches for storm water management programs is to provide mechanisms that will help optimize the location, size, and type of BMP by shifting implementation when required from sub-optimal solutions to ones that are more cost-effective and/or that deliver greater benefits than would otherwise occur. This can be accomplished in a credit-based system where some landowners may pay other parties to implement BMPs for them. Depending on various aspects of program design, the program sponsor (in this case, the City), can influence and incentivize the type and location of BMPs.

The Project Team examined the City’s current requirements for storm water management within new development and other types of land use changes to determine what incentives exist for landowners to perform beyond minimum requirements. Currently, the City does not require the installation of post-construction storm water BMPs and no market value is applied to pollutant load reductions. A storm water BMP credit bank and/or market in


EXECUTIVE SUMMARY

credits would provide incentives and rewards for land owners, including developers, who install and maintain BMPs.

ES.5.2 Recommended Storm Water Credit Market To create a storm water quality credit market that will encompass current City regulatory requirements and provide water quality protection, it will be necessary to establish baselines for the credit market. Performance above the baselines would generate credits that could be banked, sold, or otherwise traded, and performance below the baselines would require the purchase of credits as offsets under several possible schemes.

Two types of baselines are recommended for Denton’s consideration:

An existing baseline of water quality protection would be based on estimates of the effectiveness of current requirements and practices in each area of regulation using best professional judgment; and

New baselines (performance requirements) would integrate credit mechanisms into implementation of (1) the Drainage Code, and (2) the City’s code covering development applications in designated Environmentally Sensitive Areas (ESAs).

Exhibit ES-14 presents proposed levels for assumed pollutant control baselines of current practices and two tiers of new baselines for consideration as requirements or goals for a credit market. Current practices are assigned baselines based on estimates of pollution control provided by compliance with the Drainage Code. The Tier 2 baseline is based on Leadership in Energy and Environmental Design (LEED) criteria for sustainable development and is consistent with NTCOG’s iSWM guidance. This baseline represents a significant improvement in pollutant loading control, but also implies a significant change in the current program. In the event that the Tier 2 level is deemed too big a first step, the Tier 1 baselines are provided for consideration as an interim step or as an intermediate level of performance where credits and debits might be counted differently than when Tier 2 is attained. The Tier 1 baseline represents an enhancement over current results and the levels suggested are based on best professional judgment about what would be an achievable improvement.

EXHIBIT ES-14

Storm Water Credit Market Structure Recommended for Consideration

Water Quality Protection (% Removal)

TSS Total P Total N

Baseline of Current Practices:

Drainage Design Criteria MS4 Permit Compliance ESA Regulation

20

20

5

New Baselines for Market Goals:

Tier 1 Baseline (1/2 of iSWM, LEEDs)

40 20 20

Tier 2 Baseline (iSWM, LEEDs) 0 40 40


EXECUTIVE SUMMARY

ES.5.3 Phased Implementation for a Storm Water Credit Market Because market-based approaches are new to City staff as well as the development community and other stakeholders, and because they have the potential to be very far reaching and influential on the development process, the City of Denton will consider moving forward by implementing a pilot program. This pilot program will be designed to test applications of the credit market approach within existing regulatory and plan review structures prior to codifying such programs in the planned code revisions. City staff will evaluate results on a rolling basis, possibly modifying the parameters of the pilot as needed, and eventually finalizing the pilot by determining how market based approaches could be formalized within the Denton Development Code and/or plan review guidance/policy.

The City of Denton staff have begun the process of reviewing and potentially revising the City of Denton’s Comprehensive Plan, which is the main planning guidance document employed by the City. As the Comprehensive Plan is being reviewed, staff will recommend changes needed to implement credit market approaches to municipal decision makers. If successfully adopted, the Denton Comprehensive Plan will be used as a guideline for suggesting and implementing changes to the Denton Development Code to help facilitate market based approaches.

ES.6 The Watershed Protection Plan Establishes an Adaptive Blueprint for Water Quality Protection

This Plan highlights a series of watershed management objectives and related actions that are designed to minimize increases in pollutant loadings within the Hickory Creek watershed. Pollutant loads will be managed by installing BMPs in the watershed and enhancing education outreach programs. This document establishes a set of objectives and actions that are specifically tailored to address both the challenges and opportunities that are detailed in previous sections of this Plan. Where appropriate and necessary, these objectives and actions will be integrated with the City’s Watershed Management Program, the Denton Comprehensive Plan, and Denton’s Code of Ordinances.

Based on the evaluations of both challenges and opportunities presented in this Plan, four management objectives were established and interim milestones associated with each management objective were developed for a period of one to three years. A fifth set of objectives was developed to address the longer term, four to five years from now. These are described below and summarized in a graphic schedule (see Exhibit ES-15).

ES.6.1 The WPP’s Four Management Objectives and Highlighted Milestones 1. Minimize net increases in pollutant loadings of sediments and nutrients in the face of

continuing population growth and development.

Use the analysis and tools presented in this Plan to benchmark “current” conditions.

Utilize stakeholder input provided during the development of this Plan to guide BMP siting, selection, and implementation under code compliance, credit trading, and voluntary programs, considering: cost-effectiveness; good economics (e.g., the party changing the land use, thus increasing loading, pays for a portion or all of the BMP implementation costs; compliance with WPP goals and local codes; aesthetic


EXECUTIVE SUMMARY

appeal; and usable area (e.g., where possible the BMP creates recreational areas and/or habitat in addition to pollutant removal functions).

Use existing models and tools, as may be enhanced or augmented by other tools and procedures to track land use changes, estimate the impacts of these changes without BMPs, and account for pollutant reductions achieved by compliance with applicable codes, achieved under the credit trading pilot, produced by City-funded activities, or provided by other voluntary actions associated with the other management objectives.

Continue current instream and other water quality monitoring programs and utilize that data and associated analyses to update and populate the models and tools.

2. Minimize or mitigate the net impact of new development and other land use changes that must comply With Denton’s Development Code with respect to pollutant loading contributions to Hickory Creek.

Review the proposed recommendations to establish new pollutant baselines under the Drainage and Environmentally Sensitive Areas Codes and the proposed credit banking and trading pilot.

Seek out opportunities to implement the pilot program strategies with the purpose of testing the application of stricter performance baselines and trading strategies. Because the MPCs generally must meet both the ESA and drainage codes, specifically test trading approaches with these land uses, if possible.

Conduct periodic reviews of interim achievements to determine how well the trading process fits within the current regulatory structure of the City of Denton.

As the pilot program becomes more established and accepted, begin to explore the options of executing actual credit exchanges with the City operating as a “banker”, followed by the City acting as a facilitator with only occasional activities as a banker.

Use the lessons learned during the pilot program to shape revision recommendations for both the City of Denton Comprehensive Plan and the Denton Development Code.

3. Target and direct voluntary actions to priority locations.

Continue to review and evaluate the source and loadings data and conclusions underpinning this plan relative to the locations of development and land use change.

Review in more detail the results of the rankings of the 282 priority sites, including relative weighting and possibly color coding a map of the sites by ranking percentile.

Develop a list, map, and/or other means to document important attributes of the priority sites, including the 282 that have been identified and may be amended through the review process, and maintain the information in such a way that it can be used to target credit creation by private parties, BMP investments by the City, and other voluntary actions associated with these areas.

Continue evaluation and maintenance of the three demonstration BMPs designed and installed under the project for which this Plan was developed.


EXECUTIVE SUMMARY

Identify City resources that could be deployed to fund design and implementation of additional demonstration BMPs and allocate available City resources to fund the design and construction of additional demonstration BMPs in priority areas.

Link information/activities related to site location and BMP-type prioritization to: the credit banking/trading pilot, for example by providing relevant information and guidance to City staff and development applicants; and the education and outreach programs, for example by providing relevant information and guidance to City staff and development applicants.

4. Education and outreach designed to increase awareness and participation, and foster changes in behavior that support proactive contributions to watershed management efforts (see also Section ES-6.3 for additional detail).

Develop and implement an outreach campaign in concert with the construction of the demonstration BMPs at the Lake Forest Dog Park, the Denton Airport facilities, and the new Denton Firehouse Number 7.

Utilize the existing planning framework associated with the review and possible revision to the Comprehensive Plan and Development Code to begin and support the process of public outreach within the entire Hickory Creek watershed as relates to watershed management generally and storm water BMP implementation specifically.

Build on existing public information and participation activities.

Disseminate information regarding any new performance requirements and/or credit trading opportunities to the relevant parties.

Disseminate information regarding the City’s priority areas associated with BMP implementation and any preferred BMPs to the relevant parties.

Periodically solicit feedback on the reach and effectiveness of the City’s education and public outreach efforts, through informal communications and more systematic stakeholder meetings, focus groups, or surveys as may be planned.

Solicit ongoing and specific feedback from the actual and potential participants in the activities associated with implementation of any new performance baselines or the credit trading pilot and utilization of the City’s BMP priority scheme, with an emphasis on learning what factors affect their ability to attain compliance and their willingness and ability to exceed compliance baselines and generate credits and/or otherwise implement “green” projects.

ES.6.2 Measuring Progress and Success in the Longer Term Evaluating progress on the primary objective of this watershed management plan—minimizing net increases in pollutant loadings of sediments and nutrients in the face of continuing population growth and development—involves assessing the results of implementation actions associated with the interim milestones detailed above (individually and collectively), as well as broader assessments conducted at more distant time intervals.

Specific measures of progress and success over the longer term are derived from the early indicators of success established for interim milestones as results are achieved. However,


EXECUTIVE SUMMARY

Plan objectives may need to be refined in response to initial successes, persistent challenges, and new opportunities that may arise. Longer term progress measures described below provide a strong evaluation framework, as well as providing opportunities for Plan adaptation and/or evolution in response to changing conditions.

1. Keep a record of landowners’ development and land use change proposals with respect to key indicators of their understanding, ability, and willingness to invest in BMPs.

2. Track BMP implementation and estimated pollutant load reductions using the credit framework.

3. Develop new baseline pollutant loadings and trend projections and evaluate results.

4. Evaluate instream monitoring data against historical conditions and future trends.

Generally, the Watershed Protection Plan itself, as well as the watershed and demonstration BMP monitoring activities, will be reviewed on a quarterly basis.

ES 6.3. Education and Outreach For BMP implementation to be successful, the City must have the support and participation of the citizenry. To develop this involvement, the City plans to create new initiatives to educate people and motivate them to change their personal behaviors to support this effort.

Leveraging the Demonstration BMPs The overall framework recommended for the City of Denton’s approach is to develop and implement an outreach campaign in concert with the construction of the demonstration storm water best management practices at the Lake Forest Dog Park, the Denton Airport facilities, and the new Denton Firehouse Number 7. Each of these new BMPs can establish an outreach program as discrete steps, with each step building on the previous ones. The steps are as follows (USEPA 2008): define the driving forces, goals, and objectives; identify and analyze the target audience; create the message; package the message; distribute the message; and evaluate the outreach campaign. The demonstration projects will serve as excellent mechanisms to continually reinforce the concept of the influence of human activities on storm water quality and how modifications to these activities can help minimize impacts. However, a broader approach will be necessary to apply this effort to the entire Hickory Creek watershed.

Utilizing the Planning Framework Through this watershed protection planning process, the City of Denton is developing a planning framework for the City and its Extra Territorial Jurisdiction (ETJ) that aids analysts in making supportable, cost-efficient decisions on management practices to restore and protect water quality in the Hickory Creek watershed. The planning framework will be utilized to begin the process of public outreach within the entire Hickory Creek watershed. This aspect of public outreach will be directed towards citizens, the development community, municipal decision makers, and City staff. The information available through the planning framework tool will be used to inform municipal decision makers, influence the storm water management component of Denton’s currently developing Master Planned Communities, and influence municipal policy through modifications to the Denton Comprehensive Plan and the Denton Development Code.


EXECUTIVE SUMMARY

Building on Existing Public Information and Participation Activities The City of Denton currently has a number of public education and involvement activities that are centered on the topics of watershed protection and water quality. Future outreach campaigns will be designed to incorporate elements of the Hickory Creek Watershed Protection Plan into these existing public outreach efforts. These existing programs are expected to serve as a conduit to convey information specific to the watershed protection efforts and can be used in conjunction with the public outreach approaches outlined above to efficiently convey public information.

ES 6.4 Summary WPP Implementation Schedule The timeline for implementing management measures is (Exhibit ES-19) to the focused on dealing with future land use changes that are expected to have a negative impact on water quality and the types of impairments expected for this watershed. The Hickory Creek WPP is a programmatic approach that will require substantial policy changes and an iterative approach when shaping local regulatory processes that address development. Additionally, many of these activities are tied to development and are, therefore, subject to many of the same market challenges that influence short and long term development patterns.


EXECUTIVE SUMMARY

EXHIBIT ES-15 WPP Interim Milestones And Longer-Term Progress Measures

Milestone Year 1 Year 2 Year 3

INTERIM MILESTONES

1. MINIMIZE NET INCREASES IN POLLUTANT LOADINGS

Benchmark current conditions

Use stakeholder input to inform implementation

Track land use changes and impacts, including credits

Use data from on-going in-stream monitoring to guide efforts

Track progress toward milestones and Periodic Status Reviews

2. MINIMIZE/MITIGATE IMPACT OF NEW DEVELOPMENT

Consider establishing new pollutant baselines in codes

Implement pilot credit banking and trading under existing code

Conduct periodic reviews of credit market pilot

Explore different City roles (e.g., banker v. facilitator)

Provide input to Comprehensive Plan revision process re market-based approaches

Recommend changes to City codes following Comprehensive Plan revision

3. TARGET AND DIRECT VOLUNTARY ACTIONS TO PRIORITY LOCATIONS

Continue review of source and loadings data presented in WPP

Detailed review of 282 priority sites

Prepare summary and guidance materials to target actions to the "282" sites

Continued evaluation and maintenance of the three WPP demonstration BMPs

Identify City resources for additional demonstration BMPs, including at "282" sites

Provide location priority information/tools to credit trading pilot

Provide location priority information/tools to education and outreach programs

4. EDUCATION AND OUTREACH TO SUPPORT WPP IMPLEMENTATION

Education and outreach leveraged via the three demonstration BMPs

Public outreach throughout Hickory Creek watershed, building on existing programs

Disseminate information about credit trading pilot

Disseminate information about priority areas for BMP implementation

Periodically solicit feedback on education and outreach efforts, generally

Solicit feedback on credit trading pilot and BMP priority location scheme

LONGER TERM PROGRESS & SUCCESS MEASURES

PROJECT-SPECIFIC

Compilation of land use change proposals re ability and willingness to invest in BMPs

PROJECT-SPECIFIC AND CUMULATIVE BMP RESULTS

Compilation of BMP implementation and load reductions using credit framework

COMPARING CUMULATIVE BMP RESULTS AGAINST PREDICTIONS

Re-baseline pollutant loadings and trend projections

Evaluate updated results and develop revised projections

Compare revised projections to 2008 WPP projections

INSTREAM CONDITIONS

Evaluate data, conditions v. 2008, and trends

Recalibrate models and planning tools as appropriate

Interim Period Longer Term

interim tracking and outreach feedback feeds into Year 4

interim tracking feedback feeds into Year 4

Year 4 Year 5


EXECUTIVE SUMMARY


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CHAPTER 1

Introduction

1.1 Problem Definition

1.1.1 Denton and Lewisville Lake Denton County, whose county seat is the City of Denton, is one of the fastest growing areas in the Dallas Metropolitan Statistical Area. Twenty-five incorporated cities exist within the Lewisville Lake watershed, and the City of Denton is one of the largest. Lewisville Lake is a large, multipurpose reservoir that provides drinking water for several major cities in the area, including Denton and the City of Dallas. It also serves as a receiving water body for several municipal wastewater treatment plant discharges and provides significant recreational and ecological benefits for the metropolitan area.

Increased urbanization has a significant impact on water quality. Much of the rainfall occurring in more natural settings is absorbed into porous soils, stored as groundwater and enters surface water bodies via seeps and springs, which provides a natural treatment affect in the form of vegetation uptake and infiltration through the soil. When an area is urbanized, soil and vegetation are replaced with parking lots, roads, and other impervious surfaces. This eliminates the possibility of natural treatment and increases the velocity of the runoff traveling to a surface water body, enabling the runoff to carry more pollutants.

Development and construction not only adds impervious area, it also includes land clearing and grading. If a rainfall event occurs while these areas are unprotected, erosion occurs and sediment is transported to nearby water bodies. Excess sediment, measured via total suspended solids (TSS) causes increased turbidity, which harms aquatic life, increases water treatment costs, and decreases a water body’s recreational benefit. Sediment also clogs drainage infrastructure, stream channels, water intakes, and reservoirs and destroys aquatic habitats.

In addition, nutrients (e.g., nitrogen and phosphorus) are introduced to our surface water bodies through increased wastewater treatment plant effluent and increased use of fertilizers, although the latter is found in rural applications as well. Excess nutrients, measured via total nitrogen (TN) and total phosphorus (TP), can cause an overstimulation of growth of aquatic plants, especially algae. Excessive algae growth can clog water intakes and other structures, deplete the ecosystem of dissolved oxygen as the plants decompose, and block light to deeper waters. This affects the respiration of fish and aquatic invertebrates, leads to a decrease in plant and animal diversity, affects our use of the water for recreational purposes, and increases water treatment costs.

Upon the initiation of this project (approximately 5 years ago), the Lewisville Lake watershed had one of the highest application rates for new or amended wastewater permits, and, as development continues, urban storm water runoff will increase because of impervious cover additions, higher traffic levels, and reductions in open spaces. While

HICKORY CREEK WATERSHED PROTECTION PLAN_FINAL_2008.DOC 1-1

CHAPTER 1: INTRODUCTION

1-2 HICKORY CREEK WATERSHED PROTECTION PLAN_FINAL_2008.DOC

Lewisville Lake is not currently on the State’s list of impaired waters (Clean Water Act Section 303(d) list), increased development in the watershed has the potential to threaten the designated uses of the lake and could result in a 303(d) listing when numerical nutrient criteria are established by the state.

In 2002, Lewisville Lake was ranked 96 out of 102 Texas reservoirs for degree of eutrophication based on a standard index (Carlson’s Trophic Index (TSI)) applied by the Texas Commission on Environmental Quality (TCEQ). In other words, the composite evaluation of chlorophyll and nutrient concentrations and secchi disk depth used in the TSI indicated that Lewisville Lake was more eutrophic than most lakes in the state. In response to eutrophication of the lake, as demonstrated by the TSI, and the high application rate for wastewater permits, the TCEQ has imposed a 1 milligram per liter (mg/L) total phosphorus (TP) effluent limit for new or amended discharge permits.

In response to water quality concerns in the City, Denton implemented a Watershed Protection Program as is described in the excerpt below from the 2004 Draft Texas Non-Point Source Pollution Assessment Report and Management Program.

“The City of Denton Watershed Protection Program was initiated as part of a plan to reduce the overall pollutants within the surface waters of Denton and to ensure compliance with the National Pollutant Discharge Elimination System Storm Water Phase II rule. The Watershed Protection Program monitors water quality throughout the City and the results are made available to the public. The City of Denton received initial funding from an EPA Environmental Monitoring for Public Access and Community Tracking (EMPACT) grant to get the program started. Through the grant, physical and chemical water quality data is measured and the results are telemetered to the University of North Texas for additional analysis. Information on water quality, including real-time water quality data, is compiled and displayed in an easily understood format and made available to the public via the internet. The Watershed Protection Program has used EMPACT data and additional watershed monitoring data to establish a preliminary baseline for the condition of the city's surface water resources. This preliminary baseline data will be used to evaluate future changes in water quality.”

1.1.2 Hickory Creek Hickory Creek is a tributary to Lewisville Lake, and the Hickory Creek watershed is located entirely in Denton County and a large portion is within the City of Denton. The City of Denton monitors 65 sub-watersheds divided among the Hickory, Pecan and Cooper Creek watersheds. The City developed a “ten worst sub-watersheds ranking analysis and this analysis indicated that 6 of these ten “worst” sub-watersheds were located in Hickory Creek. As the watershed currently has few permitted point source discharges, the fact that the majority of the City’s water quality concerns lie within the Hickory Creek watershed reflects the extent of non-point source pollution (NPS) impacts within this watershed. These impacts are expected to continue and, potentially, increase as development increases within the Hickory Creek watershed.

In the State’s 2002 Water Quality Inventory (Clean Water Act Section 305(b) Report), the presence of ammonia nitrogen in the Hickory Creek tributary to Lewisville Lake was first


identified as a “Nutrient Enrichment Concern.” In the draft 2004 Water Quality Inventory, Hickory Creek was again identified as a water body of concern for ammonia nitrogen originating from both unknown point and non-point sources. Hickory Creek was not listed as a concern in either the draft 2006 or 2008 Water Quality Inventories; however, the Stewart Creek and Little Elm Creek arms of the Lewisville Lake Watershed were with respect to ammonia, nitrate, orthophosphorus, total phosphorus, and fecal coliform. The ammonia loads may possibly be associated with increased residential fertilizer use, leakage from on-site wastewater systems, or agricultural operations. As population growth and land development increases within the Hickory Creek watershed, urban non-point source loads will become a proportionately larger source of water quality impacts.

The City of Denton’s current approach to managing the increase in NPS loads and continued degradation of water quality in the Hickory Creek watershed is limited to existing regulations, most of which do not specifically address water quality, and efforts implemented through the existing Watershed Protection Program. None of these existing approaches are aggressive enough to halt continued degradation and certainly will not reverse the level of degradation that has already occurred. Enhanced watershed management approaches, including water quality-based performance objectives for new development and market-based incentives for optimizing performance, will be required to direct sufficient resources into best management practices to overcome the declining water quality trend.

Exhibit 1-1 shows the location of the Hickory Creek watershed in relation to Lewisville Lake, the City of Denton, and surrounding urbanized areas.

EXHIBIT 1-1 Hickory Creek Watershed




1.2 Purpose of the Watershed Protection Plan According to the Clean Water Act, Section 305(b), the Texas Commission on Environmental Quality (TCEQ) must conduct a water quality assessment of its classified water bodies every two years. Each water body is assigned a “designated use”, and actual water quality information is compared to the standards set for that use and, potentially, that specific water body. If the TCEQ determines the water body is not meeting its standards, that water body is then placed on a Clean Water Act, Section 303(d) list (Impaired Waters List). Once on this list, the State must conduct a Total Maximum Daily Load (TMDL) analysis and prepare an implementation plan within a designated time period.

Many WPPs are developed as an implementation guide for a TMDL. In this case, though, there are no allocation targets or regulatory requirements to reduce pollutant loading and control options will be largely voluntary and proactive or, possibly, implemented in response to local code requirements rather than Clean Water Act (CWA) regulation.

The Hickory Creek watershed is currently meeting designated uses but the potential exists for water quality standards violations in the future. The goal of this particular WPP is to evaluate how well no net increases in sediment and nutrient loading can be achieved. This WPP is a proactive plan that is benchmarked against current conditions, designed to minimize or prevent net increases in pollutant loadings and provide the information needed to optimize the costs associated with pollutant management practices. Section 2.4.3 of the Handbook for Developing Watershed Plans (EPA 2008) states, “Watershed project sponsors can use the tools presented in this handbook to develop watershed plans for waters that are not impaired by non-point source pollution to ensure that they remain unimpaired.”

In preparing this Watershed Protection Plan (WPP), the City of Denton has taken a proactive approach to address Hickory Creek’s water quality challenges, partnering with CH2M HILL, Texas A&M University, and the University of North Texas to create and implement strategies for the control of urban, suburban, and rural non-point source pollution in the Hickory Creek watershed. This project is funded by the TCEQ through a Clean Water Act Section 319 grant.

The primary objective of this project is to identify actions to reduce pollutant loads to the Hickory Creek arm of Lewisville Lake and improve water quality in advance of the promulgation of numerical nutrient criteria because the development of these criteria may result in the addition of Lewisville Lake to the state’s 303(d) list. In a larger context, the goal of this WPP is to demonstrate an approach for the cost-effective implementation of best management practices for NPS control that may be applied throughout the Lewisville Lake watershed.

1.3 Watershed Protection Plan Requirements As NPS becomes an increasing problem, watershed protection plans have become a standard tool to mitigate the impacts of development and achieve water quality goals. This type of planning effort tends to serve as a means to organize numerous stakeholders in the name of one common goal. The process “integrates activities and prioritizes implementation projects based upon technical merit and benefits to the community, promotes a unified



approach to seeking funding for implementation, and creates a coordinated public communication and education program” (TSSWCB 2008).

A WPP has been defined by the EPA to include nine elements, as described in Exhibit 1-2 below. For convenience, the Exhibit also identifies the Chapter(s) of this Plan that addresses each element. As evident in the exhibit, the Hickory Creek WPP addresses all nine elements of the EPA requirements for watershed planning. For additional ease of reference, footnotes are attached to each chapter title that indicate the EPA element(s) addressed in the chapter.

EXHIBIT 1-2

EPA’s Nine WPP Elements and Location Within this WPP

EPA Element Addressed in Hickory Creek WWP Chapter #

(1) Identification of the causes and sources (or groups of similar sources) that need to be controlled to achieve the load reductions described in (2).

3

(2) Estimates of the load reductions expected for the management measures described in (3).

4, 5, 6, 7

(3) Descriptions of the non-point source management measures that will need to be implemented to achieve the load reductions described in (2).

4, 5, 6, 7

(4) Estimates of the amounts of technical and financial assistance needed to implement this plan.

4, 5, 6, 7,8

(5) Descriptions of the information/education component that will be used to enhance public understanding of this plan.

9, with reference to building on activities described in 2

(6) A schedule for implementing the non-point source management measures described in (3).

10

(7) Descriptions of interim, measurable milestones for determining whether the non-point source management measures described in (3) are being implemented.

10, drawing on data and information presented in 3, 4, 5, 6, 7 and 8

(8) Development of a set of criteria that can be used to determine whether the load reductions described in (2) are being achieved.

10, drawing on data and information presented in 3, 4, 5, 6, 7 and 8

(9) Descriptions of the water quality monitoring activities that can be employed to evaluate the effectiveness of the implementation efforts over time, measured against the established criteria described in (8).

10 and Appendix C

1.3.1 Unique Aspects of the Hickory Creek Watershed Protection Plan The Hickory Creek WPP follows the nine EPA elements outlined above and builds upon technical work conducted concurrently with WPP development, as well as previous efforts



to evaluate water quality challenges and possible incentive-based solutions. From 2002 through 2005, the City of Denton, CH2M HILL and Texas A&M University performed studies and analyses that resulted in a document entitled “Incentives for Action: Incorporating Trading Options into Watershed Improvement Plans for Lake Lewisville.” This project was funded through the EPA’s Clean Water Act Section 104(b)(3) grant program. The results from this project were used as a basis for the current 319 grant-funded effort.

In addition to the previous work, another unique aspect of this WPP is the concurrent selection, design and construction of demonstration structural best management practices (BMPs) at three separate sites in the City. Best Management Practices are techniques used to control storm water runoff and sediment and provide soil stabilization; BMPs can be intended to address water quality, water volume, or both. The EPA defines a BMP as a "technique, measure or structural control that is used for a given set of conditions to manage the quantity and improve the quality of storm water runoff in the most cost-effective manner." Most watershed protection plans are based on problem definition, data analyses and recommendations for solutions at a conceptual level without the benefit of previous, related analyses and direct experience with the selection, design and construction of structural best management practices (BMPs) in the project area. Moreover, many WPPs are developed as an implementation guide for a total maximum daily load (TMDL).

In this case, there are no allocation targets or regulatory requirements to reduce pollutant loading and control options will be largely voluntary and proactive or, possibly, implemented in response to local code requirements rather than Clean Water Act (CWA) regulation. Although all nine EPA-mandated elements of a WPP will be addressed for Hickory Creek, there are also some unique local and technical precedents for this project that affected the development of the plan. These precedents are:

An established City of Denton monitoring program in the Hickory Creek watershed;

A sophisticated and calibrated predictive model for sub-watershed loading and resultant instream pollutant concentrations (the combined Soil and Water Assessment Tool (SWAT) and QUAL-TX model presented in Chapter 3);

Previous economic analyses that show the cost-effectiveness of structural BMPs for total suspended solids (TSS), total phosphorus (TP), and total nitrogen (TN) control;

Implementation of structural BMPs at three demonstration sites in the Hickory Creek watershed that can be used for local cost and schedule estimation;

Preliminary evaluation of additional structural BMP candidate sites that could be employed in an initial phase of the WPP implementation;

Development of a preliminary strategy for expanding existing agricultural soil and water conservation programs with enhanced cost-sharing options;

Local code regulating development in environmentally sensitive areas (ESA) that could be refined to promote the use of structural BMPs for private development; and

Water quality credit trading expertise to evaluate options for including market-based approaches in development code implementation.

CHAPTER 2

Stakeholder Involvement6

To initiate the development of the WPP, the Project Team developed a Workplan that would define the objectives of the project funded by this Clean Water Act Section 319 grant, as well as the strategies to meet those goals. The first technical objective listed states: “The WPP … will be prepared with significant local stakeholder participation…” Within the related subtask, the Project Team was to conduct stakeholder meetings, and these meetings would be held to enhance and support the participation of stakeholders. The following provides a summary of the work that was done with stakeholders.

2.1 Formation of the Stakeholder Advisory Group During the beginning stages of the WPP, a diverse stakeholder advisory group was assembled. Members were selected from local citizens; the Sierra Club; representatives of local municipalities; developers; and representatives from the Soil Conservation Service, Texas Parks and Wildlife, the US Army Corps of Engineers, and a local River Authority. Throughout the selection process, the overall goal was to create a group of individuals that possess diverse interests related to the Hickory Creek watershed. The tasks required of the stakeholder group included providing input and guidance on the formation of the WPP itself, as well as providing guidance on locating the three demonstration BMPs that were a part of the Clean Water Act Section 319 grant.

2.2 Stakeholder Meetings A total of six meetings were held over the course of two and one-half years. Meetings were generally well attended by stakeholders. Representatives from the U.S. EPA and the TCEQ also participated in most of the meetings. The purpose of these meetings was to provide a forum for the Project Team to present information about the project to the stakeholder group and encourage discussions on targeted topics. The stakeholder group, in turn, provided suggestions and guidance regarding the topics discussed, including the development of the Hickory Creek WPP and the location of the demonstration BMPs. Additional information exchanges via emails, the project Web page, and phone calls were also an important component of the process. All meetings were open to the public and publicly announced well in advance of meeting dates. All materials presented in the meetings were added to the project web site following the meeting.

The first stakeholder meeting was held on July 26, 2005. This meeting mainly focused on providing an introduction to the Hickory Creek Watershed and the Clean Water Act Section 319 grant project, which included a discussion of the general goals of the project and a presentation summarizing historical monitoring data for the watershed. Emphasis was

6 This Section in combination with the information in Section 9 satisfies the fifth of the nine EPA required elements in a WPP description of information/out reach to enhance public understanding of the WPP.


CHAPTER 2: STAKEHOLDER INVOLVEMENT


placed on the importance of this watershed for the Lewisville Lake system, and some of the expected challenges associated with this watershed, both currently and in the future. A crude assessment of pollutant loads was presented, with an emphasis on how these loads might change as the watershed develops. The University of North Texas, the City of Denton, and Denton County had previously conducted a survey concerning general environmental issues and watershed knowledge and results from the survey were presented and discussed. Additionally, the Project Team held a general discussion concerning how water quality credit trading might function within the Hickory Creek watershed.

The second meeting was held on January 12, 2006. During this meeting, the Project Team presented assessments of point and non-point source watershed loads for the Hickory Creek watershed. Information was presented on the Project Team’s development of the Hickory Creek SWAT/QUAL-TX model (see Chapter 3 for more information), including calibration and assessment of current and future pollutant loads in the Hickory Creek watershed. The Project Team then presented information on water quality credit trading, with an emphasis on credit trading programs that are already in place and operational in the United States. The stakeholders and Project Team ended the meeting with an informal discussion about developing BMPs within the Hickory Creek Watershed. During this discussion, stakeholders were asked to help compile a list of important criteria for selecting sites and installing BMPs. These criteria included cost effective pollution reduction, initial installation of BMPs on public property and developing the aesthetic appeal and multiple uses of sites such as wildlife habitat along with pollutant control.

The third stakeholder meeting was held on April 20, 2006. The goal of this meeting was to present information from a Technical Memorandum summarizing watershed loads, non-point source pollution contributions, and candidate sites for locating demonstration BMP projects. The advantages and disadvantages of each candidate BMP site were discussed in detail with the stakeholder group. After these discussions, the stakeholder group identified the Municipal Airport and Fire station Number 7 sites as the top demonstration BMP sites. The stakeholders suggested Municipal Park lands represented good candidates for the location of a third demonstration BMP site, but they were not satisfied with the parks presented thus far. Based on these recommendations, a draft demonstration BMP plan was completed and placed on the project web page, and stakeholders reviewed the plan and noted acceptance via email. During this comment period, the Lake Forest Dog park site was proposed as a candidate site for consideration, and the stakeholder group recommended acceptance of this site as the location for the third demonstration BMP. Based on these recommendations, the draft BMP Implementation Plan was finalized and provided to the TCEQ.

The fourth meeting was held on February 23, 2007, and focused mainly on updates concerning the demonstration BMP projects and discussions concerning the development of the WPP for Hickory Creek. An overview of the U.S. EPA’s “9 elements” for WPPs (see Chapter 1) was presented and discussed in terms of implications for the Hickory Creek WPP. The Project Team also discussed how the elements of a WPP translate into specific management objectives, especially as those management objectives relate to BMP location, funding mechanisms, and construction. The level of management that can be practically achieved for this watershed was also introduced as a topic for comment. The Project Team specifically noted that the concept of practical and achievable levels of management cannot



be driven solely by scientific considerations, but must also incorporate social, economic, and political realities. The team went on to explain that a substantial amount of Hickory Creek watershed monitoring and modeling information currently exists, and the stakeholders must now focus on how to employ this information to create and execute an administratively feasible plan. Part of this discussion involved the concepts of incentives, funding mechanisms, and the opportunities for management presented by changing land uses. Other important discussion topics included potential funding sources for the agricultural community, the link between watershed protection goals and local regulatory authority, and the impact of Master Planned Communities on watershed management goals. The meeting ended with a summary of the critical topics addressed and a discussion concerning the timeline for developing the Hickory Creek WPP.

The fifth stakeholder meeting was held on June 15, 2007, and was mainly used to facilitate further discussions about the Hickory Creek WPP. The Project Team presented information that outlined “BMP scale” modeling efforts that had been conducted since the last meeting, and introduced a spreadsheet tool that prioritizes location and type of BMP from a contaminant and unit cost standpoint. This information was used to describe the Project Team’s vision of a framework for pollution control strategies, how strategies for pollutant control might be prioritized, and how these strategies could be translated into costs for implementation and estimates of pollutant load reductions. At the end of the meeting, stakeholders were asked to provide their impression of the Project Team’s proposed approach for the WPP, as well as any changes or modifications they felt might be needed to improve the proposed approach. The Project Team used this information to begin developing the framework for the draft WPP.

The last stakeholder meeting was held on December 14, 2007. This meeting was used to present a finalized framework for the Hickory Creek draft WPP and to solicit stakeholder input to ensure the proposed WPP framework meet the stakeholders’ vision. The Project Team gave a presentation on all WPP elements discussed in previous meetings and how those elements were proposed to fit into the framework of the draft WPP. The meeting ended with a final discussion concerning WPP elements, and a final opportunity for stakeholder input. Stakeholders were supportive of the proposed WPP framework, had no further comments on WPP content, and recommended progressing with the Draft WPP as proposed. The Project Team also gave a brief presentation regarding the completed demonstration BMPs.

The stakeholder process worked. The project team benefited from the stakeholder discussion, and particularly from the criteria or guidelines that they developed during the second meeting for selecting good sites for BMP installations. In addition, the encouragement by stakeholders for developing an economic basis for siting and installing BMPs was crucial to the decision by the project team to more fully develop this aspect of the WPP.

CHAPTER 3

Causes, Sources, and Projected Trends of Pollutant Loading to the Hickory Creek Watershed7

This chapter describes the results of analyses performed to identify sources and causes of sediment, phosphorus, and nitrogen additions to Hickory Creek. In particular, analyses were completed to identify the areas with the heaviest loadings of these pollutants, as well as potential locations for the construction of BMPs to control these pollutants.

3.1 Background To develop a better understanding of the contributing sources of sediments and nutrients to the Hickory Creek arm of Lewisville Lake, the Project Team developed a model of the watershed that incorporated both the Soil and Water Assessment Tool (SWAT) and QUAL-TX. This model was used to evaluate existing and baseline sediment and nutrient loadings to Hickory Creek, which could then be used to assess the impacts of expected future developments. To establish baseline conditions, datasets were developed in ArcGISTM to delineate sub-watersheds, soil classifications, and land uses in the watershed. Precipitation, flow and water quality measurements were collected at a monitoring site near the downstream end of Hickory Creek over a period of four years, from 2001 to 2005. During this period, thirteen rainfall and runoff events were measured and sampled.

The Hickory Creek SWAT/QUAL-TX model was created to determine the annual loads per unit area contributed by runoff from urban, agricultural, rangeland and forest land uses in the Hickory Creek watershed. For this study, “urban” represents residential, commercial, industrial, transportation, utilities, and similar uses. The development and calibration of this combined pollutant loading and water quality model is further described in Control of Non-Point Source Loads in the Hickory Creek Sub-basin of the Lake Lewisville Watershed, Model Development Memorandum. Also, a more complete description of the calculations for the loading estimates discussed in this chapter are described in Control of Non-Point Source Loads in the Hickory Creek Sub-basin of the Lake Lewisville Watershed, Non-Point Source Loads, Loading Estimates. These technical memorandum were completed for Tasks 4 and 5 of this project that focused on the selection and installation of BMPs at several demonstration sites.

Agricultural uses for the Denton County area tend to be predominantly crop and pasturelands, with densities of approximately 15 cattle per 100 acres in grazed lands. The predominant agricultural crops in Denton County are wheat and hay, with a small percentage (less than 12%) of cotton, soybeans, corn, miscellaneous vegetables, and orchards.

7 This chapter satisfies the first of the nine elements a WPP must contain, according to the EPA: Identification of the causes and sources (or groups of similar sources) that need to be controlled to achieve the load reductions described in Element 2.


CHAPTER 3: CAUSES, SOURCES, AND PROJECTED TRENDS OF POLLUTANT LOADING TO THE HICKORY CREEK WATERSHED


Within Hickory Creek, rangelands are often grazed at low densities, and tend to be vegetated with coastal Bermuda, shrubs and brush, and native prairie grasses such as big bluestem, little bluestem, Indian grass and switch grass. There are no concentrated animal feeding operations in the portions of the Hickory Creek watershed that are located in the city limits or extraterritorial jurisdiction of the City of Denton, and little to no row crops are grown in this area. Agricultural and rangeland uses for Hickory Creek tend to be predominantly low density cattle and horse grazing, hay and wheat production, and lightly grazed native prairies.

Forested land uses tend to be remnants of the Eastern Crosstimbers forest, and are generally comprised of post oak and blackjack oak, and are interspersed with mesquite trees and prairie grasses such as little bluestem.

According to the EPA’s watershed protection plan guidance document, “The level of detail in estimating the source loads can vary widely and will depend largely on the results of your data analysis. Therefore, it’s important to identify sources at a level that will result in effective control and improvement. For example, if you have identified specific pastures in one portion of the watershed as dominating the bacteria levels in your watershed during the summer, it would not be appropriate to quantify agricultural or even pastureland sources as an annual gross load for the entire watershed.” However, because of the relative uniformity within forested, agricultural, and rangelands in the Hickory Creek watershed, the results of initial loadings analyses (prior to this project), and the fact that impacts to water quality in Hickory Creek are anticipated to be caused by future land use changes (i.e., urbanization), the project team determined that evaluation of more detailed subcategories of land uses in the loading analyses was not necessary.

The current land use distribution in the Hickory Creek watershed is presented in Exhibit 3-1. Note that the modeling effort was performed using metric units; the results provided have been converted to English units, save for those results given in milligrams per liter (mg/L), for the purpose of ease of understanding.

SECTION 3: CAUSES, SOURCES, AND PROJECTED TRENDS OF POLLUTANT LOADING TO THE HICKORY CREEK WATERSHED


EXHIBIT 3-1

Land Use Distribution in the Hickory Creek Watershed

Land Use Drainage Area (acres)

Urban 29,447

Agriculture 38,998

Rangeland 45,734

Forest 9,182

Water 1,109

Total 124,470

3.2 Point Source Loads Wastewater discharge data from point sources within the Hickory Creek watershed was obtained from the TCEQ. The locations of the wastewater discharge permits were also obtained from the TCEQ (2006). Four point discharges were identified in the Hickory Creek watershed, including:

TX0024198 City of Krum;

TX0124494 Slidell Independent School District;

TX0118486 Acme Brick Company; and

TX0118567 Acme Brick Company.

For the City of Krum, flow, total suspended solids (TSS) , and nitrogen permitted discharge limits were available. For the Slidell Independent School District, only flow and sediment discharge limits were available. No permit monitoring data were available for the two discharge points associated with Acme Brick Company because they are small, episodic discharges. Phosphorus data were not available for any of the point discharges because most discharge permits do not currently include phosphorus limits. However, monitoring reports provided observed sediment loading for the Krum and Slidell discharges. In addition, phosphorus loading was estimated at 3.5 mg/L total phosphorus, which is typical for treated wastewater effluent with domestic waste influent.

Permitted annual TSS loading from the City of Krum was 34 tons in 2004 and 19 tons in 2007; permitted annual nitrogen loading was 2.6 tons in 2004. Observed annual TSS loading from the City of Krum was 3 tons, and the observed annual phosphorus loading was 0.7 tons. Permitted annual TSS loading from Slidell ISD was 0.44 tons in both 2004 and 2007. Observed annual TSS loading from Slidell ISD was 0.04 tons, and the observed annual phosphorus loading was 0.1 tons.

Even permitted (maximum allowed) solids, phosphorus and nitrogen loads delivered from point source discharges are negligible relative to non-point source contributions (Exhibit 3-2), which will be described in the next section of this chapter. As illustrated in the Exhibit 3-


2, the City of Krum permitted discharge constitutes 0.4% of the total TSS load to the watershed and 2.1% of the total nitrogen load. Slidell Independent School District constitutes 0.01% of the total TSS load.

EXHIBIT 3-2 Relative Annual Sediment (left) and Phosphorus (right) Loading to the Hickory Creek Watershed

99.6%

0.4% 0.01%2.1%

97.9%

City of KrumNonpoint Sources

City of KrumSlidell ISDNonpoint Sources

3.3 Non-Point Source Loads Exhibit 3-3 presents expected pollutant concentrations in storm water runoff from each of the land use categories as projected by the SWAT/QUAL-TX model cited and described above.




EXHIBIT 3-3 Constituent Concentrations (mg/L) for Each Land Use Category

Land Use Rainfall Depth Sediment (mg/L) Phosphorus (mg/L) Nitrogen (mg/L)

Urban All 65 0.55 1.48

0.79 inches 80 1.29

1.57 inches 80 1.29

Agriculture

3.15 inches 80 1.29

3.04

2.39

2.26

Rangeland All 39 0.19 1.30

Forest All 29 0.11 0.90

As illustrated in the Exhibit, the model predicted higher runoff concentrations for agricultural land than for other land uses. However, because impervious land uses usually generate more runoff than pervious land, urban areas tend to generate greater loads per unit area than rural land, even though urban areas have lower constituent concentrations per unit runoff volume. On a relative basis, among the four land uses, urban areas generate more sediment load per unit area, urban and agricultural areas generate more nitrogen, and agricultural areas contribute more phosphorus.. Exhibit 3-4 shows runoff depths for different land use and rainfall depth combinations. Clearly, these data show that urban areas have the most runoff on an annual basis and for the more frequent storms. Exhibit 3-5 presents the annual loads per unit area for the different land uses.

EXHIBIT 3-4 Runoff Depths (inches) for Various Land Use/Rainfall Depth Combinations

Rainfall Depth (inches) Land Use

28.19 inches/year 0.787 inches/event,16 events/yr

1.575 inches/event,5.3 events/yr

3.150 inches/event,2.3 events/yr

Urban 11 0.17 0.69 2

Agriculture 7 0.06 0.42 1.6

Rangeland 6 0.05 0.39 1.5

Forest 3 0.004 0.17 1



EXHIBIT 3-5 Annual Loads per Unit Area from Each Land Use (pounds/acre)

Land Use Sediment Phosphorus Nitrogen

Urban 161.49 1.34 3.66

Agriculture 123.12 1.96 3.75

Rangeland 55.32 0.27 1.87

Forest 21.41 0.09 0.71

Exhibit 3-5 illustrates that urban land does, in fact, have a higher sediment load per unit area, with agricultural land not far behind. However, as Hickory Creek has a much greater amount of agricultural land than urban land, one can see that agricultural areas are the main source of the three constituents in Hickory Creek by sheer mass.

EXHIBIT 3-6 Annual Loads in the Hickory Creek Watershed by Land Use (tons)

Land Use Sediment Phosphorus Nitrogen

Urban 1,305.14 10.80 29.54

Agriculture 2,030.46 32.41 61.84

Rangeland 1,050.50 5.07 35.60

Forest 71.65 0.33 2.43

Exhibit 3-6 presents annual constituent loads for the three pollutants of concern. Note that transformation of natural land uses (i.e., rangeland and forest) to human uses (i.e., urban and agriculture) increases the load per unit area significantly. For example, today, urban, agricultural and range land makes up 24, 31 and 37% of the area in the Hickory Creek watershed, respectively. These land uses, contribute 30, 46 and 24% of the sediment load to the creek, respectively, which demonstrates the heavier loading from human uses of the land. Exhibit 3-7 presents the Hickory Creek Watershed and the current land uses. Assuming that the areas that are currently urban and agricultural were originally rangeland, the load to Hickory Creek caused by the changes in land use that have occurred up to now is 1,984 tons per year of sediment, 36 tons per year of phosphorus, and 45 tons per year of nitrogen. Thus, the impact of this conversion represents 45% of the current sediment load, 75% of the current phosphorus load, and 35% of the current nitrogen load. The increase in load would be even more dramatic had forest land, instead of rangeland, been transformed into urban or agricultural land.

CHAPTER 2: S

EXHIBIT 3-7 Current Land Uses within the Hickory Creek Watershed

3.4 Areas of Heaviest Pollutant Loading in 2007-2008 The identification of the locations for the most effective use of BMPs was necessary to estimate the potential load reductions that could be achieved. The amount of load reductions depends on the location of BMPs and BMP removal efficiencies. The methodology that was used to identify critical areas and the results of the analyses is described below.

3.4.1 Methodology The 30-meter 30-meter Digital Elevation Model (DEM) developed by the United States Geological Survey (TNRIS 2006) was used to determine flow directions for defined areas called “cells” and to identify stream reaches, drainage divides and contributing areas for each cell. That is, for each 0.22 acres cell, a single downstream cell was determined based on the direction of the steepest descent, which was then used to identify the drainage area of each cell, its runoff and its constituent contribution. The Hickory Creek watershed included approximately 425,000 cells.

Exhibit 3-5, above, presents the annual constituent load per unit area for each land use and constituent. This load per unit area multiplied by the cell area (i.e., 0.22 acres) constitutes the contribution of each cell to the downstream cells. Thus, the load from a given cell will be the sum of the contributions of the cells in its drainage area.



"282" Priority Site Land Use Distribution: All Sites


Urban18%

Agriculture38%

Range39%

4%Forest

1%Water

Ideal BMP locations are defined as those associated with higthree constituents and a small drainage area (for cost-effectivbecause of the DEM-based methodology used to determine dacres (i.e., 360 cells) might be inaccurate. Thus, drainage areaminimum area of 80 acres. A total of 282 priority sites were ibetween 80 and 125 acres, which, based upon professional ju s a workable size for developing a BMP site plan. The drainage annual sediment load, annual phosphorus load, and annual for each of these headwater areas.

Current Land Use Distribution among the 282 Priority Sites For the 282 priority sites identified, the current aggregate lanExhibit 3-8.

lso note that the land use mix varies greatly among the 282 sites, as illustrated with the xamples presented in Exhibit 3-9. Sites on the left side of the Exhibit are largely range,

he middle have more agricultural land, and those on the right are largely urban.

h annual loads of each of the eness purposes). However, rainage areas of less than 80 s were defined to have a dentified with drainage areas dgment and experience, iarea, annual runoff volume, nitrogen load were identified

d use distribution is given in

EXHIBIT 3-8 Current Aggregate Land Use Distribution of 282 Priority Sites

Aethose in t


EXHIBIT 3-9 Land Use Distribution for Select Sites

Land Use Distribution for Selected "282" Sites

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

14 200 119 677 729 587 43 123 717 558 538 457

Site ID Number

Per

cen

t o

f T

ota

l A

rea

WaterForestRangeAgricultureUrban

3.4.2 Results of Modeling Effort Exhibits 3-10, 3-11 and 3-12 present the 282 potential BMP locations classified according to the annual sediment, phosphorus, and nitrogen loading rates, respectively. In the Exhibits, note that high sediment load areas are located just north of the Hickory Creek watershed outlet, indicating the City of Denton’s urbanized areas are contributing significantly to the loadings. High nitrogen load areas are distributed somewhat evenly throughout the watershed, and high phosphorus load areas are located predominantly in the northwest, more rural, part of the watershed.

These modeling results provide a “planning level” focus for the next steps in this effort, expected load reductions and BMP costs associated with the areas within the watershed that appear to provide relatively higher pollutant loads.



EXHIBIT 3-10 Potential BMP Locations According to the Annual Sediment Load



EXHIBIT 3-11 Potential BMP Locations According to the Annual Phosphorus Load



EXHIBIT 3-12 Potential BMP Locations According to the Annual Nitrogen Load

3.5 Land Use Change Predictions for the Hickory Creek Watershed

To predict future loading rates, impending land use changes due to continued urbanization must be predicted. To estimate the land use changes that are occurring and will continue to occur as the Denton area continues to grow, the project team employed both the City of Denton’s white paper entitled “Balanced and Sustainable/Smart Growth”, published in August of 2003, and The Denton Plan, 1999-2020: Comprehensive Plan of the City of Denton (Plan), published in May of 2000. In the Plan, the City presents projected populations within its City Limits and Extraterritorial Jurisdiction (ETJ) for each year through 2020, as well as the estimated population density for a given population, up to and including buildout. Exhibit 3-13 below presents future population predictions, the estimated population density at that population, and the anticipated year in which that population will be reached.




EXHIBIT 3-13

Projected Population Densities for Denton’s Urbanizing Area

Population Population Density (per square mile)

Anticipated Year Reached

130,000 1,300 2008

176,000 1,750 2014

224,000 (buildout) 2,250 Beyond Planning Effort (post-2020)

263,000 2,640 N/A

The projected density follows a linear trend. Thus projected populations at key time intervals (e.g., 5, 10, and 13 years from 2007 for the purposes of this analysis) can be used to estimate a corresponding density. This density allows the project team to estimate the increase in urban land by determining the projected population increase between the current and future year of interest and then dividing that increase by the projected population density for the future year. Exhibit 3-14 presents the projected increase in urban land.

EXHIBIT 3-14 Projected Increases in Urban Land Area

Year Population Density

Cumulative Population

Incremental Population Increase

Incremental Increase in Urban Land (square miles)

2007 1,200 120,290

2012 1,533 153,530 33,240 22

2017 1,922 192,010 38,480 20

2020 2,156 215,110 23,100 11

The corresponding areas were added to the urban land use category for their respective years, and this same number of acres was subtracted from the other land uses (agricultural, forest, and rangeland) such that the relative land use distribution remained constant.

Exhibits 3-15 and 3-16 present this information graphically for 2008, 2012, 2017 and 2020.


EXHIBIT 3-15 Projected Future Land Use Changes

CurrentWater

1%

Range37%

Forest7%

Agricultural31%

Urban24%

2012Water

1%

Agricultural27%

Forest6%

Range31%

Urban35%

2017

Forest5%

Water1%

Agricultural22%

Urban46%

Range26%

2020

Forest5%

Water1%

Agricultural20%

Range23%

Urban51%



EXHIBIT 3-16 Cumulative Percent Land Use Change Assumed

Cumulative Percent Land Use Change Assumed

-36%-29%

-15%

48%

115%

91%

-40%

-20%

0%

20%

40%

60%

80%

100%

120%

2012 2017 2020

AgriculturalForestRangeUrban

Almost all the loading of sediment, nitrogen and phosphorous to Hickory Creek comes from storm water runoff from non-point sources. Point sources are not a significant contributor to pollution in the watershed. The cause of the non-point source loading is land use changes from forest and range to agricultural and urban. Moreover, future population estimates indicate that the amount of urban land will increase from 24% now in 2008 to 51% in 2020 which will increase loading in the future. The heaviest areas of loading were identified for all three pollutants and this information can be used to target areas for the application of BMPs to control the pollution. Clearly, control of urban storm water runoff will be a major environmental challenge for the Hickory Creek watershed in the foreseeable future.



EXHIBIT 3-15 Projected Future Land Use Changes

CurrentWater

1%

Range37%

Forest7%

Agricultural31%

Urban24%

2012Water

1%

Agricultural27%

Forest6%

Range31%

Urban35%

2017

Forest5%

Water1%

Agricultural22%

Urban46%

Range26%

2020

Forest5%

Water1%

Agricultural20%

Range23%

Urban51%


lklein

Rectangle

CHAPTER 4

Methodology to Determine Load Reductions and Associated Costs for BMP Portfolios in Three Spatial Scales8

To determine what management measures could achieve desired and/or possible pollutant load reductions and where the City of Denton would implement these measures, the project team chose to evaluate BMP implementation at three spatial scales: watershed-wide; for those 282 optimal drainage areas identified in Chapter 3; and for three Master Planned Communities (MPCs) currently proposed for development within the City of Denton. These three scales represent approximately 195 square miles (124,470 acres), 40 square miles (25,600 acres), and 12 square miles (7,680 acres), respectively. For each scale, a set of BMP “portfolios” was simulated and evaluated with the goal of investigating how pollutant load reductions could be achieved most cost-effectively.

This chapter provides a summary of the tools and methods used to conduct the analyses as well as a summary of the results. More detail on each of the three BMP portfolio analyses is presented in Chapters 5, 6, and 7.

4.1 Microsoft-Excel Based Analysis For the purposes of constructing and evaluating alternative BMP scenarios for each of the spatial scales, the project team employed a Microsoft Excel-based tool developed by CH2M HILL. The tool allows the user to construct a BMP “portfolio” for a defined area and calculates key portfolio metrics, including total cost, load reduction, and unit costs (an indicator of cost effectiveness).

To operate the tool, the user enters assumptions about the number of acres in each of the four land use categories (urban, agricultural, rangeland and forest) for a defined scenario (e.g., watershed-wide, selected parcels associated with the 282 priority sites, or one of the Master Planned Communities). The tool automatically calculates pollutant loads by land use category for TSS, TP, and TN using the loads per unit area estimated by the SWAT model (see Chapter 3).

4.1.1 Available BMPs and Associated Costs In a “BMP Application Dashboard,” the user can select and “turn on” one or more of the BMPs available for a given land use by moving a marker that indicates the percent of the

8 This chapter satisfies the second, third and fourth of the nine elements a WPP must contain, according to the EPA: Estimates of the load reductions expected for the management measures described in the third element, descriptions of the non-point source management measures that will need to be implemented to achieve the load reductions described in the second element, and estimates of the amounts of technical and financial assistance needed to implement this plan.


CHAPTER 4: METHODOLOGY TO DETERMINE LOAD REDUCTIONS AND ASSOCIATED COSTS FOR BMP PORTFOLIOS IN THREE SPATIAL SCALES

total land area assumed to be managed by the selected BMP. The BMPs available for selection were chosen as the most common and easiest to implement BMPs used in combination with the relevant land uses. Additionally, based on best professional judgment, acreage limits were established to define the maximum amount of acreage that could be feasibly managed related to both a specific BMP and each land use category.

Where possible, assumed pollutant removal efficiencies associated with each BMP were taken from the Integrated Storm Water Management (iSWM) Manual, Design Manual for Site Development, developed by the North Central Texas Council of Governments (NCTCOG, 2006). Exceptions include grass planting, mulching, and grade stabilization; pollutant removal efficiencies associated with these BMPs were based on best professional judgment.

Installation and maintenance costs were estimated for each BMP using two sources: the Texas Department of Transportation (TxDOT 2007); and the Natural Resources Conservation Service (NRCS 2007). TxDOT supplied the Dallas District’s “Average Low Bid Unit Price – Construction”. The version used was last updated June 30, 2007 and the 12-month moving average was employed. The NRCS supplied the current (as of July 5, 2007) “EQIP Cost List for Denton, Texas, FY 2007”, which provides construction costs for practices subsidized by the Environmental Quality Incentives Program, or EQIP. The tool automatically calculates annual implementation costs or total present value costs over a defined period as selected by the user. Results are reported in 2007 dollars.

Exhibit 4-1 presents the BMP options, assumed application limits, and the assumed removal efficiencies for each land use. Exhibit 4-2 provides the unit removal costs for the three pollutants.

EXHIBIT 4-1 BMP Options, Associated Removal Efficiencies, and Maximum Land Usage

BMP Option TSS Removal Efficiency (%)

TP Removal Efficiency (%)

TN Removal Efficiency (%)

Maximum Land Usage (%)

Urban Land 75

Detention Ponds 65 50 30 20

Retention Ponds 80 50 30 0

Riparian Buffers 50 20 20 10

Treatment Ponds (Wetlands)

80 40 30 10

Vegetated Swales/Strips 80 25 40 10

Infiltration Basins 80 60 60 25

Agricultural Land 40

Grass Planting 48 19 19 5

Grading/Grassed Waterways/Filter Strips

50 20 20 25

Grade Stabilization Structures/Wet Pond

53 21 21 10




EXHIBIT 4-1 BMP Options, Associated Removal Efficiencies, and Maximum Land Usage

BMP Option TSS Removal Efficiency (%)

TP Removal Efficiency (%)

TN Removal Efficiency (%)

Maximum Land Usage (%)

Range Land 50



50 20 20 25


53 21 21 0

Forest Land 30



50 20 20 5


53 21 21 0


EXHIBIT 4-2 Unit Removal Costs

2000 TSS-LBS Phosphorus-LBS Nitrogen-LBS

LAND USE: BMP

BMP Pounds per Acre Land Controlled

$/Credit Pound by

Land Use by BMP

Relative $/lb Rank


$/Credit Pound by Land Use by BMP

Relative $/lb Rank


$/Credit Pound by Land Use by BMP

Relative $/lb

Rank

Urban Land

Detention ponds 104.96 $6.79 10 0.67 $1,064 8 1.10 $649 10

Retention Ponds 129.19 $13.59 11 0.67 $2,624 10 1.10 $1,600 12

Riparian Buffers 80.74 $0.28 3 0.27 $84 5 0.73 $31 4

Treatment Ponds (wetlands) 129.19 $0.15 2 0.54 $36 2 1.10 $18 2

Vegetated Swales/Strips 129.19 $0.04 1 0.33 $16 1 1.46 $4 1

Infiltration basins 129.19 $0.44 5 0.80 $71 4 2.19 $26 3

Agricultural Land

Grass Planting 58.48 $2.65 8 0.37 $415 6 0.71 $217 8

Grading/Grassed Waterways/Filter Strips 61.56 $0.43 4 0.39 $67 3 0.75 $35 5

Grade Stabilization/Wet Pond 64.64 $27.19 13 0.41 $4,264 12 0.79 $2,234 13

Range Land

Grass Planting 26.27 $5.89 9 0.05 $3,043 11 0.36 $435 9

Grading/Grassed Waterways/Filter Strips 27.66 $0.95 6 0.05 $491 7 0.37 $70 6


Forest Land

Grass Planting 10.17 $15.22 12 0.02 $9,129 13 0.14 $1,141 11

Grading/Grassed Waterways/Filter Strips 10.71 $2.46 7 0.02 $1,473 9 0.14 $184 7


Notes: Rankings in green are the five most cost-effective, in red are the five least cost-effective, and in black are the five values in the mid-range among the 15.



4.1.2 Special Features The tool contains some special features related to the 282 priority sites described in Chapter 3. The acreage and loading data for the 282 priority sites were pre-loaded into the tool and the user can click a button to perform the BMP analyses on these sites instead of the entire watershed or one MPC. Additionally, the tool allows the user to turn each of the 282 sites “on” or “off”, to include or exclude the site from the analysis. As a result, the user can develop a BMP portfolio for any combination of the 282 sites.

To help the user sift through the 282 sites and pick those that best match cost, total reduction, and/or effectiveness targets for a given portfolio, the tool also contains weighting and ranking features. To employ these, the user first assigns relative weights to the three pollutants. For the scenarios presented in this plan, TSS and TP were assumed to be equally important, and TN was assumed to be half as important as the other two. Therefore, TSS-TP-TN were assigned weights of 40%-40%-20%, such that the combined weights total 100%. The tool calculates estimated loads of each pollutant from each parcel and assigns an indexed score (from 0 to 100) that establishes the relative rankings based on loading, with the highest scores representing the best load reduction opportunities.

The total score for each parcel is calculated by multiplying each by the weighting factors and adding the result. So, for example, if a parcel received TSS-TP-TN scores of 51.98, 59.77, and 65.66, the tool multiplies these values by 0.4, 0.4, and 0.2 to arrive at weighted scores of 20.79, 23.91, and 13.13 and then sums these to get a combined score of 57.83.

The tool then re-indexes the combined scores of all 282 parcels using a scale of 0 to 100, such that now the lowest scores represent the best opportunities to capture load reductions. The tool will highlight in yellow the top X number of sites, with X chosen by the user from a pull-down menu. This feature helps the user easily see the priority sites that must then be manually included in the analysis by clicking on the “Include-Exclude” button for each site. Appendix A provides a listing of all 282 sites, their relative pollutant scores, and their relative ranks.

4.1.3 Strengths and Weaknesses As constructed, the tool provides a great deal of flexibility in defining the areas to be included in a BMP portfolio analysis, while hard-coding certain key assumptions, such as loading rates, BMP efficiencies, and assumed unit costs, that stay constant across different portfolios. Note that, when the BMPs are “applied” in each scenario, the most cost-effective BMPs are applied first, followed by the less cost-effective BMPs.

Providing this level of flexibility in the tool involved some tradeoffs in features and functionality. For example, the tool is temporally static: changes over time must be manually entered and calculations must be performed in separate iterations (e.g., as was done for the watershed-wide analysis for 2008, 2012, 2017, and 2020, as described later). Additionally, the user can only see results for one pollutant at a time in the portfolio “dashboard,” but can simply click the pollutant mode button to populate the dashboard with data and results for another pollutant. Despite these manual necessities, the tool has proven more than sufficient for the screening and planning level analyses presented herein.



The following chapters present the estimated load reductions based on these portfolios. Note, though, that these results are based on the projections of a conceptual model calculated at aggregated levels and that actual results from implementing any portion of these portfolios will be determined by the specific conditions of the BMP sites. Loadings associated with the different land uses, removal efficiencies and other elements obtained from the literature and applied to this system model provide guidance and planning level estimates. Removal efficiencies obtained in practice will vary and site conditions will provide opportunities for and/or constrain design options.

4.2 Summary Results of the BMP Portfolios in Three Scales A brief summary of the results of the watershed-wide, 282 priority sites, and MPC evaluations is provided below. Please see Chapters 5, 6, and 7 for detailed results.

4.2.1 Watershed-Wide At the watershed-wide scale the simulations show that a combination of relatively moderate levels of investment to implement the most cost-effective BMPs between now and 2020 could hold TSS loading increases to just 7% over the 2008 baseline, versus an estimated increase of 29% with no BMPs, and could hold TP loading increases to just a 5% increase over the 2008 baseline, versus an estimated increase of 13% with no BMPs. Simulated higher levels of investment, which involved including some less cost-effective BMPs that have higher levels of removal compared to some of the lower cost ones (i.e., more bang, but also more bucks), show that it might be possible to hold future loads to 2008 levels even with development with sufficiently higher BMP implementation.

4.2.2 282 Priority Sites Among the 282 Priority Sites, the simulations show that relatively modest investments in installing BMPs at these locations should yield signification reductions under a scenario where 22 sites are brought under BMP management every year over the 2008-2020 period until all 282 sites are BMP-managed. If the “best” 22 sites were selected the first year, and the next best 22 sites selected the second year, and so on as was done in this analysis, in this simulated Capital Improvement Program incremental load reduction opportunities diminished over the period as investments were allotted to the lower priority sites (due to the way the prioritization scheme was constructed). To practically implement the program simulated in this analysis, the City would need to balance the cost-effectiveness of opportunities over many sites (minimizing the cost per pound of removal) against the likely benefits from economies of scale for design and construction of BMPs at fewer sites.

4.2.3 MPCs At the MPC level, the simulations show that opportunities may exist to significantly control post-development loads for a relatively modest investment of less than $150 per acre per year. The analysis showed it may be possible to implement BMPs such that future loads are less than current loads, or, for less capital investment, to implement BMPs such that future loads equal current loads. The exact feasible mix of specific BMPs, the total annual costs, and the cost per acre depend on the size of the MPC (acres) and the land use distribution within that MPC. For example, the simulations also show that some BMP/Land Use




combinations are not very cost-effective and that limitations do exist as to the number of BMPs that could realistically be placed on any given site. Even so, the exercise illustrates how combining the right data, cost considerations, and load reduction analyses helps ensure the best available opportunities are identified.

4.2.4 Cross-Portfolio Summary The following bullets summarize the key findings observed among the BMP portfolios developed in three scales for the watershed-wide, 282 priority sites, and MPCs:

Watershed-wide, sufficient acreage exists where it appears very cost-effective BMPs could be installed;

Some BMP-land use combinations are not very cost-effective at all;

Limitations exist as to the practical number/level of BMPs that would realistically be placed on any given parcel;

Data, tools, and simple analyses can help point us to the best opportunities;

Many land-owners with the best opportunities will not necessarily have to act, and many with limited or poor opportunities may have to act; and

Opportunities may exist to influence and incentivize which BMPs are placed where.

CHAPTER 5

Watershed-Wide BMP Portfolio9

5.1 BMP Portfolios Four alternative BMP portfolios were analyzed at the watershed-wide scale, as follows:

Portfolio 5. No additional BMPs are added within the watershed through 2020;

Portfolio 6. BMPs are added so that total sediment and phosphorus loading does not increase above current (2008) levels;

Portfolio 7. BMPs are added so that total sediment, phosphorus and nitrogen loading does not increase above current (2008) levels;

Portfolio 8. Annual investment in additional BMPs is capped at a specified monetary benchmark to approximate a consistently funded capital improvement program.

Note that, with regard to Portfolio 4, the benchmark chosen for these purposes is $465,000 per year, which equates to the estimated annual debt payment plus annual operations and maintenance costs for nutrient removal upgrades to Denton’s Pecan Creek Water Reclamation Plant. Other financial benchmarks could be employed, although lower levels of investment will provide lower levels of pollutant control. Examples include:

Water supply rate increase of $0.01 per 1,000 gallons: $67,000/year;

Estimated money available per year from the City of Denton’s “Tree Fund”, a fund developed to encourage tree preservation amongst developers or incur a fine of $100,000/year;

Dredging 4,000 tons of sediment per year (the estimated amount lost from the Hickory Creek watershed each year with no BMPs) at $27.54/ton: $110,160;

Water supply rate increase of $0.02 per 1,000 gallons: $134,000/year; and

Water supply rate increase of $0.03 per 1,000 gallons: $201,000/year.

As an exercise in establishing the bounds of loading reduction capabilities, the Project Team developed a portfolio in which all possible BMPs were applied within the limits defined in Exhibit 4-1. This evaluation resulted in an annual cost of $15,000,000 to $20,000,000 and was not pursued any further because such an investment level was deemed unrealistic.



CHPATER 5: WATERSHED-WIDE BMP PORTFOLIO


As presented in Exhibit 5-1, the analysis predicted the following results for TSS:

Portfolio 5. No action will result in an ultimate TSS loading increase of 29% by 2020;

Portfolio 6. Attempting to maintain TSS and TP at the 2008 level results loads slightly less than the 2008 baseline;

Portfolio 7. Attempting to hold all constituents of concern at current levels results in an ultimate decrease in TSS loading of 9% below 2008 loadings; and

Portfolio 8. Managing BMP additions within a $465,000/year budget resulted in an ultimate 7% increase in TSS loading compared to 2008 levels.

EXHIBIT 5-1 Percent Increase in TSS Loading Compared to 2008 Baseline

Year Portfolio 1:

No BMPs

Portfolio 2:

Hold TSS and TP to 2008

Portfolio 3:

Hold all Pollutants to 2008 Baseline

Portfolio 4:

Benchmark Level of Investment

2012 12% -2%1 -4%1 6%

2017 23% -2%1 -8%1 7%

2020 29% 0% -9%1 7%

Notes: 1. A negative number indicates loading would be below 2008 levels.

Exhibit 5-2 plots the estimated annual costs associated with each portfolio with the estimated reduction of total sediment loading for three milestone years. Note that the BMP costs presented in this chapter include land acquisition, construction and annual maintenance in 2007 dollars. For example, the portfolio holding TSS at 2008 loading levels has an estimated cost of $282,000 in 2012, $648,000 in 2017, and $850,000 in 2020.

CHAPTER 5: WATERSHED-WIDE BMP PORTFOLIO


EXHIBIT 5-2 Cost of Each Watershed Wide Portfolio and TSS Reduction


12%

23%

29%

-2%-1% 0%

-4%

-8% -9%

6%7% 7%

$281,800

$647,800

$850,000

$394,100

$932,800

$1,188,800

$75,600

$221,000

$397,700

-15%

-10%

-5%

0%

5%

10%

15%

20%

25%

30%

35%

2012 2017 2020

Year

TS

S T

on

s/y

r P

erce

nt

+/-

v 2

008

Bas

elin

e

$(500,000)

$(400,000)

$(300,000)

$(200,000)

$(100,000)

$-

$100,000

$200,000

$300,000

$400,000

$500,000

$600,000

$700,000

$800,000

$900,000

$1,000,000

$1,100,000

$1,200,000

An

nu

al C

ost

of

BM

P P

ort

foli

o

No BMPs

Hold TSS & TP

Hold All

Benchmark

Hold TSS & TP $/yr

Hold All $/yr

Benchmark $/yr

As presented in Exhibit 5-3, the analysis predicted the following results for TP:

Portfolio 1. No action will result in an ultimate TP loading increase of 13% by 2020;

Portfolio 2. Attempting to maintain TSS and TP at estimated 2008 levels achieves this target;

Portfolio 3. Attempting to hold all constituents of concern at current levels results in an ultimate decrease in TP loading of 4% below 2008 loadings; and

Portfolio 4. Managing BMP additions within a $465,000/year budget resulted in an ultimate 5% increase in TP loading compared to 2008 levels.


EXHIBIT 5-3 Percent Increase in TP Loading Compared to 2008 Baseline

Year Scenario 1:

No BMPs

Scenario 2:

Hold TSS and TP to 2008

Scenario 3:

Hold all Pollutants to 2008 Baseline

Scenario 4:

Benchmark Level of Investment

2012 5% 0% -1%1 3%

2017 10% 0% -3%1 5%

2020 13% 0% -4%1 5%

Notes: 1. A negative number indicates loading would be below 2008 levels.

Exhibit 5-4 plots the estimated annual cost of each portfolio and the reduction in total phosphorus loading for three milestone years. Note that the BMP costs presented in this chapter include land acquisition, construction and annual maintenance in 2007 dollars.

EXHIBIT 5-4 Cost of Each Watershed Wide Portfolio and TP Reduction


5%

10%

13%

0% 0% 0%

-1%

-3%-4%

3%

5%5%

$281,800

$647,800

$850,000

$394,100

$932,800

$1,188,800

$75,600

$221,000

$397,700

-5%

-4%

-3%

-2%

-1%

0%

1%

2%

3%

4%

5%

6%

7%

8%

9%

10%

11%

12%

13%

14%

15%

2012 2017 2020

Year

TP

To

ns/

yr

+/-

v. 2

008

Ba

selin

e

$(400,000)

$(300,000)

$(200,000)

$(100,000)

$-

$100,000

$200,000

$300,000

$400,000

$500,000

$600,000

$700,000

$800,000

$900,000

$1,000,000

$1,100,000

$1,200,000

An

nu

al C

ost

of

BM

P P

ort

foli

o

No BMPs

Hold TSS & TP

Hold All

Benchmark

Hold TSS & TP $/yr

Hold All $/yr

Benchmark $/yr

While the previous exhibits presented a cost per level of reduction, Exhibits 5-5 and 5-6 present the annual cost per % reduction of TSS and TP. These exhibits illustrate that the cost to control sediment is less than the cost to control phosphorus, and Portfolio 4 (the “Benchmark”), under which investments are capped at an average level of $465,000, provides the most cost-effective control.




EXHIBIT 5-5 Cost per Year Per Percent Reduction of TSS


27500

3690040600

22800

3360037700

1520017400

23800

14%

25%

29%

12%

19%

23%

5%

13%

17%

$-

$10,000

$20,000

$30,000

$40,000

$50,000

$60,000

$70,000

$80,000

$90,000

$100,000

2012 2017 2020

Year

$ p

er

1% R

edu

ctio

n v

. No

BM

Ps

for

Giv

en Y

ear

0%

5%

10%

15%

20%

25%

30%

Per

cen

t R

edu

ctio

n v

. No

BM

Ps

for

Giv

en Y

ear

Hold All $/%/yr Hold TSS & TP $/%/yrBenchmark $/%/yr Hold All % v. No BMPsHold TSS & TP % v. No BMPs Benchmark % v. No BMPs


EXHIBIT 5-6 Cost per Year Per Percent Reduction of TP


65100

7890082700

56800

43900

50200

63200

7150076200

6%

14%

5%

9%

11%

2%

4%

12%

6%

$-

$10,000

$20,000

$30,000

$40,000

$50,000

$60,000

$70,000

$80,000

$90,000

$100,000

2012 2017 2020

Year

$ p

er 1

% R

edu

ctio

n v

. No

BM

Ps

for

Giv

en Y

ear

0%

5%

10%

15%

20%

25%

30%

Per

cen

t R

edu

ctio

n v

. No

BM

Ps

for

Giv

en Y

ear

Hold All $/%/yr Hold TSS & TP $/%/yrBenchmark $/%/yr Hold All % v. No BMPsHold TSS & TP % v. No BMPs Benchmark % v. No BMPs

5.2 Summary of Watershed-Wide BMP Portfolio Results The analysis at this scale indicates that there is sufficient land area to implement BMPs and reduce future loadings below those projected without BMPs, and for a variety of investment levels. Without any investment in BMPs, TSS and TP loadings are projected to increase 29% and 13% over 2008 estimated loads by 2020 which will contribute to the degradation of Hickory Creek and Lake Lewisville as described in the Introduction to this Plan. However, it may not be necessary, based on the current understanding of water quality conditions, to attempt to hold nitrogen, TP and TSS at or below 2008 levels because of the significant cost. Attempting to hold nitrogen loads at 2008 levels results in TSS and TP loading reductions below current levels, according to the analysis.




The two mid-range portfolios, one that holds TSS and TP to 2008 levels (while letting nitrogen increase to levels 4% above 2008 estimates) and one that caps the out-year spending appear to offer cost-effective, practical, and achievable solutions. The specific loading and investment targets selected in the future, which might include a solution between these two, may change in response to the results of continued water quality monitoring and modeling (as may be changed by any future TMDL) and resources available to the City and other parties to deploy to BMP installation and maintenance. Exhibits 5-2 and 5-4 present the annual cost of the portfolios for the three years shown on the graph. As a reference, the estimated average annual cost of the portfolio holding TSS and TP to 2008 level is $439,000, and to keep TSS and TP loading increases to only 7% and 5% respectively is $151,000. Certainly, investments in BMPs would not have to follow a linear pattern from year to year. The data presented in Exhibits 5-5 and 5-6 provide additional information that can help planners make decisions based on the additional level of reduction provided for additional incremental investments.

CHPATER 5: WATERSHED-WIDE BMP PORTFOLIO



CHAPTER 6

BMP Portfolios for the 282 Priority Sites10

6.1 Summary Characteristics of the 282 Priority Sites The selection of the 282 priority sites was described in Chapter 3. Exhibits 3-8 and 3-9 illustrated the aggregate land use distribution across all sites, and the land use distribution for selected individual sites. For convenience these are replicated here as Exhibits 6-1 and 6-2.

EXHIBIT 6-1 Current Aggregate Land Use Distribution For the 282 Priority Sites

"282" Priority Site Land Use Distribution: All Sites

Urban18%

Agriculture38%

Range39%

Forest4%

Water1%



CHAPTER 6: BMP PORTFOLIOS FOR THE 282 PRIORITY SITES

EXHIBIT 6-2 Land Use Distribution For Selected 282 Priority Sites

Land Use Distribution for Selected "282" Sites

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

14 200 119 677 729 587 43 123 717 558 538 457

Site ID Number

Per

cen

t o

f T

ota

l Are

a

WaterForestRangeAgricultureUrban

6.2 Static Portfolios for the 282 Priority Site Collective Acreage

As a first step to explore the BMP implementation and pollutant loading reduction possibilities across the 282 priority sites, the total acreage in each land use category and overall was calculated for the collective sites, and the result was treated as if it were one large site. The results were used to inform another set of portfolios that treated the sites separately.

Three alternative BMP portfolios were developed and analyzed for the 282 collective priority sites based on specified maximum, medium and minimum amounts of land treated by BMPs: 50%, 33%, and 19%, respectively. These assumptions were driven by the maximum coverage limits assumed for each BMP individually, and collectively for each land use area, as explained in Chapter 4 (see Exhibit 4-1).

Exhibit 6-3 presents the acreage assumed managed by land use for each portfolio. Unlike the watershed-wide analyses, which incorporated a temporal element examining changing loads and changing BMP portfolios over a 2008-2020 planning period, this Maximum-Medium-Minimum analysis for the 282 collective priority sites is static—a snapshot in time. A temporal element was incorporated into the examination of how BMP implementation




could be optimized among the individual 282 sites as described later. Exhibit 6-4 identifies the load reductions estimated for each portfolio, and Exhibit 6-5 provides more detail on land use distribution and estimated implementation costs.

The load reductions predicted for each of these portfolios is presented in Exhibit 6-3.

EXHIBIT 6-3 Percent Acres Managed with BMPs, by BMP (in blue) and by Land Use Category (in black)

BMP Selection #Ac/%Managed BMP Max-All 282

BMP Med-All 282

BMP Min-All 282

Agricultural Land 40% 25% 20%

Grass Planting 5% 0% 0%

Grading/Grassed Waterways/Filter Strips 25% 25% 20%

Grade Stabilization/Wet Pond 10% 0% 0%

Range Land 50% 25% 10%




Forest Land 30% 5% 0%




Urban Land 75% 75% 40%

Detention ponds 20% 15% 0%

Retention Ponds 0% 5% 0%

Riparian Buffers 10% 10% 10%

Treatment Ponds (wetlands) 10% 10% 10%

Vegetated Swales/Strips 10% 10% 10%

Infiltration basins 25% 25% 10%

EXHIBIT 6-4 Amount of Contaminant Reduced Per Year in Tons

Portfolio TSS Reduced P Reduced N Reduced

Maximum 382.54 1.90 4.83

Medium 308.19 1.55 3.85

Minimum 178.50 0.84 2.14



EXHIBIT 6-5

Additional Detail, Including Estimated Implementation Costs for the Three 282 Priority Site Portfolios

282 Collective Portfolio BMP Max-All 282 BMP Med-All 282 BMP Min-All 282

Total Acres 24,749 24,749 24,749

Agricultural 9476 9476 9476

Range 9590 9590 9590

Forest 1118 1118 1118

Urban 4565 4565 4565

Acres Managed 12,289 8,246 4,680

Acres Managed % 50% 33% 19%

Total Cost/yr $3,008,550 $1,102,216 $122,739

$ total Pounds $3.86 $1.76 $0.34

$ per Acre $121.56 $44.54 $4.96

TSS Tons Reduced/yr 382.54 308.19 178.50

P Tons Reduced/yr 1.90 1.55 0.84

N Tons Reduced/yr 4.83 3.85 2.14

TSS $/Ton $7,865 $3,576 $688

P $/Ton $1,583,825 $709,716 $146,009

N $/Ton $622,985 $286,598 $57,292

TSS Percent Reduction

31% 25% 15%

P Percent Reduction 14% 11% 6%

N Percent Reduction 14% 11% 6%

TSS $/Lb $3.93 $1.79 $0.34

P $/Lb $791.91 $354.86 $73.00

N $/Lb $311.49 $143.30 $28.65

The results in Exhibit 6-5 are driven entirely by the BMPs selected for each portfolio as shown in Exhibit 6-2, the BMP efficiencies and imposed coverage limits presented in Exhibit 4-1, and the relative unit costs presented in Exhibit 4-2. As is evident, there are stark differences among the three portfolios with respect to key metrics such as cost per year, $/ac, and $/lb. At first glance, this may appear counter-intuitive. However another look at Exhibit 6-2 explains the relative relationship and some differences in order of magnitude for the metrics across the three portfolios.

For example, that the BMP Min-All 282 portfolio only uses "grading/grassed waterways/filter strips" for agricultural and range land, and no BMPs for forest land. These are among the most cost-effective BMPs. Similarly, this portfolio includes the four most



cost-effective urban BMPs. These selections of BMPs result in extremely low unit costs, by pollutant mass and acreage, compared to the other two portfolios.

Comparatively, the BMP Med-All 282 portfolio includes more of the same low cost agricultural and range "grading/grassed waterways/filter strips" BMPs, but also necessarily includes this BMP for forest land, which is more expensive. Additionally, this portfolio not only included more infiltration basins, but some detention and retention ponds as well. As the application limits of the lower cost BMPs were reached in this portfolio, it was necessary to select the higher cost BMPs in order to reach the loading reduction targets of approximately 25% for TSS and 11% for TP and TN. This results in the extreme (order of magnitude) difference in cost between the Med and Min portfolios.

The differences between the Max and the other portfolios can also be explained by the differences in BMPs included in the portfolio and their relative cost. For example, the Max portfolio includes some grass planting and grade stabilization/wet ponds and neither the Med nor the Min portfolios included these relatively higher cost options (again see Exhibit 4-2 for unit removal costs by BMP by pollutant).

While these results are particular to the land use distribution of the 282 sites collectively, they do illustrate the effect of having limited the coverage of a particular BMP for a land use category overall, as explained in Chapter 4 (see maximum land use percent values in Exhibit 4-1). As discussed, these limits were based on best professional judgment about average expected site conditions within a land use category. To the extent that these limits are higher than experienced in practice, more low cost BMPs could be applied and some of the differences in alternatives would not be so significant. Alternatively, if site conditions warrant lower limits, cost and performance differences across BMP packages could be even greater than presented here, all else being equal.

6.3 Dynamic Portfolio Incorporating Individual 282 Priority Sites

Drawing on the results of the static portfolios, a “capital improvement program” approach was taken to simulate investments in BMPs on the 282 sites over a temporal period from 2008 to 2020. For mathematical convenience, it was assumed that BMPs would be installed on 22 sites in the first year of the program, on another 22 sites the second year of the program, and so on until all 282 sites had BMPs. Further, the priority ranking system described in Chapter 4 was used to select the first best 22 for the program’s first year (ranking 1-22), the second best 22 for the program’s second year (ranking 23-44), etcetera. The financial benchmark of $465,000 established for the watershed-wide portfolio, as described in Chapter 5, was used as a target for the dynamic portfolio such that the average annual cost over the 2008-2020 period would approximate that benchmark. The BMP acreage results from the static portfolios were used to guide BMP selection for the dynamic portfolios.

Exhibit 6-6 shows how the land use distribution underlying the portfolio changed over time. As is apparent from the bars, agricultural and urban land dominates the early year portfolios, and the relative proportion of these land areas decrease over time as range increases. The reason for this pattern is that the tool described in Chapter 4, using the


weighting scheme that TSS and TP were equally important to reduce, and TN was half as important to reduce, and the loading rate assumptions by land use category developed following the methodology described in Chapter 3, calculated that the best TSS and TP reduction opportunities were on parcels that had predominantly agricultural and urban land uses. So as each next set of 22 sites was “brought on-line” under BMP management, each set of 22 contained relatively more rangeland.

EXHIBIT 6-6 Land Use Distribution Changes Over Time in the 282 Dynamic Portfolio as Each Set of 22 Sites is Added to the Portfolio

56%52% 51% 49% 49% 48% 47% 46% 45% 44% 42% 40% 38%

18%19% 20% 21% 23% 25% 27% 28% 30% 32% 34% 37% 39%

24% 27% 27% 28% 26% 25% 24% 23% 22% 21% 20% 19% 18%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

Urban

Forest

Range

Agricultural

Exhibit 6-7 presents the annual total cost of the simulated BMP 282 program from assumed 2008 inception through 2020 and also shows the estimated cumulative pollutant load reduction for each year of the program. The data showed—and as may be apparent in Exhibit 6-7 to some viewers—the pace at which expenditures increase lessens over the period. Exhibit 6-8 shows this more clearly as the incremental annual expenditures decrease over time along with the incremental additional load reduction provided each year by the set of 22 newly BMP-managed sites. This pattern is explained in part by the same underlying land use data and also BMPs (see Exhibit 4-1). Since the best sites are brought into the portfolio in priority order, later additions have relatively lower loads to begin with and therefore lesser relative opportunity to achieve load reductions. Additionally, as the overall acreage increased, later year investments in BMPs had to be managed such that the average annual spending cap target was not violated.




EXHIBIT 6-7 Cumulative BMP Cost Per Year and Cumulative Pounds of Pollutant Reduced Per Year: Dynamic 282 Priority Site Portfolio

(700,000)

(600,000)

(500,000)

(400,000)

(300,000)

(200,000)

(100,000)

-

100,000

200,000

300,000

400,000

500,000

600,000

700,000

800,000

900,000

2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

Cu

mu

lati

ve

BM

P $

/yr

Total Cost/yr

TSS Lbs Reduced

P Lbs Reduced

N Lbs Reduced

Cum

ulat

ive

Poun

ds R

educ

ed/y

r

EXHIBIT 6-8 Incremental BMP Cost Per Year and Incremental Pounds of Pollutant Reduced Per Year: Dynamic 282 Priority Site Portfolio

Incr

emen

tal

BM

P $

/ yr

Incr

emen

tal

Poun

ds R

educ

ed/ y

r

(80,000)

(70,000)

(60,000)

(50,000)

(40,000)

(30,000)

(20,000)

(10,000)

-

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

100,000

110,000

120,000

2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

Incremental $ Over Previous Yr

Incremental TSS Lbs Reduced

Incremental P Lbs Reduced

Incremental N Lbs Reduced



Based on the results presented in this report, the Project Team concluded that using relative loading among the sites was an effective way to select and prioritize sites for the installation of BMPs to achieve the most load reduction.

6.4 Summary of BMP Portfolio Results for the 282 Priority Sites

The results of the static and dynamic portfolios involving the 282 priority sites illustrate how a prioritization scheme can be used to select a list of specific sites to target for BMP implementation, and how investments could be prioritized among those sites to produce the most cost-effective load reductions as soon as possible. As with the watershed-wide scale, the higher levels of investment produce more reduction than appears necessary now, while a modest investment of $122,700 annually reduced TSS, TP, and TN loadings by 15%, 6%, and 6% respectively, compared to the estimated loadings from the sites with no BMPs.

The dynamic portfolio delivers about the same level of pollutant reduction by the last year (2020) as the BMP Med-All 282 static portfolio did. With an average annual cost of $564,032, the dynamic portfolio costs about 20% more than the benchmark of $465,000 established in Chapter 5 as a guide for these analyses. To put these results in perspective, the 282 sites represents 24,749 acres compared to 124,470 acres for all of the Hickory Creek watershed—or 20%of the total. So, the cumulative reductions estimated from the 282 sites achieved by 2020 of 25% for TSS and 11% each for TP and TN are an equivalent mass to watershed-wide reductions of 5.5% for TSS and 2.5% each for TP and TN over 2020 estimated loadings.

Without additional BMPs beyond those simulated in this analysis, either on the 282 sites or other locations, even if the dynamic BMP portfolio for the 282 sites was implemented at 100% immediately, it would only offset future loads from population growth and development for a few years: sometime between 2010 and 2011 TSS, TP, and TN loads would increase beyond the offsets provided by the “282” BMPs. So the 282 sites are a good place to start prioritizing BMP investments, but by themselves they will not be enough. If these were the only BMPs implemented between now and 2020, projected loads for TSS, TP, and TN would still increase 24%, 10%, and 15%, respectively, compared to the 29%, 13%, and 18% projected with no BMPs.

CHAPTER 7

BMP Portfolios for the Master Planned Communities (MPCs)11

7.1 Current & Assumed Future Land Use Distributions for the MPCs

Three Master Planned Communities (MPCs) are currently in the planning and design stages and the associated developers have agreed to work jointly with the City of Denton to incorporate BMPs in the respective site plans. These MPCs are called Cole Ranch, Inspiration, and Rayzor Ranch. For this, the smallest scale of the BMP portfolio evaluations in this WPP, existing land use varied quite a bit, as evident in Exhibit 7-1. For convenience and to somewhat normalize BMP portfolio results across the MPCs, the analysis assumed all MPCs will be built out to a distribution of approximately 80% urban and 20% range land use, based in part on a review of the development proposals.

EXHIBIT 7-1 Existing and Future Land Uses for the Three Master Planned Communities

MPC Existing and Future Land Use

31%

19%

57%

58%

21%

68%

20%

27%

17%

7% 9%

0%

4%

79%

4%

80%

17%

83%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Existing Future Existing Future Existing Future

Pe

rce

nt

of

To

tal

Urban

Forest

Range

Agriculture




CHAPTER 7: BMP PORTFOLIOS FOR THE MASTER PLANNED COMMUNITIES (MPCS)

7.2 MPC BMP Portfolios Three alternate BMP portfolios were employed for each of the MPCs of interest:

Portfolio 1. A maximum amount of BMPs possible, employing the land use-related limits illustrated in Exhibit 4-1;

Portfolio 2. BMPs are added such that total sediment loading does not increase above current (2008) levels; and

Portfolio 3. BMPs are added such that total phosphorus loading does not increase above current (2008) levels.

Note that Portfolio 3 was developed following a review of the results for Scenario 2, in which phosphorus levels were predicted to continue to increase through the year 2020 even when TSS loadings could be held at estimated 2008 levels.

7.2.1 Cole Ranch Exhibit 7-2 presents both existing and future (predicted) land use distributions in the Cole Ranch MPC.

EXHIBIT 7-2 Existing and Predicted Future Land Use Distributions in the Cole Ranch MPC


The load reductions predicted for each of the portfolios evaluated are shown in Exhibit 7-3.

Existing

Water2%Urban

4%Forest

7%

Range57%

Ag30%

FutureWater

2%

Range21%

Urban77%



EXHIBIT 7-3 Estimated Load Reductions in Cole Ranch Compared to Estimated Future Loadings at Build out with No BMPs

Portfolio TSS Reduction TP Reduction TN Reduction

1. Maximum BMPs 51.49% 32.28% 27.54%

2. Hold TSS to 2008 levels 42.21% 24.88% 23.43%

3. Hold TSS and TP to 2008 levels 41.08% 23.98% 22.93%

As seen in Exhibit 7-4, annual costs predicted for BMP implementation within Cole Ranch range from approximately $440,000 for the Maximum Implementation Scenario to approximately $124,000 for ensuring TP loading does not increase above current levels.

EXHIBIT 7-4 Annual Costs for BMP Implementation in the Cole Ranch MPC

BMP Max Out BMP = Zero TSS

Increase over pre-

development

Same as 11 except get Phos

to pre

development

Acres Available 3,219 3,219 3,219

Acres Managed 2,243 1,848 1,800

Acres Managed % 69.68% 57.40% 55.91%

Total Cost/yr $ 440,302 $ 158,668 $ 124,366

$ total Pounds $ 1.88 $ 0.83 $ 0.67

$ per Acre $ 136.78 $ 49.29 $ 38.64

7.2.2 Inspiration Exhibit 7-5 presents both existing and future (predicted) land use distributions in the Inspiration MPC.


EXHIBIT 7-5 Existing and Predicted Future Land Use Distributions in the Inspiration MPC

ExistingUrban

4%

Water1%

Forest9% Ag

19%

Range67%

FutureWater

1%

Urban79%

Range20%


EXHIBIT 7-6 Estimated Load Reductions in Inspiration Compared to Estimated Future Loadings at Build Out with No BMPs


1. Maximum BMPs 51.66% 32.37% 27.70%



As seen in Exhibit 7-7, annual costs predicted for BMP implementation within Inspiration range from approximately $1 Million for ensuring TP loading does not increase above current levels to approximately $408,000 for ensuring TSS loading does not increase above current levels.




EXHIBIT 7-7 Annual Costs for BMP Implementation in the Inspiration MPC

BMP Max Out BMP = Zero TSS Increase over pre-

development

BMP = Zero TP Increase over pre-

development target .82 Tons

Acres Available 3,274 3,274 3,274

Acres Managed 2,292 2,292 2,292

Acres Managed % 70.00% 70.00% 70.00%

Total Cost/yr $452,692 $407,911 $1,000,078

$ total Pounds $1.87 $1.74 $4.25

$ per Acre $138.25 $124.57 $305.41

7.2.3 Rayzor Ranch Exhibit 7-8 presents both existing and future (predicted) land use distributions in the Rayzor Ranch MPC.

EXHIBIT 7-8 Existing and Predicted Future Land Use Distributions in the Rayzor Ranch MPC

Existing

Urban17%

Ag56%

Range27%

Future

Range17%

Urban83%




EXHIBIT 7-9 Estimated Load Reductions in Rayzor Ranch Compared to Estimated Future Loadings at Build Out with No BMPs


1. Maximum BMPs 52.06% 32.57% 28.08%



As seen in Exhibit 7-10, annual costs predicted for BMP implementation within Rayzor Ranch range from approximately $37,500 for the Maximum Implementation Scenario to approximately $522 for ensuring TSS loading does not increase above current levels. These numbers are much lower as the land use change is mostly agricultural to urban, resulting in a relatively high existing loading and cost-effective removal of pollutants by BMPs.

EXHIBIT 7-10 Annual Costs for BMP Implementation in the Rayzor Ranch MPC

BMP Max Out BMP = Zero TSS

Increase over pre-development

BMP = min N, allow TSS bout 10%, TSS

reduction 2.76

Acres Available 265 265 265

Acres Managed 188 74 43

Acres Managed % 70.75% 27.89% 16.18%

Total Cost/yr $37,565 $1,493 $522

$ Total Pounds $1.87 $0.17 $0.09

$ per Acre $141.74 $5.63 $1.97

7.2.4 Summary Comparison Among MPCs Exhibit 7-11 presents selected BMP portfolio performance metrics for all three MPCs, including percent pollutant reduction versus estimated loadings at build out with no BMPs, cost per acre, and cost per pound of TSS controlled. As is evident in the exhibit, there are some similarities as well as some readily observable differences across the MPCs.

Pollutant load reduction percentages are similar for Cole Ranch and Inspiration, and significantly less for Rayzor. The very similar before and after land use distributions for Cole Ranch and Inspiration, along with their similar size, explain the consistency in their estimates. Because Rayzor is much smaller in size, fewer load reduction opportunities existed.

The apparently significant differences in the cost metrics (apparent because with only three examples it is not possible to tell) are the result of a few factors. Despite their similar before and after land use distributions, these were different enough that in order to achieve the



desired control target, the BMP portfolio for Inspiration had to rely on relatively more acreage being managed with detention ponds, which are more expensive, compared to Cole Ranch which needed less acreage managed by detention ponds to achieve the target. By comparison, due to its smaller size overall, the Rayzor BMP portfolio did not exhaust the limits of lesser cost BMPs, and so requires no detention ponds to meet the target. With more case studies of MPCs, it might be possible to determine certain acreage thresholds that would foretell BMP costs; however, it is just as possible that, at this scale, the site-specific nature of each MPC would result in a broad range of costs without any predictive features.

EXHIBIT 7-11 Comparison of Pollutant Reduction and BMP Cost, MPCs

MPC Comparison: Hold TSS to PreDevelopment Levels Scenario

$84

$177

$18

$49

$125

$6

0%

10%

20%

30%

40%

50%

60%


Master Planned Community

Per

cen

t R

edu

ctio

n v

. No

BM

P

$-

$20

$40

$60

$80

$100

$120

$140

$160

$180

$200

Un

it C

os

t S

cale TSS Reduction v. No BMP

TP Reduction v. No BMP

TN Reduction v. No BMP

$/100lb/yr TSS

$/Ac/yr

CHAPTER 8

Market-Based Approaches to Incentivize BMP Implementation12

As summarized at the end of Chapter 4 and covered in more detail in the three preceding chapters, it appears that cost-effective opportunities exist to install BMPs throughout the watershed, in priority locations, and in planned communities that could significantly reduce future loadings compared to levels estimated with no BMPs. As noted at the conclusion of Chapter 4, these are theoretical opportunities. In practice, under current regulations, policies, and site plan review and approval processes, it is quite likely that many land owners with the best opportunities for BMP implementation may have little or no need for BMPs, and some number of land owners with limited or poor opportunities for BMP implementation may in fact be required to act.

One purpose of market-based approaches is to provide mechanisms within storm water management programs that will help optimize the location, size, and type of BMP by shifting implementation when required from sub-optimal solutions to ones that are more cost-effective and/or that deliver greater benefits than would otherwise occur. This is accomplished in a market-based system where some landowners may pay other parties to implement BMPs for them off-site. Depending on various aspects of program design, the program sponsor (in this case the City), can create the ability to influence and incentivize the type and location of BMPs.

This chapter presents the Project Team’s analysis and recommendations regarding developing a credit market in the City of Denton for the purposes of enhancing the storm water management program. The Project Team first examined the City’s current requirements for storm water management within new development and other types of land use changes to determine what incentives exist for landowners to perform beyond minimum requirements, then evaluated how a credit market for pollutant load reductions might increase and expand such incentives. Background information on storm water credit markets can be found in Appendix B.

8.1 Assessment of Denton’s Current Storm Water Control Requirements

8.1.1 Market Objectives This assessment is framed by the following assumptions: (1) storm water BMPs are designed to remove water quality pollutants at the source, alleviating the need for more logistically challenging and more expensive downstream controls; and (2) the purpose of a storm water

12 The Information in this Section addresses the fourth, seventh and eighth elements required in an EPA WPP; technical and financial assistance required, interim milestones for implementing BMP and criteria that can be used to determine if load reductions are being achieved.


CHAPTER 8: MARKET-BASED APPROACHES TO INCENTIVIZE BMP IMPLEMENTATION


quality credit market would be to promote the installation of permanent BMPs in areas of existing and future development through incentives and credit trading mechanisms.

8.1.2 Current Requirements Currently, Denton imposes no regulatory requirements for the installation of storm water quality-specific BMPs after construction. However, the benefits of source controls are widely recognized and temporary BMPs are currently required during construction as part of the City’s Municipal Separate Storm Sewer System (MS4) TPDES permit. The City’s Drainage Code does require that new development control up to the 100 year flood at full site build out. This code is “flow-focused” and not “pollutant-focused”. As a result, compliance with the Drainage Code does not necessarily deliver pollutant control benefits at the level desired under the storm water management program.

Exhibit 8-1 presents the best estimate of existing removal occurring under current practices (but not required by regulation) and Exhibit 8-2 presents what should be feasibly achieved. Together these assumptions will provide a basis for establishing the baselines necessary to create a credit market, as discussed following the exhibits.

EXHIBIT 8-1 Estimated Pollutant Removal Rates of Current Practices

Assumed Baseline Pollutant Removal (%) Current Activities by Area of Code

TSS Total P Total N

Drainage Standards:

Install runoff conveyance 0 0 0

Install detention pond 20 20 5

MS4 Permit Compliance:

Street sweeping 20 0 0

SWPPP compliance 10 5 5

Environmentally Sensitive Areas:

Install detention pond in developed floodplain 20 20 5

EXHIBIT 8-2 Feasible Pollutant Removal Rates of BMPs

Expected Pollutant Removal (%) BMPs by Type of Practice

TSS Total P Total N

Drainage Code Compliance Areas13

Ponds:

Dry extended detention pond 65 50 30

Wet extended detention pond 80 50 30

Storm Water Wetlands: All types 80 40 30

Filtration:

Bioretention area 80 60 50

Vegetated filter strip 50 20 20

13 Removal rates based on iSWM Site Design Manual (NCTCOG, 2006)



EXHIBIT 8-2 Feasible Pollutant Removal Rates of BMPs

Expected Pollutant Removal (%) BMPs by Type of Practice

TSS Total P Total N

Sand filter (surface and perimeter) 80 50 25

Infiltration:

Infiltration trench 80 60 60

Porous pavement NA 80 80

Open Channel: Dry Swale 80 25 40

Environmentally Sensitive Areas:

Maintain existing riparian buffer (with Bioretention Area)

80 60 50

Maintain existing water related habitat (with Storm Water Wetland)

80 40 30

Maintain existing upland habitat (based on difference of projected Annual Constituent Load from forest and urban areas)

85 90 80

8.1.3 Assessment Conclusion The purpose of a market is to provide incentives and trading mechanisms that promote the installation of storm water BMPs. Currently, the City does not require the installation of post-construction storm water BMPs and no market value is applied to pollutant load reductions. A storm water BMP credit bank and/or market in credits would provide incentives and rewards for land owners, including developers, who install and maintain BMPs.

8.2 Market-Based Approach Recommended To create a storm water quality credit market that will encompass current City regulatory requirements and provide water quality protection, it will be necessary to establish baselines for the credit market. Performance above the baselines would generate credits that could be banked, sold, or otherwise traded, and performance below the baselines would require the purchase of credits as offsets under several possible schemes described later in this section.

Two types of baselines are recommended for Denton’s consideration:

An existing baseline of water quality protection would be based on estimates of the effectiveness of current requirements and practices in each area of regulation using best professional judgment; and



New baselines (performance requirements) would integrate credit mechanisms into implementation of (1) the Drainage Code, and (2) the City’s code covering development applications in designated Environmentally Sensitive Areas (ESAs).

Exhibit 8-3 presents proposed levels for assumed pollutant control baselines of current practices and two tiers of new baselines for consideration as requirements or goals for a credit market. Current practices are assigned baselines consistent with estimates of levels of control provided under compliance with the Drainage Code (see Exhibit 8-1). The Tier 2 baseline is based on Leadership in Energy and Environmental Design (LEED) criteria for sustainable development and is consistent with NTCOG’s iSWM guidance. This baseline represents a significant improvement in pollutant loading control, but also implies a significant change in the current program. In the event that the Tier 2 level is deemed too big a first step, the Tier 1 baselines are provided for consideration as an interim step or as an intermediate level of performance where credits and debits might be counted differently than when Tier 2 is attained (see discussion below regarding implementation schemes for more detail about these options). The Tier 1 baseline represents an enhancement over current results and the levels suggested are based on best professional judgment about what would be a reasonably achievable improvement.

EXHIBIT 8-3

Market Structure Recommended for Consideration

Water Quality Protection (% Removal)

TSS Total P Total N

Baseline of Current Practices:

Drainage Design Criteria MS4 Permit Compliance ESA Regulation

20

20

5

New Baselines for Market Goals:

Tier 1 Baseline (1/2 of iSWM, LEEDs)

40 20 20

Tier 2 Baseline (iSWM, LEEDs) 80 40 40

The City has some options in exactly how to implement the baselines with respect to the minimum equivalent water quality protection level (with on-site BMPs and/or credit purchases) that must be attained for compliance and the protection level(s) beyond which credits may be generated. The options revolve around two primary, independent questions:

1. What is the protection “floor” that must be attained before credits may be purchased?

2. Is there more than one level of protection above which credits will be generated?

For the first question, the floor can be set anywhere from zero up to the first applicable baseline. If the floor is zero, then a landowner would be allowed to purchase credits to satisfy 100% of his protection level (pollutant load reduction) obligation. Alternatively, the floor could be set somewhere between zero and the first baseline and only after a landowner



satisfied the floor requirement would he be allowed to satisfy the rest of his obligation with credit purchases. A compromise position might involve setting a floor, but allowing for a waiver of the floor requirements under certain circumstances, and/or requiring more credits to offset shortfalls below the floor than required to offset shortfalls above the floor. For example, this latter option could be implemented by setting the trading ratios higher for offsets below the floor than for offsets above the floor (e.g., 3:1 v. 2:1, respectively).

The advantage of a floor is it helps reinforce concepts about and commitments to environmental protection and can help establish a level playing field among prospective traders. The floor has disadvantages in situations where the BMPs needed for compliance are not very cost-effective compared to credit options and where landowners facing a floor requirement make an economic or convenience decision to simply comply with the entire requirement on-site, without trading.

The second question arises from how the two-tiered system might be applied. If, for example, Tier 1 applied to Drainage Code situations and Tier 2 applied to ESA areas, then it would be presumed that any performance above the applicable new baseline would generate credits. Alternatively, if both Tier 1 and 2 were applied to Drainage Code situations and/or ESA areas, then two “credit creation zones” would be established. Consider for example the 40-80 levels suggested for TSS in Exhibit 8-3. Under a two-tiered system, credits could be awarded differently depending on which zone is attained: 50% (e.g., ½ pound for every pound) for performance between 40 and 80; and 100% (e.g., 1 pound for every pound) for performance above 80. The advantage of only having one applicable baseline (a one zone system) is that it is much simpler to explain and implement; its disadvantage is that it presents equal incentives and rewards for any performance above the baseline.

The advantage of instituting a two-tiered system that would be applied in the same circumstance (as opposed to one tier for Drainage Code and one tier for ESA) is that it provides an opportunity to create stronger incentives and rewards for proportionately better performance; its disadvantage is that it can be more complicated to explain and implement from a credit accounting perspective.

Exhibit 8-4 illustrates these considerations about floors and one tier versus two for the TSS baselines suggested in Exhibit 8-3. The concepts would be the same for TP and TN.

EXHIBIT 8-4 Two Implementation Schemes, Credit Purchase Options, and Resulting Credit Awards

Floors and Tiers Scheme 114 Scheme 2

Eligibility Floor to Purchase Credits

Floor set at 0: credit purchases allowed up to 100% of compliance obligation.

Set floor at current estimated performance : no credit purchases until 20% attained

Tier 1 40 Credit generation baseline for non-ESA areas: all reductions above 40% awarded same credit.

Tier applies to both ESA and non-ESA: For performance between 40 and 80, X%15 of (80-40) credit awarded.

Tier 2 80 Credit generation baseline for ESA Tier applies to both ESA and non-ESA:

14 Note that this scheme effectively means raising the baseline requirements above current levels. 15 Percentages could be different for ESA and non-ESA situations.



EXHIBIT 8-4 Two Implementation Schemes, Credit Purchase Options, and Resulting Credit Awards

Floors and Tiers Scheme 114 Scheme 2

areas: all reductions above 80% awarded same credit.

For performance above 80, X+% of (performance – 80) credit awarded.

The example schemes outlined in Exhibit 8-4 are intended to illustrate possibly the simplest (Scheme 1) and a more complex (Scheme 2) approach to implementing the tiered baselines, as represented by only using the TSS baselines (the concept would be the same if TP or TN baselines were used).

Under Scheme 1, with a floor of zero, those subject to the drainage and/or ESA codes would be allowed to offset their entire obligation through credit purchases. Non-ESA areas would have a single baseline of 40% control: performance below the baseline would represent debits (that would have to be offset through credit purchases and/or in lieu fees); and performance above the baseline would generate credits (that could be sold or banked). All credits generated above the 40% baseline would be awarded the same value. ESA areas would have a single baseline of 80%, and debits and credits would be calculated as under Tier 1.

Scheme 2 illustrates how a more complex application of the floor and tiers could create more targeted and potentially stronger incentives to either comply with credit purchases, comply on-site (credit neutral), or over-comply and generate credits. Setting a floor of 20% would require that something be done on-site prior to being eligible to create credits. The advantages and disadvantages of such a floor were discussed above and are not repeated here. Rather than applying a single baseline of 40% and 80% to non-ESA and ESA areas, respectively, Scheme 2 establishes two tiers for both non-ESA and ESA areas. In each area, the credits awarded for performance above the first tier but below the second tier (in the 40-80 range) would be discounted compared to credits awarded for performance above the second tier. For example, if first tier credits were awarded at 0.75:1 or 1:1, and second tier credits awarded at 1:1 or 1.25:1, such an approach would create a relatively greater incentive to reach the second tier.

8.3 Implementation Mechanisms and Process The City of Denton believes that the type of credit schemes recommended above are well tailored to the opportunities and challenges faced by the City. The long term goals of the City of Denton are described in the Denton Comprehensive Plan, which in turn is used as a guidance document for municipal codes. The Denton Comprehensive Plan currently contains a large section that outlines the long range environmental quality goals of the City, and specifically addresses issues such as environmentally sensitive areas (ESAs), floodplain management, and management to protect “ecosystem services.” The Denton Comprehensive Plan is currently being reviewed and updated for the first time since it was adopted in 1999.

It is anticipated that the information contained in this WPP will influence and guide revision recommendations for the Denton Comprehensive Plan. The revised Comprehensive Plan



will then be used as a guidance document for a series of recommended changes to the Denton Development Code and potentially other municipal code revisions. It is anticipated that revisions to the Drainage and Environmentally Sensitive Area Codes, which are part of the Development Code, can be imparted in ways that will maximize benefits to the watershed ecosystem, including reducing pollutant loads and preserving and/or creating riparian buffers and habitat. Many of these strategies will likely include elements of the market-based approaches that are proposed within this WPP.

Because market-based approaches are new to City staff as well as the development community and other stakeholders, and have the potential to be very far reaching and influential on the development process, the City of Denton will consider moving forward by implementing a pilot program designed to test applications of market-based approaches within existing regulatory and plan review structures prior to codifying such programs in the planned code revisions mentioned above.

It is envisioned that this pilot could occur over a period of one to three years, depending on early results and the number of applicants participating in the program. City staff will evaluate results on a rolling basis, possibly modifying the parameters of the pilot as needed, and eventually finalizing the pilot by determining how market based approaches could be formalized within the Denton Development Code and/or plan review guidance/policy. It is anticipated that the approaches to testing market based approaches will vary somewhat under the drainage code, ESA code, and Master Planned Community (MPC) programs, as described below.

8.3.1 Pilot Testing under the Drainage Code As described above, currently, submittals for land use changes that do not involve ESA areas are reviewed primarily based on compliance with the drainage code. In general terms, compliance with the drainage code is mostly dependant on water quantity (conveyance) and not on water quality. As has been stated above, it is believed that simple compliance with the drainage code reduces TSS-TP-TN loadings, on average, by approximately 20%-20%-5%, respectively. In the pilot program setting, City staff reviewing these applications could ask for additional information to confirm that these minimum TSS-TP-TN baselines are being met, and for the applicant to demonstrate if the submitted plan will in fact provide higher levels of pollutant control than these assumed baselines.

During the pilot phase, the City of Denton could keep an accounting of credits and debits created by applying the baseline to individual proposals. Under this program, performance above the 20-20-5 pollutant control baselines would generate credits, and performance below them would generate debits. Note that although an applicant must be compliant with the drainage code with respect to water quantity, it is conceivable that this compliance may not meet the 20-20-5 baseline. During the pilot, the City could evaluate the costs to create credits, the costs avoided from entering debit situations, and possible market values (i.e., price ranges) for the individual credits, debits, and collective pools. However, under this minimum program, no money and no credits would actually change hands.

If sufficient interest existed and depending on the balance of credit supply and demand during the pilot period, the City could consider introducing a credit exchange component to the pilot. This component could be implemented in several ways. For example, the



program could involve landowners with debits directly purchasing credits from landowners that generated credits. The program could also involve the City acting as a “banker” and accepting in lieu fees from landowners generating debits. In this scenario, fees would be calculated on a “per debit” basis, and the City could purchase credits from landowners to balance the debit accounts.

In a well-functioning credit market, it can be helpful to have an entity that will play a “market-making” role to help smooth market operations by purchasing credits when demand is short relative to supply, or accepting revenues and creating credits when supply is low relative to demand. This role involves certain responsibilities, and during the pilot testing phase, decision-makers at the City of Denton will need to consider whether these responsibilities are feasible and appropriate for the City of Denton to accept. For example, in situations where demands are greater than supplies, the credit buyers could supply the resources needed to fund City-implemented credit generation projects. However, in situations where supplies are greater than demands, in a market manager role, the City would need to have sufficient revenues to fulfill credit purchase obligations.

8.3.2 Pilot Testing under the ESA Code The current Development Code limits development within Environmentally Sensitive Areas. Any development beyond what is allowed by the code involves enacting an Alternative Development Plan process, which involves a public meeting with the City of Denton Planning and Zoning Commission and a public meeting and public hearing with the City Council. The Alternative Development Plan process usually involves negotiations between City staff and the applicant to minimize and offset negative impacts through some form of mitigation, and ultimately culminates in City Staff recommending approval or denial of the application to the Planning and Zoning Commission and City Council.

One of the weaknesses of the current process is that there is no specific approach to framing negotiations or establishing mitigation requirements. However, within the water quality-based credit system proposed above, impacts to ESAs could be estimated by comparing pre- and post-development loads of TSS, TP, and TN. Because impacts to these sensitive areas can be measured by their reduced function for pollution control, a credit system involving best management practices that also address pollution control is justified for riparian zones, wetlands, and upland habitats.

By evaluating these loads, City Staff and municipal decision makers could determine if the post-development plan met the applicable credit baselines (e.g., 80%-40%-40% control of TSS-TP-TN) or if the loads triggered mitigation strategies such as buying or creating credits to offset shortfalls, meet the baselines, or possibly generate extra credits.

The flexibility provided for ESAs within the current Denton Development Code, coupled with the fact that negotiations over development in ESA areas are based more upon water quality than water quantity, offers a number of potential avenues for integrating water quality credit trading into the ESA process. However, for simplicity during the pilot period, it is likely the City would use the same approach for both the drainage and ESA codes. In both cases, the role of the City will be to serve as a banker and/or market facilitator, and no money and / or credits are expected to change hands during the initial



stage of the pilot project, unless the City were to move to actual credit exchanges during the pilot, as described above for pilot testing under the drainage code.

8.3.3 Implementation Testing for Master Planned Communities Master Planned Communities (MPCs) are a new type of development challenge within Denton. Currently, Denton has one MPC that is working through the municipal review process, and several more MPCs are planned for development in the near future. As currently implemented, the MPC review and approval process can involve either or both the Drainage and ESA codes. However, it is important to note that developments within MPCs are controlled by a master zoning overlay, and this overlay spells out the standards which will be applied during development.

In some cases, standards do not deviate from those outlined in the Denton Development Code, and those components of the resulting zoning overlay will not deviate from the City’s adopted development codes. However, the key difference with a MPC is that the zoning overlay is designed to provide flexibility to MPC developer(s) by creating a zoning document that controls all deviations from the development code at one time, with one public meeting and one public hearing process. Such flexibility is deemed necessary because MPCs typically represent very large land areas, multiple types of land uses, and complex developments over long time frames, and as such the review and approval process for a typical MPC involves significant negotiations between City staff and the applicant.

Due to their size, all MPCs typically have ESA and drainage components, and it is anticipated that most MPCs will seek to deviate from drainage and ESA standards, and will seek to offset these deviations through mitigation. However, the City is currently lacking a quantitative water quality based system in which to evaluate impacts and determine sufficient mitigation.

Similar to the approach planned for testing a credit scheme under the Drainage and ESA codes, the City would require calculations of the pre- and post-development loadings of TSS, TP, and TN for MPC proposals. The level of post-development control would be reviewed against the applicable baseline (e.g., 80%-40%-40% for ESA areas and 40%-20%-20% for non-ESA areas). To the extent the proposal fell short of the baseline levels of control, the applicant would have the opportunity to either purchase sufficient credits to offset the shortfall, adjust the proposal to meet the requirements, or even adjust the proposal to exceed the requirements and generate credits that could be banked and/or exchanged.

The MPCs offer the most flexible development review and approval mechanism currently available within the City of Denton. The large size and varied land uses associated with the typical MPC offers the opportunity to explore credit trading within the development itself, or between adjacent MPCs. The water quality aspects of ESA standards, coupled with the flexibility provided by the MPC zoning overlay, offers a wide variety of different frameworks for water quality credit trading. However, for simplicity during the pilot period, the City would likely use the same approach outlined above for drainage and ESA codes for MPCs. The City’s role as banker and/or market facilitator would be the same as described above.



8.4 Suggested Path Forward The City of Denton staff has begun the process of reviewing and potentially revising the City of Denton’s Comprehensive Plan, which is the main planning guidance document of the City. As the Comprehensive Plan is being reviewed, staff will recommend changes needed to implement market based approaches to municipal decision makers. If successfully adopted, the Denton Comprehensive Plan will be used as a guideline for suggesting and implementing changes to the Denton Development Code to help facilitate market based approaches.

Concurrently, City of Denton staff will begin the process of implementing the pilot program strategies outlined above. It is the opinion of the project team that a pilot program approach is needed to test trading strategies and to determine how well the trading process fits within the current regulatory structure of the City of Denton. City of Denton staff will use the lessons learned during the pilot program to shape revision recommendations for both the City of Denton Comprehensive Plan and the Denton Development Code. Staff will also examine ways to trade credits across the three program subtypes.

Since it is likely that the most flexible and easily implemented credit trading approach will be associated with MPCs, the MPCs may offer the best mechanism to examine how credit trading might work when overlap exists between ESA and drainage codes. The MPCs also offer the attractive benefits of often being under the operational control of a single developer, and often having multiple ESA / drainage issues that could be resolved with credit trades within the specific MPC itself.

As the pilot program becomes more established and accepted, staff will begin to explore the options of trading where the City operates as a “banker”, followed by the City acting as a facilitator with only occasional activities as a banker.

Note that specific load reductions, as a product of the pilot program, can not be stated as unique numeric targets. As the actions of the Hickory Creek WPP are designed to be directed towards future land use changes, aggregate load reduction targets depend on the current land use, current loadings, proposed land use, and anticipated loadings both with and without management measures. At the site-specific level, baseline load reduction targets will be determined by the application of the relevant ordinances and site plan review policies as they currently exist and as may be modified under the pilot program. Additionally, the participants in the site-specific implementation are unknown at this time. Thus, resulting site-specific load reduction targets can and will vary. However, it is crucial to note that the suggested site-specific targets and trading program framework are designed to produce outcomes that minimize and/or mitigate net increases in pollutant loads.

Specific recommendations on a schedule of activities and short term milestones are presented in Chapter 10.

CHAPTER 9

Information/Education Component16

For BMP implementation to be successful, the City must have the support and participation of the citizenry. To develop this involvement, the City plans to create new initiatives to educate people and motivate them to change their personal behaviors to support this effort. Many people do not make the connection between activities that they perform every day in and around their homes and how these activities may lead to pollution in runoff. Changing personal behavior is sometimes difficult, and changing from pollution-generating behaviors to pollution-preventing behaviors will require education, enlightenment, and new attitudes. When citizens know, understand, and change how they do things, polluted runoff challenges can be reduced.

9.1 Public Outreach Approaches Changing behavior through education and developing responsible attitudes among citizens and communities within a watershed is not a simple task, but experience has shown that it can be done. For example, Denton residents have learned that it really is not so hard to separate recyclables from trash. One of the most effective ways to get people to change their behavior is through the application of public outreach tools. In this context, public outreach is a systematic application of marketing principals in an attempt to change behaviors. Instead of selling products or services, public outreach sells ideas, attitudes, concepts, and behavioral goals. The goal of public outreach is not to make money, but to improve society and the environment. Public outreach campaigns explain to the public that a problem exists that problem can only be solved by including public input, participation, and involvement.

Public outreach involves identifying and removing barriers that prevent citizens from “buying” recommended behaviors. For example, if the City of Denton is trying to get people to test their soil before they apply lawn fertilizer, it becomes easier if the City were to sponsor a soil test day, upon which local garden supply stores would hand out free soil test kits and demonstrate their use. Such an approach goes further toward getting people to test their soil than merely sending out flyers in the mail.

The overall framework recommended for the City of Denton’s approach is to develop and implement an outreach campaign in concert with the construction of the demonstration storm water best management practices at the Lake Forest Dog Park, the Denton Airport facilities, and the new Denton Firehouse Number 7. Each of these demonstration sites was carefully chosen to represent relatively new facilities that were highly publicized when they were created or expanded, frequented by the public, and have been topics of interest for local news media and citizens.

Each of these new BMPs can establish an outreach program as discrete steps, with each step building on the previous ones. The steps are as follows (USEPA 2008): 16 This chapter satisfies the fifth of the nine elements a WPP must contain, according to the EPA: Descriptions of the information/education component that will be used to enhance public understanding of this plan.


CHAPTER 9: INFORMATION/EDUCATION COMPONENT


• Define the driving forces, goals, and objectives;

• Identify and analyze the target audience;

• Create the message;

• Package the message;

• Distribute the message; and

• Evaluate the outreach campaign.

9.1.1 The Role of Demonstration Best Management Practices in the Public Outreach Approach

Lake Forest Wiggly Fields Dog Park The Lake Forest Dog Park, for example, is a newly constructed park that is specifically designed to allow for dog owners to recreate with their pets. The dog park is part of the larger Lake Forest Park complex, and the City enjoys a high rate of public use in this park during most of the year.

The demonstration BMP implemented in this park offers a great opportunity for an educational campaign aimed at demonstrating the link between pet waste and storm water quality. The park will have signs installed that reinforce this concept, as well as free dog waste bags for use at the park. As monitoring at the park commences, the monitoring information will be used to demonstrate the link between pet waste and storm water quality to neighborhood organizations, the Denton Park board, interested citizens, and the Denton County Master Naturalists, and this will likely be the subject of a short news story on the local Denton Cable channel. The information will also be added to the Hickory Creek 319 Grant Project web page. Preliminary monitoring information is located in Appendix C.

Denton Public Safety Training Facility

The Denton Public Safety Training Facility is a developing site; the proposed final site plan includes Denton Fire Station No. 7 (constructed in 2007), as well as future buildings, roadways, and parking lots for classrooms and driver’s training. The facility design and construction process has and will continue to incorporate “green” building standards. Fire Station 7 is one of only a few fire Stations in the United States that has achieved a “Gold” Leadership in Energy and Environmental Design (LEED) rating from the United States Green Building Council (USGBC). Fire Station No. 7 was designed and built using LEED standards to provide a state of the art fire station and incorporate the concepts of sustainable site development, water savings, energy efficiency, environmentally “friendly” materials selection, and indoor environmental quality. The LEED rating at the Fire Station was heavily publicized and has been an ongoing topic of news coverage.

The demonstration storm water BMP installed at this facility has been a component of this ongoing positive public message and will serve as a highly visible educational component of the facility as it develops. The Fire Station is just the first component of the much larger fire and police training facility that will be built over the course of the next many years. The demonstration BMP chosen for this site has been designed to accommodate runoff from the



entire complex at full buildout and will likely be used as a component of LEED certification for additional complex components. This effort should serve to continually feature the storm water BMP through future news media coverage and presentations to City Council, neighborhood organizations, and interested citizens. Monitoring data will be provided on the Hickory Creek 319 Grant Project web page and will serve to demonstrate how storm water can be managed during the development and operation of a large training facility. Preliminary monitoring information is located in Appendix C.

Denton Airport The Denton airport has been in operation for many years, but the City has recently undertaken a significant airport expansion. This expansion has attracted many new businesses to the area and has resulted in a number of new construction sites on the airport property, as well as a general increase in airport traffic.

The demonstration BMP project constructed at the airport site is in an area that is highly visible and easily accessed. Signage will be installed at this BMP site in the near future to inform visitors of the purpose of the BMP. This particular BMP represents an area that is somewhat “natural” and is heavily planted with trees and with plants that were chosen both due to their ability to mitigate contamination through biological processes and to produce an area that is visually appealing and that will have a number of blooming plants during certain times of the year.

Volunteers from the Denton Native Plant Society helped to determine the plant species to add to the biological component of the airport demonstration BMP, and Denton citizens and Denton Native Plant Society members volunteered to help install the plants. This arrangement has already engendered support and a sense of ownership with these volunteers and should serve as an excellent platform for future public outreach and education efforts as this area becomes established and data are collected during monitoring efforts. Preliminary monitoring information is located in Appendix C.

9.1.2 Public Outreach: From the Demonstration projects to the Hickory Creek Watershed

The demonstration projects will serve as excellent mechanisms to continually reinforce the concept of the influence of human activities on storm water quality and how modifications to these activities can help minimize impacts. Because of their location and the public interest in these facilities, there should be numerous opportunities for sharing information about storm water quality with the public, thus constantly reinforcing the concept of changing behaviors to elicit storm water improvements. However, a broader approach will be necessary to apply this effort to the entire Hickory Creek watershed.

Through this watershed protection planning process, the City of Denton is developing a planning framework for the City and its Extra Territorial Jurisdiction (ETJ) that aids analysts in making supportable, cost-efficient decisions on management practices to restore and protect water quality in the Hickory Creek watershed. The planning framework will be utilized to begin the process of public outreach within the entire Hickory Creek watershed. This aspect of public outreach will be directed towards citizens, the development community, municipal decision makers, and City staff. The information available through



the planning framework tool will be used to inform municipal decision makers, influence the storm water management component of Denton’s currently developing Master Planned Communities, and influence municipal policy through modifications to the Denton Comprehensive Plan and the Denton Development Code. Overall, the goals of this approach are to:

Increase awareness about water quality problems and solutions to protect water quality;

Increase understanding of the linkages between land use activities and water quality/ quantity;

Improve storm water quality and quantity management through modifications to the Denton Comprehensive Plan, the Denton Development Code, and Master Planned Community development agreements; and

Create a transferable process that can be utilized by other municipalities.

9.1.3 BMP Implementation in the Development Process As stated in this watershed protection plan, many of the opportunities for implementing BMPs will occur during the development process, and many of these initial development processes will be related to Master Planned Communities. It is important to note that, unlike traditional developments, Master Planned Communities are not required to follow the regulations outlined in the Denton Development Code. Instead, Master Planned Communities are controlled by their own unique regulations that are negotiated between City of Denton staff and site developers during the planning process. Public interactions occur between the developer and citizens / decision makers during neighborhood meetings, presentations to the Planning and Zoning Commission, and presentations to the City Council. Staff members of the City of Denton have already worked with developers of one Master Planned Communities to incorporate storm water BMPs into the site’s design, and to establish minimum targets for pollutant load reductions as a component of the controlling overlay district for this development. Similar language has been suggested by staff for incorporation into the regulations controlling the other Master Planned Communities currently being planned in Denton. The processes established by the City of Denton require the regulations controlling Master Planned Communities to be discussed in public meetings and public hearings at both the Planning and Zoning Commission and the City Council. These meetings are publicly posted according to state and local requirements, and backup materials are publicly accessible. This process should provide ample opportunities for citizen notification and participation. BMPs implemented through the Master Planned Communities are also expected to serve as examples for the development community and should help guide future regulatory updates to the Denton Development Code.

9.2 Building on Existing Public Information and Participation Activities

The City of Denton currently has a number of public education and involvement activities that are centered on the topics of watershed protection and water quality. One example is Denton’s “Find your Watershed” web page, which allows citizens to input their address and



find out which watershed they live in. The web page also provides water quality data from samples that have been collected within the specific watershed. Denton currently has a very successful benthic monitoring training class and associated “adopt a stream” program that is facilitated through the Denton County Master Naturalists and has been ongoing for the last four years. Denton has recently joined the Texas Watch water monitoring program and is facilitating local monitoring initiatives through this program.

Ongoing water quality monitoring efforts for the watersheds in Denton are published monthly on the City of Denton’s watershed web page, and reports specific to the Hickory Creek watershed are posted on the a web page that has been dedicated to the Hickory Creek 319 Grant Project. Denton’s Public Information Office currently airs several “news spots” on Denton Cable concerning watersheds, storm water quality, and general water quality. The Public Information office also creates watershed oriented bill stuffers that are sent out with utility bills. Watershed bill stuffers are typically sent out in the spring to target activities such as lawn chemical applications and in the fall to target leaf disposal and similar issues. Booths containing educational material related to watershed protection, recycling, and similar topics are currently set up at several Denton events, such as Jazz Fest and the Dog Days of Summer event.

Additional public information activities include classes / workshops concerning storm water and watershed protection, guest lecturers, benthic macro-invertebrates-related training and monitoring opportunities, water and wastewater treatment plant tours that have a storm water BMP component, and a watershed signage program. City of Denton Watershed Division staff members also intend to establish a Storm Water / Watershed Citizen Advisory Committee as part of the Storm Water Management / Watershed Protection Program, as outlined in the City’s Storm Water Management Plan (SWMP). Current and future outreach campaigns will be designed to incorporate elements of the Hickory Creek Watershed Protection Plan. Existing programs are expected to serve as a conduit to convey information specific to the watershed protection efforts and can be used in conjunction with the public outreach approaches outlined above to efficiently convey public information. The following sources are recommended for additional information: Watershed web page: www.cityofdenton.com/watershed Hickory Creek web page: http://www.cityofdenton.com/pages/mygovenvironmentalwater319grant.cfm

Watershed Protection Division: 940-349-7123

Public Information Office: 940-349-8171

http://www.cityofdenton.com/pages/mygovenvironmentalwater319grant.cfm

SECTION 10

Watershed Protection Plan Implementation17

10.1 Overview of Management Objectives Addressed By This Plan

This Plan highlights a series of watershed management objectives and related actions that are designed to minimize increases in pollutant loadings within the Hickory Creek watershed. Pollutant loads will be managed by installing BMPs in the watershed and enhancing education outreach programs. These two activities can provide a cost effective return on investment. In addition to the actions outlined in this Plan, the City of Denton, other governmental entities, and private citizens are implementing a variety of formal programs and participating in informal activities that vary in scale and scope but collectively represent significant watershed management actions. It is not the purpose of this Plan to exhaustively catalog these actions. Rather, this document establishes a set of objectives and actions that are specifically tailored to address both the challenges and opportunities that are detailed in previous sections of this Plan. Where appropriate and necessary, these objectives and actions will be integrated with the City’s Watershed Management Program, the Denton Comprehensive Plan, and Denton’s code of ordinances.

Based on the evaluations of both challenges and opportunities presented in this Plan, the following four management objectives were established:

1. Minimize net increases in sediment and nutrient loadings despite continuing population growth and development. This is the overarching objective from which the other three objectives originate. There are currently no numerical water quality criteria, TMDLs, or other water quality management targets that have been established by a regulating entity or that can defensively be established by the City of Denton. Thus, this WPP is a proactive plan that is benchmarked against current conditions, designed to minimize or prevent net increases in pollutant loadings and provide the information needed to optimize the costs associated with pollutant management practices. This will be accomplished through a combination of strengthening existing municipal codes, conducting a pilot credit trading program that employs market-based mechanisms to create incentives for reducing pollutant loads, proactively targeting priority locations with BMPs, and leveraging education and outreach programs to preempt or support these other elements.

2. Minimize or mitigate the impact of new development and other land use changes that must comply with Denton’s Development Code. Without a more quantitative

17 This chapter satisfies elements 6, 7, 8, and 9 of the nine elements a WPP must contain, according to the EPA: A schedule for implementing the non-point source management measures described in (3); Descriptions of interim, measurable milestones for determining whether the non-point source management measures described in (3) are being implemented; Development of a set of criteria that can be used to determine whether the load reductions described in (2) are being achieved; and Descriptions of the water quality monitoring activities that can be employed to evaluate the effectiveness of the implementation efforts over time, measured against the established criteria described in (8).

HICKORY CREEK WATERSHED PROTECTION PLAN_2008.DOC 10-1

CHAPTER 10: WATERSHED PROTECTION PLAN IMPLEMENTATION


approach for plan review and approval linked to water quality concerns, new development will continue to cause net increases in pollutant loading as the watershed population grows. Minimizing and mitigating these impacts will be accomplished by the proposed changes to baseline code requirements and the water quality credit trading pilot program as described in Chapter 8.

3. Target and direct voluntary actions to priority locations. This objective involves two components. First, the City must compile and maintain any data or other relevant information collected and any analyses performed in list, map, and other formats as appropriate so that when opportunities arise, voluntary investments can be directed to geographic locations where they are most needed, and in a manner in which resources are most cost-effectively deployed. The technical basis for this component is provided by the data and analyses presented in Chapters 3 through 7, and includes watershed-scale loadings analyses, identification of the areas of heaviest pollutant loadings, preliminary identification of 282 priority locations, and BMP portfolios illustrating possible BMP applications and their related cost-effectiveness and returns on investment. The second component involves linking the credit trading pilot and education-outreach programs to the mitigation, credit creation, voluntary actions, and priority location programs.

4. Education and outreach designed to increase awareness and participation, and foster changes in behavior that support proactive contributions to watershed management efforts. This objective involves the contributions individuals can make everyday, as well as creative thinking on the part of developers and other land owners to evaluate their proposals by using financial metrics that reflect the quantitative and qualitative benefits that can be derived from “greener” approaches. The use of green approaches within development projects is more likely if those involved in causing land use changes have a greater understanding of the options, costs, and benefits of these approaches.

10.2 Interim Measurable Milestones For purposes of implementing this plan in its current form, interim milestones were developed for a period of one to three years, depending on specific objectives as described below. The City may define these milestones more specifically and may make more formal commitments to address the milestones within other City planning processes and documents, including, but not limited to, the upcoming revisions to the Denton Comprehensive Plan, additions to capital improvement program plans, changes to the Denton Development Code, and guidance for City staff that implement these plans and codes. Thus, the milestones presented below are intended to reflect actions the City plans to take, while retaining the necessary flexibility required to successfully implement and coordinate the various components of the overall watershed management program and watershed protection plan.

5. Minimize net increases in pollutant loadings of sediments and nutrients in the face of continuing population growth and development.

a) Use the analysis and tools presented in this Plan to benchmark “current” conditions (Year 1-2).



b) Implement the actions summarized above in the descriptions of the management objectives and as detailed under the objectives’ milestones presented later in this chapter (Year 1-3).

c) Utilize stakeholder input provided during the development of this Plan to guide BMP siting, selection, and implementation under code compliance, credit trading, and voluntary programs covered under objective/milestone areas 2 through 4 of this Plan. During this process, considerations will be given to the following (Year 2-3):

i) “cost-effectiveness”, which is defined as being lowest possible cost per pound of removal;

ii) “good economics”, in which the party changing the land use (thus increasing loading) pays for a portion or all of the BMP implementation costs ;

iii) “compliance”, both with the goals of this WPP, the watershed management program, and local code and ordinances;

iv) “aesthetic appeal”, i.e., the BMP should “match” or “fit” the landscape; and

v) “usable area”, where possible the BMP creates recreational areas and / or habitat in addition to pollutant removal functions.

d) Use existing models and tools, as may be modified, enhanced, or augmented by other tools and procedures to track land use changes, estimate the impacts of these changes without BMPs, and account for pollutant reductions achieved by compliance with applicable codes, achieved under the credit trading pilot, produced by City-funded activities, or provided by other voluntary actions associated with the other management objectives (Year 1-3).

e) Continue current instream and other water quality monitoring programs and utilize that data and associated analyses to update and populate the models and tools described in (d) (Year 1-3).18

f) Track progress toward this Plan’s milestones, conduct periodic status reviews, and make adjustments as necessary. Update this milestone list and schedule as appropriate to support progression toward milestones (Year 1-3).

6. Minimize or mitigate the net impact of new development and other land use changes that must comply With Denton’s Development Code with respect to pollutant loading contributions to Hickory Creek.

a) Review the proposed recommendations to establish new pollutant baselines under the Drainage and Environmentally Sensitive Areas Codes and the proposed credit banking and trading pilot described in Chapter 8 of this plan (Year 1-3 ).

b) Seek out opportunities to implement the pilot program strategies outlined in Chapter 8, as may be modified and adopted, with the purpose of testing the application of stricter performance baselines and trading strategies (Year 1-3).

18 A detailed description of relevant monitoring programs to support the continued and updated use of the models and tools described in this Plan and prepared in conjunction and in support of the study effort that guided the development of this Plan are provided in Appendix C.



c) Because the MPCs generally must meet both the ESA and drainage codes, specifically test trading approaches with these land uses, if possible (Year 1-3).

d) Under the pilot, also examine ways to trade water quality credits across the program areas (drainage and ESA codes, with an emphasis on MPCs, as they must comply with both) (Year 1-3).

e) Conduct periodic reviews of interim achievements to determine how well the trading process fits within the current regulatory structure of the City of Denton (Year 1-3).

f) As the pilot program becomes more established and accepted, begin to explore the options of executing actual credit exchanges with the City operating as a “banker”, followed by the City acting as a facilitator with only occasional activities as a banker, as described in Chapter 8.

g) Use the lessons learned during the pilot program to shape revision recommendations for both the City of Denton Comprehensive Plan and the Denton Development Code (ahead of and concurrent with Plan revision process—see below).

h) Recommend changes needed to implement market-based approaches to municipal decision makers as part of the process of reviewing and potentially revising the City of Denton’s Comprehensive Plan, as this plan is the main planning guidance document of the City (this process has already begun as of the date of this Watershed Projection Plan). (Year 1-3).

i) If successfully adopted, use the changes to the Denton Comprehensive Plan as a guideline for suggesting and implementing changes to the Denton Development Code to help facilitate market based approaches (Year 2-3 and possibly beyond, to be determined by review and revision of timetable).

7. Target and direct voluntary actions to priority locations.

a) Continue to review and evaluate the source and loadings data and conclusions presented in Chapter 3 of this plan relative to the locations of development and land use change (Year 1).

b) Review in more detail the results of the rankings of the 282 priority sites, including examining the relative weighting and possibly color coding a map of the sites by ranking percentile (Year 1-2).

c) Using the information and results of items 3(a) and (b), develop a list, map, and/or other means to document important attributes of the priority sites, including the 282 that have been identified and may be amended through the review process, and maintain the information in such a way that it can be used to target credit creation by private parties, BMP investments by the City, and other voluntary actions associated with these areas (Year 1–3).

d) Continue evaluation and maintenance of the three demonstration BMPs designed and installed under the project for which this Plan was developed (Years 1-3).



e) Identify City resources that could be deployed to fund design and implementation of additional demonstration BMPs (Year 1-2).

f) Allocate available City resources to fund the design and construction of additional demonstration BMPs in priority areas (Year 2-3).

g) Use the information gathered in milestones d, e and f to refine BMP cost estimates.

h) Link information and activities related to site location and BMP-type prioritization to the credit banking/trading pilot, for example by providing relevant information and guidance to City staff and development applicants (Year 2-3).

i) Link information and activities related to site location and BMP-type prioritization to the education and outreach programs, for example by providing relevant information and guidance to City staff and development applicants (Year 1-3).

8. Education and outreach designed to increase awareness and participation, and foster changes in behavior that support proactive contributions to watershed management efforts.

a) Develop and implement an outreach campaign in concert with the construction of the demonstration BMPs at the Lake Forest Dog Park, the Denton Airport facilities, and the new Denton Firehouse Number 7 as described and detailed in Chapter 9 of this Plan (Year 1-2).

b) Utilize the existing planning framework associated with the review and possible revision to the Comprehensive Plan and Development Code to begin and support the process of public outreach within the entire Hickory Creek watershed as relates to watershed management generally and storm water BMP implementation specifically, as described in Chapter 9 of this Plan (Year 1-2).

c) Build on existing public information and participation activities, as described by way of example in Chapter 9 of this Plan (Year 1-2).

d) Disseminate information through actions identified in (a) – (c) above regarding any new performance requirements and/or credit trading opportunities associated with objective #2 above to the relevant parties.

e) Disseminate information through actions identified in (a) – (c) above regarding the City’s priority areas associated with BMP implementation and any preferred BMPs associated with objective #3 above to the relevant parties.

f) Periodically solicit feedback on the reach and effectiveness of the City’s education and public outreach efforts, through informal communications and more systematic stakeholder meetings, focus groups, or surveys as may be planned (Year 2-3).

g) Solicit ongoing and specific feedback from the actual and potential participants in the activities associated with implementation of any new performance baselines or the credit trading pilot and utilization of the City’s BMP priority scheme, with an emphasis on learning what factors affect their ability to attain compliance and their willingness and ability to exceed compliance baselines and generate credits and/or



otherwise implement “green” projects. Use this information to enhance implementation of those activities (Year 1-3).

10.3 Measuring Progress and Success in the Longer Term Evaluating progress on the primary objective of this watershed management plan—minimizing net increases in pollutant loadings of sediments and nutrients in the face of continuing population growth and development—involves assessing the results of implementation actions associated with the interim milestones detailed above (individually and collectively), as well as broader assessments conducted at more distant time intervals.

Specific measures of progress and success over the longer term are derived from the early indicators of success established for interim milestones as results are achieved. However, Plan objectives may need to be refined in response to initial successes, persistent challenges, and new opportunities that may arise. The longer term progress measures described below provide a strong evaluation framework, as well as providing opportunities for Plan adaptation / evolution in response to changing conditions. Measures are presented in order from the smallest to largest scale of measurement. Generally, the Watershed Protection Plan itself, as well as the watershed and demonstration BMP monitoring activities outlined in Appendix C, will be reviewed on a quarterly basis using Worksheet 13-2 from the USEPA 2008 “Handbook for Developing Watershed Plans to Restore and Protect Our Waters”, EPA 841-B-08-002, or equivalent.

10.3.1 Project-Specific Keep a record of landowners’ development and land use change proposals with respect to key indicators of their understanding, ability, and willingness to invest in BMPs. These activities will help measure the effectiveness of the education and outreach programs and also provide a more meaningful set of measures than the tallies of load reductions alone (see below).

Examples of useful information include the numbers, percentages, and types of proposals that: comply with existing and/or any new requirements on-site, request offsets, include BMPs that create credits, or otherwise include best management practices or new development schemes that minimize or mitigate impacts to water quality.

This information could help explain the results observed under the other progress measures described below, and would certainly represent the first evidence of successes. Later evidence of successes includes the number of BMPs installed, loads reduced by these BMPs, and, ultimately, in-stream water quality improvements. This information will also help the City make adjustments to the programs as conditions warrant.

10.3.2 Project-Specific and Cumulative BMP Results Track BMP implementation and estimated pollutant load reductions using the credit framework. Whether BMPs are implemented in compliance with the Development Code, as part of a project that generates credits (loads reduced are more than required), as part of the City’s capital improvement program, or as part of some other implementation strategy, track and tally the load reductions by mass, location, and temporal attributes.



As described in Chapter 8, a credit system provides a way to quantitatively document and track load reductions compared to what would have been provided under the previous compliance requirements for the drainage and ESA codes. This approach will produce an inventory of BMPs and associated credits that documents load reductions accomplished as a result of implementing this Plan’s objectives.

By labeling created credits as “banked” or “traded”, the City can calculate the net gains provided by banked credits that are not being used to offset compliance responsibilities and traded credits that are being used for compliance offsets. It is important to note that credit trading can provide net reductions as compared to no trading scenarios as long as trading ratios are set at levels greater than 1:1.

10.3.3 Comparing Cumulative BMP Results against Predictions Develop new baseline pollutant loadings and trend projections and evaluate results. Use the models and tools described in this plan to revise estimates of pollutant loadings to Hickory Creek at periodic future intervals. If appropriate and feasible, recalibrate the models and tools using monitoring data. Once revised loading estimates are completed, compare these revised estimates to the loading estimates predicted by the 2008 analyses.

Determine whether revised future loads represent a decrease, no change, or increase as compared to load predictions from the 2008 study. Use the new “revised ” loads to develop revised projections of subsequent year loads. Depending on the speed and success of the management measures described in this Plan, as well as those being implemented under other programs, significant results may not be apparent during the first revision effort.

Indications of success include reductions in the upward trends of pollutant loadings predicted by the analyses presented in Chapters 5 through 7 of this plan. In particular, revised projections should be below the increases of 12%-23%-29% projected for sediment loadings and the increases of 5%-12%-13% projected for phosphorus loadings for the years 2012-2017-2020 (as compared to estimated 2008 loads).

10.3.4 Instream Conditions Evaluate instream monitoring data against historical conditions and future trends.19 Using the historical data available for Hickory Creek, as well as data collected during the first three years of Plan implementation and thereafter, evaluate current in-stream concentrations of and trends associated with water quality parameters. Identify where water quality has improved, not changed, or may be of concern by comparing data and model predictions, as well as using best professional judgment. As with loading estimates, it may take substantial time before improvements in water quality are distinguishable from natural variability.

Success will be defined as evidence that impacts of future development have been minimized or mitigated. Examples might include loads or in-stream concentration data that are lower than those predicted in the absence of any action or trends in water quality degradation that are increasing at a slower rate than predicted under the “no-action”

19 A detailed description of relevant monitoring programs to support the continued and updated use of the models and tools described in this Plan and prepared in conjunction and in support of the study effort that guided the development of this Plan are provided in Appendix C.



alternative. Some evaluations may be conducted at the sub-watershed scale, although the majority of assessments will likely be conducted at the main outflow of Hickory Creek and / or at the outflows of the major tributaries to the main channel of Hickory Creek.

10.4 Funding Sources Within Portfolio 4 of the watershed-wide BMP portfolios, examples of potential funding sources for the City were identified as financial benchmarks. These included:

Water supply rate increase of $0.01 per 1,000 gallons: $67,000/year;

Estimated money available per year from the City of Denton’s “Tree Fund”, a fund developed to encourage tree preservation amongst developers or incur a fine of $100,000/year;

Water supply rate increase of $0.02 per 1,000 gallons: $134,000/year; and

Water supply rate increase of $0.03 per 1,000 gallons: $201,000/year.

Other possibilities include the City of Denton operations and capital improvements budgets, the development community, future grant funds, and private donations. It is a challenge to identify future funding with a high degree of accuracy in a municipal setting because all City funding is subject to Public Utility Board and Council discretion during the budget process, capital improvement funds are subject to the Capital Improvement Program review and approval process, applications of tree fund money require Council approval, grants are competitive and, therefore, uncertain, and funds from the development community are subject to a negotiation process between developers and staff.

Additionally, identifying funding sources for the implementation of this WPP is difficult to describe because the focus of the WPP is on enacting water quality improvement measures when future actions and activities occur that are detrimental to water quality; thus, funding hinges on these events actually occurring and the associated timing. Section 12.7.1 in the EPA’s watershed plan development guidance (EPA 2008) does provide information and venues through which to acquire funding. In particular, it directs the reader to the Guidebook of Financial Tools: Paying for Sustainable Environmental Systems (EPA 1999). Section 8 of this Guidebook, Tools To Pay For Community-Based Environmental Protection (CBEP), provides numerous other funding options, as well.

10.5 Summary Schedule The timeline for implementing management measures has been outlined to the extent possible considering the nature of the Hickory Creek WPP and the types of impairments expected for this watershed. Recall the WPP is focused on dealing with future land use changes that are expected to have a negative impact on water quality, thus the project team cannot specify exact timelines for management measures. This challenge illustrates the fundamental difference between the proactive Hickory Creek WPP and other, reactive WPPs, i.e., future impairment oriented versus existing impairment oriented.


The Hickory Creek WPP is a programmatic approach that will require substantial policy changes and an iterative approach when complying and shaping local regulatory processes that address development. Additionally, many of these activities are tied to development and are, therefore, subject to many of the same market challenges that influence short and long term development patterns. Thus, the timeline created for this project focuses on the initiatives for implementing these programmatic measures rather than actual timelines.

Exhibit 10-1 below summarizes the schedule for the interim milestones and longer term progress measures described above. As evident, most of the activities occur in parallel during the interim period. The milestones were purposefully designed in this temporal pattern to best support coordinating activities and leveraging resources.

EXHIBIT 10-1 Interim Milestones and Longer-Term Progress Measures

Milestone Year 1 Year 2 Year 3

INTERIM MILESTONES

1. MINIMIZE NET INCREASES IN POLLUTANT LOADINGS

Benchmark current conditions

Use stakeholder input to inform implementation

Track land use changes and impacts, including credits

Use data from on-going in-stream monitoring to guide efforts

Track progress toward milestones and Periodic Status Reviews

2. MINIMIZE/MITIGATE IMPACT OF NEW DEVELOPMENT

Consider establishing new pollutant baselines in codes

Implement pilot credit banking and trading under existing code

Conduct periodic reviews of credit market pilot

Explore different City roles (e.g., banker v. facilitator)

Provide input to Comprehensive Plan revision process re market-based approaches

Recommend changes to City codes following Comprehensive Plan revision

3. TARGET AND DIRECT VOLUNTARY ACTIONS TO PRIORITY LOCATIONS

Continue review of source and loadings data presented in WPP

Detailed review of 282 priority sites

Prepare summary and guidance materials to target actions to the "282" sites

Continued evaluation and maintenance of the three WPP demonstration BMPs

Identify City resources for additional demonstration BMPs, including at "282" sites

Provide location priority information/tools to credit trading pilot

Provide location priority information/tools to education and outreach programs

4. EDUCATION AND OUTREACH TO SUPPORT WPP IMPLEMENTATION

Education and outreach leveraged via the three demonstration BMPs

Public outreach throughout Hickory Creek watershed, building on existing programs

Disseminate information about credit trading pilot

Disseminate information about priority areas for BMP implementation

Periodically solicit feedback on education and outreach efforts, generally

Solicit feedback on credit trading pilot and BMP priority location scheme

LONGER TERM PROGRESS & SUCCESS MEASURES

PROJECT-SPECIFIC

Compilation of land use change proposals re ability and willingness to invest in BMPs

PROJECT-SPECIFIC AND CUMULATIVE BMP RESULTS

Compilation of BMP implementation and load reductions using credit framework

COMPARING CUMULATIVE BMP RESULTS AGAINST PREDICTIONS

Re-baseline pollutant loadings and trend projections

Evaluate updated results and develop revised projections

Compare revised projections to 2008 WPP projections

INSTREAM CONDITIONS

Evaluate data, conditions v. 2008, and trends

Recalibrate models and planning tools as appropriate

Interim Period Longer Term

interim tracking and outreach feedback feeds into Year 4

interim tracking feedback feeds into Year 4

Year 4 Year 5




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CHAPTER 11

Chapter References

Natural Resource Conservation Service. 2007. “EQIP 2002 Cost List for Denton, Texas FY 2007”. Obtained through personal communication with Susan Baggett.

Texas Commission on Environmental Quality. 2006. “Municipal & Industrial Wastewater Outfalls”. Accessed via http://www.tceq.state.tx.us/gis/metadata/outfalls_met.html

Texas Department of Transportation. 2007. “Average Low Bid Unit Price - Construction - Dallas District” Accessed via http://www.dot.state.tx.us/insdtdot/geodist/dal/cserve/bidprice/s_0101.htm.

Texas Natural Resources Information System. 2006. “Stratmap”. Accessed via http://www.tnris.state.tx.us/StratMap.aspx?layer=122.

Texas State Soil and Water Conservation Board. “Watershed Protection Plan Program”. Accessed via http://www.tsswcb.state.tx.us/wpp.

U.S. EPA. 2008. Draft Handbook for Developing Watershed Plans to Restore and Protect Our Waters. EPA 841-B-08-002; Washington, DC.

U.S. EPA. 1999. Guidebook of Financial Tools: Paying for Sustainable Environmental Systems. http://www.epa.gov/efinpage/guidebook.htm. Accessed July 7, 2008.

HICKORY CREEK WATERSHED PROTECTION PLAN_2008.DOC 11-1

http://www.tceq.state.tx.us/gis/metadata/outfalls_met.html

http://www.dot.state.tx.us/insdtdot/geodist/dal/cserve/bidprice/s_0101.htm

http://www.tnris.state.tx.us/StratMap.aspx?layer=122

http://www.tsswcb.state.tx.us/wpp

http://www.epa.gov/efinpage/guidebook.htm

CHAPTER 11: CHAPTER REFERENCES

11-2 . HICKORY CREEK WATERSHED PROTECTION PLAN_FINAL_2008.DOC


Appendices

APPENDIX A

Parcel Summary Worksheet

PARCEL SUMMARY WORKSHEET

Combined Pollutant BMP Weighting

Highlight Top # of Segments Based Upon Weighted Criteria 282TSS Phos Nit

40.00% 40.00% 20.00%

of 900 m2 draining to the TSS Score Phos Score Nit Score Combined Score

PACO_ID cells Score Score ScoreLand use area in

km2Land use area in

km3Land use area in

km4Land use area in

km5Land use area in

km6area_urban area_agric area_range area_fores area_water

1 399 19.48 19.33 12.42 51.24 158 Include 0.0198 0.162 0.1782 0 0

2 374 20.67 23.96 13.14 57.78 93 Include 0.009 0.2277 0.0954 0.0045 0.0009

3 380 14.83 11.77 9.92 36.52 251 Include 0.0027 0.0846 0.2556 0 0

6 424 23.60 26.53 14.83 64.96 42 Include 0.0225 0.243 0.1143 0.0027 0

7 460 21.43 20.09 13.72 55.25 124 Include 0.0234 0.1602 0.2313 0 0

8 401 17.99 17.09 11.75 46.83 196 Include 0.0063 0.1431 0.2106 0.0018 0

11 429 23.37 25.89 14.69 63.95 56 Include 0.0234 0.2349 0.1071 0.0216 0

12 371 20.79 23.91 13.13 57.83 91 Include 0.0144 0.2241 0.0927 0.0036 0

13 367 18.84 20.38 12.02 51.24 157 Include 0.0117 0.1845 0.1314 0 0.0036

14 364 11.64 6.10 8.07 25.80 280 Include 0 0.0207 0.306 0.0018 0

15 431 20.42 21.02 13.31 54.74 125 Include 0.0027 0.1881 0.1935 0.0036 0.0009

18 362 20.66 15.38 11.40 47.44 191 Include 0.1332 0.0522 0.1413 0 0

22 360 17.68 18.49 11.42 47.59 188 Include 0.0063 0.1656 0.153 0 0

23 365 20.26 20.45 12.32 53.04 138 Include 0.0504 0.162 0.1161 0.0009 0

25 360 20.39 21.04 12.36 53.78 132 Include 0.0504 0.1701 0.0945 0.0099 0

26 382 23.91 30.98 15.15 70.04 21 Include 0 0.3159 0.0207 0.0081 0

27 367 23.09 30.04 14.62 67.75 28 Include 0 0.3069 0.0135 0.0108 0

29 362 17.08 16.02 10.84 43.95 213 Include 0.0234 0.126 0.1719 0.0036 0.0018

32 383 20.29 19.08 12.30 51.67 153 Include 0.0576 0.1386 0.1494 0 0

35 373 19.42 19.55 12.08 51.05 160 Include 0.0342 0.1602 0.1314 0.0108 0

37 398 15.97 13.66 10.63 40.25 235 Include 0.0009 0.1071 0.2178 0.0333 0

41 364 19.88 22.97 12.67 55.52 120 Include 0.0072 0.2187 0.0873 0.0153 0

42 481 23.99 26.28 15.50 65.78 36 Include 0.0027 0.2457 0.1395 0.0459 0

43 427 23.82 26.33 14.68 64.82 44 Include 0.0396 0.2322 0.0891 0.0126 0.0117

45 373 22.36 27.98 14.21 64.55 48 Include 0.0018 0.2799 0.0549 0 0

48 507 25.84 28.93 16.70 71.47 16 Include 0.0009 0.2736 0.1746 0.0027 0.0054

50 532 30.04 32.60 18.55 81.18 6 Include 0.0504 0.2835 0.1404 0.0054 0

52 387 18.99 17.47 11.80 48.26 184 Include 0.0405 0.1296 0.1683 0.0108 0

53 410 22.86 27.18 14.58 64.61 46 Include 0.0045 0.2646 0.0747 0.0261 0

54 370 21.41 25.93 13.60 60.95 71 Include 0.0054 0.2538 0.0738 0 0.0009

55 426 16.16 12.25 10.86 39.26 242 Include 0.0027 0.0837 0.2979 0 0

56 362 17.56 18.58 11.35 47.49 189 Include 0.0045 0.1692 0.1152 0.0378 0

62 393 23.70 29.49 14.99 68.19 26 Include 0.0063 0.2925 0.0531 0.0027 0

64 436 23.88 25.81 14.90 64.59 47 Include 0.0324 0.2268 0.1296 0.0045 0

65 381 18.31 19.14 11.91 49.36 176 Include 0.0027 0.1728 0.1656 0.0009 0.0018

68 405 18.61 16.64 11.83 47.08 192 Include 0.0279 0.1242 0.2106 0.0027 0

69 360 15.56 12.51 9.66 37.73 248 Include 0.0387 0.0792 0.1098 0.0963 0.0009

72 459 21.13 16.73 13.01 50.88 162 Include 0.0621 0.0972 0.2502 0.0045 0

73 367 15.89 11.96 9.97 37.82 246 Include 0.0396 0.0666 0.225 0 0

76 363 17.71 17.46 11.27 46.44 200 Include 0.0198 0.1449 0.1593 0.0036 0

77 405 23.36 19.48 13.22 56.06 113 Include 0.1251 0.0999 0.1404 0 0

78 367 19.37 21.34 12.32 53.02 139 Include 0.0126 0.1953 0.1188 0.0027 0.0018

81 366 14.47 10.91 9.47 34.85 262 Include 0.0153 0.0693 0.2322 0.0135 0

Rank1-282

1 is best

Highlight # of Segments




40.00% 40.00% 20.00%



km2Land use area in

km3Land use area in

km4Land use area in

km5Land use area in


Rank1-282

1 is best


82 390 12.31 6.19 8.55 27.05 278 Include 0 0.018 0.3339 0 0

83 386 17.08 15.56 11.06 43.70 214 Include 0.0135 0.1233 0.1935 0.018 0

84 372 19.91 22.79 12.65 55.35 123 Include 0.009 0.216 0.0585 0.0522 0

86 373 19.32 21.71 12.42 53.46 134 Include 0.0036 0.2052 0.099 0.0288 0

87 395 19.84 17.19 12.03 49.05 177 Include 0.0621 0.1116 0.1827 0 0

90 506 29.66 35.83 18.76 84.26 4 Include 0.0126 0.3483 0.0954 0 0

92 428 19.65 19.67 12.90 52.21 149 Include 0 0.1737 0.2124 0 0

94 508 21.27 19.04 14.13 54.44 128 Include 0 0.1548 0.3033 0 0

96 375 24.65 32.81 15.55 73.01 12 Include 0 0.3384 0 0 0

98 391 21.28 26.41 13.52 61.22 68 Include 0.0027 0.2628 0.0567 0.0009 0.0297

99 458 23.72 25.85 15.09 64.67 45 Include 0.0162 0.2349 0.1467 0.0108 0.0045

103 364 21.96 21.94 12.80 56.70 108 Include 0.0837 0.1611 0.0702 0.009 0.0045

106 404 15.93 11.50 10.38 37.81 247 Include 0.0216 0.0666 0.2754 0.0009 0

111 439 16.56 11.91 10.98 39.45 239 Include 0.0126 0.0729 0.2907 0.0189 0.0009

114 372 16.48 14.59 10.61 41.69 227 Include 0.018 0.1107 0.198 0.009 0

116 360 16.48 15.00 10.52 42.00 224 Include 0.0216 0.1152 0.1818 0.0045 0.0018

119 407 15.43 11.90 10.38 37.72 249 Include 0.0009 0.0837 0.2772 0.0045 0.0009

120 380 22.16 24.19 13.56 59.91 77 Include 0.0432 0.2088 0.0909 0 0

122 543 27.35 26.11 16.97 70.42 19 Include 0.0558 0.2016 0.2151 0.0171 0

123 365 18.21 17.15 11.30 46.66 198 Include 0.0378 0.1305 0.1494 0.0117 0

124 478 27.07 28.27 16.47 71.81 15 Include 0.063 0.2322 0.1296 0.0045 0.0018

139 374 23.12 25.27 13.85 62.23 64 Include 0.0603 0.2124 0.063 0.0018 0

140 364 17.59 17.38 11.25 46.22 202 Include 0.0162 0.1458 0.1665 0 0

141 535 30.21 33.82 18.86 82.89 5 Include 0.036 0.306 0.1404 0 0

143 462 23.64 21.66 14.38 59.68 78 Include 0.0666 0.1539 0.1728 0.0234 0

147 365 19.09 19.19 11.87 50.15 170 Include 0.0342 0.1566 0.1368 0.0018 0

148 361 23.18 29.22 14.40 66.80 31 Include 0.018 0.2871 0.018 0.0009 0.0018

150 420 18.89 17.17 12.13 48.19 185 Include 0.0207 0.1332 0.2205 0.0009 0.0036

155 391 17.79 16.73 11.45 45.97 204 Include 0.0162 0.135 0.1944 0.0027 0.0045

158 389 25.34 31.34 15.59 72.27 14 Include 0.0306 0.3006 0.0189 0.0009 0

163 457 27.91 31.15 16.91 75.97 10 Include 0.0603 0.2709 0.0783 0.0027 0

168 371 21.42 23.16 13.10 57.68 94 Include 0.0432 0.198 0.0909 0.0018 0.0009

173 505 30.44 38.48 19.36 88.28 2 Include 0 0.3879 0.0612 0.0063 0

174 376 20.52 23.78 13.13 57.43 98 Include 0.0045 0.2277 0.1062 0.0009 0

176 480 25.51 23.98 15.44 64.94 43 Include 0.0738 0.1737 0.1845 0.0009 0

178 380 18.69 19.09 11.98 49.77 173 Include 0.0135 0.1656 0.1638 0 0

183 360 19.35 20.60 12.10 52.05 151 Include 0.0261 0.1791 0.1188 0 0.0009

184 368 17.00 15.11 10.73 42.84 219 Include 0.0297 0.1107 0.1827 0.0072 0.0018

188 361 18.92 16.70 11.26 46.88 194 Include 0.0693 0.1071 0.1449 0 0.0045

191 484 26.22 23.93 15.58 65.73 37 Include 0.0936 0.1611 0.1728 0.0081 0.0009

196 368 17.50 17.34 11.27 46.11 203 Include 0.0117 0.1476 0.1701 0.0027 0

197 439 24.13 20.27 13.95 58.36 86 Include 0.1134 0.1116 0.1683 0.0027 0

200 501 17.26 10.54 11.73 39.54 238 Include 0.0063 0.0504 0.3951 0 0




40.00% 40.00% 20.00%



km2Land use area in

km3Land use area in

km4Land use area in

km5Land use area in


Rank1-282

1 is best


202 374 21.31 20.02 12.54 53.87 131 Include 0.0801 0.1377 0.1197 0 0

203 392 22.27 26.98 14.20 63.45 60 Include 0.0027 0.2655 0.0711 0.0126 0.0018

205 363 21.20 24.80 13.28 59.28 80 Include 0.0189 0.2331 0.0756 0 0

211 379 21.50 25.96 13.75 61.22 67 Include 0.0009 0.2556 0.0828 0.0027 0

214 371 18.96 19.10 11.85 49.91 171 Include 0.0297 0.1584 0.1233 0.0234 0

217 361 16.46 14.81 10.51 41.78 226 Include 0.0216 0.1125 0.1863 0.0054 0

218 475 28.41 33.52 17.61 79.53 8 Include 0.0333 0.3141 0.0486 0.0324 0

219 362 22.89 21.66 12.93 57.48 97 Include 0.1134 0.1395 0.0711 0 0.0027

220 360 13.52 10.17 9.12 32.80 268 Include 0.0009 0.0693 0.2547 0 0

227 379 22.70 28.07 14.27 65.04 40 Include 0.0108 0.2763 0.0243 0.0288 0.0018

228 387 31.22 21.93 14.84 68.00 27 Include 0.3303 0.009 0.0081 0.0018 0

231 364 19.15 19.99 11.93 51.07 159 Include 0.0297 0.1701 0.1152 0.009 0.0045

232 382 20.34 22.27 12.84 55.45 121 Include 0.0189 0.2007 0.1197 0.0018 0.0036

244 361 19.31 20.13 11.84 51.28 155 Include 0.0396 0.1674 0.0954 0.0126 0.0108

246 375 23.45 26.46 14.07 63.97 55 Include 0.0567 0.2295 0.0459 0.0009 0.0054

247 364 24.01 28.08 14.41 66.49 34 Include 0.054 0.2511 0.0234 0 0

249 454 27.44 27.49 16.10 71.03 17 Include 0.099 0.2043 0.1053 0.0009 0

253 365 20.81 23.47 12.97 57.25 100 Include 0.0252 0.2133 0.0864 0.0045 0

254 424 18.85 16.49 12.10 47.44 190 Include 0.0234 0.1224 0.2349 0.0018 0

256 362 20.25 15.12 11.16 46.53 199 Include 0.1305 0.0522 0.1215 0.018 0.0045

262 372 21.19 19.20 12.33 52.71 144 Include 0.09 0.1224 0.1215 0.0009 0.0009

266 405 27.19 20.49 14.03 61.71 65 Include 0.225 0.0531 0.0765 0.0072 0.0036

268 362 19.41 22.49 12.51 54.41 129 Include 0 0.2169 0.1098 0 0

269 364 21.11 22.14 12.76 56.01 115 Include 0.0531 0.1809 0.0918 0.0018 0.0009

270 421 15.24 9.84 10.04 35.11 260 Include 0.0198 0.0468 0.3033 0.0009 0.009

271 389 20.14 19.92 12.47 52.54 146 Include 0.0396 0.1593 0.1395 0.0117 0.0009

272 364 18.19 19.79 11.79 49.77 172 Include 0.0018 0.1836 0.1413 0 0.0018

278 395 19.49 19.09 12.25 50.82 164 Include 0.0297 0.1548 0.1548 0.0144 0.0027

281 362 23.34 21.87 13.09 58.30 88 Include 0.1215 0.1368 0.0675 0.0009 0

285 368 13.39 9.60 9.08 32.07 271 Include 0 0.0621 0.2655 0.0045 0

286 365 17.07 17.01 11.06 45.14 208 Include 0.0081 0.1467 0.1692 0.0027 0.0027

287 379 14.58 11.19 9.73 35.50 258 Include 0.0054 0.0765 0.2547 0.0045 0.0009

295 414 14.73 8.52 9.73 32.98 266 Include 0.0216 0.0297 0.3213 0 0.0009

299 361 20.06 16.91 11.39 48.37 183 Include 0.1044 0.09 0.1071 0.0153 0.009

301 374 21.11 18.48 12.20 51.80 152 Include 0.0963 0.1098 0.1296 0.0009 0.0009

305 440 28.79 34.19 17.41 80.39 7 Include 0.0558 0.3123 0.0261 0.0027 0

309 447 22.93 19.16 13.58 55.67 119 Include 0.0909 0.1116 0.1764 0.0243 0

315 363 17.76 14.77 10.78 43.30 217 Include 0.0576 0.09 0.1791 0.0009 0

327 361 20.43 19.90 12.11 52.45 147 Include 0.0693 0.1458 0.0918 0.0162 0.0027

329 364 18.23 18.65 11.59 48.47 181 Include 0.018 0.1602 0.144 0.0063 0

332 364 18.36 15.06 10.94 44.36 212 Include 0.0711 0.0855 0.1692 0.0018 0.0009

333 488 15.83 9.53 10.84 36.20 252 Include 0.0018 0.0459 0.3681 0.0072 0.0171

336 375 18.59 18.53 11.79 48.91 178 Include 0.0216 0.1548 0.162 0 0




40.00% 40.00% 20.00%



km2Land use area in

km3Land use area in

km4Land use area in

km5Land use area in


Rank1-282

1 is best


338 368 20.50 13.97 11.16 45.64 205 Include 0.1449 0.0279 0.1503 0.009 0

340 377 21.55 22.24 13.04 56.83 106 Include 0.0549 0.1791 0.1026 0.0036 0

344 370 22.12 21.79 12.97 56.88 105 Include 0.0819 0.1584 0.0936 0 0

347 378 21.10 22.97 13.05 57.12 102 Include 0.0342 0.2007 0.0972 0.0054 0.0036

351 383 23.40 23.25 13.64 60.29 75 Include 0.09 0.1692 0.0846 0.0018 0

353 365 24.24 28.84 14.60 67.68 29 Include 0.0495 0.2628 0.0171 0 0

354 388 21.08 21.74 13.01 55.83 116 Include 0.0405 0.18 0.1287 0.0009 0

356 367 22.75 20.27 12.75 55.77 118 Include 0.1233 0.1161 0.0873 0.0045 0

358 374 17.52 14.36 10.77 42.66 220 Include 0.0504 0.0882 0.1953 0.0018 0.0018

362 361 18.04 17.75 11.25 47.04 193 Include 0.0315 0.1431 0.1251 0.0225 0.0036

368 516 24.64 23.65 15.70 64.00 54 Include 0.0288 0.1917 0.2412 0.0036 0

375 451 28.94 25.25 15.90 70.10 20 Include 0.1755 0.1323 0.0981 0 0.0009

376 369 28.03 19.53 13.59 61.14 69 Include 0.2835 0.0108 0.0387 0 0

383 435 22.25 26.05 14.26 62.57 63 Include 0.0018 0.2529 0.0792 0.0387 0.0198

385 371 21.43 17.62 11.70 50.76 165 Include 0.1377 0.0792 0.0837 0.0108 0.0234

387 541 27.47 24.73 16.67 68.87 25 Include 0.081 0.171 0.2052 0.0306 0

394 395 19.20 17.28 11.92 48.40 182 Include 0.0432 0.1242 0.1881 0 0.0009

403 455 22.85 20.06 13.83 56.75 107 Include 0.0711 0.1332 0.1791 0.027 0

405 407 23.76 28.24 14.96 66.96 30 Include 0.0153 0.27 0.0819 0 0

406 364 18.57 17.61 11.43 47.61 187 Include 0.0432 0.1332 0.135 0.0171 0

409 366 24.51 25.22 13.99 63.71 58 Include 0.1062 0.1854 0.0387 0 0

411 374 17.45 14.90 10.89 43.23 218 Include 0.0396 0.1008 0.1944 0.0027 0

413 364 16.25 12.89 10.16 39.30 241 Include 0.0396 0.0783 0.207 0.0036 0

419 398 24.89 24.94 14.43 64.26 51 Include 0.099 0.1818 0.0783 0 0

423 360 21.92 23.98 13.20 59.10 81 Include 0.0531 0.2034 0.0657 0.0027 0

424 397 18.28 18.38 11.99 48.65 179 Include 0 0.1629 0.1917 0.0036 0

425 381 17.43 16.28 11.22 44.93 209 Include 0.0162 0.1305 0.1926 0.0036 0.0009

430 398 18.34 14.89 11.37 44.59 211 Include 0.0486 0.0918 0.2178 0.0009 0

431 360 21.64 23.05 12.95 57.63 96 Include 0.0594 0.189 0.0648 0.0108 0.0009

432 379 24.42 18.51 12.88 55.80 117 Include 0.1872 0.0549 0.0972 0.0027 0

437 448 25.35 29.49 15.90 70.74 18 Include 0.0216 0.2772 0.0765 0.0243 0.0045

438 412 22.40 24.20 14.01 60.61 72 Include 0.0288 0.2133 0.1224 0.0072 0

441 360 18.35 16.75 11.16 46.26 201 Include 0.0522 0.1179 0.1476 0.0045 0.0027

450 393 14.11 9.80 9.55 33.47 264 Include 0.0018 0.0603 0.2817 0.0099 0.0009

452 404 19.59 20.65 12.44 52.68 145 Include 0.0171 0.1827 0.1134 0.036 0.0153

453 378 22.06 21.37 12.97 56.40 110 Include 0.081 0.153 0.1017 0.0054 0

456 368 13.19 8.09 8.75 30.04 273 Include 0.0153 0.0351 0.2736 0.0081 0

457 511 40.00 28.19 19.17 87.35 3 Include 0.4149 0.0162 0.0189 0.0072 0.0036

458 360 12.39 8.25 8.43 29.07 274 Include 0.0009 0.0477 0.2673 0.0009 0.0081

460 365 23.49 28.74 14.44 66.67 33 Include 0.0297 0.2736 0.0225 0.0036 0

474 391 23.69 25.80 14.28 63.76 57 Include 0.0576 0.2178 0.0774 0 0

476 375 14.87 10.62 9.60 35.08 261 Include 0.0252 0.0585 0.2511 0.0009 0.0027

483 362 23.68 26.36 13.98 64.02 53 Include 0.0702 0.2214 0.0333 0.0009 0.0009




40.00% 40.00% 20.00%



km2Land use area in

km3Land use area in

km4Land use area in

km5Land use area in


Rank1-282

1 is best


488 364 21.76 20.94 12.66 55.36 122 Include 0.0873 0.1458 0.0954 0 0

490 398 21.98 21.98 13.33 57.29 99 Include 0.0567 0.1719 0.1287 0.0009 0.0009

491 363 20.18 20.87 12.21 53.26 135 Include 0.0513 0.1683 0.0972 0.0009 0.0099

498 490 28.79 21.20 15.51 65.50 38 Include 0.2061 0.0612 0.1656 0 0.009

502 378 23.51 20.04 12.73 56.28 112 Include 0.153 0.0972 0.0405 0.0396 0.0108

504 363 15.51 14.33 10.17 40.01 236 Include 0.0045 0.1188 0.1539 0.0504 0

505 447 33.81 25.15 16.63 75.59 11 Include 0.3222 0.045 0.0063 0.0297 0

508 362 19.09 18.72 11.66 49.47 175 Include 0.0459 0.1458 0.1026 0.0324 0

511 448 25.18 24.17 15.00 64.34 50 Include 0.0837 0.1746 0.1449 0.0009 0

515 370 22.73 22.63 13.23 58.59 85 Include 0.0882 0.1647 0.0792 0.0018 0

517 366 20.75 23.98 13.08 57.80 92 Include 0.0153 0.225 0.0891 0.0009 0

518 362 17.99 19.90 11.65 49.53 174 Include 0 0.1881 0.09 0.0486 0

523 369 20.55 22.87 12.88 56.30 111 Include 0.0225 0.207 0.1035 0 0

524 459 25.56 28.23 15.97 69.77 22 Include 0.0315 0.2529 0.1278 0.0018 0

528 372 15.34 11.02 9.76 36.11 254 Include 0.0333 0.0585 0.2421 0.0018 0

529 458 29.66 24.07 15.91 69.64 23 Include 0.207 0.0981 0.108 0 0

530 390 30.69 21.37 14.65 66.71 32 Include 0.3222 0.0072 0.0117 0.0099 0.0009

533 399 19.07 18.99 12.26 50.31 169 Include 0.0135 0.162 0.1764 0.0081 0

535 360 29.20 20.21 13.79 63.20 62 Include 0.315 0.0018 0 0.0081 0

538 382 29.66 20.63 14.17 64.45 49 Include 0.3105 0.0072 0.0054 0.0189 0.0027

539 383 22.94 20.89 13.12 56.95 103 Include 0.1089 0.1296 0.1071 0 0

542 389 16.01 10.15 9.52 35.68 256 Include 0.0729 0.0279 0.153 0.0828 0.0144

543 363 11.61 5.82 8.00 25.44 281 Include 0.0036 0.0153 0.3087 0 0

546 393 20.69 17.93 12.25 50.87 163 Include 0.0801 0.1107 0.1539 0.0081 0.0018

551 490 22.29 18.38 13.86 54.53 127 Include 0.0558 0.117 0.2628 0 0.0063

553 469 23.22 22.48 14.61 60.31 74 Include 0.036 0.18 0.2061 0.0009 0

558 364 27.60 18.83 13.21 59.64 79 Include 0.2889 0.0018 0 0.0369 0.0009

560 361 24.10 16.72 12.07 52.89 140 Include 0.2232 0.0171 0.0405 0.0396 0.0054

564 361 19.76 16.55 11.34 47.66 186 Include 0.0972 0.0891 0.126 0.0081 0.0054

573 368 12.73 7.06 8.49 28.28 276 Include 0.0153 0.0225 0.2925 0.0018 0

578 457 21.92 17.20 13.23 52.35 148 Include 0.0792 0.0927 0.2403 0 0

579 374 14.08 9.52 9.28 32.88 267 Include 0.0162 0.0504 0.2709 0 0

584 437 35.84 24.85 16.88 77.56 9 Include 0.3888 0.0018 0 0.0036 0

586 434 18.31 13.45 11.56 43.32 216 Include 0.0432 0.0729 0.27 0.0054 0

587 513 31.77 40.00 20.00 91.77 1 Include 0.0117 0.3978 0.0495 0.0036 0

592 363 20.61 22.65 12.77 56.02 114 Include 0.0315 0.1998 0.0963 0 0

593 365 14.85 11.74 9.59 36.18 253 Include 0.0198 0.0783 0.1854 0.045 0.0009

594 361 18.10 16.14 11.02 45.26 207 Include 0.0522 0.1107 0.1476 0.0144 0.0009

596 382 25.67 21.72 13.68 61.08 70 Include 0.18 0.0981 0.0486 0.0162 0.0018

597 363 16.47 12.77 10.12 39.37 240 Include 0.0504 0.0711 0.1953 0.009 0.0018

598 410 20.47 18.99 12.65 52.11 150 Include 0.0468 0.1404 0.1809 0 0.0018

601 388 21.98 16.51 11.94 50.44 167 Include 0.1503 0.0549 0.1071 0.0252 0.0126

605 474 16.81 11.63 11.38 39.83 237 Include 0.0018 0.072 0.3096 0.0441 0




40.00% 40.00% 20.00%



km2Land use area in

km3Land use area in

km4Land use area in

km5Land use area in


Rank1-282

1 is best


606 405 17.53 13.67 11.06 42.27 221 Include 0.0387 0.0828 0.2304 0.0135 0

609 361 17.42 16.88 11.05 45.35 206 Include 0.0216 0.1377 0.153 0.0135 0

621 369 15.62 14.40 10.24 40.27 234 Include 0.0054 0.1179 0.1926 0.0072 0.0099

622 365 27.07 20.76 13.52 61.35 66 Include 0.2457 0.0495 0.027 0.0027 0.0045

623 366 19.31 20.16 12.11 51.57 154 Include 0.0261 0.1728 0.1314 0 0

628 365 22.09 18.50 12.24 52.84 142 Include 0.1314 0.0909 0.0909 0.0162 0

633 545 21.29 17.28 14.28 52.86 141 Include 0 0.1287 0.3573 0.0054 0

635 363 26.58 19.26 12.81 58.65 84 Include 0.27 0.0207 0.009 0.0018 0.0261

637 380 19.22 16.07 11.49 46.78 197 Include 0.0711 0.0954 0.1674 0.009 0

639 367 11.97 7.37 8.18 27.52 277 Include 0 0.0396 0.1998 0.0918 0

640 438 22.65 21.47 13.81 57.93 90 Include 0.0594 0.1593 0.1701 0 0.0063

641 370 15.98 15.14 10.55 41.67 228 Include 0 0.1287 0.1953 0.0063 0.0036

644 371 23.78 22.90 13.45 60.13 76 Include 0.1152 0.1521 0.0549 0.0126 0

645 385 20.11 18.69 12.18 50.98 161 Include 0.0585 0.1341 0.135 0.0198 0

648 421 23.31 25.78 14.61 63.69 59 Include 0.0261 0.2322 0.1215 0 0

649 378 22.04 19.70 12.59 54.33 130 Include 0.1062 0.1188 0.0954 0.0189 0.0018

650 387 10.89 4.91 7.53 23.33 282 Include 0 0.0117 0.1539 0.1818 0.0018

652 362 11.71 6.43 8.07 26.22 279 Include 0.0009 0.0252 0.2817 0.0189 0

655 364 21.27 20.97 12.36 54.60 126 Include 0.0837 0.1512 0.0585 0.0243 0.0108

657 361 13.93 9.11 8.91 31.95 272 Include 0.0306 0.0405 0.2169 0.0378 0

658 364 21.50 18.98 12.24 52.72 143 Include 0.1071 0.1107 0.1071 0.0036 0

667 364 14.38 11.61 9.58 35.57 257 Include 0.0036 0.0846 0.2349 0.0054 0

669 423 29.92 20.83 14.71 65.45 39 Include 0.2916 0.0162 0.0378 0.0288 0.0072

670 417 17.28 12.15 10.86 40.29 233 Include 0.045 0.0594 0.2538 0.0171 0.0009

675 369 18.05 13.45 10.44 41.94 225 Include 0.09 0.0576 0.1143 0.0675 0.0036

677 518 15.61 8.15 10.74 34.49 263 Include 0 0.0315 0.2511 0.1845 0

678 407 33.60 23.33 15.80 72.73 13 Include 0.3654 0.0018 0 0 0

679 363 24.47 19.37 12.79 56.63 109 Include 0.1899 0.0666 0.0549 0.0153 0.0009

680 373 29.23 22.24 14.36 65.84 35 Include 0.2781 0.0459 0.0126 0 0

683 430 17.48 12.84 11.24 41.57 229 Include 0.0306 0.0738 0.2772 0.0063 0

684 382 15.44 12.55 10.19 38.17 244 Include 0.009 0.09 0.2403 0.0054 0

685 421 22.09 16.81 12.37 51.27 156 Include 0.1287 0.0693 0.0558 0.1251 0.0009

687 370 25.67 19.78 13.22 58.67 83 Include 0.2115 0.0567 0.0657 0 0

689 361 15.16 12.07 9.34 36.57 250 Include 0.0414 0.0747 0.0792 0.1215 0.009

690 367 18.80 15.02 10.81 44.63 210 Include 0.0927 0.0756 0.0801 0.0792 0.0036

693 381 14.80 10.85 9.74 35.38 259 Include 0.0144 0.0666 0.2574 0.0054 0

698 361 17.46 11.10 9.67 38.23 243 Include 0.1152 0.018 0.0594 0.1332 0

699 379 15.21 8.88 8.89 32.98 265 Include 0.0783 0.0135 0.0828 0.1584 0.009

702 360 24.64 19.68 12.86 57.18 101 Include 0.1917 0.0693 0.0594 0.0027 0.0018

706 373 17.99 13.83 10.44 42.26 222 Include 0.0864 0.0648 0.1134 0.0594 0.0126

707 373 19.85 17.26 11.53 48.64 180 Include 0.0873 0.1035 0.1026 0.0342 0.009

710 384 29.07 21.56 14.35 64.99 41 Include 0.2754 0.0378 0.0333 0 0

712 517 23.10 20.01 14.53 57.64 95 Include 0.0432 0.1431 0.1953 0.0837 0.0009




40.00% 40.00% 20.00%



km2Land use area in

km3Land use area in

km4Land use area in

km5Land use area in


Rank1-282

1 is best


714 508 23.19 21.05 14.83 59.08 82 Include 0.0288 0.162 0.2583 0.009 0

717 366 27.93 22.23 13.97 64.14 52 Include 0.2493 0.0648 0.0108 0.0009 0.0045

718 405 22.58 17.90 12.62 53.10 137 Include 0.1314 0.0801 0.09 0.0639 0

723 361 18.19 14.46 10.75 43.41 215 Include 0.0765 0.0756 0.1665 0.0072 0

725 363 16.42 14.29 10.19 40.90 230 Include 0.0378 0.0999 0.1233 0.0594 0.0072

727 365 20.78 26.42 13.20 60.41 73 Include 0 0.2673 0.0279 0.0144 0.0198

728 374 13.87 9.79 9.07 32.74 269 Include 0.0162 0.0576 0.1764 0.0873 0

729 361 13.15 7.60 8.24 28.99 275 Include 0.0396 0.0216 0.1278 0.1368 0

731 364 17.26 13.29 10.20 40.74 231 Include 0.0729 0.0666 0.1179 0.0675 0.0036

734 371 16.04 10.45 9.39 35.89 255 Include 0.0783 0.0315 0.081 0.1431 0.0009

737 377 14.32 9.07 8.96 32.35 270 Include 0.0414 0.0351 0.1458 0.1161 0.0018

740 392 23.17 20.61 13.16 56.94 104 Include 0.1161 0.1215 0.1044 0.009 0.0027

741 363 17.67 13.82 10.53 42.01 223 Include 0.0702 0.072 0.1647 0.0207 0

742 366 21.20 20.22 12.26 53.67 133 Include 0.0891 0.1386 0.0594 0.036 0.0072

744 434 24.94 19.56 13.81 58.30 87 Include 0.1539 0.081 0.1269 0.0279 0.0018

748 384 16.14 11.99 10.03 38.15 245 Include 0.0441 0.0657 0.1503 0.0864 0

751 360 21.69 19.21 12.24 53.14 136 Include 0.1134 0.1107 0.0909 0.009 0.0009

759 363 24.53 20.42 13.03 57.99 89 Include 0.1755 0.0873 0.0585 0.0063 0

762 371 16.35 13.69 10.41 40.45 232 Include 0.027 0.0945 0.207 0.0063 0

764 451 27.62 20.88 14.79 63.29 61 Include 0.1998 0.0666 0.1125 0.0279 0

765 378 19.19 16.24 11.43 46.86 195 Include 0.072 0.0981 0.1476 0.0216 0.0018

768 365 22.91 15.75 11.79 50.45 166 Include 0.1962 0.0207 0.0639 0.0486 0

770 361 20.56 18.06 11.80 50.42 168 Include 0.0972 0.1071 0.0954 0.0261 0

777 513 28.48 24.55 16.46 69.50 24 Include 0.1314 0.1422 0.1737 0.0135 0.0018

APPENDIX B

Stormwater Credit Market Background

B-1

Storm Water Credit Market

Background

Market-based mechanisms attempt to incorporate economic incentives in the form of rewards (and sometimes penalties) to achieve desired outcomes at less cost than without such mechanisms. Since the publication of United States Environmental Protection Agency’s (USEPA) 2003 policy on Water Quality Trading, subsequent USEPA and state prioritization of grant applications involving trading, and related work in watershed-based regulation (such as watershed permitting), more than 50 studies, pilot programs, and operational programs involving pollutant credit markets have been started.

Though these efforts have been well reported on and hold important lessons for evaluating storm water credit markets, there are relatively few storm water-specific programs among them. As a result, there are important challenges to overcome when developing and implementing credit trading programs involving urban storm water sources, including:

• The cost of producing storm water credits is often more expensive than other options on a per unit basis;

• The baseline responsibilities for creating and applying credits are not readily calculable where mass loading limits are absent;

• Managing for several parameters—average volumes, peak flows, and pollutant load reduction—can present optimization problems and may require tradeoffs; and

• If requirements are for controls at maximum extent practicable levels, no room may exist for trading.

Markets embody a specific set of incentives created when parties have the option to exchange commodities, such as goods or services. There is a wide variety of incentive-based approaches for storm water management that do not involve commodity exchanges and that have been used successfully in many communities for many years. These include fee rebate programs, fee-in-lieu programs, and tiered or performance based fee structures (e.g., with or without storm water utilities in place).

The focus of this evaluation is on explicit market-based approaches as defined by the creation of an exchangeable commodity in the form of a credit representing a unit of pollutant reduction. Within the context of urban storm water management programs, potential buyer and seller participants include communities with MS4 permits or general storm water permits, other facilities and land owners subject to individual or general permits issued by local governments or storm water utilities, and developers and landowners subject to local storm water ordinances, fees, or other requirements.

A few of the most critical elements to a viable market-based approach for storm water management are discussed below. This is followed by a description of several model approaches where selected elements are discussed in more detail.

APPENDIX B: STORMWATER CREDIT MARKET

B-2

Trading Baselines: Clear and Quantifiable

In the regulatory context of programs governed by the Clean Water Act, whether someone could be a buyer, seller, both, or neither is determined by their “trading baseline,” as defined in USEPA’s 2003 Final Policy on Water Quality Trading. A “trading baseline” is the performance level necessary for regulatory compliance (e.g., with storm water ordinances), as defined, for example, by a maximum flow volume, a pollutant loading cap, or a level of environmental benefit or improvement that must be delivered.

Buyers are then most typically regulated parties that have not met their baseline and must purchase credits to offset exceedences. If allowed, buyers could also be parties without any regulatory responsibility, such as non-profit organizations that want to support environmental programs by taking credits off the market and retiring them (so they cannot be applied to regulatory compliance).

Sellers can come from the regulated or unregulated sector. There will be those that perform better than their baseline responsibilities and generate credits, and those that have no baseline and perform a creditable action.

In the storm water management arena, the following could be potential buyers, sellers, or both, depending on how their trading baselines are specified by state or local requirements:

• A city, county, or other governmental unit that holds an MS4 or general storm water permit;

• An industrial facility, commercial site, or other landowner that holds an individual or general storm water permit;

• A public works program involving land disturbances that temporarily or permanently alters runoff profiles for infrastructure networks, such as highways, roads, and bridges;

• A landowner developing or re-developing property subject to local storm water control ordinances, including construction-related and permanent BMPs; and

• A landowner subject to a fee-for-service levied by a public entity with storm water management responsibilities, such as a storm water utility or local public works department.

A quantifiable trading baseline is arguably the first critical element of creating a market—without it there is no way to determine who the buyers and sellers are, or what they are trading. The following three elements relate to credit generation and use, compliance-enforcement, and reporting.

Meaningful Credit Units

For the buyer with a regulatory responsibility, the units of exchange must be defined in, or readily translatable to, regulatory performance metrics. If they are not, then they are meaningless and there will be no demand. For this reason, successful trading programs typically develop credit units identical to or consistent with the unit(s) in which trading baselines are expressed. Examples of potentially meaningful credit units in the storm water management context include: flow, volume, pollutant load, and impervious area.


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Buyers and Sellers Finding Each Other

Different types of market structures and support mechanisms make it easier or harder for buyers and sellers to find each other. The harder it is for partners to connect, the more likely it is that the cost, inconvenience, and frustration of searching will result in fewer or no transactions. Some examples presented later in this section show how, with little or no enhancements, existing storm water management program components can readily facilitate matching buyers and sellers. By definition, some of the models presented establish clear and familiar pathways for locating partners.

Exchanges of Stormwater-Related Benefit Units

Typically, at least three things must happen to enact a trade:

• The credits generated must be authenticated, often through a third-party verification system;

• The cognizant regulatory or oversight authority must recognize the credits as valid and applicable to the buyer’s baseline for compliance purposes (assuming the buyer is regulated); and

• The credits must change ownership from the seller to the buyer through a paper-based, electronic, or other type of process that executes and records the trade.

Exactly how these can be accomplished and who should be involved in a storm water management context will depend on the pre-existing storm water management program structure, including roles and responsibilities, information systems, recording and documentation processes, and oversight mechanisms. The most appropriate exchange mechanism will depend on the size and scope of the market, with respect to the number of potential buyers and sellers, and the number and frequency of transactions. The “horsepower” of the methods chosen should match the programmatic needs, participants’ preferences, and available resources.

Models for Consideration

The following market-based approaches to storm water management are defined for discussion purposes:

• Commodity-Enhanced Existing Program;

• Single Buyer;

• Single Seller; and

• Multi-Buyer/Multi-Seller.

The models will exist or co-exist within a service area, governmental jurisdiction or for a defined watershed. The program rules establish the boundaries within which credit exchanges (or other transactions) are allowed.


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Commodity-Enhanced Existing Program

In this model, the program manager would re-define the compliance and/or fee unit in terms of an exchangeable commodity, such as those identified above. At a minimum, the change could serve to present a fee structure that is more understandable by the ratepayers and provide the manager with a more precise way of developing full-cost rates, assessing fees, and projecting future revenues. Or, it also could be a purposeful interim step toward a more market-based approach, whether or not the new program resembled one of the other models identified below.

Single Buyer

In this model, a single entity buys credits, defined, for example, in pollutant- or flow-based units, from one or more other parties. The buyer will typically be expected to have storm water management responsibilities (effected by an ordinance or permit), but, as discussed earlier, the buyer also could be undertaking voluntary actions. The seller(s) will either have no storm water management responsibilities, or will have done better than required to satisfy the seller’s compliance obligation (in addition to, or in lieu of, on-site actions).

Illustrations of this model include the following:

• A single developer fulfills storm water requirements through a combination of on-site BMPs and credit purchases, or entirely through credit purchases from individuals or a regional entity, as allowed by the program;

• A city institutes a program where it buys credits on a rolling basis at a pre-set price from landowners that perform retrofits or install new BMPs above and beyond their requirements with the objective of generating landowner incentives for greater on-site controls and reducing flows to the storm water system;

• A storm water utility takes some of its resources and annually holds a “reverse auction” where landowners, non-profits, and contractors can submit bids to construct and maintain various storm water BMPs—the bids are ranked based on cost effectiveness in delivering the desired performance metric(s), such as pounds of TSS reduced and/or flow controlled, and funding is awarded to the top-ranking bids; and

• A non-profit environmental advocacy organization, fulfilling a broad stewardship mission, launches a program to buy credits from landowners as a way of targeting BMPs in locations that the organization could not reach otherwise.

Single Seller

In this model, an entity with significant storm water management responsibilities, such as a unit of government or a developer with large landholdings that does better than its own compliance obligation or unregulated entity with no storm water management obligations, sells credits, such as pounds of TSS or gallons of flow controlled, to one or more other parties that cannot or chose not to fulfill their responsibilities on-site.

Illustrations of this model include the following:

• A developer of a large property, such as a subdivision or commercial complex, does better than the storm water requirements and sells credits back to the storm water


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management agency or to multiple smaller developers that cannot fulfill their on-site obligations as cost effectively;

• A county conducts a major restoration of stream and treatment wetland complex, in effect creating a giant BMP for a sub-watershed with more flow and treatment control than previously existed, which is not required under its own storm water permit, and sells credits to developers that elect to take the in-lieu-fee option the county offers;

• A storm water utility sells credits to small developers that would otherwise be installing small, isolated BMPs that do not have good maintenance track records, and uses the proceeds to fund several regional BMPs, or BMPs in target locations that are above and beyond those required for its own regulatory compliance;

• A non-profit fulfilling its stewardship mission related to habitat documents the storm water credits it creates and uses the proceeds to support larger projects than it otherwise could; and

• A for-profit entrepreneurial firm acts as a syndicate, signing up “subscribers” for storm water credits, and develops creditable BMPs to meet the aggregate demand.

Multi-Buyer/Multi-Seller

As implied by the name, this model defines a broader market, in terms of participants, number of transactions, and types of arrangements ongoing over a defined space and time period than represented in the single buyer or single seller models described above.

This model could describe the following types of programs:

• Situations where landowners conduct credit transactions directly with each other, in a stand-alone program, or as part of other options as described above;

• An exchange system implemented under a watershed permit, where a wide variety of permitted and un-permitted sources, including wastewater treatment facilities, may trade credits with each other; and

• Multi-credit opportunities, where a permitting or other framework supports recognition of more than one ecological currency in a way that increases the potential buyer pool and raises the revenue opportunities as those that create storm water credits could also sell habitat, carbon, or other recognized credits.

APPENDIX C-1

Best Management Practice Monitoring



Addendum to Report for Task 4.1, Watershed Assessment, to Fulfill the Requirements Task 2.11 “Monitoring of

Demonstration Best Management Practices” for the Grant Entitled

Control of Nonpoint Source Loads in the Hickory Creek Sub-basin of the Lake Lewisville Watershed as a

Component of a Watershed-Based Water Quality Trading Program

By

Kenneth Banks, Ph.D. Manager, Division of Environmental Quality

City of Denton 901-A Texas Street Denton, TX 76209,

Phone: (940)349-7165 Fax: (940)349-7134


12-17-07

PREPARED IN COOPERATION WITH THE Texas Commission on Environmental Quality

The preparation of this report was financed through grants from the Texas Commission on Environmental Quality

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mailto:[email protected]

This Page Intentionally Left Blank

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1.0 Introduction The requirement of Task 4.1 was to “Evaluate existing water quality monitoring program and other data to determine if the watershed is adequately assessed to properly characterize nonpoint source loadings in the Hickory Creek watershed. Additional or revised monitoring locations may be determined to adequately monitor the watershed. A plan for additional monitoring will be prepared that identifies specific water quality monitoring locations”. Task 2.11 required the project team to “describe the monitoring component that will be used to evaluate the effectiveness of the implementation efforts over time, measured against the criteria established in the plan, based on the results of Tasks 5 and 6”. A large component of Tasks 5 and 6 involves targeting and implementation activities to determine where to locate demonstration best management practices within the watersheds of Denton.

The details of the site selection process for demonstration Best Management Practices (dBMPs), including stakeholder involvement, load reduction estimates, and ultimate sites chosen to implement dBMPs is summarized in the “Technical Memorandum No . 3, City of Denton, Hickory Creek Watershed 319 Grant: (Draft) BMP Implementation Plan”. In summary, a list of ten candidate sites was presented to the 319 grant stakeholder group after an initial scoping meeting to establish selection criteria. Once sites were presented, the stakeholder group conducted an iterative evaluation process to narrow the potential dBMP list down to three sites. As stated, the details of this decision making process, as well as the final design characteristics of the three chosen dBMP sites are outlined in Technical Memorandum No. 3. The dBMP sites chosen are located at Fire Station Number 7, the Denton Municipal Airport, and Denton’s Lake Forest Dog Park. This addendum has been assembled to supplement information provided in the original Hickory Creek Watershed Monitoring Plan and document the sampling approaches used for the dBMP sites.

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Section 1.0 Denton Municipal Airport 1.1 General Description of airport dBMP The Denton Municipal Airport dBMPs include an extended detention area that receives runoff from a substantial portion of the runway as well as some of the developing areas of the airport. Storm water from overland flow is collected through a series of inlets and swales and directed into the detention area via a pipe at the end of Sabre drive. The water flows into the detention area, then into a biorention / rain garden area, where it slowly percolates through the soils of this area and is acted upon by plants and microbes. After the water has flowed through the bioretention area, it is collected by a series of pipes within the gravel layer that underlies the bioretention facility and then conveyed through a pipe and into the drainage swale adjacent to Masch Branch Road. A larger bypass inlet prevents flooding by conveying larger storm volumes from the detention area immediately into the Masch Branch Channel. Figure 1 illustrates the location and general design of the Denton Municipal Airport dBMP.

Figure 1. dBMP project located at Denton Municipal Airport, at the intersection of

Sabre and Aeronica.

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1.2 Monitoring All dBMP components drain to the main channel that flows adjacent to and eventually under Masch Branch Road. The City of Denton’s Watershed Protection group has collected some samples at the east side of the Masch branch culvert, which may provide some baseline data. However, this culvert receives a large amount of storm water drainage from areas that are not influenced by dBMPs, which will make it difficult to impossible to ascertain any dBMP effects from background variability. It is also important to note that BMPs themselves will require time for vegetation / revegetation development, which will influence our already short timeframe.

Because of these issues, monitoring will center on the bioretention area. Storm water will be sampled at the pipe that drains into the detention area immediately prior to stormwater encountering the “transition slope” and flowing down into the bioretention area. An automated storm water sampler has been installed at this location, and is programmed to perform volume-portioned sampling. The size of the pipe and the height of the water within the pipe were used to program volume portioned sampling routines. Storm water that has flowed through the biorention area is sampled in a similar manner, using the same instrumentation and volume-portioned sampling protocol. The intake for the sampler is located within the pipe that drains the bioretention area, and sample water as it leaves the biorention area and flows into the Masch Branch drainage channel. Large storms may bypass the bioretention area once the capacity of the detention pond and bioretention area are exceeded. A flow monitoring device has been installed at the bypass inlet to determine the volume of water that bypasses treatment during large storms. Since there is minimal treatment once water begins to bypass the bioretention area, water quality samples will not be collected at the bypass inlet.

Although only preliminary sampling efforts have been conducted to date, it appears that the lag time between inflow and outflow storm water discharges can be substantial under many storm conditions. At both the inflow and outflow sites, volume proportioned samples will be combined to create a single composite sample that will be analyzed to create an event mean concentration. It is anticipated that several storms may need to be sampled before the flow characteristics can be refined enough to yield accurate flow-proportioned samples.

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Section 2.0 Denton Fire Station No. 7 2.1 General Description of Fire Station No. 7 dBMP Fire Station No. 7 has a series of rainwater harvesting devices that capture precipitation from the rooftop of the main building and use this water as a supplement for site irrigation needs. Although the rainwater harvesting devices at Fire Station No. 7 are not a part of the Hickory Creek 319 grant, these devices provide a valuable addition to the dBMPs at the site. The dBMPs at the site are comprised of vegetated swales and a large extended detention pond. In general, storm water runs off the paved areas at the site and is routed through one of two vegetated swales that are located on either side of the Fire Station (see Figure 2). These two swales join together and are then conveyed through a single vegetated swale, through several rock check dams, and eventually into an extended dry detention pond (Figure 3). The pond is designed to slowly release water through an inlet that flows into a branch of Hickory Creek. Contaminant loads are reduced through the grass swales, rock check dams, and especially through the action of vegetation and the decrease in water velocity once water enters the pond.

2.2 Monitoring Monitoring has been designed to estimate the load reductions associated with the extended dry detention basin, which is by far the largest component of the management practices established at the site. The swale that conveys water from the two small vegetated swales around the fire station into the detention basin is a regularly shaped trapezoidal channel and therefore is amenable to direct flow measurement using the relationship between channel geometry, water column height, and flow. An automated monitoring device has been installed to collect samples within the channel, approximately 10 feet upstream of the first rock check dam. Samples from this area should provide a good estimate of pollutant loads just prior to the pollutants being removed by the rock check dam and the detention pond

After being treated by the pond, water enters the inlet structure through a series of small drains. This design allows water to slowly drain from the pond, thus providing the maximum amount of contact time with vegetation as well as substantial time for sediments to settle onto the pond bottom. In the event of a large storm, the inlet will be overtopped and convey a large amount of water directly into Hickory Creek. The pond is also equipped with an emergency spillway to ensure adequate drainage during very large, intense storms. Sampling storm water that leaves the pond through the inlet structure is relatively straightforward. The outlet that drains into Hickory Creek is a circular pipe of known dimensions and roughness. An automated sampler has been installed to sample water leaving as it leaves the pond and enters this pipe, and has been programmed to take volume portioned samples based on pipe / inlet box geometry and the height of the water column. Since the pond is designed to slowly release water, the lag time between inflow and outflow storm water flow can be substantial. At both the inflow and outflow sites, volume proportioned samples are combined to create a single sample that is reflective of event mean concentrations. It is anticipated that several storms may need to be sampled before the flow characteristics can be refined enough to yield accurate flow-proportioned samples.

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Figure 2. Vegetated swales that convey storm water from Fire Station No. 7 and

surrounding areas to the detention pond.

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Figure 3. Extended dry detention pond at Fire Station No. 7.

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Section 3.0 Lake Forest Dog Park 3.1 General Description of Lake Forest Dog Park The Lake Forest Dog Park dBMP is comprised of a small detention area that receives runoff from the dog park area (Figure 4). Storm water flows from the dog park area across a gravel spreader that serves to dissipate velocity, and into the detention area. The berm on the down-flow side of the detention area causes water to pond up during small storms and to be slowly released through a series of small 1” PVC pipes installed in the berm. If storm flows are large, the capacity of the detention area is exceeded and water flows out an overflow weir and is discharged with minimal treatment. Vegetation planted in the detention area serves to uptake nutrients, and the loss of water velocity due to the velocity dissipaters and impoundment in the detention area should cause a large portion of the sediments to drop out of suspension. A small vegetated filter strip has also been installed between the berm and the existing pond downgradient of the site.

Figure 4. Lake Forest Dog Park dBMP.

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Monitoring Monitoring this site is complicated by the fact that water entering the dBMP is mainly in the form of sheet flow. Since water flow is not concentrated, volume portioned sampling is difficult without a flow control structure. For this reason, the project team intends to install a small flow control structure to concentrate a portion of the sheet flow as it enters the site. Although all sheet flow cannot be captured, this sampling approach should allow analysts to characterize water quality entering the dBMP with an reasonable degree of accuracy. The flow control structure will likely be a simple gutter or half-pipe design that is used to intercept and convey sheet flow. Channels will be installed at the ground level of the final grade. Dimensions will have to be calculated but since the capture area is fairly small, channels will not have to be very deep or wide. The channels will intercept overland flow, convey the flow to capture device, volume portioned samples will be collected in the capture device, and then water will be discharged from the capture device. Some treatment may be lost when using this design, although it is likely that this treatment loss will be relatively small. There is no reason to design a sampling system to capture any storm larger that the storm that would exceed the volume of the filter strip / berm (and thus bypass the system through the overflow weir).

The 1” PVC outlets will route water into a similar flow capture device, the water will be sampled, and then discharged. Depending on flow and elevation, both pipes may be plumbed into a single channel, or just one of the two pipes may be sampled. The capacity of the capture device will be determined by the maximum volume of water discharged from the PVC pipe(s), so the capture device will likely be small. This design should give a reasonable estimate of loads as water leaves the BMP.

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Appendix C-2 Watershed Assessment Monitoring



Report for Task 4.1, Watershed Assessment, of the Grant Entitled

Control of Nonpoint Source Loads in the Hickory Creek Sub-basin of the Lake Lewisville Watershed as a

Component of a Watershed-Based Water Quality Trading Program

By

Kenneth Banks, Ph.D.

Manager, Division of Environmental Quality City of Denton

901-A Texas Street Denton, TX 76209,

Phone: (940)349-7165 Fax: (940)349-7134


Draft Created: 06-07-05

Revised: 02-14-07

Final Revision: 06-20-08

PREPARED IN COOPERATION WITH THE


The preparation of this report was financed through grants from the


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Task 4.1 Request

Evaluate existing water quality monitoring program and other data to determine if the watershed is adequately assessed to properly characterize nonpoint source loadings in the Hickory Creek watershed. Additional or revised monitoring locations may be determined to adequately monitor the watershed. A plan for additional monitoring will be prepared that identifies specific water quality monitoring locations.

1.0 Introduction

The question of whether the watershed has been adequately assessed to properly characterize non-point source loadings should be considered in the context of the monitoring objectives for this project. The project-specific objectives for monitoring are to establish a sampling protocol that can be used to calibrate and validate BMP models, as well as to demonstrate overall BMP effectiveness through demonstrating reductions in target pollutant parameters. The data collected as a part of Denton's on-going Watershed Protection Program (discussed below) provide a good understanding of the water quality challenges present within the Hickory Creek watershed. The spatial and temporal resolution of the data set can be used to examine the influences of land uses, short-lived meteorological conditions, and seasonality on Denton's surface water resources. Overall, the data will be very useful to guide future monitoring efforts and to generally assess modeling efforts. However the data are not sufficient to approximate pollutant loadings, mainly due to the lack of concurrently collected hydrologic data.

Although the Hickory Creek watershed is intricate, several data collection efforts have added to our understanding of this system. Due to efforts by the City of Denton, a large monitoring network comprised of approximately 38 stations has been established within the Hickory Creek watershed for more than four years, resulting in hundreds of water quality samples. A constantly deployed water quality-monitoring device was installed near the end of the Hickory Creek watershed in 2001 (Station 19), and has been collecting water quality data at regular intervals from installation through the present date (see Figure 1). As a part of Denton’s watershed monitoring program (referred to subsequently as “the Program”), City staff also collect water quality samples once a month at all 38 of these stations, including station 19. The samples from the 38 screening stations are subjected to routine water chemistry measurements such as conductivity, pH, total dissolved solids, turbidity, etc. The samples collected monthly from station 19 are subjected the same analyses as the screening station, plus a wide variety of water quality analyses including metals, nutrients, and total suspended solids. Occasional storm water samples have also been collected at the station 19, and are subjected to the same analyses.

This technical memorandum will provide a brief summary of key points concerning the Hickory Creek watershed, as well as examining data limitations and recommendations for future efforts. The data set for Hickory Creek is extensive, and has already been evaluated through a series of monthly and yearly reports generated by the City of Denton. The purpose of this technical memorandum is not to present this information in

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detailed form, but to use the understanding gained by the monitoring effort to make recommendations for efforts aimed at assessing pollutant loads.

This memorandum is comprised of three sections. The first section will be used to briefly outline monitoring efforts that have been conducted on Hickory Creek by the City of Denton’s Watershed Protection Program. To the author’s knowledge, the Watershed Protection Program data set represents the only available regularly collected monitoring information for the Hickory Creek watershed. The second section of the technical memorandum will be used to generally discuss the limitations of the current data set for assessing pollutant loadings for the Hickory Creek watershed. Section 3 presents recommendations for future monitoring efforts, with special emphasis on assessing pollutant loadings and more adequately assessing long term non-point source pollution. A separate addendum to this monitoring document has been devoted to the special case of monitoring pollutant reductions from the demonstration Best Management Practices (dBMPs) that have been developed as a component of the Hickory Creek 319 grant.

2.0 Hickory Creek Watershed: past and current data collection efforts

Most of the data available for the Hickory Creek watershed were collected as a part of the

City of Denton's Watershed Protection Program (“the Program”). The Program was initiated in January 2001 as part of a plan to monitor water quality within the surface water resources of the City of Denton. When the program was initiated, pollutants of concern included pesticides such as atrazine and diazinon, metals, sediments, nutrients, and bacteriological contamination. At a small subset of stations, routine parameters such as dissolved oxygen, conductivity, pH, temperature, total dissolved solids, and turbidity were also monitored to assess water quality. The overall goals of the program included assessing the status of Denton's surface water resources, determining the spatial and temporal dynamics of contaminants, safeguarding the public water supply, evaluating aquatic ecosystem health, monitoring stream depths at selected locations, and providing information needed to comply with regulations at both the state and federal level.

As the Program’s monitoring effort progressed, the complex nature of surface water contamination within Denton's watersheds became increasingly apparent. Initial findings also indicated that successful strategies for monitoring the surface water resources within the City must take into account the immense range of variability that exists within the natural environment, including the spatial and temporal distributions of the pollutants of concern. Such characterization is particularly important for understanding contaminant distributions within highly variable, diverse urban systems. Based on this understanding, Denton staff made a commitment to continue the monitoring effort for multiple years. The Program’s monitoring efforts are currently still active, representing over 7 years of surface water quality monitoring data.

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From the beginning, the Program relied on the use of the watershed as a logical framework for water resource planning and management. It is important to note that in this context, the term watershed not only refers to a drainage area bounded by lines of high ground, but also includes the broader components of a watershed such as the water, soils, vegetation, land use, and organisms associated with this drainage area. As such watersheds should be not only considered as receivers, collectors, and conveyors of precipitation that falls within a given boundary, but also as systems where the nature of water is influenced by complex interactions of chemical, physical, meteorological, and biological activities.

The Program’s monitoring efforts provide useful baseline information for improving the understanding of watershed processes. Data from monitoring activities within the watershed framework allow analyses and interpretation of problems and causes, assessment of watershed resources, detection of trends, and better informed decision-making. Data are summarized in a series of monthly reports that are designed to provide an overall assessment of surface water quality and to examine the relationship between water quality and land uses. During the first two years of the Program, a more extensive annual report was also used to summarize Program activities, outline initial findings, and to provide recommendations for future program activities.

2.1 Site descriptions

There are three main watersheds that drain the majority of the city. The Cooper Creek watershed is located in the northeast section of the City, and is a highly developed commercial and residential area of the city, comprised of mixed rangelands (972 hectares) urban development (672 hectares) and cropland / pasture (546 hectares). The Pecan Creek watershed is somewhat larger and more diverse than Cooper Creek, with the main land use divided among urban (1821 hectares), mixed range land (1350 hectares), and cropland / pasture (1180 hectares). Pecan Creek drains the central section of the City, east of I-35. Hickory Creek is a large and predominantly agricultural watershed, although a large portion of the watershed, particularly near the I-35 corridor, is experiencing rapid conversions from rural to urban land uses. Cropland / pasture (3871 hectares), mixed range-lands (3854 hectares) and forest (976 hectares) are currently the most predominant land use categories for Hickory Creek.

Precipitation falling within the watersheds of the City is ultimately conveyed to the City’s main drinking water source, Lake Lewisville. This lake is located south of Denton, and is used by several other cities in the area as a drinking water source, as well as being a significant recreational, ecological, and flood mitigation resource. The City of Denton also maintains a 21 million gallon per day (MGD) water reclamation plant, which provides wastewater treatment for the entire city. Effluent from this plant flows into Pecan Creek approximately 5 miles upstream from Lake Lewisville. Since Pecan Creek is classified as an ephemeral stream with perennial pools, effluent from the plant must pass all NPDES permit requirements with no dilution factor.

Surface waters in the Cooper Creek and Pecan Creek watersheds are mainly influenced by urban land uses such as residential housing and commercial / industrial businesses. Due to a high degree of impervious cover, water falling within these watersheds typically flows very rapidly, regularly producing minor flooding events as stream order

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increases towards the southeastern sections of the city. Water quality issues associated with these watersheds include sediment loading from construction activities and pesticide loading from lawn care activities and residential / commercial insect control.

Urban land uses as well as significant amounts of mixed croplands and rangelands influence surface waters in the Hickory Creek watershed. Water tends to move through this watershed less rapidly than either Cooper Creek or Pecan Creek, due to a larger catchment area and much less impervious cover. The agricultural land uses within this watershed have the potential to significantly affect water quality due to nutrient loading from fertilizers, sediments, and pesticide usage. Areas around the I-35 corridor are experiencing rapid conversions from agriculture and rangelands to residential neighborhoods and are also a concern for nutrient, sediment, and pesticides loadings.

2.2 History of watershed monitoring efforts at Denton

Monitoring efforts within the watersheds of Denton can be traced back at least as far as the late 1990's. Larger monitoring efforts began in 1998, when the City of Denton and the University of North Texas co-wrote a USEPA EMPACT (Environmental Monitoring for Public Access and Community Tracking) grant. The USEPA EMPACT program was a non-regulatory program designed to provide local governments with resources to provide the public with relevant, timely, and useful information about local environmental conditions. The purpose of Denton’s EMPACT project was to use environmental monitoring technologies to collect real time and time relevant data to inform citizens of current and historical environmental conditions. The project used instruments that collected a wide variety of physical and chemical parameters at a station located in Pecan Creek and a station located on Lake Lewisville, near the city’s water intake structure. Under this project, most water parameters were measured at least every 30 minutes, with some instruments also collecting meteorological and stream flow data at several stations dispersed throughout the City. Although federal funding for this project ceased several years ago, the City of Denton has continued some components of the project.

Watershed monitoring within the watersheds increased dramatically when the City of Denton was awarded a 104B3 grant from the USEPA (Grant GX828308-01) entitled "Establishing a City Watershed Protection Program". The grant was awarded in the fall of 2000. The purpose of the grant was to integrate and coordinate watershed protection activities at the City of Denton to ensure the integrity of our surface water ecosystems. Under this grant, a large number of monitoring stations were established throughout the three main watersheds of Denton. In general, the goal of the project was to collect simple water quality measurements at these stations on a regular basis in order to screen the watersheds and provide a rapid assessment of Denton's surface water resources. Approximately 70 of these “screening stations” were established within Denton's three major watersheds. Although federal funding for this project ceased during 2002, the City of Denton successfully combined the activities of the Watershed Protection Program as a component of its storm water program to provide an ongoing watershed-based monitoring program. Through this program, a wide variety of different water quality parameters (including pesticides) are assessed once a month. Storm water samples for a number of physical, chemical, and biological parameters are also collected at the four “permanent monitoring stations” at the ends of the major watersheds in

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Denton. These monitoring efforts are currently still being conducted, and have resulted in a detailed characterization of the water quality within the watersheds of the City. Data collected as a component of the USEPA EMPACT program, the Program, and related research activities have been used to produce over 24 publications and reports, and approximately 55 technical presentations.

2.2.1 Screening data

"Screening" sampling stations were chosen to best represent the greatest number of sub-watersheds that make up the major watersheds draining the City of Denton. These sub-watersheds were initially established using GIS coverages designed to identify sub-watersheds based on topography. The Hickory Creek screening sample locations are illustrated in Figure 1. Each site on the map is visited on a monthly basis, however not all of the stations have sufficient water to provide a sample every month. Although sub-watersheds were generally classified using topography, field visits and visual assessments of aerial photographs resulted in some non-topographical divisions based on current, modified drainage patterns. Sampling stations are located as near as practical to the ends of the sub-watersheds. There are approximately 38 screening stations within the Hickory Creek watershed.

2.2.2 Base flow and storm water samples

Storm-water samples are collected by deploying Storm Water Sampling Devices at a monitoring station located near the end of Denton's three major watersheds. The first generation of automated sampling devices simply collected a “first flush” sample and a composite sample based on a programmed, time-based sampling schedule. For the purposes of the Program, the first flush of the storm event was defined as the time when the water level within the stream first begins to rise. At this point, the sampling devices are programmed to collect approximately 4 liters of in situ water. After the first flush sample is collected, the samplers are programmed to collect 200 milliliters every 10 minutes until approximately 4 liters have been collected (in a separate container). The currently used automated sampling devices are programmable devices capable of collecting both time-portioned and flow-portioned samples. These samplers have been used to collect discrete samples based on flow volumes or time, and have also been used to collect composite flow-portioned samples. Flow portioned samples collected either discretely or as a single composite sample can be used to derive contaminant loadings for the sampled storm event through calculation of the event mean concentration and associated calculations of loadings through the event hydrograph. Base flow water samples are collected at the same sites, during periods of normal flow, using grab sampling approaches.

After collection, samples are analyzed for pH, conductivity, hardness, total suspended solids, alkalinity, total dissolved solids, turbidity, nitrates, salinity, ammonia, chlorides, orthophosphate, total phosphorus, CBOD5, arsenic, cadmium, chromium, copper, lead, manganese, nickel, silver, zinc, and acute toxicity (48 hour test using Ceriodaphnia dubia). Results from these sampling efforts are summarized in a series of reports produced by the Program team, and are maintained in either MS Excel spreadsheets or MS Access databases.

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2.2.3 Continuous monitoring data for Hickory Creek

The station near the end of Hickory Creek (Station 19, near the Old Alton bridge) has been equipped with a continuous water quality-monitoring instrument. This instrument measures a variety of water chemistry and physical parameters, including water temperature, water depth, conductivity, dissolved oxygen concentrations, dissolved oxygen saturation, total dissolved solids, pH, and turbidity. The device is serviced on a regular basis according to manufacturer recommendations, and routine calibrations are also performed to ensure accuracy. Currently, data are transferred directly from the water quality instrument to a computer.

2.2.4 Landuse and meteorological data

Recently, the City of Denton utilities department has completed translating a 2004 satellite image into landuse types. Similar work was completed on a satellite image obtained in 1999 and 2001. Having this information provides an excellent understanding of current landuses, as well as providing the ability to examine land use changes over time. It is expected that this information will be a valuable asset for work to be completed under the Hickory Creek 319 project. The City of Denton has been collecting meteorological information for a number of years, and has access to data from a NOAA weather station located at the municipal airport, as well as several other weather stations dispersed throughout the City at Municipal facilities. Obtaining adequate historical and current precipitation information is therefore easily accomplished.

2.2.5 Findings from historical water quality monitoring

Results for screening samples have been used to examine the relationships between water chemistry and land uses by combining land-use data and water quality data within a geographical information system (GIS). The temporal resolution of the water quality data also provides the opportunity to evaluate water quality at a given sub-watershed over time, which allows the separation of persistent water quality concerns from those that are sporadic. Using the physical and chemical data collected to date, several preliminary conclusions can be made concerning the watersheds of Denton. However, it should be noted that although the Program data set is temporally and spatially dense, large amounts of data are needed to even begin to fully characterize the variability inherent in a moderately sized watershed like Hickory Creek. Although many shorter-term patterns are apparent from the data sets, there may not be enough data to describe longer-term patterns ("multiple-year" to "decade" timeframes).

In general, water levels at the ends of Denton’s watersheds respond fairly rapidly to rainfall inputs, although those that are smaller and possess a high amount of impervious cover (Cooper Creek and Pecan Creek) respond much more rapidly than those that are larger and have less impervious cover (Hickory Creek). Depending on rainfall intensity, duration, and preceding weather conditions, Hickory Creek reaches maximum discharge at least half a day later, on average, than either Pecan or Cooper Creeks. Although stream flows can be quite variable, the streams of Denton are generally at highest stage during April through June and then September through November. The stage heights of all streams also increase in response to periodic rain events of sufficient duration and precipitation.

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Direct (TSS) and indirect (turbidity) measurements of sediment concentrations indicate that sediment loads in Pecan Creek (<1 to 148 NTU, average 25 NTU; average TSS = 16.1 mg/L) and Cooper Creek (<1 to 130 NTU, average 17 NTU; average TSS = 19.5 mg/L) are relatively low during periods of normal flow. Hickory Creek, however, tends to have moderately high sediment concentrations during normal flows (1.5 to 181 NTU, average 38 NTU; average TSS = 30.7 mg/L). The difference in sediment values between these watersheds is likely a combination of land uses, hydrologic differences, extent of impervious cover, and existing streambed loads. The sediment concentrations at all sites increase dramatically in response to storm-induced flow increases. However, stage-discharge relationships must be established before the sediment concentrations observed during storm events can be translated into actual sediment loadings.

The water near the ends of all of the watersheds of Denton is relatively hard (average 172 mg/L) and moderately alkaline average (average 180 mg/L). Relatively high total dissolved solids (average 394 mg/L) and conductivity (average 603 uSi/cm) measurements indicate that water within the sub-watersheds generally contains a moderate amount of soluble ions and minerals. These parameters exhibited seasonal patterns, with the highest amounts of dissolved constituents generally occurring during the lower flow months of summer. The influence of precipitation is also readily apparent, with most streams exhibiting a decrease in dissolved constituents in response to rainfall inputs. From a toxicity standpoint, the characteristics of relatively high hardness and high soluble ions generally make the watersheds of Denton fairly insensitive to metals inputs.

Within the sub-watersheds, occasionally high total dissolved solids, turbidity, and pesticides concentrations are the most persistent water quality concerns. Pesticides have definite seasonal fluctuations, which are related somewhat to application rates. Total dissolved solids tend to fluctuate on a seasonal basis as well, although changes are related to the amount of water flowing through the systems at the time of measurement. Turbidity is related to land disturbance activities and the amount of flow through the system in question. Water quality appears to generally decline in response to increasing urbanization.

2.3 General statements concerning sampling design and techniques

Overall, the sampling design and techniques used during the current Program monitoring efforts are adequate for making general assessments concerning the water quality of Denton's surface water resources. Watershed-level changes typically occur on large time scales, even within areas where land uses are rapidly changing. Having several years of monitoring provides enough data to determine the temporal and spatial variation of Denton's water resources, and to make informed management decisions for areas of water quality concerns. Land use analyses, for example, indicate that Total Housing and Planned Development-Developing land uses are consistently associated with elevated conductivity and total dissolved solids concentrations, while high turbidity values are predominantly associated with Planned Development-Developing lands. Occasionally, high turbidity is associated with agricultural land uses, although this association tends to occur on a seasonal basis and likely reflects seasonal land management activities. For permanent monitoring stations, turbidity and total suspended solids for all sites increase substantially as storm water-induced flows

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increase. However, whether the greatest turbidity values and total suspended solids concentrations occur during the first flush of the storm or later in the event depends appears to depend on the nature of the storm, the weather conditions leading up to the event, and the season in question. Nutrient levels (nitrate and phosphate) appear to be generally low during periods of normal flow and moderate during storm events, although nutrient concentrations are notoriously difficult to analyze due to the complex interactions that exist within the aquatic environment.

Continuous monitoring water quality equipment offers several advantages over the more traditional water quality monitoring approach of grab sampling. As currently programmed, these monitors produce a near-complete record of environmental conditions on an approximately 30-minute basis. Using this approach, patterns in diurnal fluctuations, stream responses to storm events, and assessment of unpredictable short-lived events can be more completely characterized.

Although continuous monitoring offers several advantages, the instruments and approaches used for continuous monitoring do have limitations. Only certain parameters can be measured, and adding additional parameters to existing equipment is expensive. The equipment used for these monitoring efforts is expensive and difficult to install. Maintenance requirements are relatively extensive, requiring collection, cleaning, lab calibration, and data transfers every 2 to 3 weeks. Occasionally, large storm events may bury equipment in sediments or even destroy equipment, resulting in data losses and additional maintenance activities. Although rare, vandalism and battery failures have also presented problems.

Assessments of initial water quality datasets illustrate that many of the problems leading to local water pollution are complex and interrelated. Although it is generally accepted that energy, elements, soil and pollutants move through a given watershed within the common medium of water, processes affecting these movements are often not well understood. Further, since most watersheds are complex systems with numerous components, the level of understanding of watersheds is often overly simplistic. This lack of knowledge about watershed processes is one of the key barriers to successful watershed management. The data sets that have been collected within Hickory Creek over the last several years offer a firm foundation for understanding general water quality characteristics within this watershed, and offer the ability to generally characterize the Hickory Creek watershed. However, the data are limited for assessing pollutant loads, since hydrologic data was not collected during routine monitoring. The following section further examines data limitations.

3.0 Data limitations

3.1 Assessment of current data

Through the Hickory Creek monitoring effort, Denton staffs have been able to gain a greater understanding of the variable, complex interaction between weather, landuses and water quality. However, since hydrologic characterization is not typically conducted for the Denton program’s sampling effort, most of the samples are not considered adequate for assessing pollutant loadings. In order to truly assess loadings, the volume of water that is being conveyed past the monitoring point in question is

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crucial. Sampling during a wide variety of flow regimes, including both storm and non-storm conditions is also required. In general, none of the samples that have been collected within the Hickory Creek watershed to date meet these criteria, although it is important to note that stage height has been monitored at regular intervals near the end of Hickory Creek (Station 19). If a stage height / volume discharge relation is developed for this site, a rough approximation of loadings for monitored parameters may be possible. However, even with this information, it is important to realize that the vast majority of samples collected at this site were during periods of normal flow. Until recently, the storm water monitoring events that have been collected for this site were collected using a time weighted sampling approach, and are thus severely limited for adequately reconstructing accurate loading estimates.

3.2 Screening data

The water quality monitoring data collected at the screening stations has produced a useful baseline data set. Although this data set is limited in terms of analyzed parameters and does not have the hydrologic data needed to assess pollutant loads, the data set is useful for understanding the physical and chemical differences that exist within the surface waters of Denton. Since several years of data have been collected, enough information is available to provide a good understanding of seasonal dynamics and the interaction between surface water resources and meteorological conditions.

In general, many human activities influence water quality, although the nature and extent of this influence is often difficult to determine. However, the amount of data collected by the program and the scale of the program's design appears to be adequate for demonstrating the effects of land uses on water quality. Short-lived perturbations or long-term responses of aquatic systems are often unnoticed or inadequately characterized using temporally and spatially sparse monitoring efforts. Although large changes in aquatic systems may be relatively easy to determine, slow processes, subtle changes, and rare events are often missed using standard monitoring approaches. The program’s design, however, appears to have produced a sufficient amount of quality information to make general spatial and temporal statements about the status of the surface water resources of Denton.

3.3 Permanent monitoring stations: storm samples versus base flow samples

As mentioned previously, Station 19 near the end of the Hickory Creek watershed is sampled approximately monthly for a wide variety of water quality parameters, including nutrients and sediments. An in situ water quality-monitoring device is also deployed at this site, collecting water quality data and stage height at approximately 30-minute intervals. Occasional storm water samples have been collected on a time-weighted basis, and are analyzed for the same set of water quality parameters as used during base flow sampling. Although not specifically related to the Hickory Creek 319 project, it is important to note that Pecan Creek and Cooper Creek have stations that are sampled in the same fashion, which allows comparisons between these systems under a wide variety of different conditions.

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The base flow samples collected at the permanent monitoring stations provide much more extensive data than the screening station samples. In effect, the permanent monitoring stations are integrators of watershed processes and therefore provide an understanding of water quality as it leaves the City of Denton and flows into Lewisville Lake. The storm water samples that have been collected at these sites are useful for assessing how pollutant concentrations change in the system from the first flush through the storm event, and provide a means of contrasting pollutant concentrations within the three main watersheds of Denton under a variety of different storm scenarios. However, the sampling approaches used to collect both base flow and storm water samples were not designed to provide an accurate assessment of loadings. Since time-weighted sampling has been predominantly used, any reconstruction of pollutant loads from stage heights recorded at the time of sampling will be subjected to potential errors. Thus, the main utility of the samples collected by the Program is the use of these data for assessing long-term trends, differences among watersheds and differences among storms. To accurately assess loadings, different sampling methods must be used.

4.0 Sampling approach for assessing pollutant loads

4.1 Need for flow characterization at monitoring sites

In order to accurately estimate pollutant loadings, it is imperative to develop stage-discharge relationships for all pertinent monitoring stations. If possible, these relationships should be derived from direct measurements of flow under a variety of different stage heights. At minimum, the discharge should be estimated using survey methods, although this approach will likely be somewhat less accurate than direct measurements. Once adequate stage- discharge relationships are developed, discharge may be estimated using continuously deployed stage height monitoring devices. Although the water levels that are currently logged as a part of the current continuous monitoring effort can indicate the general seasonality of flow and stream responses to storm events, no clear estimate of discharge is possible without an accurate stage-discharge relationship.

Natural channels present a challenge when developing stage discharge relationships. In general, these channels are complex, change over time, and are subject to estimation errors when simple survey methods are used to approximate discharge. Although direct measurements of flow general produce more accurate discharge estimates, obtaining these measurements can be very difficult or even impossible during periods of storm flow. However, acoustic Doppler flow measuring devices have been increasingly used to overcome these problems in recent years. Regardless of methods, it is imperative to develop accurate stage-height discharge relationships for all monitoring sites that will be used to assess pollutant loadings.

4.2 Additional monitoring efforts for Hickory Creek

Any watershed monitoring must address the issues of scale and watershed size to be successful. The issue of scale is not trivial, and must be based on drainage patterns, stream sizes, prevailing meteorological conditions, land uses, and program resources. A critical step in the monitoring design program is to concisely define the overall

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monitoring objectives. Once monitoring objectives are defined, adequate monitoring programs are much easier to design.

Previous monitoring efforts conducted as a part of the Program have been generally adequate to compare pollutant concentrations among watersheds, determine watershed impairments, assess the extent of the impairments, demonstrate the relationships between land uses and water quality, and demonstrate water quality improvements. Given enough time, the current monitoring effort should also be adequate to assess long-term trends. However, the monitoring effort is not adequate for assessing pollutant loadings, especially on a watershed scale. The use of Program data for the purposes of model validation is also limited, especially for models designed to assess pollutant loads. This should come as no surprise, as the Program’s monitoring plan was never designed for the purposes of assessing pollutant loads.

4.2.1 Assessing pollutant loads for major watershed components

Based on the current understanding of the Hickory Creek watershed, it is extremely unlikely that the water quality effects of the demonstration Best Management Practices (BMP) that will be constructed as a part of the 319 grant will be apparent on the scale of the entire Hickory Creek watershed, especially within the timeframe of the grant. Based on this understanding, the proper monitoring objective for the entire Hickory Creek watershed should therefore be “to assess the pollutant loadings from major components of watershed in order to determining the extent of pollutant loadings within the major tributaries of the Hickory Creek”. To accomplish this goal, monitoring should be conducted as near as practical to the ends of the three major sub-watersheds that comprise Hickory Creek, namely the North, South, and Dry forks of the creek, as well as at the station currently located at the end of the Hickory Creek watershed near the Old Alton bridge (Station 19). Monitoring at the mouths of major tributaries can be used to determine the extent and nature of pollution, and which tributaries are the major sources for these pollutants. By comparing tributaries, the relative magnitude of pollutants loadings can be derived.

4.2.2 Proposed monitoring activities for Hickory Creek

Stage-discharge relationships should be developed for the north, south, and dry forks of Hickory Creek. However, since these areas are often dry for much of the year, sampling will be somewhat limited. City of Denton Watershed Protection staff will evaluate the flow characteristics of these areas, and will recommend monitoring activities for nitrogen, total phosphorus, and total suspended sediments if site conditions are conducive for monitoring. Sampling for the 38 screening stations in the Hickory Creek watershed will be continued, and these samples will be evaluated (at minimum) for conductivity, pH, and turbidity.

Currently, resources at the City of Denton should allow continued sampling of Station 19 on a monthly basis, with at least 3 to 4 flow based storm water sampling events conducted per year. Continuous monitoring for temperature, pH, conductivity, turbidity, total dissolved solids, salinity, dissolved oxygen, and stage height will also be continuously monitored at this site. Samples collected at Station 19 will be monitored (at minimum) for total nitrogen (TKN), total phosphorus, and total suspended solids. The City of Denton will attempt to develop stage height to volume discharge

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relationships at this site during the first year of the Watershed Protection Plan, although the site represents some challenges in this regard due to the influence of backwater conditions from Lake Lewisville.

The City of Denton is currently working with the United States Geological Survey (USGS) and the Texas Commission on Environmental Quality to reinstate a USGS monitoring station at Country Club Road and Hickory Creek, and equip the monitoring station with monitoring equipment to analyze pH, dissolved oxygen, conductivity, ammonia, nitrate, total reactive phosphorus, and turbidity. The USGS has already began installation of flow monitoring equipment, and should be done by fall 2008. Once the USGS completes the station, the City of Denton will likely shift monitoring efforts from Station 19 to the new station. The new station is not far upstream from Station 19, and there are no major inputs to Hickory Creek between the two stations. The new station, however, will offer the benefit of USGS flow data, and is not influenced by the backwater conditions of the lake that have hindered loading assessments at Station 19. At minimum, the project team should be able to take time-paced samples at the site and calculate loadings for the site using the volume discharge information from the USGS station and associated time stamp. Analyses of stage height information and both normal flow and storm water samples will give some indication of appropriate sampling intervals, although the sampling protocol will need to be flexible during the initial stages of monitoring to allow for optimization based on initial data collection. As understanding of the site improves, samples should be collected based on a “flow-proportional” method by combining individual samples into a single composite to provide a single sample estimate of the event mean concentration (EMC). Since measuring within-storm concentration changes is not the goal of this monitoring effort, the strategy of using the EMC in conjunction with the concurrently collected discharge data should provide an adequate assessment of the pollutant loads for the event without creating excessive analytical costs (see Harmel et al., 2003).

It should be noted that this proposed monitoring effort (north, south, and dry forks, as well as station 19) is beyond the scope of the current 319 grant, in terms of both analytical costs and the time needed to observe any changes in pollutant loads due to changes within the watersheds. Monitoring Station 19 and the 38 screening stations on a monthly basis during periods of normal flow, coupled with 3 to 4 storm water sampling events at Station 19, should be able to be accomplished with existing resources. Samples collected at the screening stations should provide information on the average condition of water quality for the sampling period, as well as potentially indicating small scale impacts. Since Station 19 is near the end of the watershed, samples collected at this station should provide an integration of water chemistry and loadings from the entire watershed, as well as provide a data set for evaluating trends in the entire Hickory Creek watershed, at a point near where this watershed discharges into Lewisville Lake.

As mentioned above, Station 19 may be moved a small distance upstream to the intersection of Country Club road and Hickory Creek to coincide with the USGS station being installed at this location. If the TCEQ water quality monitoring group establishes a continuous water quality monitoring device at this location, sampling and data collection will be greatly enhanced. However, even without the continuous monitoring

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device, the site will still be sampled by the project team using time or volume portioned sampling methods. Monitoring activities will focus on constituents of concern outlined in the Watershed Protection Plan, namely total nitrogen, total phosphorus, and total suspended sediments.

4.2.2 Evaluations using sampling data

The goal of the monitoring component of the 319 project is to determine the effectiveness of management activities in the watershed through targeted monitoring efforts. Currently, Hickory Creek is meeting designated uses, and the goal of the Watershed Protection Plan is to ensure that the watershed continues to meet these uses. Assessing the success of this goal is a long term effort, and will require evaluations of sampling data through time. At minimum, sampling data will be reviewed annually based on the start date of the Watershed Protection Plan. Part of the analyses should involve a comparison of current data against past data trends. During this review, data assessments must account for data variability, and must use statistically based methods that can separate true trends from data “noise”.

5.0 Conclusions

The data collection efforts that have been conducted as a part of Denton's Program provide a good understanding of the water quality challenges present within the Hickory Creek watershed. The spatial and temporal resolution of the data set offers the ability to examine the influence of landuses, short-lived meteorological conditions, and seasonality on Denton's surface water resources. Having a large amount of data within multiple watersheds also offers the ability to compare the Hickory Creek watershed to the more urbanized Pecan and Cooper Creek systems and provides a comprehensive assessment of water quality conditions within Denton. Overall, the data will be very useful to guide future monitoring efforts and to generally assess modeling efforts. However the data are not sufficient to approximate pollutant loadings, mainly due to the lack of concurrently collected hydrologic data. Following the recommendations for obtaining pollutant-loading estimates for the entire watershed, as well as for targeted dBMPs assessments, should provide adequate data for the short and long term goals of this grant and the Hickory Creek Watershed Protection Plan.

6.0 Reference

Harmel, R.D; King, K.W.; and R.M Slade. 2003. Automated Storm Water Sampling on Small Watersheds. Applied Engineering in Agriculture 19(6): 667-674.

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FIGURE 1

Map of Hickory Creek showing sampling locations

Appendix C-3 Anticipated Pollutant Loading, Demonstration

BMP Sites

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Introduction

This section documents the calculations of non-point source (NPS) pollutant loads for the demonstration best management practice (BMP) sites. Load calculations were made for each of the sites under three conditions: pre-development, post-development, and post-development with BMPs. NPS loads were calculated using two methods: the Revised Universal Soil Loss Equation (RUSLE) to estimate sediment loads, and the Schueler “Simple Method” to estimate sediment, total nitrogen, and total phosphorus loads. Where the sediment load estimated using the Simple Method and the RUSLE did not agree, the results from the RUSLE method were adopted for use.

Revised Universal Soil Loss Equation (RUSLE)

The Revised Universal Soil Loss Equation (RUSLE) is defined as:

A = R * K * LS * C * P

where:

A = estimated average annual soil loss in tons per acre

R = rainfall-runoff erosivity factor

K = soil-erodibility factor

LS = topographic factor

C = cover-management factor

P = support practice factor A more detailed description of each variable in the RUSLE and how these variables were assigned or determined is presented below.

Rainfall-Runoff Erosivity Factor (R)

The Rainfall-Runoff Erositivity Factor (R factor) is an empirical value derived from several different sources. The literature indicates that when factors other than rainfall are held constant, soil losses from cultivated fields are directly proportional to a rainstorm parameter: total storm energy (E) * the maximum thirty-minute intensity (I). This parameter incorporates both raindrop impact and overland flow.

Isoderent maps covering the entire United States with R factor “contours” are available from the United States Department of Agriculture (USDA) and the Environmental Protection Agency (EPA). These maps must be visually interpolated to assign an R factor to the area of interest.

The area of interest is located within a hydrologic unit named Elm Fork Trinity, Hydrologic Unit Code (HUC) #12030103, which is halfway between the contours for an R factor of 250 and an R factor of 300. Thus, an R value of 275 was used.

Soil-Erodibility Factor (K)

The Soil-Erodibility Factor (K factor) describes the ease with which soil is detached by splash during rainfall or by surface flow or by a combination of both. It can also be thought

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of as the average long-term soil and soil-profile response to the erosive processes of rainstorms. These processes include soil detachment and transport by raindrop impact and surface flow, localized deposition due to topography and tillage-induced roughness, and rainwater infiltration into the soil profile. K is the rate of soil loss per rainfall erosion index unit as measured on a unit plot, which is 72.6 feet long with a 9 percent slope.

There are a few different soil series within the area of interest, thus different soil textures and K values. Because of this, each site had a different K value.

Topographic Factor (LS)

The effect of topography on erosion is measured in the topographic factor (LS factor). This value is calculated using the rill susceptibility, slope length, and slope incline, providing a ratio of soil loss on a given slope length and steepness to soil loss from a reference slope that has a length of 72.6 feet and a steepness of 9 percent, all other conditions being the same.

Slope Length Factor (L)

Erosion increases as slope length increases, and this is taken into account using the slope length factor (L factor). Slope length is defined as the horizontal distance from the origin of overland flow to the point where either (1) the slope gradient decreases enough that deposition begins, or (2) runoff becomes concentrated in a defined channel. Slope lengths, as well as steepness values, are typically estimated from topographic contour maps. In this study, contour maps were used to estimate the longest length of flow and the steepest possible elevation drop for the site. These values were then used in the calculations to provide the worst case scenario. The slope length is the horizontal projection of plot length, not the length measured along the slope.

An important factor to consider in the calculation of L is the ratio of rill erosion, caused by flow, to interrill erosion, caused mainly by raindrop impact. Land use is the main issue affecting the rill to interrill ratio. For example, for rangeland and pasture, the ratio of rill to interrill erosion is low. For cropland, the ratio of rill to interrill erosion is moderate. For construction sites, the ratio of rill to interrill erosion is high and the soil has a strong tendency to rill. For the purposes of this study, the project team assumed the rill to interrill ratio is moderate in the area of interest.

Slope Steepness Factor (S)

Slope steepness plays an even greater role in erosion than slope length. There are separate equations for slopes longer than 15 feet in length and slopes shorter than 15 feet. Slopes with steepness values of 9 percent or less are also calculated differently from those slopes having steepness values greater than 9 percent. Contour maps were used in this study to estimate the slope steepness for each individual site in the area of interest, thus this value is site specific.

Cover Management Factor (C)

The cover management (C factor) is the ratio of soil loss with specific cropping and management practices to the corresponding loss with up-slope and down-slope tillage and continuously fallow conditions. This factor includes the effects of cover, crop sequence,

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productivity level, length of growing season, tillage practices, residue management, and the expected time distribution of erosive rainstorms. The Natural Resources Conservation Service (NRCS) provides charts of C-factor values for various land uses. This value is not only site specific but also varies between pre and post-development conditions.

Support Practice Factor (P)

The support practice factor (P factor) is the ratio of soil loss with a specific support practice to the corresponding loss with up slope and down slope tillage and continually fallow conditions. These practices mainly affect erosion by modifying the flow pattern, grade, or direction of surface runoff and by reducing the amount and rate of runoff (Renard and Foster, 1985). For cultivated land, the support practices considered include contouring, strip cropping, terracing, and sub-surface drainage. On dry land or rangeland areas, soil-disturbing practices oriented on or near the contour that result in storage of moisture and reduction of runoff are also used as support practices.

The reduction in soil loss at a given slope is about 50 percent for the next more intensive practice. An overall P factor value is computed as a product of P subfactors for individual support practices (those mentioned above), which are typically used in combination. Factor values can be found on charts provided by the USDA, among other entities. In this study, however, few, if any, erosion reducing practices are used. Therefore, a P factor of 1.0 was used for each site representing practices that neither inhibit erosion nor encourage erosion.

Delivery Ratio

The edge of stream load is not always equal to the edge of field load because not all of the sediment created by upland erosion reaches the watershed outlet. Several processes occur within each site that prohibits the eroded material from reaching the watershed outlet. These processes include redeposition in surface water storage, trapping by vegetation and plant residues, and local scour and redeposition in rills and channels. Also, many factors inhibit the eroded material’s delivery to the watershed outlet, including climate, soil particle size and texture, size and proximity of the upland erosion source, the ratio of rill versus sheet erosion, total watershed area, watershed length and relief, and drainage density (the ratio of total stream length within the system divided by the area).

To determine the delivery ratio, a calculation can be performed using the area, relief, length and bifurcation ratio of the stream of interest, or it can be found on graphs provided by the USDA. These graphs show that as drainage area increases, the delivery ratio decreases. For this study, a delivery ratio of 0.3 was assumed. This is a fairly typical value for developed yet mostly pervious areas.

The RUSLE calculations for each of the sites in their developed and undeveloped stages are presented in Table 1.

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TABLE 1

RUSLE Coefficient Values LoadingCalcs.doc

Site Land Use Soil Series

Soil Erodibility

(K)

Rainfall and

Runoff (R)

Topography (LS)

Cover and Management

(C)

Support Practice

(P)

Segment Area

(acres)

Edge of Field Load (tons/yr)

Delivery Ratio (DR)

Edge of Stream Load

(tons/yr)

Lake Forest Park

Pre-Development

Birome 0.33 275 1.59 0.01 1 5.27 8 0.3 2

Lake Forest Park

Post-Development

Birome 0.33 275 1.59 0.09 1 5.27 68 0.3 20

Airport Pre-Development

Ponder 0.35 275 0.45 0.003 1 24.81 3 0.3 1

Airport Post-Development

Ponder 0.35 275 0.45 0.01 1 24.81 11 0.3 3

Fire Station No. 7

Pre-Development

Altoga 0.32 275 0.47 0.003 1 41.57 5 0.3 2

Fire Station No. 7

Post-Development

Altoga 0.32 275 0.47 0.01 1 66.86 28 0.3 8

5

Schueler’s “Simple Method”

Schueler’s Simple Method was also employed to calculate stormwater runoff pollutant loads. Input consists of the subwatershed drainage area and impervious cover percentages, stormwater runoff pollutant concentrations, and annual precipitation. The method enables the user to either break up land use into specific areas, such as residential, commercial, industrial, and roadway to calculate annual pollutant loads for each type of land, or to utilize more generalized pollutant values for land uses such as new suburban areas, older urban areas, central business districts, and highways.

The Simple Method estimates pollutant loads for chemical constituents as a product of annual runoff volume and pollutant concentration, and is defined by the following equation:

L = 0.226 * R * C * A

Where: L = Annual load (lbs) R = Annual runoff (inches) C = Pollutant concentration (mg/l) A = Area (acres) 0.226 = Unit conversion factor

To determine the value for R, the Simple Method calculates annual runoff as a product of annual runoff volume, and a runoff coefficient (Rv). Runoff volume is calculated as:

R = P * Pj * Rv

Where: R = Annual runoff (inches) P = Annual rainfall (inches) Pj = Fraction of annual rainfall events that produce runoff (usually 0.9) Rv = Runoff coefficient, based on the impervious cover in the subwatershed.

To determine the value of C, stormwater pollutant concentrations divided by land use can be estimated from local or regional data, or from national data sources. Numerous references are available for these values.

The Simple Method load calculations for each of the sites in their developed and undeveloped stages are presented in Table 2.

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TABLE 2

Simple Method Coefficient Values LoadingCalcs.doc

Annual Load

Site P Pj I (%) Rv R Csed Cphos Cnit A (acres)

Lsed (lb/yr)

Lsed (tons/yr)

Lp (lb/yr)

Ln (lb/yr)

Airport

Undeveloped 35 0.9 0 0.05 1.6 10 0.05 0.1 24.81 90 0.0 0.449 0.897

Developed 35 0.9 50 0.48 15.1 120 0.4 2.5 24.81 10,631 5.3 35.437 221.479

Fire Station No. 7

Undeveloped 35 0.9 2 0.068 2.1 10 0.05 0.1 41.57 197 0.1 0.986 1.973

Developed 35 0.9 36 0.374 11.8 75 0.2 2 66.86 13,373 6.7 35.660 356.604

Lake Forest Park

Undeveloped 35 0.9 0 0.05 1.6 10 0.05 0.1 5.27 19 0.0 0.095 0.191

Developed 35 0.9 5 0.1 3.2 50 0.1 2 5.27 191 0.1 0.381 7.623

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The difference between the sediment loading values estimated using the RUSLE method versus the Simple Method can be attributed to a number of things. First, the Simple method was developed more for urban areas, where the RUSLE method was developed more for non-urban areas. As the majority of the BMP sites are pervious areas, the RUSLE method seems more appropriate. Additionally, the RUSLE method incorporates soil type and texture, as well as local topography (slope and slope length, to be specific), which provides a more site-specific value. This is most important related to the Lake Forest Dog Park site as the area is relatively steep. Finally, obviously, the RUSLE provides a worst-case scenario relative to loading, which is almost always beneficial for planning purposes. It is for these reasons, that the project team chose the RUSLE values developed for sediment loading rather than the Simple Method. Relative to phosphorus and nitrogen, however, the project team believed the Simple Method to be the best available estimating tool. Table 3 presents the estimated pre and post-development loadings.

TABLE 3

Summary of RUSLE Loads

Edge of Edge of Selected

Field Ld. Stream Ld. Sediment

(tons/yr) (tons/yr) Load

Airport

Permanent Grass 3 1 1

Urban Areas 11 3 3

Fire Station No. 7


Urban Areas 28 8 8

Lake Forest Park


Parks 68 20 20

Proposed Best Management Practices

The following section is intended to provide more information regarding each of the proposed BMPs for each site.

Denton Airport

Enhanced Grass Swale

Enhanced swales are vegetated open channels designed to capture and treat the water quality volume for a given drainage area. The proposed design improves an existing drainage swale at the Airport. The drainage area to the existing swale is 8 acres in size. Impervious area covers 32% of the drainage area. The existing swale will be improved by

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expanding the cross section, leveling the slope, improving the vegetation, and adding a riprap basin at the inlet for erosion protection. The intent is to force the stormwater flow to be slow and shallow, thus allowing particulates to settle and limiting the effects of erosion.

Extended Detention Dry Basin

Dry detention basins are surface facilities intended to provide temporary storage and some water quality treatment through settling and infiltration, as well as reduction of runoff peaks. Standing water is not allowed at the Denton Airport to prevent the attraction of birds. Therefore it is necessary that the pond will drain in a relatively short period (less than 24 hours). For more effective water quality treatment, a portion of the dry detention pond will be developed as a bioretention area.

Runoff from an existing drainage system will be diverted into the pond. The pond will also capture local runoff from adjacent areas. The total drainage area to the pond will be approximately 17 acres. An outlet structure will be constructed with small weep holes that will detain small runoff events for settling and larger overflow weirs to release larger runoff events with some attenuation of the peak flow. The outlet structure discharges into Masch Branch. A riprap apron will be provided for erosion protection at the outfall.

Bioretention Area

Bioretention areas are designed to capture the water quality protection volume, the treatment volume required to remove a significant percentage of the storm water pollution load, from relatively small drainage areas using vegetation and infiltration through an engineered soil profile to remove pollutants. The proposed bioretention area at the Airport will be incorporated into the shallow detention pond. The pond outlet structure is constructed to provide a typical ponding depth of 6 inches to facilitate slow infiltration for the detained runoff volume of small storms. The overflow weirs are set to drain storage above the 6-inch level. The soil profile consists of a mulch layer, planting soil, pea gravel layer, and gravel layer. Perforated pipe is used to create an underdrain system in the lower gravel layer. The ponded water volume will slowly infiltrate the upper mulch and soil layers providing filtration and uptake of pollutants by the vegetation. Once the water reaches the lowest point of the gravel layer, it is collected in the underdrain and conveyed to Masch Branch. A flap gate will be installed on the outfall to prevent high flows in Masch Branch from backing up into the underdrain area.

Lake Forest Dog Park

Vegetated Filter Strips

Filter strips are uniformly graded and densely vegetated areas designed to treat stormwater runoff using vegetative filtering and infiltration. To be effective, flow must enter filter strips as shallow, sheet flow (typically only 1-2 inches in depth), and either travel slowly through the strip or pond behind a low berm in order to provide time for settling and infiltration. The intent of the filter strip at the Lake Forest Park is to treat runoff from the dog park prior to entering an existing pond. A strip of gravel is provided above the filter strip to intercept concentrated runoff and promote sheet flow through the filter strip. A low berm will be constructed to allow for ponding. Small outlets will be used to slowly release the ponded

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volume, promoting vegetative filtering and infiltration. An overflow channel is provided for runoff volumes in excess of the typical 8-inch ponding depth.

Denton Public Safety Training Facility

The Denton Public Safety Training Facility is expected to be developed in several phases. The first phase, currently under construction, includes Fire Station No. 7 with a surrounding road and parking areas. A conceptual BMP plan was prepared based on the City’s current master plan for the entire site. The post-development load calculations presented in this study are based on the expected ultimate development of the site.

Vegetated Filter Strips

The design for the Denton Public Safety Training Facility includes the use of vegetated filter strips. Initially, filter strips will be constructed to surround the Fire Station No. 7 development, which covers approximately 2 acres. The site is built on a slight rise with the runoff draining evenly in all directions. The filter strips will be built adjacent to the surrounding road. The strips will be built on a 2% slope away from the road and will be 50 feet wide. A gravel spreader will be incorporated to ensure sheet flow. Upon further development, vegetated filter strips should be constructed as appropriate. Based on the current master planning effort, the project team assumed approximately 50 percent of the ultimate site development will be treated by vegetated filter strips.

Extended Detention Dry Basin

A dry detention basin will be constructed in the Southern portion of the site to capture as much runoff as possible from the ultimate site development. As described above, dry detention basins are surface facilities intended to provide temporary storage and some water quality treatment through settling and infiltration. Although not intended primarily for runoff control, some reduction in peak flows may be provided. The total pre-development area draining to the pond site is 42 acres. When development of the site is completed, this is expected to become approximately 67 acres. However, due to uncertainty in the master plan, the proposed pond will initially be constructed with enough volume to treat approximate two-thirds of the development. Additional storage volume will need to be provided for future development at the site.

Within the basin, an outlet structure will be constructed such that small runoff events are retained for settling purposes and larger runoff events will be transported to the Branch Creek, the stream located directly to the south of the pond. A riprap apron will be provided for erosion protection at the outfall.

Table 4 provides the pollutant removal efficiencies for each of these BMPs as provided by the Design Manual for Site Development, written by the North Central Texas Council of Governments.

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TABLE 4

Contaminant Removal Efficiencies per BMP LoadingCalcs.doc

BMP Percent Removal Sediment

Percent Removal Phosphorus

Percent Removal Nitrogen

Detention 65% 50% 30%

Bioretention 80% 60% 50%

Filter Strip 50% 20% 20%

Grass Swale 80% 25% 40%

Table 5 provides the estimated contaminant removal associated with the BMPs described above.

TABLE 5

Summary of Loads

Simple Simple RUSLE Simple Simple

Site Lsed (lb/yr)

Lsed (ton/yr) L sed (ton/yr)

Lp (lb/yr) Ln (lb/yr)

Airport

Undeveloped 90 0.0 1 0.0 1

Developed 10631 5 3 35 221

With BMPs 1 19 133

Fire Station No. 7

Undeveloped 197 0.0 2 1 2

Developed 13373 7 8 36 357

With BMPs 3 25 274

Lake Forest Park

Undeveloped 19 0.0 2 0.0 0.0

Developed 191 0.0 20 0.0 8

With BMPs 10 0.0 6

Appendix C-4 Monitoring Results to Date, Demonstration BMP

Sites

1

Introduction

The following presents a comparison between monitoring data collected from the demonstration BMPs to date to removal efficiencies estimated during the planning phases of the project. Note these results are preliminary. At this time, the project team has collected monitoring data from relatively few storms. Additionally, too little time has passed for effective biological establishment to have occurred in the BMPs. In other words, the BMPs are only partially vegetated, currently; construction BMPs remain in place until the vegetation is well established.

Different storms produce different loading rates and different removal efficiencies, ranging from small storms that are completely captured, i.e. effectively removing 100% of the loading, to storms that produce runoff such that some must bypass the BMPs. The number of storm events with associated sampling events is too few to represent anywhere near the complete spectrum of possible loadings. Thus, the project team believes presenting comparisons of actual mass loadings extrapolated to an annual load to the annual loads estimated during the planning stages of this project would not be valid. However, the predicted annual loading rates were based on a percent reduction between the incoming pollutant load and the pollutant load leaving the BMP. Thus, the following tables present actual removal efficiencies as well as the weighted estimated removal efficiencies developed earlier in the project.

Denton Public Safety Training Facility/Fire Station No. 7

Eight storm events occurred at the Denton Public Safety Training Facility during the monitoring period. Four of these sampling events were successful; four were not. Unsuccessful sampling events occurred due to large storm events, which led to partial weir failure and runoff from adjacent areas, and sampling equipment malfunctions.

Table 1 presents removal efficiencies calculated from successful sampling events. Note actual removal efficiencies were well above estimated removal efficiencies. Removal efficiencies for nitrate and ammonia were between 57 and 100%, compared to an estimated 40.1% reduction of nitrogen. Removal efficiencies for phosphorus were between 95 and 100%, compared to an estimated 46% reduction. Finally, removal efficiencies for suspended solids were between 97 and 100%, compared to an estimated 83.55% removal.

EXHIBIT C4-1

Monitoring Results Thus Far: Denton Public Safety Training Facility/Fire Station No. 7, Successful Sampling Events

Date Rainfall (inches)

Inflow Volume

(gallons)

Outflow Volume

(gallons)

Nitrate Total Phosphorus

Total Suspended

Solids

Ammonia

Weighted Anticipated Reduction 40.1% 46% 83.55% 40.1%

3/4/2008 1.86 123,276 10,239 93% 99% 99% 94%

3/5/2008 0.26 21,833 none 100% 100% 100% 100%

4/17/2008 0.53 28,984 none 100% 100% 100% 100%

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EXHIBIT C4-1

Monitoring Results Thus Far: Denton Public Safety Training Facility/Fire Station No. 7, Successful Sampling Events


Inflow Volume

(gallons)

Outflow Volume

(gallons)


Total Suspended

Solids

Ammonia

4/24/2008 1.21 110,351 31,139 57% 95% 97% 78%

Table 2 presents actual removal efficiencies calculated based on unsuccessful sampling events. Three storms simply overwhelmed the equipment. A partial weir failure occurred during the March 10th storm, and the March 19th and May 28th storms contributed a great deal of “offsite” runoff. This data will help direct future sampling procedures related to larger storms.

EXHIBIT C4-2

Monitoring Results Thus Far: Denton Public Safety Training Facility/Fire Station No. 7, Unsuccessful Sampling Events


Inflow Volume

(gallons)

Outflow Volume

(gallons)


Total Suspended

Solids

Ammonia

Weighted Anticipated Reduction 40.1% 46% 83.55% 40.1%

3/10/20081 1.55 195,379 330,579 6% 79% 40% -37%

3/19/20082 2.01 41,877 121,077 -229% -73% 78% -633%

4/9/2008 0.79 not

sampled 31,227 N/A N/A N/A N/A

5/28/20082 2.73 184,403 381,126 -265% -153% N/A N/A

1. Partial Weir failure on this event.

2. The pond actually receives a substantial amount of runoff from areas that are not part of the “measured” vegetated swale system. This tends to happen more frequently during larger storm events, especially if soils are relatively moist. The inflow of a significant amount of unmeasured runoff through unchannelized overland flow is the reason why the outflow of the detention basin is substantially greater than the measured inflow volume for certain storms, and why output loads are sometimes greater than measured input loads.

Generally speaking, and considering the very limited data, the BMP seems to be performing as intended for the predominantly physical process of sediment removal; it also appears to be functioning reasonably well with regards to the chemical / biological processes (there are some physical processes as well) needed to reduce nitrate, total phosphorus, and ammonia. Over time, we expect the removal efficiencies to become more pronounced as biological processes become more firmly established.

Denton Airport

Five storm events occurred at the Denton Airport during the monitoring period. Table 3 presents removal efficiencies calculated based on actual sampling events. Note actual removal efficiencies, with the exception of one, were above estimated removal efficiencies.

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Removal efficiencies for nitrate and ammonia were between 37 and 91%, compared to an estimated 40% reduction of nitrogen. Removal efficiencies for phosphorus were between 59 and 93%, compared to an estimated 46% reduction. Finally, removal efficiencies for suspended solids were between 78 and 93%, compared to an estimated 75% removal.

EXHIBIT C4-3

Monitoring Results Thus Far: Denton Airport


Inflow Volume

(gallons)

Outflow Volume

(gallons)


Total Suspended

Solids

Ammonia

Weighted Anticipated Reduction 40% 45.556% 74.861% 40%

3/4/2008 1.67 105,973 Not

sampled N/A N/A N/A N/A

3/10/2008 1.41 384,223 142,324 37% 66% 78% 58%

3/19/2008 2.56 697,318 68,137 91% 93% 93% 89%

3/19/20081

347,127 79% 59% 86% 52%

4/17/2008 0.60 163,433 Not

sampled N/A N/A N/A N/A

5/28/2008 2.99 samp. failed

samp. failed N/A N/A N/A N/A

1. This is the piped overflow bypass. Flow occurs in this bypass for large storms, particularly if soils are saturated. Some treatment is derived from decreases in water velocities and settling that occurs in the detention area, but the water flowing out of this flow line does not pass into the bioretention area. During this rain event, water also flowed out of the spillway, which reflects the difference in water volume between inflow and the two measured outflows. The spillway water was unmetered and was not sampled.

Thus, generally speaking and considering the very limited data, the BMP seems to be performing as intended for each of the processes associated with nutrient and sediment removal. Over time, we expect the removal efficiencies to become more pronounced as biological processes become more firmly established.

Lake Forest Dog Park

Two storm events occurred at the Lake Forest Dog Park during the monitoring period. Table 4 presents removal efficiencies calculated based on actual sampling events. Note actual removal efficiencies were sometimes above and sometimes below the estimated removal efficiencies. Nitrate actually increased during the first storm event, and ammonia increased during the second, as did phosphorus. However, all other removal efficiencies were at or above the estimated removal efficiencies, e.g. the one storm event associated with solids removal illustrated a 92% removal efficiency as compared to the estimated 50%.

EXHIBIT C4-4

Monitoring Results Thus Far: Lake Forest Dog Park1


Fecal Coliform


Total Suspended Solids

Ammonia

Weighted Anticipated N/A 20% 20% 50% 20%

4

EXHIBIT C4-4

Monitoring Results Thus Far: Lake Forest Dog Park1


Fecal Coliform


Total Suspended Solids

Ammonia

Reduction

5/14/2008 NR 59% -200% 17% 92% 30%

5/28/2008 2.73 N/A2 26% -109% N/A -40%

1. Currently, samples collected at the Lake Forest Dog park are collected using time based methods instead of volume portioned sampling. Since no flow data were collected, there is no resulting hydrograph for these events. Without a hydrograph, time based sampling cannot be used to calculate loadings, so values were presented as concentrations of the time composited samples instead of loads per events.

2. The fecal coliform in the inflow sample were too numerous to count.

One potential reason for the increase in nutrient loading includes improper use of the BMP, e.g. pet owners could be allowing the dogs to defecate in the BMP itself. Additionally, park maintenance procedures should be reviewed. If the park staff members are, for example, allowing grass clippings to remain in the park, the biological processes occurring during the break down of those clippings could add to nutrient loading.

City of Denton

Watershed Protection

Addendum to the Hickory Creek Watershed Protection Plan

July 1, 2016

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Table of Contents

Table of Contents .......................................................................................................................................... 2

List of Figures ................................................................................................................................................ 3

Introduction and Statement of Purpose ....................................................................................................... 4

Background ................................................................................................................................................... 5

Rainfall Patterns for the Dallas-Fort Worth Metroplex and the City of Denton ........................................... 6

Flow monitoring activities and flow patterns ............................................................................................... 8

Historical Monitoring Information .............................................................................................................. 10

Water Quality Monitoring Data (2014-2016) ............................................................................................. 12

Water Quality Criteria ................................................................................................................................. 14

Data evaluation to establish screening values for total nitrogen, total suspended solids, and total

phosphorus for Hickory Creek Watershed Protection Plan. ....................................................................... 14

Summary of Water Quality Parameters for Monitoring ............................................................................. 16

Load Duration Curve Development ............................................................................................................ 17

Additional LDC and Load Related Monitoring and Model Development ............................................... 20

Adaptive Management and Uncertainty .................................................................................................... 21

Hickory Creek WPP Draft Proforma ............................................................................................................ 22

REFERENCES ................................................................................................................................................ 22

List of Figures

Figure 1 -- Hickory Creek ............................................................................................................................... 4

Figure 2 -- Rainfall patters for Dallas-Fort Worth Metroplex ....................................................................... 7

Figure 3 Annual Rainfall Patterns for City of Denton 1998-2016 ................................................................. 7

Figure 4 -- USGS Hickory Creek Station 1988-2016 ...................................................................................... 8

Figure 5 - Hickory Creek USGS Station 2008-2016 ........................................................................................ 9

Figure 6 - Clear Creek USGS Station 1951-2016 .......................................................................................... 10

Figure 7 -- Water Quality Monitoring Parameters ...................................................................................... 11

Figure 8 - Total Phosphorous Results (mg/L) - Hickory Creek at Country Club USGS Gaging Station ........ 12

Figure 9 - Total Ammonia Results (mg/L) - Hickory Creek at Country Club USGS Gaging Station .............. 12

Figure 10 - -Total Nitrate-Nitrogen Results (mg/L) - Hickory Creek at Country Club USGS Gaging Station 13

Figure 11 - Total Suspended Solids Results (mg/L) - Hickory Creek at Country Club USGS Gaging Station 13

Figure 12 - Water Quality Screening Levels for Selected Parameters (TCEQ, 2012; those with “*” derived

from analyses below) .................................................................................................................................. 14

Figure 13 - Flow Duration Curve Hickory Creek Gaging Station ................................................................. 18

Figure 14 - Hickory Creek Load Duration Curve Phosphorous .................................................................... 18

Figure 15 - Hickory Creek Load Duration Curve Total Nitrate, Nitrite and Ammonia ................................ 19

Figure 16 - -- Load Duration Curve for Total Suspended Solids .................................................................. 19

Figure 17 -- Proposed process for evaluation of WPP Load Reduction ...................................................... 22

Introduction and Statement of Purpose

The purpose of this document is to provide a framework for the Hickory Creek Watershed

Protection Plan to fully meet the requirements of the Nine Elements for Watershed Planning

established by the EPA. The Hickory Creek Watershed Protection Plan was established in the

absence of any water quality impairment as such there are some potential challenges with its

administration as opposed to the typical 9 element WPP process that is used to address 303d

listed Impairments and support the process of section 319 of the CWA.

Figure 1 -- Hickory Creek

This document introduces a strategy the will allow The City of Denton and its partners and

related stakeholders with the structure needed to move forward with plans for various types of

Best Management Practice Implementation while at the same type providing a certain degree of

regulatory flexibility to alter the plan and various related administrative processes as more and

more information is gathered about various metrics such as changes in load for the watershed

and related subbasins and performance of implemented BMPs.

Background

Hickory Creek is a predominantly rural watershed that is currently meeting designated uses,

but is under significant development pressures. Hickory Creek serves as a good example of

conditions in the larger Lake Lewisville Watershed and many places in the Dallas-Fort Worth

Metropolitan Area. More than one TCEQ water quality inventory has resulted in nutrient

concerns throughout the lake’s watershed. Sub-watershed level modeling and associated

research conducted during the development of the WPP indicates that future development

planned in the Hickory Creek Watershed will cause further degradation in water quality,

threaten designated uses, and possibly result in a future impaired water designation and

associated Total Maximum Daily Load (TMDL) implementation for Hickory Creek and/or

Lewisville Lake.

Based on modeling efforts, continued development within the watershed will result in

substantial increases in nonpoint source (NPS) loads. In the absence of action, loadings for total

phosphorus (TP), total nitrogen (TN), and sediments (as depicted by total suspended solids,

TSS) are expected to increase from the land surfaces in the Hickory Creek watershed, which will

negatively impact water quality in both Hickory Creek and Lewisville Lake. As development

continues in the larger Lake Lewisville watershed, similar impacts are expected.

Water Quality Goals: The overarching goal of the project is to ensure Segment 0823 continues

to support all associated designated uses, specifically related to nutrient and sediment loading.

Major Objectives: To directly address the goal, the project included the installation of 8 Best

Management Practices (BMPs), with BMP types depending on the size, cost, estimated pollutant

load reductions, and specific site conditions related to each BMP. The BMPs consisted of a

combination of natural treatment techniques with proven nutrient and sediment removal

abilities. Indirectly, code modifications and the initiation of project partner collaboration were

intended to support water quality protection for years to come.

This project had two original parallel and integrated tracks: (1) efforts focused on implementing

and advancing the Hickory Creek Watershed Protection Plan (WPP), completed in 2008, and (2)

activities designed to expand and adapt the analytical methods and policy frameworks

developed for Hickory Creek for broader geographic application within the Lewisville Lake

watershed.

The main project activities and objectives associated with the first project track are:

Continuing and extending the Denton stakeholder process initiated to support the development of the WPP and siting of best management practices (BMPs) to support the current project, including participation in siting additional BMPs and fostering understanding of and involvement in other aspects of implementing the Hickory Creek WPP.

Implementing the BMP site selection optimization and prioritization approach developed for the WPP by screening previously identified, top-ranked candidates and using stakeholder input to choose sites and particular BMPs that will deliver pollutant load reductions cost-effectively.

Further evaluate the recommended modifications to Denton’s local development codes including, but not limited to, environmentally sensitive areas (floodplain and riparian) and drainage identified in the WPP, which would formalize and strengthen nonpoint source pollutant reduction requirements and incentivize voluntary actions, and make recommendations for implementing the code modifications.

The main project activities associated with extending the nonpoint source management

framework developed for Hickory Creek for application to other areas in the Lewisville Lake

watershed are:

Inclusion of key water resources management agencies within the Lewisville Lake watershed as formal “project partners”. The partners will be offered additional opportunities to participate and provide input beyond the local stakeholder process identified previously.

A specific track dedicated to educating the partners about the Hickory Creek analytical process and results, identifying needs and applications for the partners’ existing programs, and designing a framework to tailor and transfer Hickory Creek WPP elements to support cost-effective nonpoint source control in other Lewisville Lake sub-watersheds.

Other public agency project partners include the Upper Trinity Regional Water District (UTRWD) and the North Texas Municipal Water District (NTMWD). These agencies provide staff and financial resources to support the project, specifically in providing information on existing programs and previous efforts related to watershed protection and in review of suggested methods to complete the goals of this project.

Rainfall Patterns for the Dallas-Fort Worth Metroplex and the City of

Denton

North Central Texas is approximately 250 miles (400 km) north of the Gulf of Mexico. It

includes the headwaters of the Trinity River, which lie in the upper margins of the Coastal

Plain. Elevation of the area's rolling hills range from 500 to 800 feet (150 to 240 m) above sea

level. The climate is humid-subtropical with hot summers. It is also continental, characterized

by a wide annual temperature range. Precipitation also varies considerably, ranging from less

than 20" to more than 50" per year.

Figure 2 -- Rainfall patters for Dallas-Fort Worth Metroplex

During approximately the last two decades North Central Texas and much of the Southeast

United States has experienced weather associated with more extremes such as extended

drought or periods of high rainfall and flooding (NOAA, 2009). Denton’s and surrounding

watersheds have had similar weather and climate as the overall metroplex. There is significant

variability with the occurrence of storms in the region but overall similarity in regional

climatology.

Figure 3 Annual Rainfall Patterns for City of Denton 1998-2016

0

10

20

30

40

50

60

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016

Denton, Texas Precipitation 1998-2016

Precip(in) Average Precipitation (38.36 in)

Flow monitoring activities and flow patterns

There are two main locations in the vicinity of the City of Denton where long-term flow data is

available from the United States Geological Survey (USGS): Hickory Creek (USGS 08082780)

and Clear Creek (USGS 08051500):

The Hickory Creek UGSG location is also the location for monitoring site #9 (Hickory Creek

road at Country Club road), one of the City of Denton’s Long-Term Dry Weather Screening

station. This site is approximately 3 miles upstream of one of the City of Denton’s Permanent

Monitoring Location #19 (Hickory Creek at Old Alton, Hickory Creek Lift Station). The

permanent monitoring sites have more extensive water quality information than standard

monitoring sites, including continuous monitoring data from deployed sondes. The USGS

flow monitoring station in Hickory Creek was originally established in 1985, and was closed in

1987. It was restarted in 2008, and has continued to the present (See figure 4).

Figure 4 -- USGS Hickory Creek Station 1988-2016

Data overlap of City of Denton Water Quality Monitoring data with USGS flow data for the

Hickory Creek station do not occur until 2008 with the reestablishment of the USGS station. It

should be noted that there are some extended drought periods where zero flow values occur.

Also, during the spring of 2015 unusually high rainfall and flooding occurred. Many entities

are still evaualuating what impact this large event will have on any long-term analysis of flow

patterns and design storms within local watersheds.

Figure 5 - Hickory Creek USGS Station 2008-2016

The USGS Clear Creek site has a longer uninterrupted data set beginning in beginning in March

1949 and continuing to the present. It is significantly downstream from the City of Denton’s

Permanent Monitoring Station Clear Creek at Bolivar. Although water quality data at the USGS

site at Clear Creek is sparse, the site does provide additional flow information that can be used

to support the goals of the Hickory Creek WPP. Development of decision support products will

be implemented using information from both USGS sites. The Clear Creek site is particularly

useful since the site’s data set includes the historic flooding that occurred in 1982 and the

historic drought of the 1950s. The City of Denton will use the Clear Creek site as a

complimentary location for analysis since it currently does not have similar development

patterns as Hickory Creek but it does have somewhat similar hydrology.

Figure 6 - Clear Creek USGS Station 1951-2016

Historical Monitoring Information

The City of Denton Watershed Protection Division has established a high resolution monitoring

network consisting of approximately 80 stations monitored on a monthly bases and continuous

monitoring locations throughout the watershed that monitor water quality, level and

precipitation (See http://www.cityofdenton.com). The program has been in place since 2001

and has generated a large amount of useful data. Water quality samples are collected as

frequently as every 30 minutes and include physical, chemical and biological measurements. In

addition the City has a monitoring location established in Clear Creek far northwest of the City

that can serve as a reference stream since this areas is currently not subject to many urban

influences. In the last few years the City has also added a real-time continuous chlorophyll

probe to it monitoring system downstream of Hickory Creek in Lake Lewisville.

Indicator Group Indicator Frequency of Sampling

(Sampling varies at locations)

Field Measurements Dissolved Oxygen, pH, Specific Conductance, Temperature, Total Depth, Turbidity

Monthly, Every 30 minutes at specific continuous monitoring sites

Biological, Microbiological

Chlorophyll a Every 30 minutes at specific continuous monitoring sites

Environmentally Sensitive Area Assessment Periodically

Fecal Coliform, E. Coli Monthly, Quarterly

Organics and Nutrients

Ammonia, Nitrate, Bimonthly, Quarterly, Periodically

Total Phosphorous, Orthophosphorous Bimonthly, Quarterly, Periodically

Pesticides Monthly During Growing Season, Quarterly during growing season

Metals

Aluminum, Arsenic, Cadmium, Chromium, Lead, Copper, Iron Bimonthly, Quarterly, Periodically

Manganese, Magnesium, Zinc Bimonthly, Quarterly, Periodically

Nickel, Silver Bimonthly, Quarterly, Periodically

Major Ions

Calcium, Chloride, Fluoride, Magnesium, Potassium, Sodium Bimonthly, Quarterly, Periodically

Sulfate Bimonthly, Quarterly, Periodically

Physical Properties

Alkalinity, Hardness, Solids, Turbidity, Bimonthly, Quarterly, Periodically

Rainfall, Level, Flow* 10-30 minute increments.(Flow from USGS stations. City working on additional sites)

Total Suspended Solids Bimonthly, Quarterly, Periodically

Figure 7 -- Water Quality Monitoring Parameters

Water Quality Monitoring Data (2014-2016)

Figure 8 - Total Phosphorous Results (mg/L) - Hickory Creek at Country Club USGS Gaging Station

Figure 9 - Total Ammonia Results (mg/L) - Hickory Creek at Country Club USGS Gaging Station

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Figure 10 - -Total Nitrate-Nitrogen Results (mg/L) - Hickory Creek at Country Club USGS Gaging Station

Figure 11 - Total Suspended Solids Results (mg/L) - Hickory Creek at Country Club USGS Gaging Station

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Water Quality Criteria

Since Hickory Creek is a non-impaired watershed the typical numeric criteria that would be

normally established as part of a TMDL process do not exist. Further, the state of Texas

currently does not have water quality standard for nutrients or sediments (the specific

pollutants of concern in the Hickory Creek watershed).

Current Water Quality Screening Criteria established by the TCEQ include Ammonia –Nitrogen

(NH3-N), Nitrate/Nitrite-Nitrogen (NO3-N), Orthophosphorous (OP), Total Phosphorus (TP)

and Chlorophyll a (Chla). Total Nitrogen (TN) and Total Suspended Solids (TSS) were

established via the analyses included below, which were reviewed by staff at the TCEQ and the

United States Environmental Protection Agency (USEPA). The general screening level for these

parameters are summarized in Figure 13.

Water Body Type Nutrients Screening level

Fresh Water Stream NH3-N 0.33 mg/L

NO3-N 1.95 mg/L

TN 1.60 mg/L*

OP 0.37 mg/L

TP 0.69 mg/L

TSS 50.0 mg/L*

Chla 14.1 ug/L Figure 12 - Water Quality Screening Levels for Selected Parameters (TCEQ, 2012; those with “*” derived from analyses below)

Screening value development process for selected pollutants in Hickory

Creek Watershed

Several sources of information were reviewed to provide a basis for establishing screening

values for total nitrogen, total phosphorus, and total suspended solids for use in the Hickory

Creek Watershed Protection Plan. These screening values will be used in a manner that is

similar to the numerical criteria (water quality parameter concentrations) established in the

Texas Surface Water Quality Standards. Overall, the screening values will provide a

quantitative basis for managing loadings in Hickory Creek by establishing maximum instream

concentrations that may result from point and nonpoint sources.

Total Nitrogen

Denton has collected samples from the lower portion of Hickory Creek approximately monthly for many years. These samples have not been analyzed for Total Nitrogen (TN), but have been analyzed for nitrate-nitrite and ammonia. Adding both of these parameters together, the 90th percentile concentration for samples collected in Hickory Creek is 1.44 mg/L, and the 95th percentile is 3.24 mg/L.

The 2012 Guidance for Assessing and Reporting Surface Water Quality (GARSW) in Texas (May, 2012), establishes a screening level for freshwater streams for nitrate-nitrite and ammonia combined at 2.28 mg/L.

In the National Rivers and Streams Assessment (NRSA) 2008–2009 Technical Report Draft for

the Southern Plains Ecosystem, Total Nitrogen is differentiated from “good-fair” to “fair-poor”

range differentiated at 1.60 mg/L.

Evaluation

Samples that Denton has collected at Hickory Creek have not been analyzed for TN, but have

been analyzed for nitrate-nitrite and ammonia. Adding both of these parameters together, the

90th percentile concentration for samples collected in Hickory Creek is 1.44 mg/L, and the 95th

percentile is 3.24 mg/L. Many of these samples have been collected under normal flow

conditions, although there are some samples that have been collected during storm flow

conditions. Since samples collected to date are reflective of nitrate-nitrite + ammonia, it is

unknown at this point whether organic nitrogen is a major component of the total nitrogen in

this stream. The proposed value of approximately 1.6 mg/l (derived from 1,570 ug/L) is above

the 90th percentile of the concentration of HC samples collected to date, but is substantially

below the 95th percentile value of 3.24 mg/L. With this in mind, Denton proposes to tentatively

adopt 1.6mg/L for total nitrogen as the draft screening value, with the understanding that this

value may need to be revisited as more information is collected regarding the TN

concentrations of Hickory Creek, as well as analyses examining the TN/TP ratio.

Total Phosphorus (TP)

The 2012 GARSW (May, 2012) lists the screening level TP in for freshwater streams as 0.69 mg/L.

The TP from the NRSA for Southern Plains ecosystem ranges from <0.052 to 0.095 mg/L, with the good-fair to fair-poor range differentiated at 0.052 mg/L. A simple average would indicate that the fair to poor range is around 0.073 mg/L.

The Ambient Water Quality Criteria Recommendations (December 2000), Ecoregion IX, sub-ecoregion 29, lists TP reference condition as a range from 0.0225 – 0.100 mg/L.

Denton’s Hickory Creek monitoring data for TP has the 90th percentile of 0.621 mg/L and the 95th percentile of 0.767 mg/L.

In this case, the GARSW value was proposed and approved, so the TP screening value did not change.

Evaluation

The proposed screening value of 0.69 mg/L, which is based on the TCEQ 2012 GARSW

screening value, appears appropriate.

Total Suspended Solids (TSS)

The RG-194 report entitled “Procedures to Implement the Texas, Surface Water Quality Standards” lists a TSS concentration for segment number 0823 (Lewisville Lake) of 6 mg/L. However, this is derived from reservoir samples taken within Lewisville Lake, and thus is not a value that can be compared to TSS values expected in streams.

Additional literature review was unsuccessful in finding a “reference” or “quality- based” concentrations for TSS in Texas.

The 85th percentile for Hickory Creek TSS is 42.9 mg/L., the 90th is 56.8 mg/L and the 95th percentile is 101.9 mg/L. A value of 50.0 mg/L is somewhere between the 85th and 90th percentile.

Figure 15 in the Hersh 2007 research entitled “An Integrated Stream Classification System for the State of Texas indicates this may be a reasonable “average” TSS for the region of Texas that includes Denton. However, when examining the data in the larger report that Hersh published with Maidment (CRWR Online Report 07-02: An Integrated Stream Classification System for Texas E.S. Hersh and D.R Maidment. 2007), it is notable that this average value has a substantial amount of variability, so this may need to be revisited as we gain more knowledge.

Summary of Water Quality Parameters for Monitoring

TN: 1.60 mg/L**

TP: 0.69 mg/L

TSS: 50.0 mg/L

**Note: at this time we are considering TN as the combination of Nitrogen from Ammonia-

Nitrogen and Nitrate-Nitrite Nitrogen. We will be monitoring Total Kjeldahl Nitrogen to

establish an understanding of the contribution of organic nitrogen.

Load Duration Curve Development

Load Duration Curve (LDC) analysis was performed for Hickory Creek site where the water

quality data have been collected and where the USGS station is located. The analysis results

currently indicate that Loads for the pollutants of concern (nutrients – Phosphates, Nitrate-

Nitrogen, Nitrate-Nitrogen, and Ammonia-Nitrogen, and Sediments) have not typically

exceeded screening criteria limits. However during the 2015 calendar year there were some

sampling events that were performed during record flooding in the month of May. These

abnormally high flows account for some exceedances that under typical high flow conditions.

Load duration have been have been utilized for the prediction of the occurrence of pollutants

and whether pollutants are coming from point and/or nonpoint sources. Duration curves

characterize the percent occurrence of flow rates over a long period of time (Bonta, 2002).

Discharge rates are typically sorted from the highest value to the lowest. Using this convention,

flow duration intervals are defined, which are expressed as a percentage with zero

corresponding to the highest stream discharge in the record (i.e. flood conditions) and 100 to the

lowest (i.e. drought conditions). Thus, a flow duration interval of eighty associated with a

stream discharge of “y” cubic feet per second (cfs) implies that eighty percent of all observed

stream discharge values are at or above “y” cfs (Cleland 2002).

The Load duration curve is first developed by creating a flow duration curve using historical

streamflow. Flow and load duration curves have been developed for Hickory Creek using

recent data. In addition, the City has collected weekly samples at the Hickory Creek gaging

station. The flow and load duration curves for Hickory creek are provided below. Load

duration graphs are produced by using flow and concentration data to provide an assessment

of daily load. The water quality criteria established and agreed upon by the City of Denton, the

TCEQ and the EPA are included in the load duration curves. The City will continue to develop

LDC for a number of parameters to further characterize the watershed and better understand

the processes that affect water quality.

Figure 13 - Flow Duration Curve Hickory Creek Gaging Station

Figure 14 - Hickory Creek Load Duration Curve Phosphorous

Figure 15 - Hickory Creek Load Duration Curve Total Nitrate, Nitrite and Ammonia

Figure 16 - -- Load Duration Curve for Total Suspended Solids

Additional LDC and Load Related Monitoring and Model Development

The City is in the process of beginning to develop load duration curves in other locations

around the City. The USGS Gaging station for Clear Creek is located north of Denton and

represents a large undeveloped watershed. Although there is development expected in this

watershed, the majority of this development is anticipated to be south and east (or downstream)

of the monitoring location. This watershed draining to this station is roughly similar in size to

Hickory Creek, and may have a similar hydrologic response. As such, the Clear Creek

watershed may be able to serve as a stable metric to assess changes in the Hickory Creek

Watershed.

Additional work

The City is currently working with the USGS to develop additional flow monitoring sites where

a rating curve and level to flow relationship has been established. This will allow the City to

monitor and evaluate additional locations within the Hickory Creek and elsewhere in

watersheds affected by development in and around the City of Denton.

Adaptive Management and Uncertainty Successful implementation of the Hickory Creek Watershed Protection Plan will require careful

consideration of the various social, economic and political issues that are a part of the WPP.

Changes continue to occur rapidly within the watershed, and it is important to adaptively

respond to these changes as they occur. The WPP should therefore continue to be implemented

using an adaptive management approach. In this context, adaptive management is an iterative

process of implementation, evaluation, and course correction, which could be described as

“learning by doing”, and “adapting based on what’s learned”. Adaptive management is

necessary, given uncertainties associated with predicting the effectiveness of management

measures, as well as time scales and ultimate interactions between BMP implementation

activities and changes in stream loads.

Additionally, the City of Denton understands the importance of incorporating the variability of

environmental processes into Watershed Modeling activities, especially since the outputs of

watershed models will directly support and affect decisions. The basic approach used to

evaluate and adapt the WPP is, as follows:

• Conduct literature and data reviews and establish screening values for TN, TP, and TSS.

• Derive Flow duration curves for Hickory Creek using USGS Gaging station information.

• Translate screening value concentrations into loads using flow duration curve to

produce load duration curves.

• Use SWAT landuse based loadings factors from the Hickory Creek WPP in the EPA

STEPL model (or other appropriate model).

• Monitor nitrate-nitrite and ammonia (TN surrogate), TP and TSS for Hickory Creek at

the established monitoring point (USGS Gaging station). Other potential pollutants will be

evaluated during this process.

• Use STEPL (or other appropriate model) to evaluate loads from landuse changes and

load reductions via BMPs on a project-specific basis as development occurs. Installed BMP load

reductions (via model) will be documented. Staff will attempt to also obtain BMP cost data.

• A new SWAT model will be built for Hickory Creek, and landuse change data will be

entered on a yearly basis. Landuse change data will be obtained from the Denton Planning /

GIS department, with additional information from Denton County Central Appraisal district.

• A proforma will be created which summarizes actual yearly landuse changes and

associated (model-derived) load increases without BMPs, load increases with BMPs, as well as

estimated instream load increases w/o BMPs, and instream load increases with BMPs. The

same information will be projected forward for five years in the proforma under assumptions of

growth and development, and will also be used to populate a 20 year projection. All projections

will be updated yearly. Cost information will be used to assess BMP efficiencies.

• Instream load and concentration data from monitoring will be examined using trend

analyses. The goal is to have a stable or decreasing trend through time.

An example of the proforma is provided below.

Hickory Creek WPP Draft Proforma

Hickory Creek Watershed Protection Plan

Draft Proforma, 08.20.14

14-15 14-15 15-16 16-17 17-18 18-19 19-20

(Loads in pounds) Estimate2

Actual

Modeled 1 Estimate2 Projected2 Projected2 Projected2 Projected2

Load increases via landuse w/o

BMPs

Load increases with BMPs

In stream load increase w/o BMPs

In stream load increase BMPs

Costs for BMPs3

BMP efficiency TSS4

BMP efficiency TP4

BMP efficiency TN4

1. Actual modeled is the model estimates at year end of loadings from actual landuse changes, load reductions from implemented BMPs, and

resulting estimates of stream loading using meteorological conditions of the year

2. Estimates and projections will use estimates of future growth and future BMP load reductions to estimate loads, load reductions, and stream

loadings using average meteorological conditions

3. Costs for BMPS will be added as available, and may not fall within the exact timing of the rest of the proforma actual, estimated, and projected

data. Costs for BMPs should include complete installation costs (based on comments from EPA staff).

4. Defined as dollars spent per pound of

contaminant reduced

Figure 17 -- Proposed process for evaluation of WPP Load Reduction

REFERENCES

Berg, Matthew, Mark McFarland, Nikki Dictson, Plum Creek Watershed Protection

Plan, Texas Agrilife Extension Service, Plum Creek Watershed Partnership,0020 Texas

AgriLife Extension Service, 2474 TAMU, College Station, Texas 77843-2474, 2008

Bonta, James V, Framework for Estimating TMDLs with Minimal Data, Pp. 6-12 in Total

Maximum Daily Load (TMDL) Environmental Regulations: Proceedings of the March

11-13, 2002 Conference, (Fort Worth, Texas, USA) Publication Date March 11, 2002.

ASAE Publication Number 701P0102, ed. Ali Saleh.

Cleland, Bruce TMDL Development from the “Bottom Up” PART IV: CONNECTING

TO STORM WATER MANAGEMENT PROGRAMS. U. S. Environmental Protection

Agency. Conference Proceedings: Presented at Water Environment Federation TMDL

2007 Conference, Bellvue, WA June 24-27, 2007

Coffey, S.W. , Spooner, J., and M.D. Smolen. 1993. The non-point source manager’s guide

to water quality and land treatment monitoring. NCSU Water Quality Group, Department

of Biological and Agricultural Engineering, North Carolina State University, Raleigh,

North Carolina.

DeSilets, L.; Golden, B.; Wang, Q.; and R. Kumar. 1992. Predicting Salinity in the

Chesapeake Bay Using Backpropagation. Computer Ops. Res. 19(3/4):277-285.

Dilks, David W. and James F. Pendergast, Comparison of Dynamic and Steady-State

Models for Determining Water Quality BasedNational Pollutant Discharge Elimination

System Limits for Toxicsand Source: Water Environment Research, Vol. 72, No. 2 (Mar.

- Apr., 2000), pp. 225-229

Engdahl, J. 1999. Impacts of Residential Construction on Water Quality and Quantity

in Connecticut. University of Connecticut. Storrs, CT.

Green, R.H. 1979. Sampling design and statistical methods for environmental biologists.

Wiley and Sons Publishing, New York, New York, USA.

Nevada Division of Environmental Protection, 2003 Load Duration Curve Methodology

for Assessment and TMDL Development. http://

ndep.nv.gov/bwqp/file/LOADCURV.PDF

NOAA, Dallas/Fort Worth Climate Overview, 2009 National Weather Service,

Dallas/Fort Worth Forecast Office, Fort Worth, TX 76137

Spooner, J.; Maas, R.P.; Dressing, S.A.; Smolen, M.D.; and F.J. Humenik. 1985.

Appropriate Designs for Documenting Water Quality Improvements from Agricultural

NPS Control Programs. In Perspectives on Nonpoint Source Pollution. Proceedings of

National Conference, May 19-22, Kansas City, Missouri. EPA 440/5-85-001.

Washington, D.C.

Spooner, J.; Jamieson, R.P.; Maas, R.P.; Dressing, S.A.; Smolen, M.D.; and F.J. Humenik.

1986. Rural Clean Water Program Status Report on the CM&E projects 1985 –

Supplemental Report: Analysis Methods. Biological and Agricultural Engineering

Department, North Carolina State University, Raleigh, North Carolina.

Streckner, E., 1994. Constituents and Methods for Assessing BMPs. Proceedings of the

Engineering Foundation Conference on Stormwater Related Monitoring Needs. August

7-12, Crested Butte, CO. ASCE.

Streckner, E.; Quigley, M.M.; and B.R. Urbonas. 2000. Determining Urban Stormwater

BMP Effectiveness. In the proceedings of the National Conference on Tools for Urban

Water Resource Protection. February 7-10, 2000. Chicago, IL. USA.

TNRCC. 1999. State of Texas 1999 Clean Water Act Section 303(d) List and Schedule

for Development of Total Maximum Daily Loads. SFR-58/99. Prepared by the Strategic

Development Division, TNRCC, Austin Texas.

USEPA. 1995. Watershed Protection: A Project Focus. EPA/841/R-95/003. United

States Environmental Protection Agency, Washington, D.C.

USEPA. 1996. Guidance for Data Quality Assessment: Practical Methods for Data

Analysis QA96 Version. United States Environmental Protection Agency, Office of

Research and Development, Washington, D.C. 20460. EPA/600/R-96/084.

USEPA, 2008, Handbook for Developing Watershed Plans to Restore and Protect Our

Waters, United States Environmental Protection Agency, Office of Water, Nonpoint

Source Control Branch, Washington, DC 20460, EPA 841-B-08-002

Watershed Analysis Risk Management Framework: Update One: A Decision Support

System for Watershed Analysis and TMDL Calculation, Allocation, and

Implementation. EPRI, Palo Alto, CA: 2001, 1005181

http://www.epa.gov/athens/wwqtsc/html/warmf.html.

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