engineering report for the phase 5b project—salmon · pdf filewastewater management...

D I S C O V E R Y C L E A N W A T E R A L L I A N C E

Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements Phase 5 Expansion Program

An Alliance Capital Project delivered by Clark Regional Wastewater District as Administrative Lead for the Discovery Clean Water Alliance

Prepared for

Washington State Department of Ecology October 2017

2020 SW Fourth Avenue, 3rd Floor Portland, Oregon 97201

DISCOVERY CLEAN WATER ALL IANCE

Engineering Report for the Phase SB Project-Salmon Creek Treatment Plant Improvements Phase 5 Expansion Program

() C T 1 D, 2 o If

An Alliance Capital Project delivered by Clark Regiona l Wastewater District as

Administrative Lead for the Discovery Clean Water Alliance

Prepared for

Washington State Department of Ecology

October 2017

2020 SW Fourth Avenue, 3'd Floor Portland, Oregon 97201

III

Contents Section Page

Acronyms and Abbreviations .............................................................................................................. vii

1 Introduction ......................................................................................................................... 1-1

2 Owner and Authorized Representative ................................................................................. 2-1

3 Project Description and Location .......................................................................................... 3-1

4 Treatment Plant Influent Flows and Loads Analysis .............................................................. 4-1 4.1 Current Flows and Loads .................................................................................................. 4-1 4.2 Projected Flows and Loads .............................................................................................. 4-2 4.3 Plant Recycle and Additional Flows ................................................................................. 4-3

4.3.1 Return Activated Sludge Flow ............................................................................. 4-3 4.3.2 Imported Wasted Activated Sludge Flow ........................................................... 4-3

5 Plant Hydraulics .................................................................................................................... 5-1

6 Unit Process Capacity Analysis .............................................................................................. 6-1 6.1 Preliminary Treatment ..................................................................................................... 6-1

6.1.1 System overview and current performance ....................................................... 6-1 6.1.2 Projected Performance ....................................................................................... 6-1

6.2 Primary Treatment ........................................................................................................... 6-2 6.2.1 System Overview and Current Performance ...................................................... 6-2 6.2.2 Projected Performance ....................................................................................... 6-3 6.2.3 Redundancy Requirements ................................................................................. 6-4

6.3 Aeration Basins ................................................................................................................ 6-4 6.3.1 System Overview and Current Performance ...................................................... 6-4 6.3.2 Projected Performance ....................................................................................... 6-5 6.3.3 Redundancy Requirements ................................................................................. 6-6

6.4 Secondary Clarifiers ......................................................................................................... 6-6 6.4.1 System Overview and Current Performance ...................................................... 6-6 6.4.2 Projected Performance ....................................................................................... 6-7 6.4.3 Redundancy Requirements ................................................................................. 6-8 6.4.4 Hypochlorite Dosing Station for RAS Chlorination ............................................. 6-8

6.5 Disinfection .................................................................................................................... 6-10 6.5.1 System Overview and Current Performance .................................................... 6-10 6.5.2 Projected Performance ..................................................................................... 6-10 6.5.3 Redundancy Requirements ............................................................................... 6-10

6.6 Effluent Pump Station .................................................................................................... 6-11 6.6.1 System Overview and Current Performance .................................................... 6-11 6.6.2 Projected Performance ..................................................................................... 6-11 6.6.3 Redundancy Requirements ............................................................................... 6-11 6.6.4 Effluent Pump Modifications ............................................................................ 6-11

6.7 Waste Activated Sludge Thickening ............................................................................... 6-14 6.7.1 System Overview and Current Performance .................................................... 6-14 6.7.2 Projected Performance ..................................................................................... 6-14 6.7.3 Redundancy Requirements ............................................................................... 6-14

6.8 Anaerobic Digestion ....................................................................................................... 6-14 6.8.1 System Overview and Current Performance .................................................... 6-14

CONTENTS

Section Page

IV

6.8.2 Projected Performance ..................................................................................... 6-15 6.8.3 Redundancy Requirements ............................................................................... 6-15

6.9 Digested Biosolids Dewatering ...................................................................................... 6-15 6.9.1 System Overview and Current Performance .................................................... 6-15 6.9.2 Projected Performance ..................................................................................... 6-15 6.9.3 Redundancy Requirements ............................................................................... 6-16

6.10 Summary of Unit Process Capacities ............................................................................. 6-16

7 Air Quality and Odor Control ................................................................................................ 7-1 7.1 Regulatory Context and Requirements............................................................................ 7-1

7.1.1 Nuisance Odors ................................................................................................... 7-1 7.1.2 Toxic Air Pollutants ............................................................................................. 7-1 7.1.3 Odor Criteria Requirements ................................................................................ 7-1

7.2 Odor Control .................................................................................................................... 7-1 7.2.1 Overview and Current Performance ................................................................... 7-1 7.2.2 Alternative Analysis and Projected Performance ............................................... 7-2 7.2.3 Recommended Alternative ................................................................................. 7-6

8 Selected Alternative Description ........................................................................................... 8-1

9 Preliminary Cost Estimate ..................................................................................................... 9-1

10 Project Funding .................................................................................................................. 10-1

11 Staffing Requirements ........................................................................................................ 11-1

12 Environmental Impacts ....................................................................................................... 12-1

13 Project Schedule ................................................................................................................. 13-1

14 Permitting and Regulations ................................................................................................ 14-1

15 Supplemental Information .................................................................................................. 15-1

16 References .......................................................................................................................... 16-1

Appendixes

Appendix A—SCTP Flow Diagram

Appendix B—Projected Mass Balance for the SCTP

Appendix C—Salmon Creek Treatment Plant Phase 4 Odor Control Update

Appendix D—Tier II Antidegradation Analysis

Tables

4-1 Annual Influent Flows and Loads .................................................................................................. 4-1

4-2 Maximum Month to Annual Average Flow and Load Peaking Factors ......................................... 4-2

4-3 Project Flows and Loads ............................................................................................................... 4-2

6-1 Aeration Basin Dimensions ........................................................................................................... 6-4

6-2 Operational Parameter for the Secondary Treatment at 17 mgd ADMM .................................... 6-6

CONTENTS

Page

V

6-3 RAS Chlorination Design Criteria ................................................................................................... 6-9

6-4 Design Peak-hour Flow by Phase ................................................................................................ 6-11

6-5 Peak-hour Flow Data ................................................................................................................... 6-12

6-6 Operational Parameters for the SCTP at 17 mgd ADMM ........................................................... 6-18

7-1 Bio-trickling Filter Approach, 1-Hour Peak Average H2S Concentrations at Sensitive Receptors ...................................................................................................................................... 7-5

7-2 Bio-trickling Filter Design Criteria ................................................................................................. 7-6

9-1 Project Costs ................................................................................................................................. 9-1

15-1 Requirements for Engineering Reports ...................................................................................... 15-1

Figures

1-1 Salmon Creek Treatment Plant Design Capacity versus Projected Demand for Influent Flow ................................................................................................................................. 1-1

1-2 Salmon Creek Treatment Plant Design Capacity versus Projected Demand for Influent Loading .......................................................................................................................................... 1-2

5-1 Hydraulic Profile ............................................................................................................................ 5-3

6-1 Screens Rebuilt in 2017 ................................................................................................................. 6-2

6-2 BOD5 Percentage Removal versus Primary Clarifier SOR .............................................................. 6-3

6-3 MLSS Concentration and SVI Over Time ....................................................................................... 6-5

6-4 Effluent TSS versus SVI .................................................................................................................. 6-7

6-5 Effluent TSS versus Secondary Clarifier SOR ................................................................................. 6-8

6-6 Skid-mounted Hypochlorite Pump System, from ProMinent Fluid Controls LTD ....................... 6-10

6-7 Existing Pump Curves at 100% Speed and System Curve ........................................................... 6-13

6-8 Existing Pump Curves at 108% Speed and System Curve ........................................................... 6-13

6-9 Unit Process Capacity Summary ................................................................................................. 6-17

7-1 Simplified Schematic Diagram of a Bio-trickling Filter System ..................................................... 7-3

7-2 Isopleths Showing Lines of Constant H2S Concentration in mg/m3 —1-Hour Annual Peak, Bio-trickling Filter Approach ......................................................................................................... 7-4

7-3 Isopleths Showing Lines of Constant Odor Concentration in D/T—1-Hour Annual Peak, Bio-trickling Filter Approach ......................................................................................................... 7-5

7-4 Covered Primary Clarifiers ............................................................................................................ 7-6

7-5 Preliminary Layout of Odor Control System ................................................................................. 7-9

13-1 Preliminary Schedule for Phase 5B Project ................................................................................. 13-2

VII

Acronyms and Abbreviations °C degrees Celsius

AA annual average

AAF average-annual flow

ADMM average-day maximum month

Alliance Discovery Clean Water Alliance

ASIL Acceptable Source Impact Level

BFP belt filter press

BOD biochemical oxygen demand

BOD5 5-day biochemical oxygen demand

DNS determination of non-significance

DO dissolved oxygen

D/T dilutions-to-threshold

Ecology State of Washington Department of Ecology

EPA U.S. Environmental Protection Agency

F/M food to microorganisms

fpm feet per minute

GBT gravity belt thickener

gpd/ft2 gallons per day per square foot

gpm/m gallons per minute per meter

H2S hydrogen sulfide

hp horsepower

lb/ft3 pound per cubic foot

lb/hr/m pounds per hour per meter

MG million gallons

mgd million gallons per day

mg/L milligrams per liter

mg/m3 milligrams per cubic meter

mg/m3/ppbV milligrams per cubic meter per parts per billion volume

mL/g milliliter per gram

MLSS mixed liquor suspended solids

MLVSS mixed liquor volatile suspended solids

MMF maximum-month flow

MMWW maximum month wet weather

ACRONYMS AND ABBREVIATIONS

VIII

NA not applicable

NH3-N ammonia-nitrogen

NPDES National Pollutant Discharge Elimination System

O&M operations and maintenance

ORS organic reduced sulfur

P.E. Professional Engineer

PHF peak-hour flow

ppd pounds per day

R&R repair and replacement

RAS return activated sludge

RCW Revised Code of Washington

rpm revolutions per minute

scfm standard cubic feet per minute

SCTP Salmon Creek Treatment Plant

SEPA State Environmental Policy Act

SOR surface overflow rate

SRT solids retention time

SVI sludge volume index

SWCAA Southwest Washington Clean Air Agency

TKN total Kjeldahl nitrogen

TSS total suspended solids

UV ultraviolet

VS volatile solids

WAC Washington Administrative Code

WAS waste activated sludge

WEF Water Environment Federation

WWTP wastewater treatment plant

SECTION 1

1-1

Introduction The Discovery Clean Water Alliance (Alliance) legally formed on January 4, 2013, representing the culmination of several years of evaluation to determine the optimum long-term framework for delivery of regional wastewater transmission and treatment services to the urban growth areas in the central portion of Clark County, Washington. The Alliance serves four Member agencies: City of Battle Ground, Clark County, Clark Regional Wastewater District, and the City of Ridgefield. The Members jointly own and jointly manage regional wastewater assets under Alliance ownership through an interlocal framework established under the State of Washington Joint Municipal Utility Services Act (Revised Code of Washington [RCW] Chapter 39.106).

The Alliance is responsible for managing the capacity of its assets. The Salmon Creek Treatment Plant (SCTP) is the Alliance’s primary regional asset. The State of Washington Department of Ecology (Ecology) requires the Alliance to submit a plan and schedule maintaining adequate capacity in its treatment facilities when one of the following two conditions is met:

• Actual flow or actual waste load reaches 85 percent of the rated capacity of the facility for 3 consecutive months, or

• Projected flow or projected waste load will reach the design capacity of the facility within 5 years

SCTP capacity has been assessed relative to these criteria for both flow and waste load. Phase 3 and Phase 4 projects have been completed previously at the facility. The assessment identified the need for the Alliance to pursue the Phase 5 Expansion Program concepts established in the Salmon Creek Wastewater Management System Wastewater Facilities Plan/General Sewer Plan Amendment (Facilities Plan) (CH2M, 2013), approved by Ecology in a letter dated September 4, 2013. Flow and load trends are depicted in Figures 1-1 and 1-2, respectively.

Figure 1-1. Salmon Creek Treatment Plant Design Capacity versus Projected Demand for Influent Flow

Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements (mgd = million gallons per day)

SECTION 1 – INTRODUCTION

1-2

Figure 1-2. Salmon Creek Treatment Plant Design Capacity versus Projected Demand for Influent Loading

Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements (BOD = 5-day biochemical oxygen demand; ppd = pounds per day; TSS = total suspended solids)

The Phase 5 Expansion Program consists of two separate elements:

• Phase 5A Project—Columbia River Outfall and Effluent Pipeline project constructs a new effluent pipeline and outfall to address long-term system hydraulic capacity and diffuser performance. This project is required to address aging infrastructure and support future expansion phases of SCTP.

• Phase 5B Project—Salmon Creek Treatment Plant Improvements addresses facility loading and treatment capacity with an updated process and hydraulic analysis, and facility improvements. This project is required to address shorter-term capacity needs related to flow and organic loading on the facility.

While both occur under the overall Phase 5 Expansion Program, the Phase 5A Project is distinctly separate from Phase 5B Project. The Phase 5B Project results in an increased treatment and discharge capacity while the Phase 5A Project supports future phases of expansion. The projects are functionally independent. Each project can be executed independently for its intended purpose.

This report presents the Phase 5B Project, including an overview of existing conditions and updated capacity analysis of the treatment plant. This report also documents air quality regulatory requirements and associated odor control features and describes the proposed alternative to maintain adequate treatment capacity. A separate engineering report will be developed for the Phase 5A Project.

SECTION 2

2-1

Owner and Authorized Representative The Owner of the SCTP is the Alliance. The Owner's authorized representative for this facility is John Peterson. His contact information is as follows:

John M. Peterson, P.E. General Manager Clark Regional Wastewater District (Administrative Lead for Discovery Clean Water Alliance) 8000 NE 52nd Court P.O. Box 8979 Vancouver, Washington 98668 Telephone: 360-993-8819

SECTION 3

3-1

Project Description and Location The project proposed in this report addresses influent flow and waste load trends, which indicate capacity at the SCTP may be reached by approximately 2023–2024. The project seeks recognition of the existing embedded secondary treatment capacity through a formal re-rating process. The project involves updating the capacity of the SCTP to accommodate an incremental 5-day biochemical oxygen demand (BOD5)/total suspended solids (TSS) capacity increase and corresponding flow increase from 14.95 to 17.0 mgd. The project includes odor control improvements consisting of covering the primary clarifiers and constructing a new odor control system that will treat air from the preliminary treatment facility (headworks) and the primary treatment facility (primary clarifiers). The project also includes a revision to control of the effluent pump station to accommodate updated flows. The SCTP is located at 15100 Northwest McCann Road in Vancouver, Washington.

SECTION 4

4-1

Treatment Plant Influent Flows and Loads Analysis This section analyzes current and projected SCTP influent flows and loads and discusses plant recycle and additional flows.

4.1 Current Flows and Loads CH2M conducted a review of historical flows and loads to determine if and how the loading to the facility has changed as compared to those used in the Facilities Plan (CH2M, 2013). Historical plant data from January 2011 to June 2017 were obtained from plant staff. Table 4-1 summarizes the annual average influent flows and loads from 2011 through June 2017.

Table 4-1. Annual Influent Flows and Loads Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Year Flow (mgd)

BOD5 (ppd)

TSS (ppd)

NH3-N (ppd)

Minimum 30-day Average

Temperature (°C)

2011 7.30 14,885 15,303 2,031 14.1

2012 7.55 15,531 17,093 2,191 14.1

2013 7.03 15,899 16,724 2,087 14.6

2014 7.33 16,434 18,988 2,206 14.4

2015 7.29 16,295 19,179 2,220 15.7

2016 7.84 16,863 19,358 2,282 14.3

2017 (January - June) 9.25 18,818 21,990 - 14.7

Average 7.58 16,441 18,599 2,174 14.6

NH3-N = ammonia-nitrogen.

It should be noted that the effluent temperature data from 2010 to 2015 indicate that the minimum 30-day average effluent temperature was 14.0 degrees Celsius (°C).

Maximum month to annual average flow and load peaking factors from 2011 through 2017 are presented in Table 4-2. The design peaking factors for the flow and loads presented in Table 4-2 correspond to 95th percent level of occurrence. The 95th percentile was chosen based on Section 5.5.4 of the U.S. Environmental Protection Agency (EPA) document Technical Support Document for Water Quality-Based Toxics Control (1991) where it states that the average monthly limit (i.e., maximum month) should be based on the 95th percentile level.

SECTION 4 – TREATMENT PLANT INFLUENT FLOWS AND LOADS ANALYSIS

4-2

Table 4-2. Maximum Month to Annual Average Flow and Load Peaking Factors Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Year Flow (mgd)

BOD5 (ppd)

TSS (ppd)

NH3-N

(ppd)

2011 1.29 1.11 1.21 1.24

2012 1.26 1.13 1.15 1.26

2013 1.32 1.09 1.11 1.13

2014 1.24 1.12 1.24 1.11

2015 1.49 1.13 1.20 1.12

2016 1.41 1.20 1.24 1.13

2017 1.18 1.11 1.13 -

Average 1.32

Design (95th Percentile) 1.46 1.18 1.24 1.26

A 2.5 peaking factor (value recommended by Ecology in Criteria for Sewage Works Design [2008]) was used to calculate the peak-hour flow.

4.2 Projected Flows and Loads The average flows and loads presented in Table 4-1 were used to calculate the BOD5, TSS, and NH3-N annual average concentrations. The flow design peaking factors listed in Table 4-2 were used to calculate the annual average flow associated with an average-day maximum month (ADMM) flow of 17 mgd. The annual average concentrations and average flow were used to calculate the projected annual average BOD5, TSS, and NH3-N loads. Then the projected annual average loads were multiplied by the design load peaking factors to calculate the projected ADMM loads used for this evaluation. Table 4-3 presents the projected flows and loads associated with an ADMM of 17 mgd.

Table 4-3. Project Flows and Loads Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements (Unit processes capacity evaluation projected flows and loads* at ADMM = 17 mgd) Item Value

Annual Average (AA), mgd 12.9

ADMM, mgd 17.0

Peak Hour, mgd 32.2

5-day Biochemical Oxygen Demand (BOD5), pounds per day (ppd) 29,800

Total Suspended Solids (TSS), ppd 34,700

% Volatile Solids (VS) 92%

Ammonia-Nitrogen (NH3-N), ppd 4,224

Alkalinity – lb-CaCO3/d 29,100

*The projected loads were calculated using SCTP historical data from January 2011 to June 2017.

SECTION 4 – TREATMENT PLANT INFLUENT FLOWS AND LOADS ANALYSIS

4-3

4.3 Plant Recycle and Additional Flows 4.3.1 Return Activated Sludge Flow Historical data from January 2014 to June 2017 show that the return activated sludge (RAS) rate is maintained between 45 to 60 percent of the plant influent flow with an average of 52 percent of the influent flow.

4.3.2 Imported Wasted Activated Sludge Flow Currently, the SCTP is treating additional waste activated sludge (WAS) from the City of Ridgefield. The SCTP receives an average of 47,500 gallons per month at an average of 3.3 percent solids concentration (11,850 dry pounds per month) of thickened WAS that is digested at the SCTP. To assess the SCTP capacity at 17 mgd, it was assumed that the SCTP will continue treating WAS from the City of Ridgefield. The Facilities Plan (CH2M, 2013) shows that the City of Ridgefield flow will approximately double between 2017 and 2023, so it was assumed that the amount of WAS from the City of Ridgefield would also double.

SECTION 5

5-1

Plant Hydraulics Hydraulic analysis was completed as part of the Phase 4 expansion of the SCTP. That analysis identified a peak capacity of 34 mgd. The current analysis has determined that the peak influent flow to the plant is 32.2 mgd. Therefore, the hydraulic loading is less than the Phase 5 facility design peak flow rate. The hydraulic capacity of each unit process is discussed in more detail in Section 6.10 of this report. The hydraulic profile from the Phase 4 Expansion is provided as Figure 5-1.

Due to attenuation in process tankage at the facility, the peak effluent flow has been demonstrated to be less than the peak influent flow. See Table 6-5, in the section detailing the effluent pump station improvements, which documents the observed peak-hour effluent flow compared to peak-hour influent flow, demonstrating attenuation effects. For the 10-year period of record, the peak-hour effluent flow is 92 percent of the peak-hour influent flow.

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RECORD DRAWINGS

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MAY 20"'09'---

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5/09 RECORD DRAWING

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SECTION 6

6-1

Unit Process Capacity Analysis 6.1 Preliminary Treatment 6.1.1 System overview and current performance The SCTP has two 6-millimeter mechanically cleaned bar screens, a bypass channel equipped with a manual bar screen, and two 20-foot vortex grit units as part of preliminary treatment. The total capacities for the existing raw screening and grit removal processes are 34 mgd and 50 mgd on a peak-hour basis, respectively.

The washer function of the washer/compactor at the headworks has been decommissioned at the plant due to maintenance difficulties with the equipment. The preliminary treatment process performs acceptably with the washer function decommissioned.

6.1.2 Projected Performance Design criteria for raw sewage screening and grit removal are based on peak-hour flow conditions, and are not impacted by load considerations. As shown in Table 4-2, the peak-hour flow associated with an ADMM flow of 17 mgd is 32.2 mgd. Since both the screening and the grit removal are rated to treat peak-hour flows higher than 32.2 mgd, both systems will be able to treat more than the peak-hour flow associated with an ADMM flow of 17 mgd.

WAC 173-308-205 requires all biosolids (including septage) or sewage sludge to be treated by a process such as physical screening or another method to significantly remove manufactured inert substances prior to final deposition. Meeting this requirement may occur at any point in the wastewater treatment or biosolids manufacturing process. At SCTP this requirement is met by the preliminary treatment facility by screening raw sewage through a fine screen with maximum aperture of 6 millimeters (which is less than the maximum requirement of 3/8 inch [0.95 centimeter]).

The manual bypass screen is used to protect the facility from damage during peak flows and simultaneous equipment failure. The high influent channel level and bypass gate function is tested annually, but anecdotal accounts from operations staff indicate that the manual screen is not known to have been required to operate in the last 10 years. No modifications to the manual bypass screens, or provisions of additional biosolids screening are proposed as a part of this project.

Ventilating the headworks for odor control will not result in any additional monitoring requirements. The headworks facility is currently equipped with a combustible gas detection unit.

The existing screens were fully rebuilt in 2017 as shown in Figure 6-1. Replacement of the washer/compactor equipment is planned as part of the Phase 6 Expansion Program.

SECTION 6 – UNIT PROCESS CAPACITY ANALYSIS

6-2

Figure 6-1. Screens Rebuilt in 2017

Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

6.1.2.1 Redundancy Requirements The SCTP has a backup manually cleaned bar screen that provides the redundancy required by Ecology’s Criteria for Sewage Works Design (2008).

6.2 Primary Treatment 6.2.1 System Overview and Current Performance Primary treatment consists of four identical rectangular clarifiers. The primary clarifiers are 20 feet by 160 feet with a side water depth of 11 feet. SCTP data from January 2014 to June 2017 show that the SCTP usually operates with one to three of the primary clarifiers online. These data also show that the minimum 30-day average BOD5 and TSS removals are 40 and 69 percent, respectively. Figure 6-2 shows that even operating at high surface overflow rates (SORs) and with only one primary clarifier online, the BOD removal is more than 40 percent most of the time. These data also show that the peak BOD5 load is 37 percent higher than the maximum-month load and the TSS peak-day load is 54 percent higher.


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Figure 6-2. BOD5 Percentage Removal versus Primary Clarifier SOR

Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements (gpd/ft2 = gallons per day per square foot; PC = primary clarifier)

The Phase 3 and 4 projects included scum removal mechanisms at the primary clarifiers, which have been decommissioned and removed by plant staff due to limited amounts of scum being realized and the maintenance needs of the equipment. Scum is conveyed to the secondary process in primary effluent and is removed in the aeration basins and secondary clarifiers. This process has worked reliably for several years and is therefore planned to continue.

6.2.2 Projected Performance Primary clarification capacity is based on the SOR at average and peak flows. Ecology’s Criteria for Sewage Works Design (2008) recommends an average design SOR between 800 and 1,200 gallons per day per square foot (gpd/ft2) and a peak design SOR between 2,000 and 3,000 gpd/ft2. It also recommends that a BOD5 removal of 30 to 35 percent and TSS removal of 50 to 60 percent. For this reason, it was decided to use a 35 percent BOD5 removal for this evaluation even when the historical data show that the minimum 30-day average BOD5 removal through the primary treatment is 40 percent. Using a lower BOD5 removal is a conservative approach since it increases the load to the secondary treatment, increasing the capacity required to treat the additional load.

At the average-annual flow rate and peak-hour flow rate associated with an ADMM flow of 17 mgd, and operating all primary clarifiers, the average and peak design SORs are 1,023 gpd/ft2 and 2,525 gpd/ft2, respectively. The primary clarifier SORs under both scenarios are well within the ranges suggested by Ecology.

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10.0

20.0

30.0

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60.0

70.0

80.0

0 500 1,000 1,500 2,000 2,500 3,000 3,500

BOD 5

perc

enta

ge R

emov

al, %

SOR, gpd/ft2

1 PC Online 2 PC Online 3 PC Online 4 PC Online

SOR at mgd 12.9 = 1,360 gallons/ft2

with 3 PCs online


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If only three primary clarifiers are in service, the SOR at average annual flows will be 1,360 gpd/ft2. Figure 6-2 shows that the SCTP sometimes operates at an SOR around 1,360 gpd/ft2 while still achieving high BOD5 removals across the primary treatment process. Figure 6-2 also shows that even operating at an SOR higher than 1,300 gpd/ft2, the BOD5 removal is above 30 percent most of the time. The existing primary clarifiers will be able to treat an ADMM flow of 17 mgd and the associated flows and loads.

Combustible gas detection equipment at each primary clarifier will be required after the primary clarifiers are covered and vented for odor control.

6.2.3 Redundancy Requirements The EPA Reliability Classification for the SCTP is Class 2, which means that with a single primary clarifier out of service, the remaining units need to treat 50 percent of the flow. With four existing equally sized primary clarifiers, the effective result is that the redundancy requirements are not the governing criteria.

6.3 Aeration Basins 6.3.1 System Overview and Current Performance The SCTP has six aeration basins. The dimensions of the basins are listed in Table 6-1. Aeration Basins 1 and 2 work in series with Aeration Basins 3 and 4 as parallel trains. Aeration Basins 5 and 6 have two passes each. It is a common practice at the plant to leave Aeration Basins 1 through 4 offline, especially during the summer months. The SCTP has two independent blower systems. One system provides air for Aeration Basins 1 through 4, and the other system provides air to Aeration Basins 5 and 6. The blower system that provides air for Aeration Basins 1 through 4 has four 3,000-standard-cubic-foot-per-minute (scfm) positive displacement blowers. While the blower system for Aeration Basins 5 and 6 has two 4,500-scfm single stage blowers and one 2,500-scfm single stage blower. The aeration basins are equipped with 12-inch, fine-bubble ceramic diffusers. The diffusers are being cleaned as part of the 2017–2018 maintenance budget to improve system performance.

Table 6-1. Aeration Basin Dimensions Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Aeration Basins Dimensions

(feet) Side Water Depth

(feet)

Aeration Basins 1 and 2 94 x 41 14

Aeration Basins 3 and 4 94 x 41 15.5

Aeration Basins 5 and 6 323 x 18 (two passes) 20

The SCTP achieves ammonia-nitrogen effluent concentrations between 0.3 and 20 milligrams of nitrogen per liter (mg-N/L) and a monthly average concentration between 0.3 and 11.3 mg-N/L. The ammonia-nitrogen effluent concentrations are well within the effluent ammonia-nitrogen permit limit of 18.7 mg-N/L average monthly and 37.5 mg-N/L maximum daily average.

Historical data from January 2014 to June 2017 show that the mixed liquor suspended solids (MLSS) concentration at the basins is maintained between 1,700 and 3,700 mg/L. Figure 6-3 shows the MLSS concentrations during this period. The data also show a high variability on the sludge volume index (SVI). During this period, the average SVI was 125 milliliters per gram (mL/g), but SVI values as high as 350 mL/g were observed. Figure 6-3 shows that the high variability of the SVI is not related to the MLSS concentration.


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Figure 6-3. MLSS Concentration and SVI Over Time


6.3.2 Projected Performance The Dynamic Pro2D2 ™ process simulation developed for the SCTP Capacity Evaluation (CH2M, 2016) was recalibrated and used to complete this evaluation. The simulation was based on the following:

• Seasonal effluent criteria as established in the National Pollutant Discharge Elimination System (NPDES) permit

• Maximum bioreactor MLSS of 3,500 mg/L (maximum MLSS concentration recommended by Ecology’s Criteria for Sewage Works Design (2008)

• Bioreactor bulk-liquid dissolved oxygen (DO) operating at 2.0 mg/L

• Nitrification safety factor of 1.5 (relative to the minimum solids retention time [SRT] required to provide nitrification at a given bioreactor temperature) (EPA, 1975)

• Maximum secondary clarifier SOR of 1,600 gpd/ft2 under peak-hour conditions (one clarifier offline), as recommended by Design of Municipal Wastewater Treatment Plants, 5th Edition – Manual of Practice No. 8 (MOP 8) (Water Environment Federation [WEF], 2010)

• A 14°C bioreactor temperature during the winter months

The major operational parameters for the secondary treatment are summarized in Table 6-2.

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100

150

200

250

300

350

400

0

500

1000

1500

2000

2500

3000

3500

4000

5/6/2013 11/22/2013 6/10/2014 12/27/2014 7/15/2015 1/31/2016 8/18/2016 3/6/2017 9/22/2017

SVI,

mL/

g

MLS

S, m

g/L

Aer MLSS (Man) Aer SVI (Man)


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Table 6-2. Operational Parameter for the Secondary Treatment at 17 mgd ADMM Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Item Model Predicted Value Recommended Value*

Primary Effluent Flow Split to Aeration Basin 1 to 4, % 50 -

Primary Effluent Flow Split to Aeration Basin 5 and 6, % 50 -

Primary Clarifier BOD Removal, % 35 30 to 35

Solids Retention Time, day 6.2 5 to 15

Aerated Zone DO, mg/L 2 1.5

lb O2/lb BOD Required, lb 1.25 1.25

lb O2/lb TKN, lb 4.6 4.6

lb O2/lb NO3 recovered, lb 2.856 -

Aeration Basin 1 through 4 Total Required Air Rate, scfm (Firm Capacity: 9,900 scfm)

8,460 -

Aeration Basin 5 and 6 Total Required Air Rate, scfm (Firm Capacity: 7,000 scfm)

6,980

MLSS 3,500 1,500 to 3,500

Yield, lb TSS/lb BOD 0.76 0.6 to 0.75

F/M, lb BOD Applied/lb MLSS-day 0.28 0.2 to 0.4

Volumetric Loading, lb BOD/1,000 ft3/day 37.2 40 maximum

Secondary Clarifiers Solids Loading Rate, ppd-ft2 30 -

Secondary Clarifier SOR at Peak-hour Flow, gpd/ft2 1,513 1,200

*Ecology’s Criteria for Sewage Works Design recommended values (2008).

F/M = food to microorganisms; ft3 = cubic feet; lb = pounds; TKN = total Kjeldahl nitrogen.

The simulation results indicate that the SCTP will be able to treat an ADMM of 17 mgd and the associated loads staying within the parameters listed above.

6.3.3 Redundancy Requirements Ecology requires that there are at least two equal-volume basins. The SCTP has six aeration basins that provide the redundancy required by Ecology. The capacity of the plant was determined assuming that all the aeration basins were online because a backup basin is not required.

Ecology requires the SCTP to have a sufficient number of blowers to satisfy the design air demand with the largest-capacity-unit out of service. The SCTP has two independent blower systems. One system provides air for Aeration Basins 1 through 4 and the other system provides air to Aeration Basins 5 and 6. As shown in Table 6-2, the air demands at an ADMM of 17 mgd for Aeration Basins 1 through 4 and Aeration Basins 5 and 6 are below the firm capacities of their respective blower systems.

6.4 Secondary Clarifiers 6.4.1 System Overview and Current Performance Four secondary clarifiers are currently in place at SCTP: two 90-foot-diameter (Secondary Clarifiers 1 and 2) and two 105-foot-diameter clarifiers (Secondary Clarifiers 3 and 4). Secondary Clarifiers 3 and 4 are


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always online. Secondary Clarifier 2 is brought online as needed while Secondary Clarifier 1 is rarely used.

Six pumps are currently in place in the RAS pump station. Each RAS pump is capable of pumping 3.3 mgd, so the system has a firm capacity of 16.5 mgd.

Historical data from January 2014 to June 2017 show that the monthly average TSS effluent concentration is between 3.6 and 13.2 mg/L, which is well within the effluent TSS permit limit of 30 mg/L. Figure 6-4 shows that the effluent TSS is generally below 30 mg/L even at high SVI values.

Figure 6-4. Effluent TSS versus SVI


6.4.2 Projected Performance Treating 17 mgd with Secondary Clarifiers 1 and 2 online and the larger clarifiers (either Clarifier 3 or 4) offline will result in an SOR of 1,513 gpd/ft2 at peak flows (32.2 mgd), which is higher than the 1,200 gpd/ft2 value recommended in Ecology’s Criteria for Sewage Works Design (2008); however, MOP 8 provides a range from 1,000 to 1,600 gpd/ft2 as the preferred overflow rate for peak flow conditions. As such, operations at 17 mgd fall within published industry design standards. To calculate the current peak overflow rates experienced at the SCTP, the daily average flow data from each day during 2015 were multiplied by a peaking factor of 2.5 (as listed in the Facilities Plan) and divided by the sum of the area of all the secondary clarifiers in service each day. Figure 6-5 shows that the daily average TSS effluent concentrations were significantly lower than the monthly average limit of 30 mg/L even during the days with high peak overflow rates. The secondary clarifier performance at 17-mgd ADMM and the associated peak-hour flow (32.2 mgd) were also evaluated running a dynamic simulation using CH2M’s PClarifier, a secondary clarifier state point analysis tool. The results obtained from the simulation indicate that the clarifiers do not lose solids over the weir, even during peak-hour flows.

An additional state point analysis determined the SVI at which the secondary clarifiers will fail assuming a MLSS concentration of 3,500 mg/L and only three clarifiers online with a peak-hour flow of 32.2 mgd.

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SVI, mL/g


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Under these conditions, the clarifiers will fail if the SVI exceeds 200 mL/g. The historical plant data indicate that the SVI is less than 200 mL/g 90 percent of the time and that even at higher SVIs the effluent TSS stays around 10 mg/L, as shown in Figure 6-4.

The recommended method to help mitigate conditions resulting in higher SVIs is to chlorinate the RAS. RAS chlorination is commonly used to control activated sludge bulking by selectively mitigating the growth of nuisance filaments, which are primarily located on the outer layer of the biomass flocs. See Section 6.4.4 for detailed recommendations.

Figure 6-5. Effluent TSS versus Secondary Clarifier SOR

Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements The existing RAS pumps will be able to pump 100 percent of the annual average flow associated with an ADMM flow of 17 mgd. The RAS system can pump a maximum flow of 16.5 mgd with one pump out of service, which is 97 percent of the 17 mgd.

6.4.3 Redundancy Requirements Ecology requires that with the largest-flow-capacity secondary clarifier out of service, the remaining secondary clarifiers shall treat 50 percent of the design flow to meet redundancy. The requirement is met by the existing secondary clarifiers at the SCTP.

6.4.4 Hypochlorite Dosing Station for RAS Chlorination RAS chlorination is one common method to help control activated sludge bulking. Excessive growth of filamentous organisms in the activated sludge can be detrimental to sludge settling and impact secondary effluent quality. Temporary injection of chlorine solution into the RAS flowstream can be used to selectively control the growth of nuisance filaments, which are primarily located on the outer layer of the biomass flocs.

The SCTP previously had the capability to add chlorine solution at the RAS/WAS Pump Station using the old control building’s chlorine gas system. Chlorine solution entered the RAS/WAS Pump Station from the west side and was injected in the RAS piping from Secondary Clarifiers 3 and 4, upstream of RAS

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SOR, mL/g


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Pumps 3, 4, and 6. However, the chlorine gas system was abandoned during Phase 3 when the plant switched to ultraviolet (UV) disinfection.

Restoring RAS chlorination requires a small chemical system. Preliminary design criteria are summarized in Table 6-3. Liquid sodium hypochlorite should be used to create the chlorine solution because it is a safe source of chlorine and readily available from chemical distributers. Chemical totes are the preferred storage method because they can be obtained with chemical containment, minimizing the need for additional infrastructure. A portable, skid-mounted chemical metering pump system, illustrated in Figure 6-6, can provide sufficient capacity using 120-volt power. The skid would include all appurtenances to dilute the hypochlorite and measure flow.

The recommended location for this hypochlorite system is in the old control building. The existing 2 ½-inch chlorine solution piping between the old control building and the RAS/WAS Pump Station will be pressure tested and replaced if necessary, to deliver hypochlorite solution directly to the RAS piping. An existing 3-inch W3 pipe to the control building will provide dilution water. The pump skid and an active tote will be placed in the old chlorine storage room and additional totes can be temporarily stored outdoors.

The following additional improvements to the RAS chlorination system are recommended as well: (1) relocation of the RAS injection point within the RAS/WAS Pump Station to downstream of all four secondary clarifiers, and (2) adding an injection quill for improved introduction of chlorine solution.

Table 6-3. RAS Chlorination Design Criteria Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Parameter Units Value

Hypochlorite Dose pounds-chlorine/pound-MLSS*day 0.002 to 0.008

Maximum Duration of Injection days 5

Biomass Inventory, maximum month pounds 106,000

Hypochlorite Solution 12.5%

Hypochlorite Solution Required, at maximum month gallons per day 200 to 800

Tote Volume, each gallons 275

Dilution Water gallons per minute 25


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Figure 6-6. Skid-mounted Hypochlorite Pump System, from ProMinent Fluid Controls LTD


6.5 Disinfection 6.5.1 System Overview and Current Performance SCTP utilizes a medium pressure, high intensity UV system for disinfection. The facility consists of 1 channel, 2 banks, and 20 modules. The system is currently rated to treat up to 34 mgd at peak-hour conditions.

6.5.2 Projected Performance The current capacity of the system exceeds the 32.2 mgd peak hour influent flow expected at 17 mgd ADMM.

6.5.3 Redundancy Requirements Ecology requires that the remaining units treat at least 50 percent of the total design flow if the largest-flow-capacity unit is out of service. The existing two lamp banks meet the performance and redundancy requirements.


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6.6 Effluent Pump Station 6.6.1 System Overview and Current Performance The existing effluent pump station is rated to meet the Phase 4 peak-hour flow of 28.3 mgd. As discussed below, a small increase in pumping capacity is required to achieve the Phase 5 peak-hour effluent flow. With the largest pump out of service, the remaining pumps have the capacity to handle peak-hour flow conditions, so redundancy requirements are met. The existing vertical, mixed flow, open line shaft effluent pumping system consists of Pumps 1 and 3 (14-inch pumps) and Pumps 2 and 4 (18-inch pumps).

6.6.2 Projected Performance Operation of the existing effluent pumps will be modified to meet Phase 5 peak-hour effluent flows. Over-speeding the existing pumps while continuing to pump through the existing effluent pipeline and outfall diffuser will meet the Phase 5 peak hour flow associated with Phase 5B Project flows and loads.

Replacement or addition of pumps will be required to meet peak-hour flows beyond Phase 5. Sizing and future phasing of the effluent pumps are beyond the scope of this Engineering Report.

6.6.3 Redundancy Requirements The Criteria for Sewage Works Design G2-8 (Ecology, 2008) and the EPA require that the effluent pump station achieve peak design flow with the largest unit out of service. Peak-hour flows are expected to be 32.2 mgd (29.6 mgd attenuated, see Section 6.6.4 for discussion of attenuation of peak flows within the facility and sizing of effluent pump station). Section C2-1.8 of the Criteria for Sewage Works Design signals that certain sewage pump station components need to be “designed with redundancy in equipment to provide capacity for peak design flows.” This pump station meets this requirement.

6.6.4 Effluent Pump Modifications Currently, the effluent pump station is rated for the Phase 4 peak-hour flow, which is 28.3 mgd. The SCTP capacity will continue to expand through Phases 5 through 9, and the effluent pump station will need to meet the final buildout peak-hour flow, which is 72.0 mgd. See Table 6-4 with peak-hour design flows required by phase.

Table 6-4. Design Peak-hour Flow by Phase Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Phase Peak-hour Flow (mgd)

Phase 4 28.3

Phase 5 32.2 (29.6*)

Phase 6 43.0

Phase 7 54.0

Phase 8 62.0

Phase 9 72.0

*8% reduction from peak influent flow due to attenuation across the plant. See Table 6-5.

Plant influent and effluent data support an 8 percent reduction in the peak-hour influent flow due to observed attenuation across the plant; see Table 6-5. The effluent peak-hour influent and effluent flows were monitored from 2003 through 2016 and the data support a reduction in the peak-hour effluent flow as basis of design for the re-rated facility. Phase 5 peak-hour influent flow is 32.2 mgd. Accounting


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for attenuation across the plant, the design Phase 5 peak-hour effluent flow for the effluent pump station is justified at 29.6 mgd.

Table 6-5. Peak-hour Flow Data Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements (Phase 5B Project basis of design, effluent peak-hour flow: 32.2 x 91.9% = 29.6 mgd)

Year

Average- annual

Flow (AAF) (mgd)

Maximum- month Flow

(MMF) (mgd)

Peak-hour Flow (PHF) (mgd)

Peak-hour Flow Date

Effluent Peak-hour Flow (mgd)

Peaking Factor

(MMF/AAF) (mgd)

Peaking Factor

(PHF/AAF) (mgd)

Ratio: Peak

Effluent to Peak

Influent Flow

2003 a 6.51 7.34 13.50 01/31/03

1.13 2.07

2004 b 6.49 7.91 11.88 02/01/04 11.30 1.22 1.83 95.1%

2005 c 6.66 7.70 13.16 12/30/05 12.28 1.16 1.98 93.3

2006 7.30 9.52 13.63 11/06/06 13.78 1.30 1.87 101.1

2007 7.02 8.54 14.20 12/03/07 13.66 1.22 2.02 96.2%

2008 6.86 8.41 13.97 12/27/08 13.95 1.23 2.04 99.9%

2009 6.80 8.35 14.40 01/02/09 13.60 1.23 2.12 94.4%

2010 7.46 9.11 15.20 12/11/10 13.76 1.22 2.04 90.5%

2011 7.30 9.06 14.54 11/22/11 13.58 1.24 1.99 93.4%

2012 d 7.55 9.37 14.80 01/18/12 13.19 1.24 1.96 89.1%

2013 7.06 8.04 14.73 01/28/13 13.94 1.14 2.09 94.6%

2014 7.32 8.77 14.98 02/17/14 13.63 1.20 2.05 91.0%

2015 7.31 10.73 18.89 12/07/15 14.82 1.47 2.58 78.5%

2016 7.84 9.40 16.28 01/17/16 14.94 1.20 2.08 91.8%

Average 91.9%

a Plant database starts in November 2003. b 11.88167 for the hour ending at 12:50 p.m. c 13.16 is the peak instantaneous flow on 12/31/2005; 13.15 is the peak instantaneous flow on 12/30/2005. The highest 1 hour average on 12/30/2005 was 12.8. The highest 1 hour average for the year was 12/31/2005, 13.10 (13.09833). d 2012 MMF data were modified from 8.86 (March) to 9.37 (December).

The existing vertical turbine style effluent pumping system consists of Pumps 1 and 3 (14-inch pumps) and Pumps 2 and 4 (18-inch pumps). To meet the EPA redundancy requirements, the effluent pump station must be hydraulically designed to pass a peak-hour flow with the largest effluent pump out of service at the 100-year flood stage. Therefore, the effluent pump station must pass peak-hour flow (29.6 mgd as shown in Table 6-5) with either Pump 2 or Pump 4 offline. Current rated capacity with Pumps 1, 2, and 3 for Phase 4 peak-hour flow is 28.3 mgd. Existing pump curves are shown in Figure 6-7 for 100 percent speed.

Over-speeding Pumps 1, 2, and 3 at 1,275 revolutions per minute (rpm) (108 percent) could increase flow to the required 29.6 mgd to meet Phase 5B Project peak-hour flows. Existing pump curves at 108 percent speed are shown in Figure 6-8. Over-speeding the pumps increases the pump horsepower (hp) demand and speed required to convey the additional flow, increases wear on bearings and mechanical parts, and efficiency is slightly reduced due to changes of the operating point on the pump curve. Pumps


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1 and 3 operate with 125 hp and 1,180 rpm. Pumps 2 and 4 operate with 200 hp and 1,190 rpm. All of the pump motors have a service factor of 1.15, and over-speeding the pumps to 108 percent falls within the range of the service factor and will not overload the existing pump motors. It is not recommended to over-speed the pumps for long durations of time, but the rare and relatively short duration operating condition can be accommodated within industry good practice. Control system programming will be adjusted to reflect the revised level control approach.

Figure 6-7. Existing Pump Curves at 100% Speed and System Curve Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Figure 6-8. Existing Pump Curves at 108% Speed and System Curve


Hydraulic calculations are based on the boundary conditions of the Columbia River 100-year flood elevation of 28.8 feet using the North American Vertical Datum of 1988 and maximum effluent wet well water surface elevation of 29.4 feet. Design criteria that affect head loss match those used in design of the Phase 4 effluent pump station improvements. An absolute roughness factor (ε) of 0.0004 feet per


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American Water Works Association (M9 Concrete Pressure Pipe, Third Edition, 2008) manual of water supply practices design guidelines were used for the entire outfall pipeline and an absolute roughness factor (ε) of 0.00015 feet per Cameron Hydraulic Data (Heald, 1998) for steel pipe for the outfall diffuser pipe. The Phase 4 project evaluated thrust conditions in the existing pipeline under the Phase 4 flows. The additional head posed by the 29.6 mgd versus the 28.3 mgd is 10 feet. The existing pipe joint thrust restraints will be evaluated during Schematic Design phase to confirm adequacy.

6.7 Waste Activated Sludge Thickening 6.7.1 System Overview and Current Performance Two 2-meter gravity belt thickeners (GBTs) are used to thicken WAS at the plant. Currently, SCTP operates one of the GBTs continuously. Wasting sludge continually can be beneficial for the stability of secondary treatment. For this reason, it is a common practice in the industry to run the WAS thickening facilities continuously.

The SCTP is currently sending the filtrate generated at the dewatering facility to the WAS influent line to reduce the solids recirculated to the front of the plant. To improve reliability, the SCTP implemented some additional control features such as interlocking the GBT thickening process and the belt filter press (BFP) dewatering process so that if a GBT drive fails, the BFPs, dewatering feed pumps, washwater, and dewatering polymer feed will also stop. The plant staff has also installed zero speed switches on GBT drive rolls that trigger an additional alarm when the drive roll zero speed is detected.

6.7.2 Projected Performance Assuming a maximum month loading rate of 250 gallons per minute per meter (gpm/m), which is the value recommended by MOP 8 (WEF, 2010), one of the GBTs will need to be operated for 6.1 hours a day. An increase in WAS production will not impact the normal operation of the system because the SCTP is operating the GBT continuously at a lower loading rate.

6.7.3 Redundancy Requirements Ecology does not identify redundancy for the WAS thickening process. The EPA does not require backup pumps or backup power supply.

6.8 Anaerobic Digestion 6.8.1 System Overview and Current Performance Two 825,000-gallon mesophilic anaerobic digesters are used to treat the primary sludge and WAS generated at the SCTP and a small fraction of imported WAS from the City of Ridgefield. Primary sludge and WAS are blended together in a 72,000-gallon blending tank before being sent to the digesters. The SCTP produces Class B biosolids.

The dewatering filtrate and washwater has been plumbed into the WAS feed line immediately ahead of the GBT.

Existing digester gas is burned in hot water boilers to heat the digestion process. As documented in the Facilities Plan (CH2M, 2013, page 20), an economic analysis for the installation of internal combustion engines at SCTP showed that this option does not have a positive net present value, and therefore gas utilization was not included in the biosolids management alternatives evaluated in the Biosolids Processing and Utilization Review for the Salmon Creek Treatment Plant (Brown and Caldwell, 2010), which was included as Appendix C to the 2013 Facilities Plan with the exception of seasonal thermal drying (Alternative 8).


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A recent Class A biosolids evaluation (Brown and Caldwell, 2017, page 4) identified that biogas could be utilized as a supplemental fuel source for thermal drying of biosolids at SCTP. However, the study noted that upon further review with equipment manufacturers, the manufacturers noted that the cost and complexity of using biogas as a supplemental fuel source may be unattractive. The study noted that additional costs for upgrading natural gas supply capacity, or for supplementing natural gas with biogas from the digesters, should be further explored in the predesign of the system. Additional funding or economic incentives for combined heat and power systems may warrant reconsideration at a future time.

The scum concentrator equipment installed during Phase 3 was decommissioned prior to the Phase 4 project and subsequently demolished. The process benefits (reduction of water to the digester) were outweighed by the maintenance needs, energy use, and degrading condition of equipment. The plant operates acceptably in this configuration and has done so for over 10 years.

6.8.2 Projected Performance The model predicts that based on the primary sludge and the WAS produced at 17 mgd ADMM, and under the operation conditions listed in Table 6-6 (in Section 6.10, Summary of Unit Process Capacities), the anaerobic digesters will operate at a volatile solids loading rate of 0.16 pound per cubic foot (lb/ft3) per day and provide an SRT of 16 days. Ecology recommends a volatile solids loading rate of between 0.03 and 0.3 lb/ft3 per day and an SRT of 15 days. Based on these, it was determined that the existing digesters can treat the sludge loading associated with 17-mgd ADMM.

6.8.3 Redundancy Requirements Ecology does not identify redundancy for the anaerobic digestion process. However, the EPA requires two digesters to be in the treatment process, with backup equipment. This requirement is met with existing facilities.

6.9 Digested Biosolids Dewatering 6.9.1 System Overview and Current Performance The SCTP uses two 2-meter BFPs to dewater the digested sludge. Currently, SCTP operates one of the BFPs continuously. As mentioned before, the filtrate generated by the BFP operation is being sent to the thickening facility.

The SCTP has four 1,300-cubic-yard storage bunkers to store the dewatered sludge cake. According to the Facilities Plan (CH2M, 2013), dewatered sludge cake in excess of that capacity will be hauled both locally and to eastern Washington as needed so that the combination of bunker storage and hauling is sufficient to manage dewatered sludge cake at the SCTP.

6.9.2 Projected Performance According to MOP 8 (WEF, 2010), typical performance for BFPs dewatering anaerobically digested sludge of combined primary sludge and WAS is 400 to 700 pounds per hour per meter (lb/hr/m). The model predicts that at a 600 lb/hr/m solids loading rate both BFPs will need to operate a bit less than 8 hours per day, 7 days per week. Even operating below the maximum recommended solids load rate, the existing dewatering system will be able to process the sludge produced while treating 17 mgd ADMM load. The dewatering unit process has significant capacity, especially given the variable of extending the weekly hours of operation. It is predicted that the dewatering system is able to accommodate future conditions up to 45-mgd ADMM.


6-16

Since solids handling costs are among the largest unit process costs at a wastewater treatment plant (WWTP), the SCTP is interested in investigating methods to optimize the dewatering process: in particular, any approach or system that can improve dewatered cake concentration and overall dewatering performance without replacing the existing equipment. An augmented approach to dewatering (and thickening) would be to condition the sludge prior to thickening in order to flocculate the biomass. An example of this technology is manufactured by Orège and given the process name SLG® or “‘solid-liquid-gas” conditioned sludge. The process removes bound water through the injection of pressurized air. Air is diffused into the sludge at the same time to aid flocculation (Inman and Capeau, 2015). This yields denser floc and allows the dewatering process to be easier.

The Orège SLG® equipment has a relatively small footprint (the approximate size of the installation is 4 feet by 6 feet). It has been shown in bench- and pilot-scale tests at several WWTPs in Europe and the United States that this pretreatment process can increase the BFP dewatered cake solids concentration from anaerobically digested biosolids by 3 to 5 percent. It has also been shown to significantly lower polymer consumption and results in an extremely clear filtrate at these other WWTPs. At a full-scale test at the Lehigh, Pennsylvania, WWTP, dewatering anaerobically digested biosolids with BFPs, the Orège SLG® process was successful and increased the cake solids by 3 to 4 percent and reduced the polymer use by 20 to 30 percent. The SCTP will be investigating and evaluating this and other similar systems for applicability at the facility.

6.9.3 Redundancy Requirements Ecology does not identify redundancy for the biosolids dewatering process. The EPA does not require backup pumps or backup power supply.

6.10 Summary of Unit Process Capacities The Alliance has closely monitored influent flows, loads, and process performance as maximum month plant influent loads approach 85 percent of the rated capacity threshold. The Alliance has conducted a SCTP wastewater unit process evaluation to identify current performance and potential limitations, confirming the recommendations from previous planning efforts.

A capacity analysis was completed for the SCTP as part of the unit process evaluation. This analysis includes the use of design criteria from industry-standard documentation (Ecology’s Criteria for Sewage Works Design, 2008; WEF, 2010; Metcalf & Eddy, 2002), together with a whole-plant dynamic process simulator. CH2M’s dynamic Pro2D2 ™ process simulation was developed for the SCTP and was used to evaluate the performance of the different unit processes at the SCTP. The resulting capacity of each unit process at the SCTP was calculated, with the limiting unit process being able to treat up to an ADMM flow of 17 mgd and the associated loads. The analysis determined that the secondary treatment process at the SCTP could treat up to an ADMM flow of 17 mgd and the associated loads, which is an increase from the capacity previously presented in the Facilities Plan. Figure 6-9 presents the unit process capacities (ADMM and peak hour) for the SCTP. Appendix A shows the SCTP flow diagram including all the unit processes at the SCTP. Appendix B presents the projected mass balance for the SCTP while operating at 17 mgd and associated loads.


6-17

.

Figure 6-9. Unit Process Capacity Summary



6-18

As part of the evaluation, it was also determined that the reliability/redundancy requirements for each unit process were satisfied while operating at 17 mgd ADMM. The SCTP is a Class 2 facility and the reliability/redundancy requirements are found in Ecology’s Criteria for Sewage Works Design (2008). Table 6-6 provides a summary of the criteria for each unit process at the SCTP, together with the performance predicted at 17 mgd ADMM.

Table 6-6. Operational Parameters for the SCTP at 17 mgd ADMM Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Unit Process Performance

at 17 mgd

Criteria for Sewage Works Design

(Ecology, 2008)

MOP 8

(WEF, 2010)

Metcalf and Eddy, 2002, 4th

Edition

Headworks

Number of Screens 2 screens with backup bar

screen

Redundancy: A backup bar screen or bypass channel

Screening Capacity, mgd 34

Screening Capacity Required, mgd

32.2

Number of Vortex Grit Units 2

Grit Removal Capacity, mgd 50

Primary Clarifier

Number of Clarifiers 4 Redundancy: with a single primary clarifier out of service,

the remaining units need to treat 50% of the flow

Number in Service 4

Peak-hour Wet Weather SOR, gpd/ft2

2,525 2,000 to 3,000 2,000 to 3,000 2,000 to 3,000

AA Wet Weather SOR, gpd/ft2 1,023 800 to 1,200 800 to 1,200 800 to 1,200

BOD Removal, % 35 30 to 35 25 to 40 25 to 40

Aeration Basins

Number of Basins 6

Number in Service 6

Total Volume (MG) 3.62

Yield, lb TSS/lb BOD 0.76 0.6 to 0.75 0.48 to 0.95 0.5 to 0.7

MLSS, mg/L 3,500 1,500 to 3,500 4,000 maximum 1,500 to 3,000

SRT, days 6.2 5 to 15 days 5 to 15 days 5 to 15 days

F/M, lb BOD Appl./lb MLVSS-day

0.28 0.2 to 0.5 0.2 to 0.4

Volumetric Loading, lb BOD/1,000 cubic feet-day

37.2 20 to 40 21 to 40


6-19



at 17 mgd


(Ecology, 2008)

MOP 8

(WEF, 2010)


Edition

Aeration Systems

lb O2/lb BOD Required, lb 1.3 0.9 to 1.3 0.9 to 1.3 0.9 to 1.4

lb O2/lb TKN, lb 4.6 4.6 4.6 4.6

lb O2/lb NO3 recovered, lb 2.9 2.9

lb O2/lb BOD Required, lb 1.3 0.9 to 1.3 0.9 to 1.3 0.9 to 1.4

Aeration Basins 1 – 4 Total Required Air Rate, scfm

8,460 Firm Capacity:

9,900 scfm

Maintain design O2 with the largest-capacity-unit out of

service

Aeration Basin 5 and 6 Total Required Air Rate, scfm

6,980 Firm Capacity:

7,000 scfm

RAS Pump Station

Number of Pumps 4

Number in Service 3

Capacity, mgd 16.6

Secondary Clarifiers

Number of Basins 4 Redundancy: with a single secondary clarifier out of service, the remaining units need to treat

50% of the flow

Number in Service 3

SVI, mL/g 125 <150

ADMM SOR, gpd/ft2 810 400 to 700 400 to 700

Peak-hour SOR Rate, gpd/ft2 1,513 1,200 1,000 to 1,600 1,000 to 1,600

AA Solids Loading Rate, ppd-ft2

26 20 to 30 20 to 30

UV Disinfection

Number of Channels 1

Number of Modules 20

Capacity, mgd 34

Effluent Pump Station

Number of Pumps 2 large

2 small

Redundancy: with any one pump out of service, the remaining

pumps will have the capacity to handle the peak flow

Peak flow conveyed with (1) large and (2) small pumps


6-20



at 17 mgd


(Ecology, 2008)

MOP 8

(WEF, 2010)


Edition

Number in Service 3

Firm Capacity Required, mgd 29.6 (achieved with existing pumps and

motors)

Thickening

Number of Units 2

Number in Service 1

MMWW Loading Rate, gpm/m

250 100 to 250

Average Daily Operation, hours

7

Anaerobic Digester

Number of Units 2

SRT, days (minimum = 15 days)

16 10 to 20 15 to 20 15 to 20

VS Loading, lb VS/cubic feet /day (maximum = 0.16)

0.16 0.03 to 0.3 0.11 to 0.16 0.1 to 0.3

Dewatering

Number of Units 2

Number in Service 2

MMWW Loading Rate, pounds/hour/meter

600 400 to 700

Average Daily Operation, hours

8

ADMM = average day maximum month; MG = million gallons; MLVSS = mixed liquor volatile suspended solids; MMWW = maximum month wet weather; VS = volatile solids.

SECTION 7

7-1

Air Quality and Odor Control 7.1 Regulatory Context and Requirements The air discharges from SCTP are regulated by the Southwest Washington Clean Air Agency (SWCAA) to limit toxic air pollution and nuisance odors. Individual odor-causing compounds are quantified as a concentration (mass per volume). Of these compounds, hydrogen sulfide (H2S) is a regulated toxic pollutant and the SWCAA has established a limiting concentration for H2S toxicity. Key regulatory requirements pertaining to required limits of SCTP air emissions are described in more detail below.

7.1.1 Nuisance Odors Because H2S is easily detected by peoples, it is commonly regulated as a nuisance odor. The SWCAA Regulations (SWCAA 400) contain a “nuisance odor” clause. This clause indicates that procedures be put in place to mitigate odors so that they are not “unreasonable” or a nuisance. Odors in general, are typically quantified using a dilutions-to-threshold (D/T) method. However, limiting values are not specifically defined by the SWCAA, so target thresholds were selected based on experience to meet these qualitative nuisance odor requirements.

7.1.2 Toxic Air Pollutants New regulations have been implemented for H2S via the Washington Administrative Code Title 173, Chapter 460, Section 150 (WAC 173-460-150), which describes an updated Acceptable Source Impact Level (ASIL) for H2S as 2.0 milligrams per cubic meter (mg/m3) over a 24-hour period. The previous WAC value was 0.9 mg/m3 over a 24-hour period. SWCAA has not adopted the new less-stringent state-regulated value; therefore, the ASIL for the SCTP is 0.9 mg/m3 H2S over a 24-hour period. To comply with both the state and local agencies, 0.9 mg/m3 over a 24-hour period is the required criterion.

7.1.3 Odor Criteria Requirements Based on the conclusions above, toxic air pollution requirements and odor criteria requirements include the following:

• H2S—For toxic air pollution control, H2S cannot exceed a 24-hour average of 0.9 mg/m3 per year at the property boundary.

• H2S—For nuisance odor control, H2S cannot exceed a 1-hour average of 10 mg/m3 per year at any receptor (residence).

• D/T—For nuisance odor control, D/T cannot exceed a 1-hour average of 10 D/T per year at any receptor.

7.2 Odor Control 7.2.1 Overview and Current Performance The SCTP Phase 4 Expansion Program included installation of a bio-trickling filter system for ventilation of the sludge blend tank and a carbon-based system for the 117th Street Pump Station Force Main discharge.

SECTION 7 – AIR QUALITY AND ODOR CONTROL

7-2

7.2.2 Alternative Analysis and Projected Performance 7.2.2.1 Previous Analysis In March 2007, odor sampling and odor dispersion modeling activities were performed to characterize the odor footprint at the SCTP. This analysis summarized the offsite odor goals for the SCTP based on the SWCAA requirements for controlling nuisance odors. The report also summarized the results of an odor survey and the results of a dispersion model describing offsite impacts. Since 2007, changes in the SCTP’s environmental setting require updating the analysis to understand current odor control needs for the facility. These changes include the following:

• Residences (odor receptors) have been and are continuing to be constructed in close proximity to the plant. This means that current and future odor receptors are located closer to the SCTP than previously identified.

• Emissions (specifically toxic air pollutants) regulatory requirements have changed since completion of the previous work.

• Technologies including bio-trickling filters and biofilter medias have evolved and improved since completion of the previous work. Specifically, acceptable loading rates have gradually increased, making required footprints smaller. In addition, media types have improved, with longer life media now available.

Refer to the technical memorandum in Appendix C for more information regarding the odor control analysis.

7.2.2.2 Technologies Evaluated CH2M’s recommendation from the 2007 analysis was to cover the primary clarifiers and preliminary treatment channels and ventilate these areas to a new odor control system. This recommendation was carried forward into the updated analysis. Two odor control technologies were evaluated in this context: (1) vapor-phase odor control system (bio-trickling filter), and (2) high rate engineered media biofilter. These are described separately below.

Vapor Phase Odor Control System (Bio-trickling Filter)

In bio-trickling filter technology, odorous air is blown into the bottom of the tower and flows up through the media material, exiting through an exhaust stack. The media may be a synthetic material or a natural material such as lava rock. The bacteria also use other odor compounds as a food source, including ammonia and various organic reduced sulfur (ORS) compounds. A schematic diagram of a typical bio-trickling filter is shown in Figure 7-1.


7-3

Figure 7-1. Simplified Schematic Diagram of a Bio-trickling filter System

Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements Earlier design bed velocities for bio-trickling filters were 50 feet per minute (fpm) maximum. However, advances in this technology have gradually shifted acceptable bed velocities to as high as 100 to 200 fpm; although 100 fpm is a high-end value that can be achieved by multiple suppliers.

The required empty bed gas residence time ranges from 10 to 14 seconds, depending on odor loading rate. The design head loss through the media bed can range from 0.2- to 0.5-inch water column per foot of bed depth, depending on bed velocity selected. The required footprint for this technology is generally smaller than for biofilters. For some bio-trickling filter systems, a scrubbant recirculation pump is required to keep the media moist and maintain some biomass in solution. Several suppliers including BioAir, Azzuro, and EcoVerde use a once-through arrangement by which makeup water is sprayed over the top of the media and drained out the bottom without recirculation. The advantage to this type of arrangement is that a pH gradient is maintained within the media that supports both low pH bacteria (autotrophic thiobacillus—specifically targets H2S) and neutral pH bacteria (heterotrophic bacteria—target ORS compounds). Nutrients are generally added for maintaining biomass health because of the synthetic nature of the media. However, supplemental nutrients are not required if secondary effluent is available and meets specific water quality requirements.

High Rate Engineered Media Biofilter

High rate engineered media biofilters are biofilter systems that utilize a proprietary media that performs under much higher loading rates than organic, soil, or mineral biofilters. High rate engineered media biofilters also exhibit similar or better performance characteristics than organic mediums. These types of systems also have longer lasting media and require smaller footprints due to the higher loading. The media is generally more expensive because it is a unique proprietary composition.

Design flow rates for high rate biofilters range from 5.0 to 11.0 cubic feet per minute per square foot. Media life is normally guaranteed for 10 to 20 years. The appropriate empty bed gas residence time for high rate media is dependent upon the target odor and respective loading rate but will typically range from 30 to 60 seconds.

Generally, high rate biofilter media do not require a nutrient source because they have a nutrient constituent built into the media recipe. The advantages of high rate packaged biofilters include the following:


7-4

• A wide range of odorous constituents may be removed.

• The system operations and maintenance (O&M) is relatively simple.

• Chemical storage and delivery is not required.

• High rate proprietary media requires less frequent change-out (generally guaranteed for 10 to 20 years).

• The control systems are either manually operated or are relatively simple.

• The collected leachate is typically not odorous, as with compost biofilters.

• The required footprint is approximately half that of organic media biofilters.

• The high-velocity stack allows for better dispersion/dilution than open area biofilters without cover and stack.

However, high rate biofilters have the following disadvantages:

• Media costs can be high.

• The system can handle gradual cyclic loadings but cannot accommodate rapid load spikes effectively because bacterial populations provide the removal mechanism.

7.2.2.3 Projected Performance Including Dispersion Modeling Results A dispersion model was developed as part of the updated analysis with current odor control technologies and updated receptors consisting of the housing development south of SCTP. Figures 7-2 and 7-3 and Table 7-1 show the results of the bio-trickling filter modeling.

Figure 7-2. Isopleths Showing Lines of Constant H2S Concentration in mg/m3 —1-Hour Annual Peak, Bio-Trickling Filter

Approach Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements


7-5

Figure 7-3. Isopleths Showing Lines of Constant Odor Concentration in D/T—1-Hour Annual Peak, Bio-Trickling Filter

Approach Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Table 7-1. Bio-Trickling Filter Approach, 1-Hour Peak Average H2S Concentrations at Sensitive Receptors Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Receptor

H2S (mg/m3/ppbV) Odor (D/T) Odor Exceedances

Hours/year above 10 D/T

2006 Control Strategy 1 Results

Updated Control Strategy 1



1 1.14/0.75 1.16/0.76 6.1 4.77 -

2 1.55/1.01 1.49/0.97 5.2 6.01 -

3 2.05/1.34 1.49/0.97 7.6 6.59 -

4 1.51/0.99 1.51/0.99 4.7 6.83 -

5 0.72/0.47 0.72/0.47 3.4 3.31 -

6 1.00/0.65 0.85/0.56 5.4 3.62 -

7 N/A 4.66/3.05 N/A 17.05 1

8 N/A 2.60/1.70 N/A 9.57 -

9 N/A 2.94/1.92 N/A 7.86 -

mg/m3/ppbV = milligrams per cubic meter per parts per billion volume; N/A = not applicable.


7-6

7.2.2.4 Design Criteria Table 7-2 shows design criteria for the bio-trickling filter odor control system.

Table 7-2. Bio-Trickling Filter Design Criteria Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Description Criteria

Tower Type Once through—counterflow

Media Type Structured synthetic (for example: BioAir or approved equal)

Media Depth 12 feet

Tower Vessel Two @ 12-foot-diameter & 28 feet high

Contact Time 14 seconds

Makeup Water Plant effluent

Fans Type: Fiberglass reinforced plastic centrifugal (1 duty, 1 standby) Capacity: 21, 000 ft3/minute @ 7.3 inches water column Motor: 60 hp

Location Adjacent to primary clarifiers

Footprint 1,660 square feet

7.2.3 Recommended Alternative Based on the updated dispersion model results, the new sensitive receptors are not shown to be a new risk but are still exceeding odor and H2S target thresholds along with other (existing) sensitive receptors without additional odor control measures. The results also indicated that the 0.9 mg/m3 requirement for toxic air pollution control at the plant boundary was exceeded. For these reasons, along with the fact that the potential for nuisance odor complaints remain significant, it is recommended that the primary clarifiers are covered and that the headworks and primary clarifiers are ventilated to an odor control system. Covering the primary clarifiers is essential to capturing all nuisance odors. This project will install aluminum covers, similar to those in the photograph shown in Figure 7-4, over the primary clarifiers.

Figure 7-4. Covered Primary Clarifier



7-7

Due to stringent air quality criteria, it is recommended that a bio-trickling filter system is installed. Space limitations at SCTP warrant siting the filter system adjacent to the primary clarifiers. The bio-trickling filter system may provide as much as 94 percent odor removal at the most sensitive receptor (Receptor 3).

Please refer to Figure 7-5 for the preliminary layout of the bio-trickling filter odor control system.

Figure 7-5. Preliminary Layout of Odor Control System

*--,,, ' ' ' •

0

0

INSTALL COVERS ON PRIMARY CLARIFIERS

688786

' ' ' ' ' ' '

DEMOLISH CARBON SYSTEM

0

~ \ FUT\JRE 810-TRICKLING FILTER ~

OPERATIONS CENTER

0 0

0 0 00

0

0 0 0 ~o -

FILENAME:

0 20 40 80 ..............................

' ...

NOTES:

\ \

SCALE IN FEET

' ' - -1<EYMAP

1. REPLACE STAIRS TO EXTEND OVER DUCT.

2. RELOCATE PIPE FROM UNDER NEW 810-TRICKLING FILTERS AND FAN ENCLOSURES, INCLUDING 4' SSM, II" PSM 4'W2 AND II" W3

PLOT DATE: 812512017 PLOT TIME: 6:47:06 PM

SECTION 8

8-1

Selected Alternative Description The SCTP has realized slightly lower ADMM flows than projected in the 2004 Facilities Plan (CH2M, 2004) and the 2013 Facilities Plan (CH2M, 2013) (likely due to domestic water conservation measures that are being broadly observed across many wastewater collections systems), but, importantly, the waste load (BOD5, TSS, and ammonia-nitrogen) has generally followed the forecasted loadings as shown in Figures 1-1 and 1-2.

The Alliance has closely monitored influent flows, loads, and process performance as maximum month plant influent loads have been approaching 85 percent of rated capacity threshold. The unit process evaluation presented in Section 6 identifies current performance and potential limitations to confirm the recommendations from previous planning efforts.

After evaluating all unit processes at the SCTP (see Section 6), it is concluded that the treatment processes can treat up to an ADMM flow of 17 mgd and the associated flows and loads without affecting the ability of the SCTP to reliably and consistently comply with wastewater permit terms and conditions. This evaluation shows that the proposed basis for re-rating the SCTP is well within acceptable design parameters. Based on this, a standard facility re-rating process is applicable.

The proposed changes do not substantially change the potential for treatment system upset, bypass, or permit violations, nor change the potential environmental and public health consequences. Provision of RAS chlorination equipment reduces risk of losing sludge inventory from high SVI conditions that could lead to overflowing sludge blanket levels in the secondary clarifiers.

The regulatory needs for air quality/odor control improvements drive the recommendation of covering the primary clarifiers and constructing a vapor-phase bio-trickling filter odor control facility. The new primary clarifier covers will reduce maintenance access space and visual observation into the primary clarifiers, but access can easily be accommodated during regular maintenance activities that required manned entry into the primary clarifier tanks. The new odor control bio-trickling filter will run continually and require similar daily operations monitoring as the existing bio-trickling filter that treats air off the headspace of the sludge blend tank. The instrumentation and equipment associated with the new bio-trickling filter are similar to others onsite. Staff expects to accommodate such filter system O&M within the existing staffing framework.

Re-rating the facility will not have a major impact on the O&M of the plant because significant process modifications are not required. Neither additional process control(s) nor monitoring will be needed. No changes to the Certified Operator requirements will be required. An operator certified for at least a Class IV plant by the State of Washington shall be in responsible charge of the day-to-day operation of the SCTP. An operator certified for at least a Class III plant shall be in charge during all regularly scheduled shifts. The data that are currently collected by the SCTP are sufficient to evaluate and demonstrate the performance and reliability of the facility at the re-rated capacity. As flows and loads increase, the plant performance will be monitored through Daily Monitoring Reports.

A Tier-II Antidegradation Analysis, conducted per WAC 173-201A-320, has been performed (copy provided in Appendix D). The results of this analysis show that the proposed re-rating is acceptable, with increased flows discharging to the Columbia River through the existing outfall diffuser.

SECTION 9

9-1

Preliminary Cost Estimate Table 9-1 provides a preliminary estimate of the total project costs for the proposed project based on the Engineering Report recommendations. The estimate assumes costs for all elements expected to be part of the final design.

The cost estimate is considered to be consistent with Class 5 estimates, as defined by the Estimate Classification system of the Association for the Advancement of Cost Engineering International (formerly known as the American Association of Cost Engineers). The estimate was developed without detailed engineering data and is considered approximate. Class 5 estimates are normally expected to be accurate within minus 50 percent to plus 100 percent. This range implies that there is a high probability that the final project cost will fall within the range.

Table 9-1. Project Costs Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Item Cost Estimate

Delivery:

Engineering & Survey $740,000

Environmental & Other Permitting $80,000

Stakeholder Engagement & Outreach $40,000

Project Management $170,000

Construction Management $750,000

Total Delivery Cost $1,780,000

Construction:

Preliminary Treatment (Odor Control) $3,800,000

Secondary Treatment (RAS Chlorination Improvements) $250,000

Effluent Pump Station Modifications $0

Solids Dewatering (Allowance for Orège SLG® implementation) $250,000

Contingency $870,000

Total Construction Cost $5,170,000

Total Project Cost $6,950,000

SECTION 10

10-1

Project Funding The capital expenditures portion of proposed project will be funded as an Alliance Capital Project. The Alliance Capital Project work is funded by a combination of Regional Service Charges and debt proceeds to fund larger capital projects. The Alliance costs are then allocated to the Alliance Member Agencies, based on the amount of capacity allocation purchased with the project. In this case, the resulting Alliance charges from the Phase 5B Project have been communicated to the City of Battle Ground and Clark Regional Wastewater District as funding partners. The City and the District, in turn, have included the Alliance costs in the respective financial planning and rate modeling efforts to ensure that retail rates and charges are adequate to fund this project.

The O&M costs associated with power and general maintenance for the proposed odor control system will be incorporated into the annual operating costs for SCTP. The current annual O&M budget for SCTP is approximately $4 million per year. The additional costs for this work will be included in the future budgets associated with the construction period and commencement of operations.

SECTION 11

11-1

Staffing Requirements The proposed project will not increase staffing requirements at SCTP. The overall degree of operator attention required for the proposed facility is similar to that required for the current facility.

The new primary clarifier covers will reduce maintenance access space and visual observation into the primary clarifiers, but access can be accommodated during regular maintenance activities that require manned entry into the primary clarifier tanks. The new odor control bio-trickling filter will run continually, and require similar daily operations monitoring as the existing bio-trickling filter that treats air off the headspace of the sludge blend tank. The instrumentation and equipment associated with the new bio-trickling filter are similar to others onsite. Staff expects to accommodate such O&M within the existing staffing framework.

SECTION 12

12-1

Environmental Impacts The Phase 5B Project does not have a federal nexus and will not utilize the Clean Water Act State Revolving Fund loan program. Therefore, neither compliance with the National Environmental Policy Act nor the State Environmental Review Process will be required.

Development of this Engineering Report requires the Alliance to consider environmental values under the State Environmental Policy Act (SEPA). Consequently, the Alliance will conduct SEPA environmental review as lead agency per SEPA rules adopted under Chapter 197-11 WAC. The Alliance will prepare a SEPA checklist and determination of non-significance (DNS), taking into account all direct and indirect environmental impacts of the proposed project. Following a SEPA public notice period and response to public comments, the final SEPA checklist and DNS will be incorporated as part of the Engineering Report record.

All physical improvements to the SCTP would occur within the existing plant site. Consequently, their direct environmental effects would be expressed at the plant. The physical improvements at the plant site would be in designated Aquatic/Urban Conservancy and within the shoreline area of Salmon Creek. The project site lies within designated Priority Species Buffer and Priority Habitat and Species Area (i.e., Riparian Habitat Conservation Area), but the project site does not contain Wetlands, nor does it contain Floodway, Floodway Fringe, or 500 Year Flood Area. The project site is outside the Priority Habitat Buffer. There are no known or expected Endangered Species Act-listed species or critical habitats; or Washington Department of Fish and Wildlife priority species or habitats at the project site.

The SCTP sits on a documented cultural property that was destroyed by past development. The proposed physical improvements are not expected to encounter or disturb cultural properties. The SEPA DNS public notice will include tribes with treaty rights to the Columbia River where plant effluent will be discharged. Tribes with usual and accustomed territory within Clark County include the following:

• Cowlitz Indian Tribe, Washington—Area throughout Clark County is usual and accustomed territory

• Confederated Tribes and Bands of the Yakama Nation, Washington—South-central Washington

• Chinook Tribe—Not currently federally recognized

Tribes with usual and accustomed territory on shorelines adjacent to Clark County and/or within the upstream Columbia River Basin downstream of the Bonneville Dam include the following:

• Confederated Tribes of the Grand Ronde Community of Oregon—Usual and accustomed territory extending throughout the Grand Ronde area of Oregon

• Confederated Tribes of the Siletz Reservation, Oregon—Usual and accustomed territory throughout Western Oregon

During construction, a variety of equipment would be used for material delivery, grading, lifting, and clean up; and may include flat beds, loader, backhoe, scissor lift, crane, impact wrenches, and compressors. Existing noise at the SCTP includes normal plant O&M, including a variety of service vehicles, and would not be measurably different after the project. Although noise from the existing clarifiers is negligible, the proposed covers and associated ductwork would reduce the noise.

Under re-rating, the plant would treat about 14 percent more influent. A corresponding increase in treated effluent from the plant would discharge into the Columbia River.

By re-rating the SCTP capacity, the plant would be able to treat about 14 percent more influent flow and generate about 14 percent more biosolids and biogas.

SECTION 12 – ENVIRONMENTAL IMPACTS

12-2

Construction equipment would produce emissions of nitrogen oxides (NOx), carbon monoxide (CO), and PM10

1 (dust) during construction, but these amounts would be minor and temporary.

RAS chlorination facilities would improve treatment performance reliability under filamentous sludge bulking conditions, and reduce risk of these filamentous bacteria causing activated sludge process upsets that result in discharge of suspended solids to the Columbia River. Biosolids removed from the plant are regularly applied to nearby farmlands. From the second week of August through mid-September, when about half of the biosolids are taken to farms near Woodland, the number of daily truck trips may increase by 2 to 3 trips. During the remainder of the year, biosolids hauling to farms near Goldendale may increase by about 14 percent.

No changes to plant lighting are proposed. By re-rating the SCTP capacity, the plant would consume about 14 percent more electrical energy. The RAS chlorination system and bio-trickling filter odor control system would be electrically powered and create additional energy demands, but these would be small percentage increases over the energy use by SCTP operation.

The RAS chlorination equipment requires liquid sodium hypochlorite. The package system includes chemical storage and containment. Hypochlorite has a limited shelf life and is readily available. It would be ordered and delivered to the SCTP (likely in totes) when needed, so onsite storage would be minimal to none during periods of system non-use. Fuel used in construction equipment would not be stored onsite. The project would be constructed in accordance with applicable state and local health and safety regulations. The plant operates under a rigorous spill prevention, containment, and countermeasures plan.

Odors originating from the preliminary and primary treatment process would be captured and treated and dispersed. Odor control would limit H2S concentration below 0.9 mg/m3 in the airshed within the SCTP property boundary.

1 PM10 describes inhalable particles (particulate matter) with diameters generally 10 micrometers and smaller.

SECTION 13

13-1

Project Schedule A preliminary project schedule was developed that shows a total project duration of approximately 2 years. The preliminary project schedule, included as Figure 13-1, shows design development and permitting occurring in 2018, final design and permitting in 2019, and construction in 2020.

ID Task

Mode

Task Name Duration Start Finish

1 Engineering Report 145 days? Wed 6/21/17 Tue 1/9/18

25 RFQ for consultant selection for design (optional) 57 days Tue 1/16/18 Wed 4/4/18

32 Task 5 Project Definition 37 days Thu 4/19/18 Fri 6/8/18

43 Task 6 Schematic Design (30% Design) 44 days Mon 6/11/18 Thu 8/9/18

67 Task 7 Design Development (60%) 47 days? Fri 8/10/18 Mon 10/15/18

75 Task 8 Contract Documents (90%) 57 days? Tue 10/16/18 Wed 1/2/19

84 Task 9 Contract Documents (100%) 26 days? Wed 1/2/19 Wed 2/6/19

88 Task 10 Bid Period Services 238 days Thu 2/7/19 Mon 1/6/20

99 Task 11 Construction Phase Services 196 days Tue 1/7/20 Tue 10/6/20

M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D

Half 1, 2017 Half 2, 2017 Half 1, 2018 Half 2, 2018 Half 1, 2019 Half 2, 2019 Half 1, 2020 Half 2, 2020

Task

Split

Milestone

Summary

Project Summary

Inactive Task

Inactive Milestone

Inactive Summary

Manual Task

Duration-only

Manual Summary Rollup

Manual Summary

Start-only

Finish-only

External Tasks

External Milestone

Deadline

Progress

Manual Progress

Page 1

Project: 20170621 SCTP Phase 5

Date: Tue 10/10/17

Figure 13-1. Preliminary Schedule for Phase 5B Project

SECTION 14

14-1

Permitting and Regulations In accordance with RCW 90.48.110, all engineering reports, plans, and specifications for new construction or improvements to existing sewage treatment systems shall be submitted to and approved by Ecology before construction may begin. RCW 90.48.110 also allows delegation of this authority to local authorities that meet Ecology’s criteria. The District meets Ecology’s criteria and has entered into a formal delegation agreement with Ecology. As a result, the District will perform as the delegated authority for certain review and approval responsibilities, as indicated below. The Alliance will serve as SEPA lead agency under their adopted SEPA rules.

For the proposed project, the Alliance will obtain the following permits and approvals:

1. Review and approval of the Engineering Report by Ecology per WAC 173-240-060.

2. Review and approval of final Plans and Specifications per WAC 173-240-020(11) and WAC 173-240-070 by the District.

3. Review and approval of Construction Quality Assurance Plan per WAC 173-240-020(2) and WAC 173-240-075 by the District.

4. Modification of NPDES Permit No. WA0023639 by Ecology.

5. Minor Source Air Discharge Permit from Southwest Clean Air Agency.

6. Shoreline Management Act Shoreline Conditional Use Permit from Clark County.

7. Building Permit from Clark County.

8. Grading and Drainage Permit from Clark County.

As SEPA lead agency, the Alliance will perform the environmental review, prepare the SEPA checklist, determine the potential for environmental impact, and distribute the public notice. The Alliance may choose to cooperate with Clark County on public notice. A DNS is anticipated because all of the work will be performed within the existing treatment plant site, with limited disturbances to existing developed surfaces, and re-rating would result from operational adjustments alone.

http://www.swcleanair.org/docs/forms/01-MasterFormPermitApplication.pdf

SECTION 15

15-1

Supplemental Information For the reviewer’s convenience, Table G1-1 Requirements for Engineering Reports, taken from Ecology’s Criteria for Sewage Works Design (2008), is included as Table 15-1. The table provides a comprehensive list of the information required for engineering reports and facilities plans and the location where the information is provided. Additional supporting information regarding the SCTP service area and treatment facility can be found in the Facilities Plan (CH2M, 2013).

Table 15-1. Requirements for Engineering Reports Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Element Requirement Location or Reference

Site Description and Map Well documented Work for this project will occur around the primary treatment area of SCTP. A layout of the proposed modifications is shown in Figure 7-4.

For a description and map of the SCTP, refer to the Salmon Creek Wastewater Management System Wastewater Facilities Plan/General Sewer Plan (2004 Facilities Plan) (CH2M, 2004).

Problem Identification Well documented Refer to Section 3 of the Engineering Report for a Project Description.

Description of Discharge Standards Well documented Refer to the 2004 Facilities Plan (CH2M, 2004), as updated by the Facilities Plan (CH2M, 2013) and supplemented by the Tier II Antidegradation Analysis in Appendix D.

Background Information Existing Environment:

• Water, air, sensitive areas • Floodplains • Shorelines • Wetlands • Endangered species • Public health

Demographics and Land Use:

• Current Population

• Present wastewater treatment

• Advanced wastewater treatment need evaluated

• Infiltration and inflow studies

• Combined sewer overflows

• Sanitary surveys for unsewered areas

Refer to the Salmon Creek Wastewater Management System Wastewater Facilities Plan/General Sewer Plan Amendment (Facilities Plan) (CH2M, 2013) and SEPA Checklist.

Future Conditions Demographics and Land Use:

• Projected population levels

• Appropriateness of population data source, zoning changes

• Future domestic and industrial flows, and flow reduction options

• Future flows and coding

Future demand projections for the SCTP are provided in Figures 1-1 and 1-2.

For additional information regarding future conditions, refer to the Facilities Plan (CH2M, 2013).

SECTION 15 – SUPPLEMENTAL INFORMATION

15-2

Table 15-1. Requirements for Engineering Reports Engineering Report for the Phase 5B Project—Salmon Creek Treatment Plant Improvements

Element Requirement Location or Reference

• Reserved capacity

• Future environment without project

Alternatives • List specific alternative categories, including no action

• Collection system alternatives

• Sludge management/use alternatives

• Flow reduction

• Costs

• Environmental impacts

• Public acceptability

• Rank order

• Recommended alternative

Unit process capacity analysis and alternatives are discussed in Section 6 of the Engineering Report. Odor control analysis and alternatives are discussed in Section 7 of the Engineering Report.

NA

Refer to Section 6 of the Engineering Report.

NA

Refer to Sections 9 and 10 of the Engineering Report.


NA

NA


Final Recommended Alternative • Site layout • Flow diagram • Sizing • Environmental impacts • Design life • Sludge management • Ability to expand • O&M/staffing needs • Design parameters • Feasibility of implementation

Refer to Figure 7-4 of the Engineering Report. Refer to Appendix A of the Engineering Report. Refer to Section 6 of the Engineering Report. Refer to Section 12 of the Engineering Report. Refer to Section 6 of the Engineering Report. Refer to Section 6 of the Engineering Report. Refer to Section 6 of the Engineering Report. Refer to Section 11 of the Engineering Report. Refer to Section 6 of the Engineering Report. Refer to Section 8 of the Engineering Report.

Financial Analysis • Costs • User charges • Financial capability • Capital financing plan • Implementation plan

Refer to Section 9 and Section 10 of the Engineering Report.

Other • Water quality management plan

• SEPA approval

• List required permits

Refer to Section 14 of the Engineering Report for information regarding SEPA approval and permitting.

For information regarding a Water Quality Management Plan, refer to the 2004 Facilities Plan (CH2M, 2004), as updated by the Facilities Plan (CH2M, 2013).

NA = not applicable.

SECTION 16

16-1

References American Water Works Association. 2008. M9 Concrete Pressure Pipe. Third Edition.

Bennoit, H., and C. Schuster. 2001. “Improvement of Separation Processes in Waste Water Treatment by Controlling the Sludge Properties.” Fachhochschule Sudwestfalen, 1-9.

Brown and Caldwell. 2010. Biosolids Processing and Utilization Review for the Salmon Creek Treatment Plant. September.

CH2M HILL, Inc. (CH2M). 2004. Salmon Creek Wastewater Management System Wastewater Facilities Plan/General Sewer Plan. June.

CH2M HILL, Inc. (CH2M). 2013. Salmon Creek Wastewater Management System Wastewater Facilities Plan/General Sewer Plan Amendment. August.

CH2M HILL, Inc. (CH2M). 2016. Salmon Creek Wastewater Treatment Plant (SCTP) Capacity Evaluation.

Heald, C.C. (ed.). 1998. Cameron Hydraulic Data. Ingersoll-Dresser Pumps.

Inman, D., and P. Capeau. 2015. “Solids-Liquid-Gas (SLG®) Separation Technology for Sludge Treatment: Results from a Pilot Scale Trial by Anglian Water. AquaEnviro. Conference Proceeding/Publication.

Metcalf & Eddy. 2002. Wastewater Engineering, Treatment and Reuse, Fourth Edition.

Orège. 2016. Supercharge Your Dewatering and Thickening. SLG® technology presentation. https://www.dropbox.com/s/4bnl1rtkmkuzrdt/2016%20SLG%20Orege%20Lunch%20and%20learn%20vF.pptx?n=108440598&oref=e

U.S. Environmental Protection Agency (EPA). 1975. Process Design Manual for Nitrogen Control. Technology Transfer.

U.S. Environmental Protection Agency (EPA). 1991. Technical Support Document for Water Quality-Based Toxics Control.

Washington State Department of Ecology (Ecology). 2008. Criteria for Sewage Works Design.

Water Environment Federation (WEF). 2010. Design of Municipal Wastewater Treatment Plants, 5th Edition – Manual of Practice No. 8. Water Environment Federation, Alexandria, Virginia.

https://www.dropbox.com/s/4bnl1rtkmkuzrdt/2016%20SLG%20Orege%20Lunch%20and%20learn%20vF.pptx?n=108440598&oref=e

https://www.dropbox.com/s/4bnl1rtkmkuzrdt/2016%20SLG%20Orege%20Lunch%20and%20learn%20vF.pptx?n=108440598&oref=e

Appendix A SCTP Flow Diagram

aarango

Snapshot

aarango

Snapshot

aarango

Line

Appendix B Projected Mass Balance for the SCTP

Table B‐1 SCTP Mass Balance for Projected Performance at 17 mgd and Associated Loads

Constituent Raw

Wastewater Recycled Stream

Primary Influent

Primary Effluent

ABs 1_4 Bioreactor

Influent

ABs 1_4 Secondary

Clarifier Influent

ABs 1_4 Secondary

Clarifier Effluent

ABs 5_6 Bioreactor

Influent

ABs 5_6 Secondary

Clarifier Influent

ABs 5_6 Secondary

Clarifier Effluent

Plant Effluent

Main Primary Sludge (PSD)

WAS Combined Discharge

GBT Thickened

WAS Imported

WAS

Meso Anaerobic Digester Influent

Meso Anaerobic Digester Effluent

BFP Dewatering

Biosolids to

Disposal Flow (gallons/day) 17,000,000 239,801 17,239,963 17,176,792 8,674,280 13,011,420 8,580,181 8,502,512 13,178,894 8,410,526 16,995,151 63,171 186,085 28,622 10,599 102,844 102,844 102,844 15,450 Carbonaceous BOD5 (lbs/day) 29,721 1,546 31,267 19,070 9,630 179,968 377 9,440 188,865 546

927 12,194 7,447 6,329

369 18,922 3,549 3,549 3,096

COD (lbs/day) 72,529 5,950 78,479 47,140 23,806 458,987 2,984 23,334 475,423 3,354 6,372 31,339 18,790 15,940 1,323 48,709 25,999 25,999 22,790 TSS (lbs/day) 34,686 4,371 39,058 16,404 8,284 379,543 732 8,120 385,269 1,053 1,785 22,669 15,456 13,138 2,392 38,329 21,489 21,489 19,340 VSS (lbs/day) 31,911 3,652 35,564 14,935 7,542 317,175 612 7,393 328,558 898 1,514 20,629 13,043 11,087 1,604 33,460 17,455 17,455 15,710 TKN (lbs/day) 5,093 838 5,932 5,497 2,776 21,330 268 2,721 22,093 284 556 434 868 734 174 1,342 1,342 1,342 586 NH3-N (lbs-N/day) 4,228 633 4,861 4,843 2,446 160 106 2,397 165 105 212 18 2 0 105 123 797 797 120 NO2-N (lbs-N/day) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 NO3-N (lbs-N/day) 0 15 15 15 8 1,304 860 7 1,181 754 1,648 0 18 3 0 3 0 0 0 Total Nitrogen (lbs-N/day) 5,093 853 5,947 5,512 2,784 22,634 1,128 2,729 23,275 1,038 2,204 434 886 737 174 1,345 1,342 1,342 586 TP (lbs-P/day) 993 489 1,482 1,187 599 14,943 288 588 13,113 341 664 295 558 470 87 834 834 834 417 Alkalinity (lbs/day as CaCO3) 29,082 2,665 31,748 31,632 15,974 9,039 5,961 15,658 9,598 6,125 11,924 116 132 20 428 566 3,172 3,172 477 H2S (lbs/day) 851 34 886 882 446 0 0 437 0 0 0 3 0 0 4 8 43 43 6 Temperature (oC) 14 21 14 14 14 14 14 14 14 14 14 14 14 14 20 15 35 35 35 BOD5 (mg/L) 209 773 217 133 133 1,657 5 133 1,717 8 7 23,130 4,795 26,496 4,171 22,046 4,135 4,135 24,013

COD (mg/L) 511 2,973 545 329 329 4,227 42 329 4,323 45 45 59,445 12,099 14,960 56,751 30,291 30,291 176,755 181,175

TSS (mg/L) 244 2,184 271 114 114 3,495 10 114 3,503 13 13 43,000 9,953 27,040 44,657 25,037 25,037 150,000 150,000

VSS (mg/L) 225 1,825 247 104 104 2,921 9 104 2,987 11 11 39,129 8,399 18,117 38,985 20,337 20,337 121,844 123,937 TKN (mg-N/L) 36 419 41 38 38 196 4 38 201 4 4 824 559 3,074 1,965 1,564 1,564 1,564 4,544 NH3-N (mg-N/L) 30 316 34 34 34 1 1 34 1 1 1 34 1 1 1,182 143 929 929 929 NO2-N (mg/L) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 NO3-N (mg-N/L) 0 7 0 0 0 12 12 0 11 11 12 0 11 11 0 3 0 0 0 Total Nitrogen (mg/L) 36 426 41 38 38 208 16 38 212 15 16 824 570 3,086 1,965 1,567 1,564 1,564 4,544

TP (mg-P/L) 7 244 10 8 8 138 4 8 119 5 4 560 359 984 972 972 972 3,233 3,308 Alkalinity (mg/L as CaCO3) 205 1,332 221 221 221 83 83 221 87 87 84 221 85 85 4,841 660 3,696 3,696 3,696

H2S (mg/L) 6 17 6 6 6 0 0 6 0 0 0 6 0 50 9 50 50 50 50

Appendix C Salmon Creek Treatment Plant

Phase 4 Odor Control Update

T E C H N I C A L M E M O R A N D U M

1

Salmon Creek Treatment Plant Phase 4 Odor Control Update

PREPARED FOR: John Peterson/Clark Regional Wastewater District

COPY TO: File

PREPARED BY: Alex Demith/CH2M

DATE: July 28, 2017

PROJECT NUMBER: 688766.03.30.04

Introduction The Salmon Creek Treatment Plant (SCTP) is a typical secondary treatment plant comprised of common unit processes that, in addition to the important work of treating wastewater, also generate odors as a byproduct of the various physical and biological treatment processes. These odors are primarily hydrogen sulfide (H2S) and smaller amounts of other organic reduced sulfur compounds (methyl mercaptans, dimethyl disulfide, etc.), all traditionally associated with secondary treatment plants. These odors can drift across plant property lines and affect nearby residents. This technical memorandum (TM) provides a comprehensive evaluation of odor control offsite impacts related to the SCTP and makes recommendations for meeting regulatory requirements pertaining to odor emissions.

Background In 2005, CH2M completed a preliminary design for the Phase 4 Expansion Program for the SCTP where a variety of odor control upgrades were explored. As a result of this effort, an odor control system was constructed for treating foul air from the Sludge Blend Tank, and a separate odor control system was constructed for serving the 117th Street Pump Station (also known as the Klineline Pump Station) force main discharge at SCTP. A preliminary design was also completed which included a bioscrubber/bio-trickling filter to treat foul air from the headworks and primary clarifiers. However, the implementation of this odor control system was deferred due to lack of an explicit regulatory permit driver at the time and lack of financial resources available for the program.

In March 2007, odor sampling and odor dispersion modeling activities were performed pertaining to the SCTP for the purpose of characterizing the odor footprint at the SCTP.

Since the work was completed in 2005 and 2007, multiple changes have occurred that justify updating the previous analysis for understanding future needs for the facility. These changes include the following:

• Residences (odor receptors) have been and are continuing to be constructed in close proximity to the plant. This means that current and future odor receptors are located closer to the SCTP than previously identified.

• Emissions (specifically toxic air pollutants) regulatory requirements have changed since completion of the previous work.

• Technologies including bio-trickling filters and biofilter medias have evolved and improved since completion of the previous work. Specifically, acceptable loading rates (both bed velocity and inlet

PHASE 4 ODOR CONTROL UPDATE

2

odor loadings) have gradually increased, making required footprints smaller. In addition, media types have improved, with longer life media now available.

Purpose This TM provides an update to previous work completed, including the following:

• Dispersion model update to account for additional odor receptors encroaching closer to the SCTP boundary.

• Dispersion model update to determine how toxic air pollutant (TAP) emissions regulatory requirements can be met.

• Updated technology evaluation of specific biological technologies to capture recent advances in the field and make recommendations for most preferred vapor phase odor control approach for SCTP.

• Updated costs for selected vapor phase odor control systems.

This TM provides a comprehensive odor evaluation that builds on previous work completed and provides a current update for facilitating funding decisions and capital improvements implementation plans moving forward.

Phase 4 Odor Control System Preliminary Design In 2005, CH2M completed a preliminary design for the Phase 4 Expansion Program for the SCTP. This effort included an evaluation of various odor control technologies capable of serving preliminary treatment (headworks) and primary treatment (primary clarifiers).

Odor Control System Sizing Criteria As part of the Phase 4 effort, detailed ventilation calculations were completed. These ventilation rates were identified as meeting the following objectives:

• Provide adequate ventilation to protect maintenance personnel within occupied spaces per National Fire Protection Association (NFPA) 820, Fire Protection in Wastewater Treatment and Collection Facilities, 1999 Edition.

• Maintain a minimum negative pressure of 0.1-inch water column (wc) within wastewater holding tanks and raw wastewater sewers to contain odors under the following conditions:

− Dynamic liquid level changes − Estimated crack openings in storage tank covers treated as sharp-edged orifices

• When a single access cover is removed, maintain sufficient velocities across the opening to prevent fugitive odors.

• Provide adequate turnover rate and air scavenging within storage tanks to reduce corrosion resulting from H2S pockets.

These criteria remain applicable with the exception of the 1999 edition of NFPA 820, which has been superseded by the 2016 version, adopted in June 2015. It should be noted that the 2016 version has no substantive changes pertaining to preliminary or primary facilities and therefore the ventilation values identified during the previous work remain applicable.

The previous predicted foul air flows from each preliminary/primary source at SCTP are summarized in Table 1.


3

Table 1. Foul Air Flow Rates and Sizing Criteria Summary

Location Air Flow

(ft3/minute) Air

(ACH) Sizing Criteria Summary

Headworks

Dumpster Room 1,000 7.2 Flow rate necessary to prevent buildup of interior odors by introducing sufficient dilution air. Based on past experience at similar process facilities.

Screen Channel 500 NA Flow rate necessary to maintain a negative 0.1-inch wc within channel under normal operating conditions assuming normal checkered plate, closed covers, and open cracks around checker plate openings. Flow rate necessary to maintain high capture velocity of > 50 fpm across open hatches.

Screen Room 11,100 15.5 Flow rate necessary to provide (1) adequate cooling in summer months due to heat generation, (2) exceedance of NFPA 820 ventilation criteria of 12 ACH, and (3) prevention of buildup of interior odors by introducing sufficient dilution air.

Primary Clarifiers

Underside of Covers 8,000 8.3 Flow rate necessary to (1) maintain a negative 0.1-inch wc under clarifier covers under normal operating conditions assuming typical cover tightness (crack opening of 0.02%), (2) maintain high capture velocity of > 50 fpm across open hatches, and (3) prevent pockets of corrosive H2S from accumulating by creating adequate scavenging velocities (~ 25 fpm).

Total at All Locations

Total 21,100 N/A N/A

ACH = air changes per hour; fpm = feet per minute; ft3/minute = cubic feet per minute; N/A = not applicable.

Vapor-phase Odor Control Technology Evaluation Four technologies were evaluated in the previous TM. These included packed chemical towers, mineral biofilters, organic biofilters, and bio-trickling filters.

Packed Chemical Towers

Packed chemical towers are a common form of wet scrubbers used for odor control in municipal wastewater treatment plants. They are a proven technology and have been the technology of choice for many wastewater treatment facilities. Odor constituents including H2S, ammonia, and various organic reduced sulfur (ORS) compounds may be reduced to very low levels using multistage packed towers. These systems are extremely effective in situations with high odor concentrations and large airflows. However, when compared to other technologies such as bio-trickling filters (or bio-trickling filters [BTFs] as described herein), these systems can be costlier and pose more safety concerns due to storage and handling of chemicals. These systems also exhibit greater complexity regarding operation due to


4

additional equipment and instrumentation when compared to other technologies. For these reasons, this technology was not selected after the evaluation in the previous TM.

Mineral Biofilters and Organic Biofilters

In an organic biofilter, organic material such as wood chips and compost are used as a medium to grow sulfur-consuming bacteria. Foul air is forced into the bottom of the biofilter bed and treated air is released from the surface. The bacteria also use other odor compounds as a food source, including ammonia, amines, and various ORS compounds.

The concept and components of a mineral (or sand) biofilter are the same as for an organic biofilter, but a different medium (proprietary sandy loam) is used to host the microbial population.

Both of these types of biofilters require large footprints and the organic media requires more frequent media replacement than a bio-trickling filter or chemical packed tower. The land needed based on the estimated required airflow made these systems less favorable than the bio-trickling filter system in the evaluation.

Selected Vapor-phase Odor Control System (Bio-trickling filter)

In the previously selected bio-trickling filter technology, odorous air is blown into the bottom of the tower and flows up through the media material, exiting through an exhaust stack. The media may be a synthetic material or a natural material such as lava rock. The bacteria also use other odor compounds as a food source, including ammonia and various ORS compounds. A typical bio-trickling filter schematic is shown in Figure 1. It should be noted that two types of systems are available; a bio-trickling filter (also known as a bioscrubber) in which scrubbant is recirculated over the media, and a BTF in which once-through irrigation water is applied over the top of the media. Bioscrubbers are generally more suitable for targeting H2S odors while BTF’s are more capable of treating a broad spectrum of odorants. This is because a gradient of bacteria (both low pH and neutral pH) generally exists within the BTF media bed, allowing for a greater removal of complex odorants. Low pH bacteria (autotrophic thiobacillus) specifically targets H2S) while neutral pH bacteria (heterotrophic bacteria) targets ORS compounds.

Earlier design bed velocities for bio-trickling filters were limited to 50 fpm maximum. However, advances in this technology as well as BTFs have gradually shifted acceptable bed velocities to as high as 100 to 200 fpm; although 100 fpm is considered an appropriate high end value that can be achieved by multiple suppliers.

The required empty bed gas residence time (EBGRT) ranges between 10 and 14 seconds, depending on odor loading rate. The design head loss through the media bed can range between 0.2 and 0.5 inch water column (WC) per foot of bed depth, depending on bed velocity selected and type of media. The required footprint for this technology is generally smaller than for biofilters. For all bioscrubber systems, a scrubbant recirculation pump is required to keep the media moist and maintain some biomass in solution. This is not the case with BTFs, in which makeup water is sprayed over the top of the media and

Figure 1. Simplified Schematic Diagram of a Bio-trickling filter System


5

drained out the bottom without recirculation. BTF suppliers include BioAir, Azzuro, and EcoVerde. Because of the synthetic nature of the media, supplemental nutrients are generally added for maintaining biomass health. However, if secondary effluent is available and meets specific water quality requirements, then supplemental nutrients are not required.

Preliminary Design Findings for Vapor-phase Odor Control Technology

The four vapor-phase odor control technologies were evaluated based on both cost and non-cost criteria. As a result of the evaluation findings, the recommended preliminary/primary odor control system for the previous Phase 4 work was determined and is summarized in Table 2.

Table 2. Bio-trickling filter Design Criteria


Tower Type Counterflow

Media Type Synthetic

Media Depth 12 feet (two 6-foot stages)

Tower Vessel Three @ 12-foot-diameter & 28 feet high

Bed Velocity 67 fpm (three duty units); 100 fpm (with one vessel down for maintenance)



Fan Type: FRP Centrifugal Capacity: 22,600 ft3/minute @ 7.2-inches wc Motor: 60 hp



FRP = fiberglass-reinforced plastic; hp = horsepower.

Bio-trickling filter technology was previously selected based on its low life-cycle cost, high qualitative rating, and consistent approach when considering the blend tank bio-trickling filter system currently operated at the plant. The main unfavorable factor related to this technology was the relatively high initial capital cost compared to the other technologies evaluated. The mineral biofilter alternative requires extensive footprint, which makes this alternative unfavorable. The compost biofilter alternative exhibits high initial costs associated with concrete work to enable media change-out in addition to high operating costs associated with frequent media change-out, which makes this alternative less favorable. The chemical packed tower scrubber alternative was the least favorable alternative, primarily because of high operation and maintenance (O&M) costs from chemical consumption as well as system complexity and safety.

One biofilter media type that was not previously considered is high-rate long-life engineered media. This media type biofilter option is compared to an updated BTF option herein.

2007 Odor Analysis Report The Odor Analysis Report completed in 2007 summarized the offsite odor goals for the SCTP based on the Southwest Washington Clean Air Agency (SWCAA) requirements for controlling nuisance odors. The report also summarized the results of an odor survey completed in August 2006 and the results of a dispersion model predicting offsite impacts. Two control scenarios were then developed to provide options for future consideration and long-range planning/programming.


6

Offsite Odor Goals The offsite odor goals described in the Odor Analysis Report were based on controlling nuisance odors, described by the SWCAA, at nearby sensitive receptor locations (neighboring houses). Target threshold values were selected for both H2S and total odor. The target chosen for H2S concentration at sensitive receptor locations adjacent to SCTP was 10 micrograms per cubic meter (µg/m3) (6.54 parts per billion by volume [ppbV]). The target chosen for total odor concentration at sensitive receptor locations adjacent to SCTP was 10 dilutions-to-threshold (D/T) with 100 percent compliance.

D/T is defined via odor tests conducted in an odor laboratory where air samples containing a combination of odorous compounds are diluted with clean air to below detectable concentrations and then introduced to a gas delivery system. A panel of eight members trained in odor response serves as the odor “detectors” for the sample. Panel members are asked to smell air samples delivered to a nose cone piece. By depressing buttons, the panelist introduces three distinct samples, one with the diluted sample and two with clean dilution air. Panel members are then asked whether they can detect a difference in the odor of the samples. If they cannot, the sample concentration is then increased by a given dilution amount, and the test is repeated. This process continues until half the panel members can detect the sample odor. This final level of sample concentration is called detection threshold (DT). Field olfactometry utilizes a field olfactometer, which dynamically dilutes the ambient air with carbon-filtered air in distinct dilution ratios known as D/T, indicating the number of dilutions of pure air required to get to the threshold of detection. The calculation method for field olfactometry (D/T) is slightly different from the calculation of the dilution factor in laboratory olfactometry (DT).

These target threshold values were chosen based on the concentrations of D/T and H2S that typically cause odor complaints. The target threshold for H2S is higher than its actual odorant detection thresholds. The detection threshold for H2S is approximately 0.5 - 1 ppbV. However, based on prior experience, odor complaints do not typically occur until H2S concentrations reach 7–10 ppbV (10.7–15.3 µg/m3). Similarly, the concentration in air at which odors from wastewater plants typically cause nuisance odor complaints is approximately 10 D/T.

Odor Survey The odor survey described in the previous report consisted of a sampling effort completed in August of 2006 that involved measuring H2S, dissolved sulfides, and odor (D/T) at the following sources:

• Primary clarifiers • Aeration basins • Secondary clarifiers • Sludge blend tank odor control • Biosolids blend tank • Biosolids Storage bunkers

It should be noted that the headworks, which is a major contributor to offsite odors/H2S, is not in the list above and was not measured as a part of this survey in 2006. This source was already identified as a large contributor and was previously measured during an earlier study.

All sources were selected based on their potential to emit odors and H2S offsite and cause complaints. Findings from this sampling effort are illustrated in Table 3.

Table 3. H2S and Total Odor Concentrations Measured During the 2006 Odor Survey

Source Description H2S (µg/m3)/(ppbV) Total Odor (D/T)

Primary Clarifiers 1–4 244 / 160 1100

Aeration Basins 1–6 18.3 / 12.0 160


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Table 3. H2S and Total Odor Concentrations Measured During the 2006 Odor Survey

Source Description H2S (µg/m3)/(ppbV) Total Odor (D/T)

Secondary Clarifiers 1–4 13.7 / 9.0 55

Biosolids Blend Tank 825 / 540 2100

Sludge Blend Tank Odor Control Stack 10.7 / 7.0 980

Biosolids Storage Bunkers 12.2 / 8.0 70

Headworks* 3057*/ 2000* 8000*

*Headworks was not sampled as a part of the survey in 2006. These values are from a prior survey and are included in table for comparison.

The conclusions of the study showed that the headworks, primary clarifiers, and biosolids blend tank had the highest concentrations and therefore the highest potential to create offsite odors. Detailed results, conclusions, and sampling methodology are further described in the Odor Analysis Report.

Air Dispersion Model

ISCST3 The previous air dispersion model was built using the Source Complex Short Term Version 3 (ISCST3) algorithm. ISCST3 is a steady-state Gaussian plume model that is used to assess pollutant concentrations from a wide variety of sources associated with an industrial complex such as a wastewater treatment plant. The ISCST3 model can account for the following:

• Settling and dry deposition of particles • Building downwash • Point, area, line, and volume sources • Plume rise as a function of downwind distance • Separation of point sources • Limited terrain adjustment

It should be noted that prior to the end of 2005, ISCST3 was the model that was recommended by the U.S. Environmental Protection Agency (EPA) for dispersion modeling. Since 2005, AERMOD became the EPA preferred model. ISCST3 is similar to AERMOD because they both use the steady-state Gaussian plume algorithm. However, ISCST3 is now considered an outdated model that is no longer supported or being used for EPA permitting.

Terrain Data Terrain data were used in the ISCST3 Model. These were taken from WebGIS.com in the form of DEM (Digital Elevation Model) files. These data were processed using AERMAP and were used to define base elevations for receptors, buildings, and sources based on the terrain surrounding the SCTP.

Meteorological Data The meteorological data used were from the year 1987. These data are now 30 years old, but they were used in the 2006 model because they are local data and considered the most representative data.

Receptors Gridded receptors, fence line receptors, along with sensitive receptors (nearby houses) were included in the modeling. The gridded receptors were defined as follows:

• Grid 1: 500-meter receptor spacing placed at 5,000 meters from the fence line.

• Grid 2: 100-meter receptor spacing placed at 1,000 meters from the fence line.


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• Grid 3: 50-meter receptor spacing placed at 550 meters from the fence line.

• Fence line: 25-meter spacing along the fence line.

• Sensitive receptors: Located at Easting and Northings of nearby houses. See Table 4 for locations. These also are illustrated graphically herein.

Table 4. Sensitive Receptors Locations: NAD

Receptor No. Easting X (m) Northing Y (m)

1 520988 5063657

2 521300 5063532

3 521413 5063682

4 521700 5064020

5 520940 5064676

6 520763 5064644

SCTP Baseline Odor/ H2S Characterization The measured D/T and H2S concentrations for the sources previously described in Table 3 were used to create the baseline odor characterization model for the SCTP. These concentrations, combined with the geometry of each source and estimated flux rates, were used to estimate odor and H2S emission rates. These emission rates were then input into the dispersion model to create a baseline for characterizing the odors and H2S being emitted from the plant.

Two separate baseline models were created from the model, one for H2S and one for D/T. Each baseline included the sources indicated in Table 3, along with the addition of the mixed liquor splitter box, primary effluent splitter box, and 117th Street Pump Station Force Main carbon stack. The model input concentrations for each baseline scenario are described in Table 5.

Table 5. Odor and H2S Average and Peak Emissions at Current Level of Odor Control*

Source Source Type

Average H2S (µg/m3/ppbV)

Average Odor (D/T)

Peak H2S (µg/m3/ppbV)

Peak Odor (D/T)

Primary Clarifier 1 Area 1,528/1,000 2,500 7,644/5,000 5,000




Aeration Basin 1 &2 Area 38.2/25 250 153/100 500

Aeration Basin 3 &4 Area 38.2/25 250 153/100 500

Aeration Basin 5 Area 38.2/25 250 153/100 500

Aeration Basin 6 Area 38.2/25 250 153/100 500

Secondary Clarifier 1 Area 153/100 100 382/250 200





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Table 5. Odor and H2S Average and Peak Emissions at Current Level of Odor Control*

Source Source Type

Average H2S (µg/m3/ppbV)

Average Odor (D/T)

Peak H2S (µg/m3/ppbV)

Peak Odor (D/T)

Primary Effluent Splitter Box Area 764/500 0.25 1,528/1,000 0.5

Mixed Liquor Splitter Box Area 764/500 0.25 1,528/1,000 0.5

Headworks Point 3,057/2,000 8,000 15,288/10,000 16,000

Biosolids Blend Tank Point 825/540 2,100 1,528/1,000 4,200

Sludge Blend Tank Odor Control Stack Point 10.7/7 980 10.7/7 1,960

Pump Station Carbon Stack Point 15.3/10 375 76.4/50 750

Biosolids Storage Bunkers Point 1,528/1,000 1.0 764/500 2.0

*Input concentrations for both peak and average are based on the measured values multiplied by correction factor.

As indicated in Table 5, two scenarios were completed for both the H2S baseline and D/T baseline models. One was based on average concentrations and the other was based on peak concentrations. The results for the peak emissions scenario are briefly described below. However, both average and peak scenarios are defined in detail in the Odor Analysis Report completed in 2007.

Hourly Peak H2S Baseline For the hourly peak H2S baseline, the dispersion model indicated that the headworks facility is the largest contributor to the offsite H2S concentrations followed by the primary clarifiers and aeration basins. The maximum offsite impact was 287 μg/m3 (188 ppbV) at the fence line.

The 1-hour annual peak H2S concentrations at the six sensitive receptors identified in Table 4 are summarized in Table 6. Figure 2, which was obtained from the Odor Analysis Report, represents H2S concentrations in μg/m3.

Table 6. Peak H2S Concentrations at Sensitive Receptors with Current Level of Odor Control

Receptor No. H2S Concentration (µg/m3) H2S Concentration (ppbV)

1 29.6 19.36

2 32.9 21.52

3 87.3 57.10

4 39.6 25.90

5 45.5 29.76

6 43.7 28.58


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Figure 2. Isopleths Showing Lines of Constant H2S Concentration in µg/m3—1-Hour Annual Peak

Hourly Peak Odor (D/T) Baseline For the hourly peak odor baseline, the model, similarly to the H2S baseline, indicated that the headworks facility is also the largest contributor to the offsite odor concentrations. The maximum offsite impact was 328 D/T at a point just outside of the fence line.

The 1-hour annual peak odor concentrations at the six sensitive receptors identified in Table 4 are summarized in Table 7. The isopleths shown in Figure 3 represent lines of constant odor concentrations in D/T.

Table 7. Peak Odor Concentrations at Sensitive Receptors with Current Level of Odor Control

Receptor No. Odor Concentration (D/T)

1 35

2 40

3 147

4 47

5 54

6 52


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Figure 3. Isopleths Showing Lines of Constant Odor Concentration in D/T—1-Hour Annual Peak

The peak H2S and peak D/T exceedances at each of the sensitive receptors for each baseline case are indicated in Table 8. This is based on the number of hours, over a 1 year period (8,760 hours), that the H2S and D/T concentrations were greater than 10 μg/m3 and 10 D/T, respectively.

Table 8. Number of 1-hour Exceedances per Year for Peak H2S and Peak Odor

Receptor No. H2S exceeding 10 µg/m3 Odor exceeding 10 D/T

1 41 133

2 361 857

3 637 1103

4 41 93

5 30 79

6 20 111


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Odor Control Alternatives Two odor control strategies were evaluated in the Odor Analysis Report, Odor Control Strategy 1 and Odor Control Strategy 2.

Odor Control Strategy 1 included covering the primary clarifiers and preliminary treatment channels and providing an odor control system for both the clarifiers and the preliminary treatment facility. This option would reduce maximum offsite H2S and odor concentrations from 287 µg/m3 (188 ppbV) and 328 D/T, respectively, to 11.3 µg/m3 (7.39 ppbV) and 53 D/T, respectively. See Figures 4 and 5.

Figure 4. 1-Hour Peak Hydrogen Sulfide Concentrations in µg/m3—Odor Control Option 1


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Figure 5. Isopleths Showing Lines of Constant Odor Concentration in D/T for Control Strategy 1—1-Hour Annual Peak

Odor Control Strategy 2 includes covering and treating air from the aeration basins in addition to the odor control system in Odor Control Strategy 1. The predicted offsite D/T and H2S concentrations with this option would be reduced to near the nuisance threshold value at the fence line. This further level of odor control was not considered to provide added benefit at the time since no homes were built closer than approximately 500 feet from the plant. See Figures 6 and 7.


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Figure 6. Isopleths Showing Lines of Constant H2S Concentration in µg/m3 for Control Strategy 2—1-Hour Annual Peak


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Figure 7. Isopleths Showing Lines of Constant Odor Concentration in D/T for Control Strategy 2—1-Hour Annual Peak

CH2M recommended Option 1, which involved covering the primary clarifiers and preliminary treatment channels and then ventilating these areas to a new odor control system. This was the best option since it provided enough odor control to maintain odors below the nuisance value at all nearby receptors. This recommendation has been carried forward programmatically as part of the definition of the Phase 6 Expansion project for the facility.

Air Emission Regulatory Requirement Update The air discharges from SCTP are regulated by the SWCAA to limit toxic air pollution and nuisance odors. Individual odor-causing compounds are quantified as a concentration (mass per volume). Of these compounds, H2S is a regulated toxic pollutant and the SWCAA has established a limiting concentration for H2S toxicity. This section describes the key regulatory requirements pertaining to required limits of SCTP air emissions.

Nuisance Odors Because H2S is easily detected by the human nose, it is also commonly regulated as a nuisance odor. The SWCAA Regulations (SWCAA 400) contain what is best termed as a “nuisance odor” clause. Section 400-


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040(4)(a) states: “Any person who shall cause or allow the generation of any odor from any ‘source,’ which may unreasonably interfere with any other property owner’s use and enjoyment of his property must use recognized good practice and procedures to reduce these odors to a reasonable minimum.” This clause indicates that procedures be put in place to mitigate odors so that they are not “unreasonable” or a nuisance. Odors in general are typically quantified using a D/T method. However, limiting values are not specifically defined by the SWCAA, so target thresholds were selected based on experience to meet these qualitative nuisance odor requirements.

Toxic Air Pollutants Since the 2006 model was completed, new regulations have been implemented for H2S at the state level but have not yet been adopted at the local level. At the state level, the Washington Administrative Code- Title 173-Chapter 460- Section 150 (WAC 173-460-150) describes an updated Acceptable Source Impact Level (ASIL) for H2S as 2.0 µg/m3 over a 24-hour period. The previous value was 0.9 µg/m3 over a 24-hour period. At the local level, which is regulated by the SWCAA, the new regulated value has not been adopted and the ASIL for H2S is 0.9 µg/m3 over a 24-hour period. To be in compliance with both the local agencies, the value 0.9 µg/m3 over a 24-hour period should be used as the required criteria. This discussion is further outlined in the Control Technology Considerations for Permitting the Expansion of the Salmon Creek Wastewater Treatment Plant report completed by CH2M in June 2016.

For the state level, these regulatory requirements can be found at http://apps.leg.wa.gov/WAC/default.aspx?cite=173-460-150. For the Local level (SWCAA), http://www.swcleanair.org/docs/regs/wac173460-1998.pdf.

Odor Criteria Requirements Based on the conclusions above, toxic air pollution requirements and odor criteria requirements include the following:

• H2S—For toxic air pollution control, H2S cannot exceed a 24-hour average of 0.9 µg/m3 at the property boundary per year.

• H2S—For nuisance odor control, H2S cannot exceed a 1-hour average of 10 µg/m3 at any receptor (residence) per year

• D/T—For nuisance odor control, D/T cannot exceed a 1-hour average of 10 D/T at any receptor per year.

Updated Odor Control Evaluation This section provides an updated odor control evaluation that builds on the previous Phase 4 work completed in 2005 as well as the previous odor survey work completed in 2007 and in the context of the current regulatory environment. This evaluation is based on influent flow and load consistent with the Phase 4 capacity of the facility.

Updated Baseline Air Dispersion Model The same model developed from the 2006 evaluation was used in this evaluation. This includes meteorological data, the modeling algorithm (ISCST3), gridded receptors, terrain data, and sources input data.

It should be noted that the meteorological data are 29 years old and the ISCST3 model algorithm used is no longer the recommended model by the EPA. This does not make the results invalid, but does affect the accuracy of the results because newer models such as AERMOD have shown to be more accurate. The year of meteorological data used is also a factor that affects the results of the model. The older the weather data and the farther the specific receptor is from the plant, the less accurate the model results will be. Ideally, the most recent onsite data are recommended. However, this requires the data to be

http://apps.leg.wa.gov/WAC/default.aspx?cite=173-460-150


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specially processed for use with the dispersion model. This processing is considered beyond the scope of this work, so the original meteorological data were used.

Further, it should be noted that while the permitting methodology is focused on incremental H2S emissions (above current permit), this analysis considers total H2S emissions compared to WAC, rather than current SWCAA, requirements. This is intended to focus the discussion specific to the potential for odor complaints and to anticipate the future possibility that SWCAA may adopt the updated WAC standards.

The only changes to the baseline model are the addition of three new sensitive receptors to account for a future housing development south of the plant. This development is much closer to the plant than the sensitive receptors described previously in the 2006 model. For this reason, the model was updated to account for these new sensitive receptor locations. See Figure 8 for illustration of these new locations (shown as yellow).

Figure 8. Google Earth Map Showing 2006 Sensitive Receptors and 2016 Sensitive Receptors

Future Housing Development


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As shown in Figure 8, the new receptors account for the future housing development and are much closer to the southwest side of the plant than any of the other receptors from the 2006 study.

The updated baseline model used the same source input concentrations as described in Table 5.

Table 9 lists two types of inputs for both H2S and odors: measured concentration without a peaking correction factor and measured concentration with a peaking correction factor. The correction peaking factor was used to account for grab sample inaccuracies, diurnal variations, and decay rates known to occur during sample hold times. The correction factor used for each source ranged between 3 and 32 based on the source and measured value.

Table 9. Baseline Peak Odor and H2S Input Concentrations, with and without Correction Factors

Area Sources H2S Measured (µg/m3/ppbV)

Peak H2S (µg/m3 /ppbV) with CF

Measured Odor (D/T)

Peak Odor (D/T) with CF

Primary Clarifier 1 245/160 7,644/5,000 1,100 5,000




Aeration Basins 1 & 2 18.3/12 153/100 160 500

Aeration Basins 3 & 4 18.3/12 153/100 160 500

Aeration Basin 5 18.3/12 153/100 160 500

Aeration Basin 6 18.3/12 153/100 160 500

Secondary Clarifier 1 13.8/9 382/250 55 200


Secondary Clarifier 3 13.8/9 382250 55 200


Primary Effluent Splitter Box NM 1,528/1,000 NM 0.5

Mixed Liquor Splitter Box NM 1,528/1,000 NM 0.5

Point Sources

Headworks NM 15,288/10,000 NM 16,000

Biosolids Blend Tank 826/540 1,588/1,000 2,100 4,200

Sludge Blend Tank Odor Control Stack 10.7/7 10.7/7 980 1,960

Pump Station Carbon Stack NM 76.4/50 NM 750

CF = correction factor; NM= not measured, peak value with correction factor was used in place.


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These correction factors, which were used for the baseline D/T and H2S nuisance model in 2006, were also used for this updated D/T and H2S nuisance baseline model (for meeting maximum thresholds of 10 µg/m3 (6.5 ppbV) H2S and 10 D/T over a 1-hour average interval). The correction factors were not used for the TAP ASIL Air Dispersion Model Analysis (H2S threshold of 0.9 µg/m3 (1.3 ppbV) over a 24-hour period) described herein.

Updated H2S and Odor Nuisance Baseline Model

Figures 9 through 12, and Table 10 illustrates the results for the updated peak odor (D/T) and H2S (µg/m3) nuisance baseline.

Figure 4. Isopleths Showing Lines of Constant H2S Concentration in µg/m3—1-Hour Annual Peak


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Figure 5. Isopleths Showing Lines of Constant H2S Exceedance of 10 µg/m3 in Hours—1-Hour Annual Peak


21

Figure 6. Isopleths Showing Lines of Constant Odor Concentration in D/T—1-Hour Annual Peak


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Figure 7. Isopleths Showing Lines of Constant Odor Exceedance of 10 D/T in Hours—1-Hour Annual Peak

Table 10. H2S and Odor Nuisance Baseline Peak, 1-Hour Average Concentration and Exceedances at Sensitive Receptors

Receptor

Concentration Exceedances

Baseline H2S (µg/m3/ppbV) with CF

Baseline Odor (D/T) with CF

Hours/year above 2 µg/m3 (1.3 ppbV)1 with

CF Hours/year above 10 D/T

Baseline with CF

1 26.28 / 17.2 29 54 133

2 31.15 / 20.4 35 361 857

3 87.39 / 57.2 103 637 1,103

4 39.58 / 25.9 41 60 93

5 45.47 / 29.7 30 46 79

6 43.65 / 28.55 20 50 111

7 44.32 / 28.99 47 68 75

8 70.16 / 45.89 73 147 147

9 62.3 / 28.99 64 285 291


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Table 10. H2S and Odor Nuisance Baseline Peak, 1-Hour Average Concentration and Exceedances at Sensitive Receptors

Receptor

Concentration Exceedances

Baseline H2S (µg/m3/ppbV) with CF

Baseline Odor (D/T) with CF

Hours/year above 2 µg/m3 (1.3 ppbV)1 with

CF Hours/year above 10 D/T

Baseline with CF

1 Pertains to future WAC ASIL limit for H2S

The results shown in Table 10 indicate that Receptor 3, which is a receptor from the previous 2006 model, still represents the highest offsite impact. Figures 10 and 12 show that the highest concentrated plume touches down directly on the Receptor 3 location outside the south tip of the plant fence line. Based on these facts, unless new developments are being constructed on the south tip of the plant, Receptor 3 is likely to remain the worst-case receptor. The conclusions from the odor analysis in 2006 therefore remain largely unchanged.

Toxic Air Pollutant ASIL Air Dispersion Model Analysis Since the 2006 model was completed, Washington State TAP regulations have been revised, including those pertaining to H2S. As previously discussed herein, the WAC ASIL for H2S concentration offsite is likely to be regulated at 2.0 µg/m3 (1.3 ppbV) over a 24-hour averaging period. This is approximately 5 times less than the H2S concentration threshold used in the nuisance model (10 µg/m3 [6.5 ppbV] over a 1-hour period). However, SWCAA has yet to adopt those revisions and still requires a value of 0.9 µg/m3 (0.6 ppbV) over a 24-hour period to be met. This is approximately 10 times less that the H2S concentration threshold used in the nuisance model (10 µg/m3 [6.5 ppbV] over a 1-hour period).

To understand potential compliance with the WAC ASIL, the H2S baseline nuisance model was updated with both the old threshold of 0.9 µg/m3 (0.6 ppbV) and the new H2S threshold of 2.0 µg/m3 (1.3 ppbV). This model also included the new sensitive receptors to account for the future housing development located south of the SCTP. Again, the threshold for compliance is based on incremental emissions associated with a change to the permitted facility; this modeling looks at total, rather than incremental, H2S emissions.

Since this model is to inform understanding of regulatory compliance based on a 24-hour average, a correction factor of 2 was used for accounting for grab sample inaccuracies . The measured H2S values for each source and the measured values with the correction factor of 2 are shown in Table 11.



H2S Measured (µg/m3/ppbV) with CF of 2.0

Primary Clarifier 1 245/160 489/320




Aeration Basins 1 & 2 18.3/12.0 37.0/24.0

Aeration Basins 3 & 4 18.3/12.0 37.0/24.0

Aeration Basin 5 18.3/12.0 37.0/24.0

Aeration Basin 6 18.3/12.0 37.0/24.0

Secondary Clarifier 1 13.8/9.0 27.5/18.0


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H2S Measured (µg/m3/ppbV) with CF of 2.0




Primary Effluent Splitter Box NM 764/500

Mixed Liquor Splitter Box NM 764/500

Point Sources

Headworks 114/75.0 305/200

Biosolids Blend Tank 825/540 1682/1100

Sludge Blend Tank Odor Control Stack 10.7/7.0 21.4/14.0

Pump Station Carbon Stack NM 15.3/10.0

Biosolids Storage 12.2/8.0 24.5/16.0

The results of the TAP dispersion model are shown in Figure 13 and Table 12 below.


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Figure 8. Isopleths Showing Lines of Constant H2S Concentration in µg/m3 —24-Hour Annual Peak

Table 12. Toxic Air Pollutant Baseline- Peak, 24-Hour Average H2S Concentrations at Sensitive Receptors

Receptor Maximum H2S (µg/m3/ppbV)

Exceedances hours/year above 0.9 µg/m3

Exceedances hours/year above 2.0 µg/m3

Highest (fence line) 3.33/2.18 23 3

1 0.24/0.16 0 0

2 0.730.48 0 0

3 1.98/1.30 3 0

4 0.51/0.33 0 0

5 0.51/0.33 0 0

6 0.22/0.14 0 0

7 0.91/0.60 1 0

8 0.42/0.27 0 0

9 0.73/0.48 0 0


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For H2S, the results from Table 12 show that, without any odor control (baseline), the fence line, and Receptors 3 and 7 all exceed the old threshold of 0.9 µg/m3 (0.6 ppbV). However, Receptor 3 is the only receptor that comes close to the ASIL for H2S of 2.0 µg/m3 (1.3 ppbV). The highest value recorded was at the fence line and was 3.33 µg/m3 (2.18 ppbV) and exceeded the new threshold 3 hours out of the 8,760 hours in the year. These results show that the plant in its current state is not in compliance at the property boundary for both thresholds. Due to the lack of compliance, odor control will be needed during the Phase 4 expansion.

Updated Odor Control Alternatives

Two strategies were described in the previous analysis, Odor Control Strategy 1 and Odor Control Strategy 2. Since Odor Control Strategy 1 was the recommended option, it was the only alternative that was updated. Strategy 2 would only be updated if the conclusions or recommendations changed.

Odor Control Strategy 1 involves covering the primary clarifiers and the headworks and ventilating these sources to three bio-trickling filters.

The results of the updated baseline model and the TAP analysis showed that Receptor 3 is still the worst-case receptor and that both the new and the old ASIL for H2S at the property boundary are not in compliance. A revised strategy was developed based on an engineered media biofilter approach and reduced number of bio-trickling filter/BTF vessels. The engineered media approach was modeled because of its simplicity, it’s ease of maintenance, and because it has now become a proven cost-effective technology. Only two bio-trickling filters/BTFs are needed to treat current loads as opposed to three because of improvements in the media and its ability to handle a higher rate of loading. Because bio-trickling filters/BTFs and engineered media biofilters have similar removal efficiencies, this revised strategy changed only the number and location of odor control stacks. Only one odor control stack is modeled for the biofilter strategy instead of the previous three (one per bio-trickling filter vessel). Only two odor control stacks are modeled for the revised bio-trickling filter/BTF strategy instead of the previous three (one per vessel). The revised control strategy was also updated to include the latest receptors. A summary of updated Odor Control Strategy 1 is indicated below:

• Updated with new receptors based on future housing development.

• Updated based on an engineered media biofilter instead of three bio-trickling filters.

• Updated based on new location of the odor control system.

• Biofilter operating efficiency assumed to have 99 percent H2S removal and 90% Odor (D/T) removal, which is the same as the bio-trickling filters modeled previously.

• All other source Inputs based on updated baseline model described above.

• Primary clarifiers and headworks sources are deleted from baseline model since they are contained.

The results for the bio-trickling filter/BTF approach are shown in Figures 14 and 15 and Table 13.


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Figure 9. Isopleths Showing Lines of Constant H2S Concentration in µg/m3 —1-Hour Annual Peak, Revised Control

Strategy 1—Bio-trickling filter/BTF Approach


28

Figure 10. Isopleths Showing Lines of Constant Odor Concentration in D/T—1-Hour Annual Peak, Revised Control

Strategy 1—Bio-trickling filter/BTF Approach

Table 13. Revised Control Strategy 1—Bio-trickling filter/BTF Approach, 1-Hour Peak Average H2S Concentrations at Sensitive Receptors

Receptor

H2S (µg/m3/ppbV) H2S (µg/m3/ppbV) Odor (D/T) Odor (D/T) Odor Exceedances






1 1.14/0.75 1.16/0.76 6.1 4.77 -

2 1.55/1.01 1.49/0.97 5.2 6.01 -

3 2.05/1.34 1.49/0.97 7.6 6.59 -

4 1.51/0.99 1.51/0.99 4.7 6.83 -

5 0.72/0.47 0.72/0.47 3.4 3.31 -

6 1.00/0.65 0.85/0.56 5.4 3.62 -

7 N/A 4.66/3.05 N/A 17.05 1

8 N/A 2.60/1.70 N/A 9.57 -

9 N/A 2.94/1.92 N/A 7.86 -


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The results of Revised Odor Control Strategy 1 show that Receptor 7 is the only receptor to exceed the nuisance odor threshold of 10 D/T. However, this only happens 1 hour per year. This is less than 0.01 percent of the time. Since this is such a small percentage of time, it is not considered a high enough risk to consider more conservative alternatives.

Table 13 also shows the values from the previous study as comparison. The slight differences are due to the change in the number of stacks for the bio-trickling filter/BTF approach.

The results for the biofilter approach are shown in Figures 16 and 17 and Table 14.

Figure 16. Isopleths Showing Lines of Constant H2S Concentration in µg/m3 —1-Hour Annual Peak, Revised Control

Strategy 1—Biofilter Approach


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Figure 17. Isopleths Showing Lines of Constant Odor Concentration in D/T – 1-Hour Annual Peak, Revised Control

Strategy 1—Biofilter Approach

Table 14. Revised Control Strategy 1—Biofilter Approach, 1-Hour Peak Average H2S Concentrations at Sensitive Receptors

Receptor

H2S (µg/m3/ppbV) H2S (µg/m3/ppbV) Odor (D/T) Odor (D/T) Odor Exceedances






1 1.14/0.75 1.16/0.76 6.1 4.73 -

2 1.55/1.01 1.49/0.97 5.2 5.83 -

3 2.05/1.34 1.47/0.97 7.6 7.02 -

4 1.51/0.99 1.51/0.99 4.7 4.68 -

5 0.72/0.47 0.72/0.47 3.4 3.31 -

6 1.00/0.65 0.85/0.56 5.4 3.62 -

7 N/A 4.66/3.05 N/A 17.05 1

8 N/A 2.60/1.70 N/A 9.57 -

9 N/A 2.94/1.92 N/A 7.86 -


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The results of Revised Odor Control Strategy 1 with the biofilter approach, indicated in Table 14, are similar to the results for the Bio-trickling filter/BTF approach shown in Table 13. Receptor 7 is the only receptor to exceed the nuisance odor threshold of 10 D/T. Similar to the bio-trickling filter/BTF approach, Table 14 shows that this exceedance only happens 1 hour per year, which is less than 0.01 percent of the time. Since this is such a small percentage of time, it is not considered a high enough risk to consider more conservative alternatives.

Table 14 also shows the values from the previous study for comparison. The slight differences are due to the change in the number of stacks from three to one.

The results for both approaches are similar and indicate that either the biofilter or bio-trickling filter/BTF approach will meet the nuisance criteria with only 1 hour of exceedance in the year.

Control Strategy 1 was also modeled to ensure compliance with the ASIL threshold of 0.9 µg/m3 over a 24-hour averaging period at the fence line. The results of this model run showed that the maximum H2S concentration at the fence line was 0.855 µg/m3. This is less than the 0.9 µg/m3 as required by the SWCAA, and, therefore, Control Strategy 1 also meets the regulatory permitting requirements. Figure 18 below illustrates the results.

Figure 18. Isopleths Showing Lines of Constant H2S Concentration in µg/m3—24-Hour Average, Revised Control

Strategy 1—Bio-trickling filter Approach


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Technology Evaluation

Originally, the proposed Control Strategy 1 system consisted of three 12-foot-diameter, once through, packed media bio-trickling filters/BTFs. This was considered the best available system that provided the most benefit to cost in the 2005 evaluation. Since 2005, BTFs and biofilters have improved in performance and efficiency. To ensure the best technology is selected, the evaluation from 2005 was revisited to account for these technology advancements. For this evaluation, two alternatives were evaluated for the SCTP odor control system: structured media BTF, as previously described herein, and a high rate engineered media biofilter.

High rate engineered media biofilters are biofilter systems that utilize a proprietary media that performs under much higher loading rates than organic, soil, or mineral biofilters. High rate engineered media biofilters also exhibit similar or better performance characteristics than organic mediums. These types of systems also have longer lasting media and require less footprint due to the higher loading. The media is generally more expensive because it is a unique proprietary composition.

Design flow rates for high rate biofilters range from 5.0 to 11.0 cubic feet per minute per square foot. Media life is normally guaranteed for 10 to 20 years. The appropriate EBGRT for high rate media is dependent upon the target odor and respective loading rate but will typically range between 30 to 60 seconds.

Generally, high rate biofilter media do not require a nutrient source because they have a nutrient constituent built into the media recipe. The advantages of high rate packaged biofilters include the following:

• A wide range of odorous constituents may be removed.

• The system O&M is relatively simple.

• Chemical storage and delivery is not required.

• High rate proprietary media requires less frequent change-out (generally guaranteed for 10 to 20 years).

• The control systems are either manually operated or are relatively simple.

• The collected leachate is typically not odorous, as with compost biofilters.

• The required footprint is approximately half that of organic media biofilters.

• High-velocity stack that allows for better dispersion/dilution than open area biofilters without cover and stack.

However, high rate biofilters have the following disadvantages:

• Media costs can be high.

• Because bacterial populations provide the removal mechanism, the system can handle gradual cyclic loadings but cannot accommodate rapid load spikes effectively.

• Can require larger footprint than BTFs

Alternative 1—Structured Media BTF This alternative is similar to the recommended alternative from the 2005 evaluation but consists of revised BTF technology that includes structured synthetic media as opposed to random packed media. Structured synthetic media improves uniformity in the BTF media and has much more resistance to breakdown and compaction. This design improvement has allowed BTFs to handle up to 200 fpm loading capacity with little to no loss in removal efficiency. Previously, the 2005 evaluation was based on bio-trickling filters with a maximum loading rate of 50 to 75 fpm. The designed loading rate for this


33

alternate is now based on 100 to 150 fpm, which reduces the number of vessels required for the design H2S loading rate. The revised alternative now consists of only two (instead of three) FRP towers with structured synthetic media and an exhaust fan with acoustical enclosure. The BTF configuration evaluated is also a once-through type BTF to minimize maintenance and create a pH gradient to increase ORS removal. System drainage water would exhibit low pH and would be drained back to a process flow stream or storage tank. Further design criteria associated with this alternative are described in Table 15.

Table 15. Alternative 1—BTF Design Criteria


Tower Type Once through—counterflow

Media Type Structured synthetic

Media Depth 12 feet

Tower Vessel Two @ 12-foot-diameter & 28 feet high



Fans Type: FRP centrifugal (1 duty, 1 standby) Capacity: 21, 000 ft3/minute @ 7.3-inches wc Motor: 60 hp



For layout drawings, see previous report completed in 2005. Note that the layout in 2005 has three vessels and only one fan. The updated evaluation herein now considers space and costs for an extra standby fan and is based on two vessels.

Alternative 2—Engineered Media Biofilter This alternative involves an in ground engineered media biofilter located next to the primary clarifiers. The biofilter consists of high rate proprietary media placed in two cells approximately 35 feet by 40 feet in size designed for 45 seconds of EBGRT. Each cell is approximately 12 feet deep in the ground, which accounts for 6 feet of media, 3 feet for the underground air distribution system, and 3 feet for concrete and space above the biofilter. Three feet of the biofilter is assumed to be above grade. Each cell will be covered with aluminum covers and ventilated through a common 15-foot stainless steel stack or coated carbon steel stack. Two odor control exhaust fans will be used to ventilate the primary clarifiers and headworks. There will be one duty fan and one standby. Table 16 summarizes this alternative.

Table 16. Alternative 2—Engineered Media Biofilter


Biofilter Type At-grade w/concrete retaining walls

Media Type Engineered media

Media Depth 6 feet

Gas Residence Time (GRT) 45 seconds

Loading Rate 8 ft3/minute/square feet

Humidification Primary: humidification chamber Secondary: irrigation type sprinklers


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Table 16. Alternative 2—Engineered Media Biofilter


Fans Type: FRP centrifugal (1 duty, 1 standby) Capacity: 21,000 ft3/minute @ 7.3 inches wc Motor: 60 hp


Footprint 5,600 square feet (80 feet x 70 feet)

Both economic (cost) and non-economic (benefit) criteria were used to evaluate the two technologies described above. A technology with the lowest cost to benefit ratio is the most appropriate technology for the SCTP.

Economic Evaluation Economic criteria include capital cost and life-cycle cost.

A conceptual level cost estimate has been developed for each evaluated technology. The cost estimates are considered a study or feasibility, Class 4 estimate as defined by the Association for the Advancement of Cost Engineering International. These estimates are considered accurate from +20 to +50 percent on the high side to -15 to -30 percent on the low side, based on a preliminary design, level of information available, and estimating techniques used.

Capital costs for all odor control technology alternatives include site work, odor control equipment, mechanical, electrical, instrumentation and control, piping, and ductwork. Site work includes excavation for equipment pads and biofilter vessels. Odor control equipment costs include the odor control fans, media, and vessels. The ductwork costs include an estimated 550 feet of collection duct from the headworks and primary clarifiers. Also included are aluminum covers for the primary clarifiers as well as a $100,000 place holder for modifying the headworks heating, ventilation, and air conditioning (HVAC) system. Capital costs are estimated using the following approach:

• Equipment costs are based on recent equipment supplier cost quotes received.

• Percentage markups applied for unknown costs such as site work, instrumentation, electrical, and yard piping.

Additional project costs were developed by escalating the equipment sub-cost by the markups illustrated below.

Markups applied to equipment cost were as follows:

• Equipment Installation: 10% • Field Painting/Finishes: 1% • Mechanical: 8% • Electrical: 8% • Instrumentation: 5%

Contractor markups applied to equipment subtotal + project costs were as follows:

• General Conditions: 7% • Overhead: 5% • Profit: 5% • Bonds/Insurance: 2.5%


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• Contingency: 20% • Escalation (3% per year): 6% (construction completed end of 2018)

Non-construction cost markups applied to construction cost after contractor markups and escalation were as follows:

• Permitting 3% • Engineering 10% • Services during Construction: 5% • Commissioning/Startup: 5% • Sales Tax: 8.4% (Sales tax in Washington)

O&M and life-cycle costs were developed using the following inputs:

• Electricity Costs: $0.06/ kilowatt-hour • Operator Labor Costs: $40/hour • Financing Costs: 20-year life, 6 percent discount rate • Nutrient Costs: $10/gallon

Table 17 summarizes the cost estimate for evaluated odor control technologies.

Table 17. Cost Estimate Summary of Technologies

Item BTF

(x$1,000) Engineered Media Biofilter

(x$1,000)

Capital Equipment Costs:

Odor Control Equipment $794 $372

Biofilter Aluminum Cover $0 $91

Primaries Aluminum Cover $239 $239

HVAC For Headworks $100 $100

Ducting and Stack $234 $243

Site work $18 $279

Subtotal- Equipment Costs $1,386 $1,324

Capital Mark-up Costs:

Allowance Costs $460 $440

Contractor Markups $360 $344

Contingency (20%) $441 $422

Escalation (3% per year) $238 $228

Non-construction Capital Costs:

Engineering $289 $276

Permitting $87 $83

Services During Construction $144 $138

Commissioning and Start-Up $144 $138

Sales Tax $242 $232


36

Table 17. Cost Estimate Summary of Technologies

Item BTF

(x$1,000) Engineered Media Biofilter

(x$1,000)

Annual Costs:

Electrical Power $10.94 $11.06

Maintenance $25.87 $36.79

Nutrients $19.16 $0.00

R&R Costs $7.70 $12.59

Water $5.37 $5.37

Subtotal – Annual Costs $70.00 $66.00

Present Worth Annual Costs $873 $823

Total Capital Cost $3,794 $3,623

Total Project Present Worth $4,667 $4,446

The updated cost evaluation shows that the total project present worth cost for the BTF is approximately $221,000 more than the engineered media biofilter. Furthermore, costs associated with the biofilter are shown to be less in every category including capital cost and annual cost.

Non-economic Evaluation The non-economic evaluation criteria have been updated to be slightly different but more applicable than those of the evaluation in 2005, as follows:

• Safety and Health: This criterion refers to day-to-day operator safety related to the type of odor control system. Both BTFs and biofilters are considered equally safe to operate and pose no major safety or health concerns.

• Risk of Odor Breakthrough: Because odor receptors are located close to the plant, this criterion is weighted high for the odor control systems evaluated. Both biofilters and BTFs are susceptible to odor breakthrough under certain peak conditions because both require a certain bacterial population to reduce different concentrations of H2S. However, engineered media biofilters tend to be a little more effective at handing these spikes due to the adsorption capabilities of the media.

• Technology Maturity and Reliability: Some alternatives evaluated have a more proven track record of success when designed and operated correctly. Others are newer technologies that have recently been introduced to the market. Both of the control technologies evaluated, BTFs and engineered media biofilters, have many proven installations in the marketplace. Both are considered equal in maturity and reliability.

• Level of Maintenance Required: This criterion refers to the day-to-day maintenance that would be performed by County staff. Biofilters and once-through BTFs both require a minimal amount of maintenance because the fans are usually the only pieces of mechanical equipment in each system. However, because BTFs require nutrient addition, they require slightly more maintenance than engineered media biofilters.

• Level of Operating Complexity: Similar to maintenance requirements, this criterion refers to the day-to-day need for operator attention. Generally, engineered media biofilters and once-through BTFs require minimum operator attention, involving periodic monitoring for odors or checking of the


37

biofilter media for moisture content. Because the BTFs require nutrient addition, the complexity is considered slightly greater than that of an engineered media biofilter.

• Energy Usage: This is based on the energy required by the entire system. For both systems the fans will be the main source of energy usage. The biofilter is slightly higher because it requires two stack fans to add static pressure that is lost due to covering the biofilter. In addition, the expected pressure drop across the biofilter media is expected to exceed that for the BTF.

• Space Requirements: Space requirements include footprint areas for odor control equipment as well as space for access for equipment. Engineered media biofilters require larger footprints than BTFs.

• Odor Removal Efficiency: Odor removal efficiency relates to the ability of a particular odor treatment technology to remove odor constituents such as H2S, reduced sulfur compounds, and other constituents. Once-through BTFs and engineered media biofilters can effectively remove both H2S and ORS compounds effectively. However, due to longer EBGRT biofilters will have slightly better efficiency.

Each criterion was given a weighting factor, depending on the importance of the criterion for this specific application. Then a score was given for each criterion to each technology. The final score is a weighted overall score of all criteria. Table 18 summarizes the weighing of the criteria and score of each evaluated technology. Figure 19 illustrates the results.

Table 18. Non-economic Evaluation of Technologies

Evaluation Criteria Criteria Weight

Weighed Score

Engineered Media Packaged Biofilter BTF

Safety/Health 10 73.68 73.68 Risk of Odor Break-through 15 47.37 31.58 Technology Maturity and Reliability 15 31.58 31.58 Level of Maintenance Required 10 84.21 63.16 Level of Operating Complexity 10 84.21 63.16 Energy Usage 10 63.16 73.68 Space Requirements 10 42.11 84.21 Odor Removal Efficiency 15 78.95 78.95

Total Weighed Score (out of 100)

63.16 62.50

Ranking

1 2


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Figure 19. Non-economic Scores for Alternatives 1 and 2

Both the BTF and engineered media biofilter technologies are ranked very close to each other. However, due to slightly less risk with odor breakthrough and less complexity and maintenance, the engineered media biofilter ranks slightly better than the BTF.

Cost-benefit Analysis The cost-benefit of each technology was estimated by dividing the 20-year life-cycle cost by the non-economic weighed score. Figure 20 shows the cost-to-benefit ratio of each odor control technology. The alternative with the lowest cost-to-benefit ratio would be the most desirable technology, since it represents the system that costs the least when providing the same non-economic benefit. As Figure 20 shows, the cost-benefit ratio is lower for the engineered media biofilter. Since both technologies exhibit essentially equal rankings in the non-economic analysis, this chart is based mainly on the cost difference between the two technologies.


39

Figure 20. Cost-benefit Analysis Results for Alternatives 1 and 2

Conclusions and Recommendations Conclusions The odor control offsite criteria were determined to be the following:

• H2S—For toxic air pollution control, H2S cannot exceed a 24-hour average of 0.9 µg/m3 at the property boundary per year.

• H2S—For nuisance odor control, H2S cannot exceed a 1-hour average of 10 µg/m3 at any receptor (residence) per year

• D/T—For nuisance odor control, D/T cannot exceed a 1-hour average of 10 D/T at any receptor per year.

In reviewing the regulatory requirements, without any odor control (baseline), the fence line, and Receptors 3 and 7 all exceed the current WAC threshold of 0.9 µg/m3 (0.6 ppbV). However, Receptor 3 is the only receptor that comes close to the future ASIL for H2S of 2.0 µg/m3 (1.3 ppbV). The highest value recorded was at the fence line and was 3.33 µg/m3 (2.18 ppbV). These results showed that the plant currently is not meeting these requirements and odor control is necessary.

The results of the updated baseline nuisance dispersion model indicate that that the new receptors located south of the SCTP do have potential for odor impacts but are still not as high as Receptor 3 from


40

the 2006 analysis, which is located southeast of the SCTP fence line. This confirms that the conclusions from the 2006 report remain valid. The potential for nuisance odors are still present based on the current plant operation.

Odor Control Strategy 1, which was recommended in 2006, was updated with the new receptors and with the latest odor control systems. The results indicate that only Receptor 7 exceeds the target odor threshold of 10 D/T with implementation of this strategy, but at less than 0.01 percent of the year. The results also showed that Odor Control Strategy 1 meets the 0.9 µg/m3 requirement for toxic air pollution control at the plant boundary.

The updated evaluation comparing the latest odor control technology alternatives indicate that both the engineered media biofilter and BTF are viable options.

Recommendations Based on the updated dispersion model results, the new sensitive receptors are not shown to be a new risk but are still exceeding odor and H2S target thresholds along with other (existing) sensitive receptors without additional odor control measures. The results also indicated that the 0.9 µg/m3 requirement for toxic air pollution control at the plant boundary is currently being exceeded. For these reasons, along with the fact that the potential for nuisance odor complaints remains significant, it is recommended that the revised Odor Control Strategy 1 continue to be carried forward for implementation. This alternative includes covering and ventilating the primary clarifiers and ventilating the headworks facility to an odor control system.

Based on the alternative evaluation results, it is recommended that both the BTF and engineered media biofilter be considered as part of a predesign effort. Considerations beyond the scope of this work that should be considered in more detail include aesthetics of the installation as well as expandability to address future process expansions and overall site constraints.

Appendix D Tier II Antidegradation Analysis

T E C H N I C A L M E M O R A N D U M

1

Draft Water Quality and Tier II Antidegradation Evaluation

PREPARED FOR: John Peterson/ Clark Regional Wastewater District

PREPARED BY: Erin Thatcher, EIT Brady Fuller, PE

DATE: August 11, 2017

PROJECT NUMBER: 688766.03.30.04

This technical memorandum provides an evaluation of the Salmon Creek Treatment Plant (SCTP) Phase 5B plant capacity expansion with regard to water quality in the Columbia River and Washington water quality standards (Washington Administrative Code [WAC] 173-201A). The Phase 5B effluent flows will be discharged into the Columbia River through the existing outfall and diffuser until the replacement outfall and diffuser are completed under the Phase 5A project. The existing outfall in the Columbia River near River Mile 96, terminates with a diffuser composed of five risers at 10-foot spacing, at a depth of approximately 17 feet during low river flows, and each riser has three 5-inch by 5-inch ports. The current permit (2012) authorizes a mixing zone of 243 feet in both the upstream and downstream direction from the diffuser, and an acute zone boundary of 24.3 feet downstream and upstream from the diffuser.

This evaluation has been prepared to be consistent with WAC 173-201A, and to align with the Washington State Department of Ecology (Ecology) Water Quality Program Permit Writer's Manual (Permit Writer’s Manual) (2015) and Water Quality Program Guidance Manual: Supplemental Guidance on Implementing the Tier II Antidegradation (Ecology, 2011).

The elements of this evaluation include the following:

• Assessment dilution performance of SCTP existing outfall diffuser with Phase 5B effluent flows,

• Assessment of discharge compliance with state water quality standards and antidegradation rules, and

• Summary of biological resources and uses of the Columbia River discharge site.

Outfall Dilution Assessment This assessment of the dilution performance of the existing SCTP outfall diffuser reviews the dilution modeling assumptions and inputs, and presents the modeling results. These dilution results are applied in the evaluation of compliance with water quality standards, and are provided for Ecology’s use in the National Pollutant Discharge Elimination System (NPDES) permit renewal.

Updated dilution modeling was used to predict dilution performance of the existing SCTP outfall diffuser under critical (worst-case) receiving water conditions and for the range of receiving water conditions at the discharge site. This additional dilution analysis was specifically performed because the Phase 5B project is proposing an incremental increase in permitted effluent flow, through the existing outfall and diffuser, while Phase 5A dilution modeling has evaluated increased flows through the new proposed Phase 5A outfall and diffuser. Outfall dilution modeling was conducted for specific effluent flows and temperatures and critical receiving water conditions of temperatures, discharge depth, tidal direction,

DRAFT WATER QUALITY AND TIER II ANTIDEGRADATION EVALUATION

2

and current velocities in accordance with guidance provided in Chapters 6 and 7 and Appendix C of the Permit Writer’s Manual.

The modeling assumptions and specific inputs of effluent flow and temperature and receiving water conditions are defined in the following section. The modeling conditions that produce the lowest predicted dilutions identify the site-specific critical conditions for the discharge. Previous dilution modeling analyses of the existing SCTP outfall diffuser developed justification for the selection and application of the model UM3 (Frick et al., 2003). This model selection was developed using the results of the field tracer study in 2004 including the review and input from Ecology technical staff.

Dilution Modeling Assumptions and Inputs Dilution modeling input and analyses were based on the site-specific current and water column measurements collected during the low river flow period in 2015 (a historically low flow water year), available effluent flow and temperature data and statistics between 2010 and 2016, and projected effluent flows for SCTP Phase 5B. Modeling was conducted to represent discharge scenarios specified in the Permit Writer’s Manual.

Eleven combinations of discharge and ambient receiving water conditions were modeled to represent the range of critical discharge conditions for the existing SCTP outfall and diffuser. The model-predicted flux average dilutions are presented at the acute criteria exceedance boundary (acute zone boundary) and at the chronic criteria compliance boundary (or mixing zone boundary) for the various effluent flows and critical receiving water conditions. Seasonal discharge scenarios were developed to match guidance provided in the following Permit Writer’s Manual tables: Table 11 (Effluent and Receiving Water Design Conditions for Temperature), Table 12 (Applicable Criteria/Design Conditions), and Appendix C Table C-1 (Point Source Steady-State Flow for Mixing Zone Analysis) and Table C-3 (Critical Ambient Conditions).

The dry season (May through October) modeling scenarios are summarized as follows:

• Acute Criteria Conditions—7Q10 dry season low river flow and the maximum daily dry weather effluent flow

• Chronic Criteria Conditions—7Q10 dry season low river flow and maximum month dry weather effluent flow

• Human Health (Non-carcinogen) Criteria Condition—30Q5 low river flow and maximum month dry weather effluent flow

• Human Health (Carcinogen) Criteria Condition—harmonic mean river flow and annual average effluent flow.

The wet season (November through April) scenarios are summarized as follows:

• Acute Criteria Condition—7Q10 wet season river flow and the maximum daily wet weather effluent flow

• Chronic Criteria Condition—7Q10 wet season river flow and the maximum month wet weather effluent flow

These dry and wet season scenarios align with the guidance defined in Tables 11 and 12 of the Permit Writer’s Manual for critical-low-flow conditions and human-health-criteria conditions for carcinogens and non-carcinogens. The 7Q10 river flow is defined as the 7-day low flow period with a recurrence interval of 10 years, and the 30Q5 river flow is defined as the 30-day low flow period with a recurrence interval of 5 years. The modeling scenarios, including effluent flows and temperature used, river flow, current velocities, and temperatures, and discharge port depths, are summarized in Table 1.

Model Seasonal River River Temperature Tidal Current Flow Equivalent No./Size Ports Diffuser Discharge Acute Zone Mixing Zone Tidally-Averaged & TimeCase No. Basisa Discharge Flow (cfs) (deg. C) Condition Speed (cm/sec) Rate (mgd) Frequency (deg. C) & Spacing (ft) Depth (feet)c (24.3 feet)e (243 feet)f Weighted (Chronic Only)g

SCTP-5B1 dry 7Q10-dry 83,506 21.1 ebb 12.9 16.5 99th percentile 23.0 5-9.8" ports at 10-ft 17.0 19 n/a n/a

(90th percentile) (downstream) (10th percentile) (highest daily (dry season) spacing

SCTP-5B2 37.6 maximum) 26 n/a n/a

(90th percentile)

SCTP-5B3 flood 4.2 15 n/a n/a

(upstream) (10th percentile)

SCTP-5B4 25.1 24 n/a n/a

(90th percentile)

SCTP5-5B5 wet 7Q10-wet 108,766 10.7 ebb 34.4 23.0 99th percentile 19.8 5-9.8" ports at 10-ft 17.6 23 n/a n/a

(90th percentile) (downstream) (50th percentile) (highest daily max.) (wet season) spacing

SCTP-5B6 dry 7Q10-dry 83,506 21.1 ebb 31.1 13.2 95th percentile 22.7 5-9.8" ports at 10-ft 17.0 n/a 62

(90th percentile) (downstream) (50th percentile) (highest monthly avg.) (dry season) spacing

SCTP-5B7 flood 15.5 n/a 49


SCTP-5B8 wet 7Q10-wet 108,766 10.7 ebb 34.4 17.0 95th percentile 19.5 5-9.8" ports at 10-ft 17.6 n/a 56

(90th percentile) (downstream) (50th percentile) (maximum monthly) (wet season) spacing

SCTP-5B9 flood 17.1 n/a 48


SCTP-5B10 annual harmonic 191,106 12.4 ebb 59.4 12.90 50th percentile 17.8 5-9.8" ports at 10-ft 18.2 n/a 116 n/a

mean (50th percentile) (downstream) (50th percentile) (annual average) spacing

SCTP-5B11 annual 30Q5 99,893 12.4 ebb 32.0 13.2 50th percentile 17.8 5-9.8" ports at 10-ft 17.1 n/a 63 n/a

(50th percentile) (downstream) (50th percentile) (highest monthly avg.) spacing

Notes:a Dry season is assumed to be the period from May 1 to October 31, wet season from November 1 to April 30.b Effluent temperature values are based on effluent measurements from January 2010 through April 2016. Effluent flow values were interpolated between actual 2016 and projected 2025 flows from the 2013 Facilities Plan, using the Phase 5B Engineering Report flow projections to align. c Discharge depth represents the approximate average depth of the diffuser ports based on (relative to) 7Q10 low flow conditions, which were developed using FlowMaster software and linear regression analysis on the bedform heights in the Columbia River at river mile 95 for the proposed Phase 5A outfall.d Based on procedures in the Water Quality Program Permit Writer's Manual (Ecology, revised 2015), model-predicted dilution factors for discharges in 'marine and rotating direction' environments (i.e., estuaries) are flux-average values for both acute and chronic conditions.e The zone where the acute criteria may be exceeded (i.e., acute zone boundary) is a distance of 24.3 feet (7.4 meters) from any discharge port in both the upstream and the downstream direction.f The mixing zone boundary is 243 feet (74 meters) in both the upstream and the downstream direction.g For chronic mixing zones located in salt water and tidally-influenced freshwater, Appendix C of the Water Quality Program Permit Writer's Manual (Ecology, 2015) specifies that the critical receiving water current velocity is defined as the 50th percentile current velocity derived from a cumulative frequency distribution analysis over at least one tidal cycle. Since site-specific current velocities (measured during the low river flow period) demonstrated that flood tides occur approximately 24 percent of the time at the proposed outfall site, this time-weighted proportion (i.e., 24% flood tide/76% ebb tide) was applied in order to represent tidally-averaged results at the chronic mixing zone boundary.

Table 1Model-Predicted Dilution Factors Under Critical Dry Season, Wet Season, and Annual Average Discharge Conditions for the Existing Salmon Creek Outfall - Projected Effluent FlowsSalmon Creek Treatment Plant Phase 5B Project

Columbia River Receiving Water Conditions Effluent Conditionsb Outfall Diffuser Configuration Model-Predicted Dilution Factors (DF) at Mixing Zone Boundariesd

Human Health Criteria: Carcinogen

Human Health Criteria: Non-Carcinogen

Temperature

Acute Water Quality Criteria

Chronic Water Quality Criteria

59

54


5

Effluent flow values were developed based on the Phase 5B Engineering Report and applying interpolation between actual 2016 and projected 2025 flows from the Salmon Creek Wastewater Management System Wastewater Facilities Plan/ General Sewer Plan Amendment (Facilities Plan) (CH2M, 2013). The record period used to develop effluent temperatures for modeling was January 2010 through April 2016. A 99th percentile effluent temperature of 23.0 degrees Celsius (°C) was calculated to represent dry season conditions, and a 99th percentile effluent temperature of 19.8°C was calculated to represent wet season conditions. Both temperatures were used to represent maximum temperature for acute water quality criteria. A 95th percentile effluent temperature of 22.7°C was calculated to represent dry season conditions, and a 95th percentile effluent temperature of 19.5°C was calculated to represent wet season conditions. These temperatures were used to represent maximum temperature for chronic water quality criteria. An effluent temperature of 17.8°C was calculated to represent annual average conditions.

Columbia River receiving water conditions used in the modeling were developed from field measurements at the proposed offshore diffuser site, and these were collected by CH2M during the August to October 2015 period under low river flow conditions. The receiving water characteristics applied in the modeling of the selected outfall diffuser configuration are also summarized in Table 1.

Other key model inputs include ambient temperature and water (discharge) depth. The current meter records and water column profiles collected in 2015 were also used to validate ambient river temperatures used for the modeling of dry season conditions. Long-term records collected by the U.S. Geological Survey (USGS) at Vancouver, Washington (Gage 14144700) for the 13-year period from August 1967 to October 1979 were used to develop a cumulative frequency distribution of river temperature.

Based on these data sources, a 90th percentile ambient river temperature of 21.1°C was calculated to represent typical dry season (May through October) conditions. Similarly, a 90th percentile ambient river temperature of 10.7°C was calculated to represent typical wet weather (November through April) conditions. An annual average temperature of 12.4°C is based on the 13-year period of record (1967 to 1979) collected by the USGS for the Columbia River at Vancouver, Washington.

Discharge depths in the modeling evaluation represent the average depth of the existing diffuser ports relative to 7Q10 low flow conditions.

The dilution performance of the SCTP outfall diffuser was modeled using UM3 and the following model input parameters:

• Number, diameter, and spacing of discharge ports: five, 9.8-inch diameter ports with a spacing of 10 feet on center. Note: the actual port configuration is as follows: five risers each with three, 5-inch by 5-inch square ports oriented in a triangular arrangement. Because the UM3 model cannot simulate this type of discharge configuration, the equivalent port size of a single 9.8-inch-diameter port on each riser was modeled. This modeling configuration was accepted by Ecology in previous analyses.

• Effluent flow rate and temperature: refer to Table 1.

• Ports’ horizontal angle: 169° relative to the ambient current direction.

• Ports’ vertical angle: 0° relative to the water surface.

• Angle of diffuser axis relative to ambient current direction: 90°.

• Discharge depth: refer to Table 1.

• Ambient temperature: 21.1°C (dry season, 90th percentile), 10.7°C (wet season, 90th percentile), and 12.4°C (annual average).


6

• Ambient current speeds: 12.9, 31.1, and 37.6 centimeters per second (cm/sec) (10th, 50th, and 90th percentile dry season ebb tide, respectively); 4.2, 15.5, and 25.1 cm/sec (10th, 50th, and 90th percentile dry season flood tide, respectively); 17.1 cm/sec (50th percentile, flood tide-7Q10 high, wet season); 32.0 cm/sec (50th percentile, ebb tide-30Q5 flow); 34.4 cm/sec (50th percentile, ebb tide-7Q10 high, wet season); and 59.4 cm/sec (50th percentile, ebb tide-harmonic mean).

Dilution Modeling Results Table 1 is the modeling summary table and it includes the defined scenarios (based on water quality criteria, effluent flow scenario, and critical river flow scenario), effluent flow and temperatures, river flow and temperature, ambient current velocity, diffuser discharge depth, and model-predicted dilution factors at the acute zone boundary (AZB) and mixing zone boundary (MZB).

The column at the right side of the summary table shows modeling results for the chronic water quality criteria. For chronic mixing zones located in tidally-influenced freshwater, Appendix C of the Permit Writer's Manual specifies that the critical receiving water current velocity is defined as the 50th-percentile current velocity derived from a cumulative frequency distribution analysis over at least one tidal cycle. Since site-specific current velocities (measured during the low river flow period) demonstrated that flood tides occur only about 24 percent of the time at the proposed discharge site, a time-weighted proportion (i.e., 24 percent flood tide/76 percent ebb tide, calculated based on 2015 site-specific current measurements under lowest river flows) was applied to the dilution factors to conservatively represent tidally-averaged results at the chronic mixing zone boundary.

The model-predicted dilution factors are summarized in Table 1 for the projected Phase 5B effluent flows. The Permit Writer’s Manual specifies that dilutions in a tidally influenced river to be flux-average dilutions at both the AZB and at the MZB. The results of the dilution modeling for dry and wet season acute dilution conditions are represented by Model Case Nos. 5B1 to 5B5; dry and wet season chronic dilution conditions by Model Case Nos. 5B6 to 5B9; and for human health conditions by Model Case Nos. 5B10 and 5B11. The UM3 model input and output are included in Attachment 1.

The modeling results for acute aquatic life criteria conditions show predicted dilution factors at the AZB (24.3 feet upstream and downstream) from 15 to 26 under all seasonal effluent and receiving water conditions. The worst-case acute dilution factor (DF) of 15 is predicted to occur under dry season conditions, a 7Q10-low river flow (83,506 cfs), the lowest 10th percentile flood tide current velocity (4.2 cm/sec), and the highest daily maximum effluent flow (16.5 million gallons per day).

The modeling results also show that the predicted DF at the chronic MZB (243 feet upstream and downstream) is 54 under critical wet season conditions and maximum monthly effluent flows, and 59 under critical dry season conditions of low river stage and velocities. The lowest predicted dilution factor at the chronic MZB is based on the tidally-averaged/time weighted DF of 54 (represented by Model Case Nos. 5B8 and 5B9). Model-predicted dilution factors applicable for human-health-criteria non-carcinogen conditions and human-health-criteria carcinogen conditions are 63 and 116, respectively.

These dilution factors that represent critical acute and chronic aquatic-life-criteria conditions and human-health-criteria conditions have been applied in the evaluation of compliance with water quality standards and antidegradation rules, which is presented in the following section.

Discharge Compliance with Water Quality Standards Water Quality and Antidegradation Standards The Water Quality Standards for Surface Waters of the State of Washington (WAC Chapter 173-201A) include narrative and numerical receiving water quality standards, as well as antidegradation rules in Chapter 173-201A-300 that are consistent with the federal Clean Water Act. These standards address


7

many water quality parameters: dissolved oxygen, temperature, toxicity, turbidity, pH, coliform bacteria, dissolved gases, aesthetic water conditions, radioisotope concentrations, and toxic substances. Effects on each of these water quality parameters have been evaluated in the sections below using projected Phase 5B effluent flows, existing wastewater data, updated dilution factors for the existing SCTP outfall diffuser, and background Columbia River receiving water data.

Ecology has designated the lower Columbia River for spawning and rearing (as well as migration) of aquatic life in WAC 173-201A-602, and this designation is protective of rearing and migration year-round as well as salmon and trout spawning and emergence during the non-summer period (defined as September 17 to June 13). This designation is relevant to the application of water quality numeric standards for dissolved oxygen, temperature, pH, and turbidity.

Ecology has listed the lower Columbia River as impaired for temperature and dissolved oxygen upstream (approximately 5 miles) and downstream (approximately 8 miles) of the existing SCTP outfall, under the Ecology 303(d) list approved by the U.S. Environmental Protection Agency (EPA) in July 2016. Both are Class 5 listings, meaning that a total maximum daily load (TMDL) study is expected to be developed unless additional data collections disqualify the listing. Reaches of the lower Columbia River have been listed for temperature for decades, and EPA has taken the lead of developing temperature TMDLs for the Columbia and Snake Rivers. The SCTP discharge compliance with temperature and dissolved oxygen standards is addressed below. This reach of the Columbia River is also listed as impaired for bacteria, based on the 1998 Water Quality Assessment and no new bacteria data have been collected since the 1998 listing.

Water Quality Compliance Evaluation This sections provides evaluations of the SCTP Phase 5B discharge compliance with water quality standards for dissolved oxygen, temperature, turbidity, pH, coliform bacteria, dissolved gases, aesthetic water conditions, radioisotope concentrations, toxicity, and toxic substances.

Dissolved Oxygen The applicable water quality standard for dissolved oxygen (WAC 173-201A-200(1)(d)) specifies a lowest 1-day minimum dissolved oxygen of 6.5 milligrams per liter (mg/L) during the summer period when salmon rearing and migration may occur, and a lowest 1-day minimum dissolved oxygen of 8.0 mg/L during the period when salmon spawning, rearing, and migration may occur (September 17 to June 13). The aquatic life dissolved oxygen criteria also state that “when a water body's dissolved oxygen (DO) is lower than the criteria in Table 200 (1)(d) (or within 0.2 mg/L of the criteria) and that condition is due to natural conditions, then human actions considered cumulatively may not cause the DO of that water body to decrease more than 0.2 mg/L.” Site-specific criteria for the lower Columbia River also specify that “dissolved oxygen shall exceed 90 percent saturation.”

The wastewater influence on the receiving waters can be identified as immediate dissolved oxygen demand that occurs during the dilution process in the river. Receiving water dissolved oxygen concentrations at the completion of wastewater dilution (at the MZB) were predicted using Ecology’s spreadsheet calculation “Dissolved oxygen concentration following initial dilution” assuming the lowest model-predicted dilution factor at the MZB boundary under 7Q10 low river flow conditions (DF = 54; see Table 1). This calculation assumes a conservative effluent dissolved oxygen concentration of 3 mg/L, and an immediate effluent dissolved oxygen demand (DOD) of 2 mg/L. These spreadsheet calculations are provided in Attachment 2.

Thus, using the mass balance calculation in Ecology’s spreadsheet and a conservative assumption that the ambient DO concentration is just above the criteria, the dissolved oxygen concentration in the Columbia River at the SCTP discharge MZB is determined as follows:


8

𝐷𝐷𝐷𝐷𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎 + �𝐷𝐷𝐷𝐷𝑎𝑎𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑎𝑎𝑎𝑎𝑎𝑎 − 𝐷𝐷𝐷𝐷𝐷𝐷𝑎𝑎𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑎𝑎𝑎𝑎𝑎𝑎 − 𝐷𝐷𝐷𝐷𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎

𝐷𝐷𝐷𝐷 𝑎𝑎𝑎𝑎 𝑎𝑎ℎ𝑒𝑒 𝑀𝑀𝑀𝑀𝑀𝑀� = 𝐷𝐷𝐷𝐷𝑎𝑎𝑎𝑎𝑚𝑚𝑎𝑎𝑚𝑚

6.6𝑚𝑚𝑚𝑚𝐿𝐿

+ �3𝑚𝑚𝑚𝑚𝐿𝐿 − 2𝑚𝑚𝑚𝑚

𝐿𝐿 − 6.6𝑚𝑚𝑚𝑚𝐿𝐿54

� = 6.5𝑚𝑚𝑚𝑚𝐿𝐿

And

8.1𝑚𝑚𝑚𝑚𝐿𝐿

+ �3𝑚𝑚𝑚𝑚𝐿𝐿 − 2𝑚𝑚𝑚𝑚

𝐿𝐿 − 8.1𝑚𝑚𝑚𝑚𝐿𝐿54

� = 8.0𝑚𝑚𝑚𝑚𝐿𝐿

The calculated worst-case decrease in dissolved oxygen is the difference between the dissolved oxygen concentration of the effluent and ambient (DOmixed) and the ambient dissolved oxygen (DOambient). According to WAC 173-201A-200(1)(d), a reduction in dissolved oxygen of less than 0.2 mg/L is allowed, even in waterbodies that do not meet the applicable dissolved oxygen criterion. Under these worst-case scenarios, the decrease in dissolved oxygen at the MZB is limited to 0.1 mg/L (during the summer salmon rearing and migration period) and 0.1 mg/L (during the September–June spawning, rearing and migration period). Therefore, the SCTP discharge proposed in the Phase 5B Engineering Report would not cause or contribute to a violation of this criterion.

Temperature The temperature standards (WAC 173-201A-200(1)(c)) include narrative and numeric criteria. The lower Columbia River has specific temperature criteria that are defined in WAC 173-201A-602, Table 602. The numeric criteria for the lower Columbia River are:

“Temperature shall not exceed a 1-day maximum (1-DMax) of 20.0°C due to human activities. When natural conditions exceed a 1-DMax of 20.0°C, no temperature increase will be allowed which will raise the receiving water temperature by greater than 0.3°C; nor shall such temperature increases, at any time, exceed 0.3°C due to any single source or 1.1°C due to all such activities combined.”

In addition, WAC 173-201A-200(1)(c) stipulates that the maximum incremental temperature increase allowed and resulting from an individual point source cannot exceed 28/T+7 (in °C) at the MZB, where T is background temperature. This maximum incremental temperature is only relevant when background river temperatures are equal to or less than 16.3°C.

The temperature standards also have guidelines for preventing acute lethality and barriers to migration of salmonids in WAC 173-201A-200(1c)(vii), as follows:

“(vii) The department will incorporate the following guidelines on preventing acute lethality and barriers to migration of salmonids into determinations of compliance with the narrative requirements for use protection established in this chapter (e.g., WAC 173-201A-310(1), 173-201A-400(4), and 173-201A-410 (1)(c)). The following site-level considerations do not, however, override the temperature criteria established for waters in subsection (1)(c) of this section or WAC 173-201A-600 through 173-201A-602:

(A) Moderately acclimated (16-20°C, or 60.8-68°F) adult and juvenile salmonids will generally be protected from acute lethality by discrete human actions maintaining the 7-DADMax temperature at or below 22°C (71.6°F) and the 1-day maximum (1-DMax) temperature at or below 23°C (73.4°F).


9

(B) Lethality to developing fish embryos can be expected to occur at a 1-DMax temperature greater than 17.5°C (63.5°F).

(C) To protect aquatic organisms, discharge plume temperatures must be maintained such that fish could not be entrained (based on plume time of travel) for more than two seconds at temperatures above 33°C (91.4°F) to avoid creating areas that will cause near instantaneous lethality.

(D) Barriers to adult salmonid migration are assumed to exist any time the 1-DMax temperature is greater than 22°C (71.6°F) and the adjacent downstream water temperatures are 3°C (5.4°F) or more cooler.”

The compliance temperatures at the MZB in the river for the SCTP wastewater discharge are summarized below. Based on an assumed maximum SCTP effluent temperature of 23°C and minimum dilution factor of 54 at the MZB, each compliance temperature condition has been assessed and the estimated maximum allowable effluent temperature is identified for each, as follows, with answers provided in brackets.

1. Aquatic life temperature criteria (1-day maximum temperature at or below 23°C)—[Maximum effluent temperature prior to discharge = 23.1°C]

2. Site-specific temperature criteria (year-round) = 20.0°C (1-DMax) due to human activities—[Maximum mixed effluent temperature at MZB = 20.06°C]

3. Site-specific temperature criteria (year-round) when natural conditions > 1-DMax of 20.0 °C, then no temperature increase greater than 0.3°C—[Maximum mixed effluent temperature at MZB = 20.06°C; temperature change of 0.06°C]

4. Individual point source (year-round) cannot exceed 28/T+7 at the MZB, where T is background temperature—[not relevant due to high dilutions]

5. Acute lethality protection (adult and juvenile salmon) = 7-DADMax temperature =/< 22°C, and 1-DMax temperature =/< 23°C —[Maximum mixed effluent temperature at AZB = 20.2°C]

6. Acute lethality protection (fish embryo) = 1-DMax temperature < 17.5°C—[not applicable to Columbia River site]

7. Acute lethality protection (fish) = plume discharge temperature after 2 seconds < 33.0°C—[Maximum effluent temperature 23.1°C]

8. Migration protection (adult salmon) = 1-DMax temperature < 22°C, and background river temperature =/> 3°C cooler—[Maximum mixed effluent temperature at MZB = 20.06°C]

To support this screening-level temperature compliance assessment of the SCTP Phase 5B discharge, the temperature calculations described below have been developed.

An energy (mass) balance equation was applied to calculate the excess temperature at the MZB (the difference between the mixed temperature of effluent and river water and the background river temperature or temperature criteria). The worst-case temperature screening evaluation assumed that the river water temperature equals the temperature criterion of 20.0°C (year-round), and applied the maximum measured effluent temperature of 23.10°C (based on effluent data for the period of May 2010 through April 2016).

Using a mass balance equation and applying the following inputs, the mixed temperature increase at the MZB was calculated:

�𝑄𝑄0×𝑇𝑇𝑎𝑎𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑎𝑎𝑎𝑎𝑎𝑎� + (𝑄𝑄𝑎𝑎𝑎𝑎𝑎𝑎𝑒𝑒𝑎𝑎𝑎𝑎𝑎𝑎×𝑇𝑇𝑐𝑐𝑒𝑒𝑎𝑎𝑎𝑎𝑎𝑎𝑒𝑒𝑎𝑎𝑐𝑐𝑎𝑎) = (𝑄𝑄0 + 𝑄𝑄𝑎𝑎𝑎𝑎𝑎𝑎𝑒𝑒𝑎𝑎𝑎𝑎𝑎𝑎)×(𝑇𝑇𝑎𝑎𝑎𝑎𝑚𝑚𝑎𝑎𝑚𝑚)


10

where Tcriterion is the temperature of the receiving stream (based on applicable temperature criterion, Tcriterion = 20.0°C), Teffluent is the maximum daily effluent temperature (Teffluent = 23.0°C), Q0 represents the effluent dilution factor prior to dilution (Q0 = 1), and Qentrain is the river dilution portion that mixes with the effluent, Qentrain = 53.

Using the model-predicted worst case dilution factor of 54 at the MZB, Qo = 1 (by definition) and Qentrain = 53, solving the equation for Tmixed yields:

(1×23.10℃) + (53×20.0℃)54

= 𝑇𝑇𝑎𝑎𝑎𝑎𝑚𝑚𝑎𝑎𝑚𝑚 = 20.06℃

The average temperature increase is the difference between the temperature of combined wastewater and stream mixture at the mixing zone boundary (Tmixed) and the applicable stream temperature criterion (Tcriterion), or (20.06°C) – (20.0°C) = 0.06°C. Therefore, at the flows proposed in the Phase 5B Engineering Report, the estimated worst-case excess temperature difference is 0.06°C, and it is, therefore, not a “measurable” temperature increase (defined as greater than 0.3°C).

Turbidity The turbidity criterion allows a maximum turbidity change at the MZB of 5 nephelometric turbidity units (NTU) when background river turbidity is 50 NTU or less, and up to a 10 percent increase in stream turbidity when background river turbidity is greater than 50 NTU (WAC 173-201A-200(1)(e). SCTP is not required to monitor effluent turbidity or receiving water turbidity, and there is no basis to estimate values.

Based on the model-predicted dilution factors at the MZB summarized in Table 1, the effluent discharged through the SCTP outfall diffuser will be diluted by a factor of 54 and the mixed effluent and river turbidity will not exceed the turbidity criterion.

Total Dissolved Gas The numeric and narrative standards for total dissolved gas are set forth in WAC 173-201A-200(1)(f), which limits dissolved gases in freshwater to less than 110 percent of saturation. The SCTP discharge will not release dissolved gases such as hydrogen sulfide, carbon dioxide, or other gases that would cause or contribute to a violation of this criterion in the Columbia River. The treated wastewater discharged to the Columbia River will contain dissolved oxygen as the only significant dissolved gas, and will not exceed 110 percent saturation for dissolved gases. Therefore, the SCTP discharge would not cause or contribute to a violation of this criterion.

pH The effluent pH limit in the NPDES permit is a daily maximum of 6.0 to 9.0 standard units. The applicable pH standard for the Columbia River (WAC 173-201A-200(1)(g)) is between 6.5 and 8.5. According to effluent data from January 2010 through June 2015, effluent pH has remained between 6.13 and 7.39. Based on a calculation of the mixed pH at the MZB using Ecology’s Reasonable Potential Analysis (RPA) calculation spreadsheet (March 2015 version), the worst-case mixed pH at the MZB would not be less than 6.5 or more than 8.5. Therefore, the SCTP discharge would not cause or contribute to a violation of this criterion.

Bacteria The numeric and narrative bacterial standards are set forth in WAC 173-201A, Table 200(2)(b). The freshwater bacteria criterion for primary contact recreation applicable in the lower Columbia River specify that “fecal coliform organism levels must not exceed a geometric mean value of 100 colonies/100 mL [milliliter], with not more than 10 percent of all samples (or any single sample when


11

less than ten sample points exist) obtained for calculating the geometric mean value exceeding 200 colonies/100 mL.”

Because the SCTP uses ultraviolet light disinfection to treat the wastewater before discharge, and the capacity of the disinfection unit process exceeds the Phase 5 flows, discharge would not cause or contribute to a violation of this criterion.

Radioisotopes WAC 173-201A-250 prohibits radioisotope concentrations in excess of maximum permissible concentrations defined in federal statutes. The influent flow and loads are not known to contain radioisotopes, and SCTP treatment unit processes are not known to create or concentrate such isotopies. Therefore, the discharge is not expected to contain any radioisotopes.

Toxic Substances WAC 173-201A-240 prohibits discharge of toxic pollutants in amounts that may be harmful to beneficial uses. WAC 173-201A-240, Table 240(3), establishes numeric criteria for the protection of aquatic organisms in freshwater and marine water, and the EPA-approved numeric criteria for the protection of human health were established in November 2016. An evaluation of the dilution factors required for the SCTP effluent maximum discharge concentrations to comply with the aquatic life and human health-based water quality criteria is presented in Table 2.

The dilution factors required for SCTP effluent compliance with acute aquatic life criteria is 8 (based on copper) and 13 (based on cyanide method detection limits). The minimum model-predicted acute dilution factor is 15 under dry season conditions. The dilution factors required for SCTP effluent compliance with chronic aquatic life criteria is 12 (based on copper) and 20 (based on ammonia in the wet season). The minimum model-predicted chronic dilution factor is 54 under dry season conditions.

For human health-based criteria, a required dilution factor of 125 is calculated for arsenic; however, the receiving water data show that the current approved human health criteria for arsenic is lower than the measured background arsenic concentrations in the Columbia River by an order of magnitude, and is therefore not attainable. In addition, three other detected chemicals that require high dilution factors were Bis(2-Ethylhexyl)Phthlate and pesticides beta-BHC and heptachlor. The pesticides beta-BHC and heptachlor are legacy pesticides and no longer sold, so these may be due to a private residence’s improper disposal of old pesticides into the sewage system, and ongoing monitoring will resolve these sources. Bis(2-Ethylhexyl)Phthlate is ubiquitous in municipal wastewater effluents and state and federal restriction could be needed to reduce their sources to sewage systems.

Acute and Chronic Toxicity The most recent permit requires the SCTP to perform quarterly acute and bi-annually chronic whole effluent toxicity (WET) testing. All of the required WET test results have been in compliance with the permit effluent limits for both acute and chronic toxicity since 2011 through 2015. Because the projected Phase 5B discharge is not expected to result in an increase in pollutant concentrations, it is not expected to cause or contribute to a violation of acute and chronic toxicity criteria.

Antidegradation Rule Washington’s antidegradation rule is defined in WAC 173-201A-300, and the rule specifies the following purpose of the antidegradation policy:

“(a) Restore and maintain the highest possible quality of the surface waters of Washington;

(b) Describe situations under which water quality may be lowered from its current condition;


12

(c) Apply to human activities that are likely to have an impact on the water quality of a surface water;

(d) Ensure that all human activities that are likely to contribute to a lowering of water quality, at a minimum, apply all known, available, and reasonable methods of prevention, control, and treatment (AKART); and

(e) Apply three levels of protection for surface waters of the state, as generally described below:

(i) Tier I is used to ensure existing and designated uses are maintained and protected and applies to all waters and all sources of pollution.

(ii) Tier II is used to ensure that waters of a higher quality than the criteria assigned in this chapter are not degraded unless such lowering of water quality is necessary and in the overriding public interest. Tier II applies only to a specific list of polluting activities.

(iii) Tier III is used to prevent the degradation of waters formally listed in this chapter as "outstanding resource waters," and applies to all sources of pollution.”

Washington’s antidegradation rule provides the three levels of protection (Tiers I, II, and III) listed above. Tier I protections include maintaining and protecting existing designated uses, improving water quality conditions to align with water quality standards and protect existing designated uses, and identifying where natural conditions (exclusive of human actions) do not allow water quality standards to be met. Washington’s antidegradation rule also provides that waterbodies “may not be further degraded” except as authorized by the rule (refer to WAC 173-201A-310(1)).

Tier II antidegradation protections address “new or expanded actions … that are expected to cause a measurable change in the quality of the water,” and such actions “may not be allowed unless the department determines that the lowering of water quality is necessary and in the overriding public interest” (refer to WAC 173-201A-320(1)). Ecology has specified in the rule that a Tier II review “will only be conducted for new or expanded actions conducted under the following authorizations. Public involvement with the Tier II review are conducted in accordance with the processes associated with NPDES discharge permits, as well as other permitting.

Ecology has interpreted “degradation” as a “measurable change in water quality” away from conditions unaffected by the source area (after allowing for mixing consistent with WAC 173-201A-400(7)). In the context of this rule, a measurable change is defined by Ecology as a:

(a) Temperature increase of 0.3°C or greater (b) Dissolved oxygen decrease of 0.2 mg/L or greater (c) Bacteria level increase of 2 colony forming units/100 mL or greater (d) pH change of 0.1 units or greater (e) Turbidity increase of 0.5 NTU or greater, or (f) Any detectable increase in the concentration of a toxic or radioactive substance

Ecology rules specifies that “to determine that a lowering of water quality is necessary and in the overriding public interest, an analysis must be conducted for new or expanded actions when the resulting action has the potential to cause a measurable change in the physical, chemical, or biological quality of a water body.” The preceding evaluation of water quality standards compliance for the SCTP Phase 5B wastewater discharge to the Columbia River provides specific results to demonstrate that the discharge will not cause a measurable change in the river water quality.

Acute Chronic No. of

Parameter (µg/L) b (µg/L) c (µg/L) Samples

Antimony -- -- 6 19 0.22 1.39 0.55 0.1 0.1 -- -- 0.04

Arsenic j 360 190 0.018 19 1.85 1.39 0.55 1.24 0.01 0.02 125

Cadmium 2.1 0.7 -- 19 0.03 1/2 DL 1.39 -- 0.1 0.1 0.2 --

Chromium (+3) 336 112 -- 19 0.56 1.39 -- 0.44 0.004 0.01 --

Copper 10.3 7.0 1300 19 59.6 1.39 0.55 0.8 8 12 0.03

Lead 36.1 1.4 -- 19 0.47 1.39 -- 0.13 0.02 1 --

Mercury 2.1 0.012 0.14 9 0.0024 1.81 0.70 0.0068 0.01 1 0.1

Nickel 904.5 97.7 80 19 1.5 1.39 0.55 0.83 0.003 0.03 0.02

Selenium 20 5.0 60 19 0.2 1.39 0.55 0.5 0.5 0.04 0.2 0.01

Silver 1.4 -- -- 19 0.03 1.39 -- 0.01 0.01 0.04 -- --

Thallium -- -- 1.7 19 0.05 1/2 DL 1.39 0.55 0.01 0.01 -- -- 0.02

Zinc 73.1 64.9 1000 19 60.0 1.39 0.55 4.5 1 1 0.04

Cyanide 1.0 5.2 9 4 5.0 1/2 DL 2.59 0.93 0.0 0 13 2 1

Bis(2-Ethylhexyl)Phthlate -- -- 0.045 4 16.8 2.59 0.93 0.0 0 -- -- 349

1,2-Dichloroethane -- -- 8.9 4 0.5 1/2 DL 2.59 0.93 0.0 0 -- -- 0.1

Dichlorobromomethane -- -- 0.73 4 0.5 1/2 DL 2.59 0.93 0.0 0 -- -- 1

Benzene -- -- 0.44 4 0.5 1/2 DL 2.59 0.93 0.0 0 -- -- 1

beta-BHC (pesticide) 0.0013 4 0.2 2.59 0.93 0.0 0 -- -- 144

Heptachlor (pesticide) 0.53 0.0036 0.00000034 4 0.019 2.59 0.93 0.0 0 0.1 14 52172

Chloroform -- -- 100 4 0.5 1/2 DL 2.59 0.93 0.0 0 -- -- 0.005

Napthalene -- -- -- 4 0.2 1/2 DL 2.59 0.93 0.0 0 -- -- --

Toluene -- -- 72 4 1.1 2.59 0.93 0.0 0 -- -- 0.01

Phenol -- -- 9000 4 10 1/2 DL 2.59 0.93 0.0 0 -- -- 0.001

Ammonia 2011-15 (Summer) i 5100 830 -- 264 11000 1.0 20 2 13 --

Ammonia 2011-15 (Winter) i 2100 470 -- 256 9400 1.0 20 4 20 --

Note:

a Freshwater acute & chronic criteria from Chapter 173-201A-240 WAC (2014) Water Quality Standards for Washington. Human health criteria are existing and 2014 proposed water quality standards. Mixed river and effluent hardness of 58.5 mg/L (acute) and 55.6 mg/L (chronic).

b The freshwater acute criteria is a 1-hour average concentration not to be exceeded more than once every three years on the average, with the exception of silver, which is an instantaneous concentration not to be exceeded at any time.

c The freshwater chronic criteria is a 4-day average concentration not to be exceeded more than once every three years on the average.

d The reasonable potential multiplying factor assumes a coefficient of variation of 0.6, based on guidance on Table 3-2 (p.54) in the Technical Support Document (EPA, 1991) and Ecology RPA spreadsheet.

e Background receiving water analytical results were used as measured values or one-half the detection limit was used if the detection limit was reported. Receiving water background data from Ecology's 2007 sampling at Vancouver and the 2006 Vancouver Westside WRF Receiving

Water Study that was conducted in October 2005 (CH2M HILL, January 2006). These background river data are based on clean sampling and low detection analytical methods.

f The acute zone boundary for the outfall is point of acute criteria compliance. Acute Dilution Factor for existing outfall is 18 (flux-average dilution) in the NPDES Permit.

g The mixing zone boundary for the outfall is the chronic aquatic life and HHC compliance point. The chronic Dilution Factor for the existing outfall is 65 (flux-average dilution) in the NPDES Permit.

h The revised water quality criteria for human health were made effective by EPA on 12/28/2016. Lowest of HHC - water & organisms or organisms only - is presented in this table.

i Total ammonia as N. Criteria calculated using receiving water pH of 8.0 and temperature of 22.0°C (summer-dry season; May-Oct) and worst-case pH of 8.46 and temperature of 15 °C (winter- wet season; Nov-April).

j Note that the current HHC for arsenic is lower than the concentration in the Columbia River and therefore not attainable.

Table 2Reasonable Potential Analysis of Dilution Requirements for Water Quality Compliance for the Salmon Creek Treatment Plant Outfall 001 Discharge to the Columbia RiverSalmon Creek WWTP Phase 5B Project

Water Quality Criteriaa

Maximum Effluent Concentration (2000-

2004) (ug/L)

Reasonable Potential Multiplying Factor (95% Confidence Limit & 95%

Probability) d

Human Health Reasonable

Potential Multiplying Factor

Background Concentration

(Maximum) (µg/L) e

Background Concentration

(Median) (µg/L) e

0.13

Aquatic Life Human Health

Aquatic Life 2016 Final CWA-Effective Human Health Criteria h

Minimum Dilution to Meet WQ Criteria at Acute Zone

Boundary f

Minimum Dilution to Meet WQ Criteria at Mixing Zone

Boundary g

Minimum Dilution to Meet Final Effective HH-WQ Criteria

at Mixing Zone Boundary g

1.24

0.1

0.44

0.8

20

20

0.0068

0.83

4.5


15

Biological Resources and Uses of the Columbia River The Columbia River supports both anadromous and non-anadromous (resident) species of fish. At the SCTP outfall discharge site, the Columbia River is used by anadromous fish primarily for migration. Fourteen salmonids are federally listed as threatened or endangered within this watershed. Juvenile salmon occur in the river estuary all year, as different species, size classes, and life history types continually move downstream and enter tidal waters from upstream.

StreamNet (2012) shows the following fish uses in the Columbia River in the vicinity of the SCTP outfall site:

• Spring, summer, and fall Chinook—migration• Coho—rearing and migration• Summer and winter steelhead—migration• Sockeye—migration• Chum—migration• Pink—migration• Bull trout—migration

Lower Columbia River Chinook salmon and Lower Columbia River steelhead are federal threatened species under the Endangered Species Act (ESA), and critical habitat was designated for both species in 2000 (National Marine Fisheries Service [NMFS] and National Oceanic and Atmospheric Administration [NOAA], 2000). The Columbia River is included as critical habitat for the lower Columbia River Chinook salmon and lower Columbia River steelhead (StreamNet, 2012). These species use the lower Columbia River for rearing and migration.

Lower Columbia River coho salmon is a state endangered and federal threatened species, and no critical habitat has been designated for the lower Columbia River coho salmon. Columbia River chum salmon is a federal threatened species, and critical habitat was designated for Columbia River chum salmon in 2000 (NMFS and NOAA, 2000).

NOAA NMFS listed river eulachon (also known as “smelt”) for protection under the ESA on May 17, 2010. Eulachon (Thaleichthys pacificus) ascend the Columbia River to spawn in the lower mainstem and tributaries. The lower Columbia River is included in the listing of critical habitat areas for eulachon (NOAA, 2012).

The SCTP discharge is rapidly diluted and it does not have any adverse effects on the listed salmonid species, eulachon, or their aquatic habitat. As reviewed in the preceding section, the SCTP discharge does not and will not cause or contribute to violations of temperature or other instream water quality standards. These standards have been developed to protect sensitive cold-water aquatic organisms, including ESA-listed species, and there are no uniquely sensitive species using the lower Columbia River that would not be adequately protected by these standards.

References CH2M HILL, Inc. (CH2M). 2013. Salmon Creek Wastewater Management System Wastewater Facilities Plan/ General Sewer Plan Amendment. August.

CH2M. 2016. Columbia River Bedform Analysis near Salmon Creek WWTP. Technical Memorandum prepared for the Discovery Clean Water Alliance. June 19.

Frick, W.E., P.J.W. Roberts, L. R. Davis, J. Keyes, D.J. Baumgartner, and K.P. George. 2003. Dilution Models for Effluent Discharges, 4th Edition (Visual Plumes). Environmental Research Division, NERL, ORD. U.S. Environmental Protection Agency. March 4.


16

National Marine Fisheries Service (NMFS) and National Oceanic and Atmospheric Administration (NOAA). 2000. Designated Critical Habitat: Critical Habitat for 19 Evolutionarily Significant Units of Salmon and Steelhead in Washington, Oregon, Idaho, and California. Final Rule. Federal Register 65(32): 7764-7787. February 16.

National Oceanic and Atmospheric Administration (NOAA). 2012. Office of Protected Resources. http://www.nmfs.noaa.gov/pr/species/fish/. Accessed on January 19, 2012.

StreamNet. 2012. StreamNet: Fish Data for the Northwest. http://www.streamnet.org/index.html. Accessed on January 19, 2012.

Washington State Department of Ecology (Ecology). 2011. Water Quality Program Guidance Manual: Supplemental Guidance on Implementing Tier II Antidegradation. Publication No. 11-10-073. September.

Washington State Department of Ecology (Ecology). 2015. Water Quality Program Permit Writer's Manual. Publication No. 92-109. January 2015 (revised).

http://www.nmfs.noaa.gov/pr/species/fish/

http://www.streamnet.org/index.html

Attachment 1 UM3 Model Input and Output

1 OF 11

/ UM3. 7/26/2017 8:17:33 AMCase 5B1; ambient file c:\plumes\ plume 10.001.db; Diffuser table record 1:00 ----------------------------------

Ambient Table:Depth Amb-cur Amb-dir Amb-sal Amb-tem Amb-pol Decay Far-spd Far-dir Disprsn Density

m m/s deg psu C kg/kg s-1 m/s deg m0.67/s2 sigma-T0 0.129 90 0.08 21.1 0 0 0.129 90 0.00068 -1.9066 0.129 90 0.08 21.1 0 0 0.129 90 0.00068 -1.906

Diffuser table:P-dia P-elev V-angle H-angle Ports Spacing AcuteMZ ChrncMZ P-depth Ttl-flo Eff-sal Temp Polutnt(m) (m) (deg) (deg) () (m) (m) (m) (m) (MGD) (psu) (C) (%)

0.249 0.61 0 169 5 3.05 7.4 74 5.18 16.5 0 23 100

Simulation:Froude number: 85.44; effleunt density (sigma-T) -2.399; effleunt velocity 2.969(m/s);

Depth Amb-cur P-dia Polutnt Dilutn CL-diln x-posn y-posn Time DistanceStep (m) (m/s) (m) (%) () () (m) (m) (s) (m)

0 5.18 0.129 0.249 100 1 1 0 0 0.0; 0.0010 5.18 0.129 0.3 82.03 1.219 1 -0.115 0.023 0.0442; 0.1220 5.18 0.129 0.366 67.3 1.486 1 -0.251 0.0516 0.108; 0.2630 5.18 0.129 0.445 55.21 1.811 1 -0.411 0.0873 0.199; 0.4240 5.18 0.129 0.541 45.29 2.207 1.133 -0.597 0.132 0.329; 0.6150 5.18 0.129 0.658 37.15 2.691 1.376 -0.813 0.188 0.512; 0.8360 5.179 0.129 0.8 30.48 3.28 1.669 -1.06 0.258 0.768; 1.0970 5.179 0.129 0.971 25 3.998 2.021 -1.341 0.346 1.122; 1.3880 5.178 0.129 1.176 20.51 4.874 2.442 -1.657 0.456 1.607; 1.7290 5.177 0.129 1.423 16.83 5.941 2.94 -2.008 0.593 2.263; 2.09

100 5.175 0.129 1.716 13.8 7.242 3.526 -2.391 0.764 3.137; 2.51110 5.173 0.129 2.064 11.32 8.827 4.205 -2.804 0.974 4.285; 2.97120 5.169 0.129 2.471 9.289 10.76 4.983 -3.243 1.231 5.77; 3.47124 5.168 0.129 2.651 8.582 11.65 5.321 -3.424 1.349 6.473; 3.68 bottom hit;128 5.165 0.129 2.837 7.958 12.56 5.687 -3.624 1.488 7.316; 3.92 merging;130 5.163 0.129 2.946 7.649 13.07 5.951 -3.827 1.635 8.22; 4.16140 5.139 0.129 3.805 6.275 15.93 7.83 -5.111 2.661 14.68; 5.76

19 7.4149 5.097 0.129 5.03 5.251 19.04 11.2 -6.451 3.908 22.79; 7.54 acute zone;150 5.092 0.129 5.198 5.148 19.42 11.52 -6.604 4.062 23.8; 7.75160 5.02 0.129 7.294 4.223 23.67 13.54 -8.104 5.726 34.96; 9.92170 4.929 0.129 10.34 3.464 28.85 15.89 -9.463 7.517 47.26; 12.09178 4.85 0.129 13.68 2.957 33.81 18.08 -10.4 8.967 57.41; 13.73 matched energy radial vel = 0.117m/s;180 4.829 0.129 14.67 2.842 35.17 18.68 -10.61 9.327 59.95; 14.13190 4.729 0.129 20.75 2.331 42.87 22.02 -11.55 11.1 72.57; 16.02192 4.709 0.129 22.23 2.241 44.61 22.77 -11.72 11.44 75.07; 16.38 surface;

Const Eddy Diffusivity. Farfield dispersion based on wastefield width of 26.4 mconc dilutn width distnce time(%) (m) (m) (hrs) (kg/kg) (s-1) /s)(m0.67/s2)

2.23727 44.68 27.07 20 0.0078 0 0 0.129 6.80E-042.2391 44.64 27.98 25 0.0186 0 0 0.129 6.80E-042.2397 44.63 28.85 30 0.0293 0 0 0.129 6.80E-04

2.23865 44.65 29.7 35 0.0401 0 0 0.129 6.80E-042.23431 44.73 30.53 40 0.0509 0 0 0.129 6.80E-042.22553 44.91 31.33 45 0.0616 0 0 0.129 6.80E-042.21282 45.17 32.11 50 0.0724 0 0 0.129 6.80E-042.19666 45.5 32.88 55 0.0832 0 0 0.129 6.80E-042.17763 45.9 33.63 60 0.0939 0 0 0.129 6.80E-042.1566 46.35 34.36 65 0.105 0 0 0.129 6.80E-04

2.13379 46.84 35.07 70 0.115 0 0 0.129 6.80E-042.11026 47.37 35.78 75 0.126 0 0 0.129 6.80E-04

count: 12;

8:17:33 AM. amb fills: 2

2 OF 11





0.249 0.61 0 169 5 3.05 7.4 74 5.18 16.5 0 23 100



0 5.18 0.376 0.249 100 1 1 0 0 0.0; 0.0010 5.18 0.376 0.3 82.03 1.219 1 -0.0916 0.0192 0.0352; 0.0920 5.18 0.376 0.364 67.3 1.486 1 -0.195 0.0442 0.0836; 0.2030 5.18 0.376 0.441 55.21 1.811 1 -0.311 0.0766 0.15; 0.3240 5.18 0.376 0.534 45.29 2.207 1.095 -0.438 0.118 0.238; 0.4550 5.18 0.376 0.645 37.15 2.691 1.311 -0.577 0.172 0.356; 0.6060 5.18 0.376 0.775 30.48 3.28 1.559 -0.726 0.239 0.509; 0.7670 5.18 0.376 0.927 25 3.998 1.841 -0.882 0.323 0.706; 0.9480 5.179 0.376 1.103 20.51 4.874 2.154 -1.044 0.427 0.954; 1.1390 5.179 0.376 1.301 16.83 5.941 2.498 -1.21 0.554 1.264; 1.33

100 5.179 0.376 1.523 13.8 7.242 2.873 -1.378 0.709 1.646; 1.55110 5.178 0.376 1.766 11.32 8.827 3.288 -1.548 0.898 2.12; 1.79120 5.177 0.376 2.029 9.289 10.76 3.758 -1.723 1.133 2.713; 2.06124 5.177 0.376 2.14 8.582 11.65 3.981 -1.795 1.242 2.992; 2.18 merging;127 5.177 0.376 2.228 8.175 12.23 4.219 -1.898 1.409 3.418; 2.36 bottom hit;130 5.175 0.376 2.361 7.703 12.98 4.563 -2.074 1.709 4.186; 2.69140 5.17 0.376 3.029 6.319 15.82 6.573 -2.669 2.86 7.143; 3.91150 5.162 0.376 4.063 5.184 19.28 9.428 -3.221 4.155 10.49; 5.26160 5.152 0.376 5.541 4.253 23.5 11.25 -3.717 5.561 14.14; 6.69

26 7.4165 5.147 0.376 6.479 3.852 25.95 12.31 -3.944 6.307 16.09; 7.44 acute zone;170 5.141 0.376 7.572 3.489 28.65 13.48 -4.159 7.086 18.12; 8.22180 5.127 0.376 10.3 2.862 34.92 16.24 -4.56 8.767 22.52; 9.88190 5.112 0.376 13.9 2.348 42.57 19.62 -4.931 10.65 27.48; 11.74192 5.109 0.376 14.74 2.257 44.29 20.38 -5.002 11.06 28.55; 12.14 matched energy radial vel = 0.278m/s;200 5.095 0.376 18.33 1.926 51.9 23.76 -5.287 12.86 33.29; 13.90208 5.071 0.376 21.61 1.644 60.8 27.73 -5.688 15.84 41.14; 16.83 surface;


1.63888 60.99 25.98 20 0.00234 0 0 0.376 6.80E-041.64081 60.92 26.3 25 0.00604 0 0 0.376 6.80E-041.64166 60.88 26.61 30 0.00973 0 0 0.376 6.80E-041.64217 60.87 26.92 35 0.0134 0 0 0.376 6.80E-041.64252 60.85 27.22 40 0.0171 0 0 0.376 6.80E-041.64277 60.84 27.53 45 0.0208 0 0 0.376 6.80E-041.64295 60.84 27.83 50 0.0245 0 0 0.376 6.80E-041.64304 60.83 28.12 55 0.0282 0 0 0.376 6.80E-04

1.643 60.83 28.41 60 0.0319 0 0 0.376 6.80E-041.64277 60.84 28.7 65 0.0356 0 0 0.376 6.80E-041.6423 60.86 28.99 70 0.0393 0 0 0.376 6.80E-04

1.64154 60.89 29.27 75 0.043 0 0 0.376 6.80E-04count: 12

;

3 OF 11

/ UM3. 7/26/2017 9:01:43 AMCase 5B3; ambient file C:\Plumes\Diffuser table record 1:00 ----------------------------------




0.249 0.61 0 169 5 3.05 7.4 74 5.18 16.5 0 23 100



0 5.18 0.042 0.249 100 1 1 0 0 0.0; 0.0010 5.18 0.042 0.3 82.03 1.219 1 -0.126 0.0247 0.0485; 0.1320 5.18 0.042 0.366 67.3 1.486 1 -0.278 0.0551 0.12; 0.2830 5.18 0.042 0.446 55.21 1.811 1 -0.461 0.0925 0.224; 0.4740 5.18 0.042 0.543 45.29 2.207 1.142 -0.681 0.138 0.377; 0.6950 5.18 0.042 0.662 37.15 2.691 1.391 -0.944 0.195 0.6; 0.9660 5.179 0.042 0.806 30.48 3.28 1.694 -1.256 0.265 0.924; 1.2870 5.178 0.042 0.982 25 3.998 2.062 -1.627 0.351 1.391; 1.6680 5.177 0.042 1.195 20.51 4.874 2.509 -2.065 0.458 2.063; 2.1290 5.175 0.042 1.454 16.83 5.941 3.051 -2.577 0.591 3.023; 2.64

100 5.171 0.042 1.768 13.8 7.242 3.708 -3.174 0.755 4.385; 3.26110 5.165 0.042 2.149 11.32 8.827 4.501 -3.863 0.96 6.302; 3.98120 5.156 0.042 2.609 9.289 10.76 5.455 -4.65 1.214 8.973; 4.81127 5.145 0.042 2.986 8.087 12.36 6.235 -5.263 1.427 11.43; 5.45 bottom hit;128 5.144 0.042 3.044 7.928 12.61 6.371 -5.355 1.46 11.83; 5.55 merging;130 5.138 0.042 3.174 7.62 13.12 6.695 -5.646 1.567 13.12; 5.86

15 7.4138 5.094 0.042 3.915 6.504 15.37 8.358 -7.21 2.174 20.87; 7.53 acute zone;140 5.076 0.042 4.156 6.251 15.99 8.891 -7.689 2.369 23.47; 8.05150 4.923 0.042 5.758 5.128 19.49 12.87 -10.58 3.636 41.25; 11.19160 4.603 0.042 8.199 4.207 23.76 15.83 -14.16 5.408 68.09; 15.16169 4.112 0.042 11.38 3.52 28.39 18.66 -17.73 7.406 100.3; 19.21 matched energy radial vel = 0.0832m/s;170 4.044 0.042 11.81 3.451 28.96 19 -18.14 7.648 104.4; 19.69180 3.22 0.042 17.03 2.831 35.3 22.73 -22.15 10.24 148.8; 24.40 stream limit reached;182 3.026 0.042 18.32 2.721 36.73 23.55 -22.92 10.78 158.5; 25.33 surface;


2.7197 36.75 24.92 30 0.0309 0 0 0.042 6.80E-042.68927 37.17 27.28 35 0.064 0 0 0.042 6.80E-042.61054 38.29 29.46 40 0.097 0 0 0.042 6.80E-042.5117 39.8 31.48 45 0.13 0 0 0.042 6.80E-04

2.41025 41.47 33.38 50 0.163 0 0 0.042 6.80E-042.31347 43.21 35.18 55 0.196 0 0 0.042 6.80E-042.22371 44.95 36.89 60 0.229 0 0 0.042 6.80E-042.14168 46.67 38.53 65 0.262 0 0 0.042 6.80E-042.06669 48.37 40.1 70 0.295 0 0 0.042 6.80E-041.99826 50.03 41.61 75 0.329 0 0 0.042 6.80E-04

count: 10;


4 OF 11





0.249 0.61 0 169 5 3.05 7.4 74 5.18 16.5 0 23 100



0 5.18 0.251 0.249 100 1 1 0 0 0.0; 0.0010 5.18 0.251 0.3 82.03 1.219 1 -0.102 0.0209 0.0393; 0.1020 5.18 0.251 0.365 67.3 1.486 1 -0.22 0.0475 0.0944; 0.2330 5.18 0.251 0.443 55.21 1.811 1 -0.355 0.0814 0.171; 0.3640 5.18 0.251 0.538 45.29 2.207 1.116 -0.508 0.125 0.278; 0.5250 5.18 0.251 0.652 37.15 2.691 1.347 -0.678 0.179 0.422; 0.7060 5.18 0.251 0.789 30.48 3.28 1.621 -0.867 0.249 0.617; 0.9070 5.179 0.251 0.951 25 3.998 1.94 -1.072 0.336 0.875; 1.1280 5.179 0.251 1.143 20.51 4.874 2.309 -1.291 0.444 1.212; 1.3790 5.178 0.251 1.366 16.83 5.941 2.728 -1.523 0.578 1.645; 1.63

100 5.178 0.251 1.624 13.8 7.242 3.196 -1.763 0.741 2.192; 1.91110 5.177 0.251 1.916 11.32 8.827 3.712 -2.01 0.94 2.877; 2.22120 5.175 0.251 2.242 9.289 10.76 4.281 -2.26 1.18 3.726; 2.55124 5.175 0.251 2.382 8.582 11.65 4.525 -2.362 1.29 4.12; 2.69 bottom hit;126 5.174 0.251 2.454 8.249 12.12 4.673 -2.413 1.348 4.331; 2.76 merging;130 5.173 0.251 2.615 7.71 12.96 5.054 -2.626 1.604 5.257; 3.08140 5.163 0.251 3.353 6.325 15.8 6.865 -3.435 2.702 9.283; 4.37150 5.148 0.251 4.532 5.188 19.26 10.07 -4.24 4.012 14.16; 5.84160 5.128 0.251 6.261 4.256 23.48 11.88 -4.97 5.442 19.54; 7.37

24 7.4161 5.125 0.251 6.47 4.173 23.95 12.08 -5.038 5.589 20.09; 7.52 acute zone;170 5.105 0.251 8.698 3.492 28.63 14.09 -5.603 6.937 25.22; 8.92180 5.08 0.251 12.05 2.864 34.9 16.8 -6.147 8.491 31.18; 10.48186 5.064 0.251 14.61 2.543 39.3 18.72 -6.438 9.46 34.91; 11.44 matched energy radial vel = 0.194m/s;190 5.054 0.251 16.59 2.35 42.54 20.13 -6.62 10.13 37.49; 12.10199 5.029 0.251 21.96 1.966 50.84 23.78 -7.001 11.71 43.62; 13.64 surface;


1.95913 51.02 26.26 15 0.0015 0 0 0.251 6.80E-041.96287 50.92 26.73 20 0.00704 0 0 0.251 6.80E-041.96403 50.89 27.2 25 0.0126 0 0 0.251 6.80E-041.96466 50.87 27.66 30 0.0181 0 0 0.251 6.80E-041.96505 50.86 28.11 35 0.0236 0 0 0.251 6.80E-041.96521 50.86 28.56 40 0.0292 0 0 0.251 6.80E-04

1.965 50.87 29 45 0.0347 0 0 0.251 6.80E-041.96421 50.89 29.43 50 0.0402 0 0 0.251 6.80E-041.96261 50.93 29.85 55 0.0458 0 0 0.251 6.80E-041.96006 50.99 30.27 60 0.0513 0 0 0.251 6.80E-041.95647 51.09 30.69 65 0.0568 0 0 0.251 6.80E-041.95174 51.21 31.09 70 0.0624 0 0 0.251 6.80E-041.94619 51.36 31.5 75 0.0679 0 0 0.251 6.80E-04

count: 13;


5 OF 11





0.249 0.61 0 169 5 3.05 7.4 74 5.4 23 0 19.8 100



0 5.4 0.344 0.249 100 1 1 0 0 0.0; 0.0010 5.4 0.344 0.3 82.03 1.219 1 -0.103 0.021 0.0282; 0.1120 5.4 0.344 0.365 67.3 1.485 1 -0.221 0.0476 0.068; 0.2330 5.4 0.344 0.443 55.21 1.81 1 -0.356 0.0816 0.123; 0.3740 5.4 0.344 0.538 45.29 2.206 1.116 -0.51 0.125 0.2; 0.5350 5.4 0.344 0.652 37.15 2.689 1.347 -0.682 0.18 0.305; 0.7160 5.4 0.344 0.789 30.48 3.277 1.621 -0.872 0.249 0.445; 0.9170 5.399 0.344 0.951 25 3.995 1.942 -1.079 0.336 0.632; 1.1380 5.399 0.344 1.143 20.51 4.869 2.312 -1.301 0.444 0.877; 1.3790 5.398 0.344 1.368 16.83 5.936 2.733 -1.535 0.578 1.191; 1.64

100 5.397 0.344 1.626 13.8 7.235 3.204 -1.779 0.742 1.589; 1.93110 5.396 0.344 1.92 11.32 8.819 3.725 -2.029 0.941 2.087; 2.24120 5.394 0.344 2.249 9.289 10.75 4.298 -2.283 1.181 2.705; 2.57124 5.394 0.344 2.39 8.582 11.64 4.544 -2.386 1.291 2.993; 2.71 bottom hit;126 5.393 0.344 2.463 8.249 12.11 4.691 -2.438 1.35 3.146; 2.79 merging;130 5.391 0.344 2.623 7.709 12.95 5.071 -2.654 1.605 3.821; 3.10140 5.38 0.344 3.364 6.324 15.79 6.874 -3.473 2.701 6.743; 4.40150 5.363 0.344 4.546 5.188 19.25 10.09 -4.29 4.011 10.29; 5.87

23 7.4160 5.341 0.344 6.284 4.256 23.46 11.9 -5.033 5.443 14.22; 7.41 acute zone;170 5.315 0.344 8.735 3.491 28.6 14.11 -5.676 6.941 18.37; 8.97180 5.288 0.344 12.11 2.864 34.86 16.82 -6.229 8.493 22.7; 10.53187 5.268 0.344 15.17 2.493 40.05 19.07 -6.57 9.624 25.88; 11.65 matched energy radial vel = 0.266m/s;190 5.259 0.344 16.68 2.35 42.5 20.14 -6.707 10.12 27.29; 12.14200 5.229 0.344 22.79 1.928 51.81 24.23 -7.132 11.88 32.25; 13.86 surface;


1.91958 52.02 27.04 15 9.27E-04 0 0 0.344 6.80E-041.92346 51.92 27.39 20 0.00496 0 0 0.344 6.80E-041.92475 51.88 27.74 25 0.009 0 0 0.344 6.80E-041.92545 51.86 28.09 30 0.013 0 0 0.344 6.80E-041.92591 51.85 28.43 35 0.0171 0 0 0.344 6.80E-041.92624 51.84 28.76 40 0.0211 0 0 0.344 6.80E-041.92647 51.83 29.09 45 0.0252 0 0 0.344 6.80E-041.92657 51.83 29.42 50 0.0292 0 0 0.344 6.80E-041.92651 51.83 29.74 55 0.0332 0 0 0.344 6.80E-041.9262 51.84 30.06 60 0.0373 0 0 0.344 6.80E-04

1.92555 51.86 30.38 65 0.0413 0 0 0.344 6.80E-041.9245 51.89 30.7 70 0.0453 0 0 0.344 6.80E-04

1.92299 51.93 31.01 75 0.0494 0 0 0.344 6.80E-04count: 13

;7:54:28 AM. amb fills: 2

6 OF 11





0.249 0.61 0 169 5 3.05 7.4 74 5.18 13.2 0 22.7 100


Depth Amb-cur P-dia Polutnt Dilutn CL-diln x-posn y-posn TimeStep (m) (m/s) (m) (%) () () (m) (m) (s)

0 5.18 0.311 0.249 100 1 1 0 0 0.0;10 5.18 0.311 0.3 82.03 1.219 1 -0.0906 0.0191 0.0435;20 5.18 0.311 0.364 67.3 1.486 1 -0.193 0.0439 0.103;30 5.18 0.311 0.441 55.21 1.811 1 -0.307 0.0761 0.185;40 5.18 0.311 0.534 45.29 2.208 1.092 -0.432 0.118 0.294;50 5.18 0.311 0.644 37.15 2.691 1.307 -0.569 0.171 0.438;60 5.18 0.311 0.774 30.48 3.28 1.553 -0.714 0.238 0.625;70 5.179 0.311 0.925 25 3.998 1.83 -0.866 0.322 0.865;80 5.179 0.311 1.098 20.51 4.874 2.138 -1.024 0.425 1.167;90 5.179 0.311 1.294 16.83 5.941 2.475 -1.184 0.552 1.542;

100 5.178 0.311 1.513 13.8 7.242 2.844 -1.347 0.706 2.006;110 5.178 0.311 1.751 11.32 8.828 3.252 -1.513 0.895 2.58;120 5.177 0.311 2.009 9.289 10.76 3.717 -1.683 1.129 3.301;124 5.176 0.311 2.112 8.629 11.58 3.925 -1.756 1.243 3.653; merging;128 5.175 0.311 2.245 8.015 12.47 4.287 -1.946 1.564 4.649; bottom hit;130 5.174 0.311 2.338 7.704 12.98 4.528 -2.065 1.775 5.302;140 5.167 0.311 3 6.32 15.82 6.559 -2.644 2.93 8.902;150 5.156 0.311 4.021 5.184 19.28 9.385 -3.18 4.224 12.96;160 5.144 0.311 5.477 4.253 23.5 11.21 -3.661 5.631 17.39;165 5.136 0.311 6.399 3.852 25.95 12.27 -3.882 6.38 19.75; acute zone;170 5.129 0.311 7.473 3.489 28.65 13.45 -4.092 7.165 22.23;180 5.112 0.311 10.15 2.862 34.92 16.2 -4.484 8.86 27.61;190 5.092 0.311 13.67 2.348 42.57 19.58 -4.847 10.77 33.69;192 5.088 0.311 14.49 2.257 44.29 20.35 -4.917 11.19 35.0; matched energy radial vel = 0.227m/s;200 5.068 0.311 17.78 1.926 51.9 23.73 -5.215 13.14 41.23;209 5.03 0.311 21.36 1.612 62.02 28.24 -5.68 16.73 52.68; surface;


1.6066 62.22 25.71 20 0.00208 0 0 0.311 6.80E-041.60889 62.13 26.09 25 0.00655 0 0 0.311 6.80E-041.60977 62.09 26.46 30 0.011 0 0 0.311 6.80E-041.61027 62.08 26.83 35 0.0155 0 0 0.311 6.80E-041.6106 62.06 27.2 40 0.0199 0 0 0.311 6.80E-04

1.61082 62.05 27.56 45 0.0244 0 0 0.311 6.80E-041.61091 62.05 27.91 50 0.0289 0 0 0.311 6.80E-041.61079 62.06 28.27 55 0.0333 0 0 0.311 6.80E-041.61037 62.07 28.61 60 0.0378 0 0 0.311 6.80E-041.60954 62.1 28.95 65 0.0423 0 0 0.311 6.80E-041.60822 62.15 29.29 70 0.0467 0 0 0.311 6.80E-041.60636 62.23 29.63 75 0.0512 0 0 0.311 6.80E-04

count: 12;


7 OF 11





0.249 0.61 0 169 5 3.05 7.4 74 5.18 13.2 0 22.7 100



0 5.18 0.155 0.249 100 1 1 0 0 0.0;10 5.18 0.155 0.3 82.03 1.219 1 -0.108 0.0218 0.0518;20 5.18 0.155 0.365 67.3 1.486 1 -0.234 0.0493 0.125;30 5.18 0.155 0.444 55.21 1.811 1 -0.379 0.084 0.229;40 5.18 0.155 0.54 45.29 2.208 1.125 -0.546 0.128 0.374;50 5.18 0.155 0.655 37.15 2.691 1.362 -0.736 0.183 0.575;60 5.179 0.155 0.794 30.48 3.28 1.645 -0.949 0.253 0.85;70 5.179 0.155 0.961 25 3.998 1.981 -1.185 0.341 1.222;80 5.178 0.155 1.159 20.51 4.874 2.375 -1.443 0.451 1.717;90 5.177 0.155 1.394 16.83 5.941 2.832 -1.72 0.587 2.366;

100 5.176 0.155 1.669 13.8 7.242 3.354 -2.014 0.754 3.204;110 5.174 0.155 1.987 11.32 8.828 3.941 -2.321 0.959 4.27;120 5.171 0.155 2.35 9.289 10.76 4.593 -2.638 1.207 5.608;124 5.17 0.155 2.507 8.582 11.65 4.872 -2.766 1.32 6.231; bottom hit;127 5.169 0.155 2.622 8.135 12.29 5.089 -2.868 1.415 6.761; merging;130 5.166 0.155 2.761 7.689 13 5.419 -3.096 1.638 8.01;140 5.146 0.155 3.547 6.308 15.85 7.211 -4.074 2.709 14.11;150 5.114 0.155 4.814 5.175 19.32 10.61 -5.105 4.054 21.94;156 5.088 0.155 5.858 4.595 21.75 11.68 -5.696 4.944 27.19; acute zone;160 5.069 0.155 6.695 4.245 23.55 12.46 -6.068 5.557 30.84;170 5.017 0.155 9.383 3.482 28.7 14.69 -6.905 7.124 40.26;180 4.962 0.155 13.14 2.857 34.99 17.4 -7.61 8.712 49.93;182 4.951 0.155 14.04 2.746 36.4 18.01 -7.736 9.031 51.88; matched energy radial vel = 0.124m/s;190 4.906 0.155 18.29 2.344 42.65 20.71 -8.2 10.32 59.79;195 4.877 0.155 21.52 2.123 47.09 22.64 -8.46 11.13 64.85; surface;


2.11558 47.25 25.85 15 0.00182 0 0 0.155 6.80E-042.12006 47.15 26.61 20 0.0108 0 0 0.155 6.80E-042.12118 47.12 27.35 25 0.0197 0 0 0.155 6.80E-042.12161 47.11 28.07 30 0.0287 0 0 0.155 6.80E-042.12096 47.13 28.77 35 0.0377 0 0 0.155 6.80E-042.11822 47.19 29.46 40 0.0466 0 0 0.155 6.80E-042.11267 47.31 30.13 45 0.0556 0 0 0.155 6.80E-042.10404 47.51 30.78 50 0.0645 0 0 0.155 6.80E-042.09291 47.76 31.43 55 0.0735 0 0 0.155 6.80E-042.07958 48.07 32.05 60 0.0825 0 0 0.155 6.80E-042.0643 48.42 32.67 65 0.0914 0 0 0.155 6.80E-04

2.04766 48.82 33.28 70 0.1 0 0 0.155 6.80E-042.02961 49.25 33.87 75 0.109 0 0 0.155 6.80E-04

count: 13;


8 OF 11





0.249 0.61 0 169 5 3.05 7.4 74 5.4 17 0 19.5 100



0 5.4 0.344 0.249 100 1 1 0 0 0.0;10 5.4 0.344 0.3 82.03 1.219 1 -0.0949 0.0197 0.0354;20 5.4 0.344 0.364 67.3 1.485 1 -0.203 0.0452 0.0843;30 5.4 0.344 0.442 55.21 1.81 1 -0.324 0.078 0.152;40 5.4 0.344 0.535 45.29 2.206 1.102 -0.459 0.12 0.243;50 5.4 0.344 0.647 37.15 2.689 1.323 -0.608 0.174 0.365;60 5.399 0.344 0.78 30.48 3.278 1.58 -0.768 0.242 0.526;70 5.399 0.344 0.935 25 3.995 1.874 -0.938 0.327 0.734;80 5.398 0.344 1.116 20.51 4.87 2.205 -1.117 0.433 0.999;90 5.398 0.344 1.323 16.83 5.936 2.572 -1.3 0.562 1.332;

100 5.397 0.344 1.556 13.8 7.236 2.974 -1.487 0.719 1.746;110 5.395 0.344 1.814 11.32 8.82 3.415 -1.678 0.911 2.258;120 5.394 0.344 2.096 9.289 10.75 3.907 -1.871 1.145 2.895;125 5.392 0.344 2.239 8.468 11.79 4.185 -1.973 1.286 3.281; merging;126 5.392 0.344 2.267 8.328 11.99 4.26 -2.01 1.34 3.429; bottom hit;130 5.389 0.344 2.436 7.711 12.95 4.685 -2.249 1.705 4.434;140 5.376 0.344 3.124 6.326 15.79 6.61 -2.896 2.83 7.554;150 5.358 0.344 4.2 5.189 19.24 9.578 -3.505 4.109 11.13;160 5.335 0.344 5.751 4.257 23.46 11.39 -4.05 5.493 15.03;164 5.325 0.344 6.531 3.933 25.39 12.22 -4.25 6.072 16.67; acute zone;170 5.309 0.344 7.9 3.492 28.6 13.61 -4.53 6.972 19.22;180 5.28 0.344 10.81 2.865 34.86 16.35 -4.957 8.566 23.75;190 5.248 0.344 14.67 2.35 42.49 19.71 -5.344 10.32 28.77;191 5.245 0.344 15.12 2.304 43.34 20.08 -5.381 10.51 29.31; matched energy radial vel = 0.257m/s;200 5.212 0.344 19.74 1.928 51.8 23.83 -5.704 12.31 34.46;204 5.197 0.344 22.12 1.781 56.07 25.73 -5.842 13.18 36.96; surface;


1.77304 56.32 26.33 15 4.70E-04 0 0 0.344 6.80E-041.77722 56.19 26.68 20 0.00451 0 0 0.344 6.80E-041.77852 56.15 27.03 25 0.00854 0 0 0.344 6.80E-041.77921 56.13 27.37 30 0.0126 0 0 0.344 6.80E-041.77965 56.11 27.7 35 0.0166 0 0 0.344 6.80E-041.77996 56.1 28.04 40 0.0207 0 0 0.344 6.80E-041.78017 56.1 28.37 45 0.0247 0 0 0.344 6.80E-041.78027 56.09 28.69 50 0.0287 0 0 0.344 6.80E-041.78021 56.1 29.01 55 0.0328 0 0 0.344 6.80E-041.77991 56.11 29.33 60 0.0368 0 0 0.344 6.80E-041.77928 56.13 29.64 65 0.0408 0 0 0.344 6.80E-041.77827 56.16 29.96 70 0.0449 0 0 0.344 6.80E-041.77681 56.2 30.26 75 0.0489 0 0 0.344 6.80E-04

count: 13;


9 OF 11





0.249 0.61 0 169 5 3.05 7.4 74 5.4 17 0 19.5 100



0 5.4 0.171 0.249 100 1 1 0 0 0.0;10 5.4 0.171 0.3 82.03 1.219 1 -0.111 0.0223 0.0413;20 5.4 0.171 0.365 67.3 1.485 1 -0.241 0.0502 0.1;30 5.4 0.171 0.444 55.21 1.81 1 -0.392 0.0853 0.184;40 5.4 0.171 0.54 45.29 2.206 1.128 -0.566 0.13 0.302;50 5.399 0.171 0.656 37.15 2.689 1.367 -0.766 0.185 0.467;60 5.399 0.171 0.796 30.48 3.278 1.655 -0.993 0.255 0.694;70 5.398 0.171 0.965 25 3.995 1.998 -1.247 0.343 1.004;80 5.397 0.171 1.166 20.51 4.87 2.403 -1.527 0.453 1.422;90 5.395 0.171 1.406 16.83 5.936 2.878 -1.832 0.59 1.976;

100 5.392 0.171 1.689 13.8 7.236 3.427 -2.16 0.759 2.701;110 5.388 0.171 2.02 11.32 8.82 4.052 -2.506 0.966 3.635;120 5.383 0.171 2.401 9.289 10.75 4.753 -2.867 1.218 4.819;125 5.38 0.171 2.611 8.414 11.87 5.133 -3.051 1.363 5.52; bottom hit;127 5.379 0.171 2.699 8.087 12.35 5.302 -3.125 1.425 5.822; merging;130 5.374 0.171 2.838 7.671 13.02 5.63 -3.343 1.615 6.756;140 5.34 0.171 3.652 6.293 15.87 7.441 -4.429 2.667 12.04;150 5.281 0.171 4.967 5.162 19.35 10.95 -5.615 4.029 19.05;153 5.258 0.171 5.48 4.864 20.53 11.49 -5.966 4.48 21.4; acute zone;160 5.197 0.171 6.932 4.235 23.58 12.85 -6.748 5.578 27.2;170 5.098 0.171 9.758 3.474 28.75 15.11 -7.743 7.205 35.91;180 4.992 0.171 13.74 2.85 35.04 17.84 -8.573 8.834 44.77;181 4.982 0.171 14.21 2.794 35.74 18.14 -8.647 8.995 45.65; matched energy radial vel = 0.144m/s;190 4.887 0.171 19.24 2.338 42.72 21.16 -9.256 10.45 53.65;194 4.846 0.171 21.98 2.16 46.24 22.69 -9.496 11.09 57.24; surface;


2.15035 46.44 26.21 15 6.46E-04 0 0 0.171 6.80E-042.15671 46.3 26.91 20 0.00877 0 0 0.171 6.80E-042.15804 46.27 27.59 25 0.0169 0 0 0.171 6.80E-042.15866 46.26 28.25 30 0.025 0 0 0.171 6.80E-042.15866 46.26 28.9 35 0.0331 0 0 0.171 6.80E-042.15742 46.29 29.53 40 0.0413 0 0 0.171 6.80E-042.15423 46.36 30.15 45 0.0494 0 0 0.171 6.80E-042.14865 46.48 30.76 50 0.0575 0 0 0.171 6.80E-042.14055 46.65 31.36 55 0.0656 0 0 0.171 6.80E-042.13046 46.87 31.94 60 0.0737 0 0 0.171 6.80E-042.11848 47.14 32.52 65 0.0819 0 0 0.171 6.80E-042.10502 47.44 33.08 70 0.09 0 0 0.171 6.80E-042.09026 47.78 33.64 75 0.0981 0 0 0.171 6.80E-04

count: 13;


10 OF 11





0.249 0.61 0 169 5 3.05 7.4 74 5.5 12.9 0 17.8 100



0 5.5 0.594 0.249 100 1 1 0 0 0.0;10 5.5 0.594 0.299 82.03 1.219 1 -0.0689 0.0155 0.0338;20 5.5 0.594 0.361 67.3 1.485 1 -0.143 0.0368 0.078;30 5.5 0.594 0.434 55.21 1.811 1 -0.221 0.0655 0.135;40 5.5 0.594 0.52 45.29 2.207 1.011 -0.302 0.103 0.207;50 5.5 0.594 0.617 37.15 2.69 1.173 -0.385 0.151 0.297;60 5.5 0.594 0.723 30.68 3.258 1.339 -0.466 0.209 0.403;70 5.5 0.594 0.834 25.5 3.919 1.51 -0.545 0.277 0.528;80 5.499 0.594 0.953 21.2 4.713 1.696 -0.624 0.362 0.678;90 5.499 0.594 1.085 17.52 5.705 1.915 -0.707 0.471 0.872;

100 5.499 0.594 1.229 14.37 6.954 2.186 -0.799 0.617 1.127;110 5.498 0.594 1.383 11.79 8.476 2.52 -0.897 0.809 1.462;120 5.498 0.594 1.547 9.67 10.33 2.94 -1.004 1.066 1.907;123 5.498 0.594 1.597 9.133 10.94 3.099 -1.043 1.175 2.095; merging;130 5.495 0.594 1.796 7.953 12.56 3.82 -1.323 2.026 3.558;140 5.489 0.594 2.268 6.524 15.31 5.899 -1.724 3.462 6.02;147 5.483 0.594 2.73 5.68 17.59 8.061 -1.979 4.551 7.883; bottom hit;150 5.48 0.594 2.965 5.352 18.67 8.534 -2.084 5.046 8.727;160 5.47 0.594 3.918 4.391 22.76 10.34 -2.419 6.841 11.79;161 5.468 0.594 4.029 4.304 23.21 10.54 -2.451 7.035 12.12; acute zone;170 5.454 0.594 4.996 3.602 27.74 12.55 -2.779 9.223 15.84;180 5.424 0.594 6.085 2.955 33.82 15.26 -3.273 13.18 22.56;190 5.383 0.594 7.411 2.424 41.22 18.58 -3.769 18.04 30.8;200 5.328 0.594 9.027 1.988 50.25 22.62 -4.264 23.95 40.8;210 5.256 0.594 11 1.631 61.25 27.56 -4.757 31.13 52.95;220 5.164 0.594 13.4 1.338 74.66 33.59 -5.248 39.87 67.71;224 5.121 0.594 14.5 1.236 80.82 36.35 -5.444 43.87 74.47; matched energy radial vel = 0.42m/s;230 5.048 0.594 16.32 1.098 91.02 40.94 -5.738 50.5 85.65;240 4.902 0.594 19.89 0.901 110.9 49.9 -6.227 63.43 107.5;242 4.869 0.594 20.69 0.866 115.4 51.91 -6.324 66.33 112.4; surface;


0.86256 115.8 24.99 70 0.00157 0 0 0.594 6.80E-040.86356 115.7 25.19 75 0.00391 0 0 0.594 6.80E-04

count: 2;


11 OF 11





0.249 0.61 0 169 5 3.05 7.4 74 5.2 13.2 0 17.8 100



0 5.2 0.32 0.249 100 1 1 0 0 0.0;10 5.2 0.32 0.3 82.03 1.219 1 -0.0898 0.0189 0.0431;20 5.2 0.32 0.364 67.3 1.485 1 -0.191 0.0436 0.102;30 5.2 0.32 0.441 55.21 1.811 1 -0.303 0.0757 0.182;40 5.2 0.32 0.533 45.29 2.207 1.09 -0.427 0.117 0.29;50 5.2 0.32 0.643 37.15 2.69 1.303 -0.561 0.17 0.432;60 5.199 0.32 0.772 30.48 3.279 1.546 -0.703 0.237 0.615;70 5.199 0.32 0.922 25 3.997 1.82 -0.852 0.321 0.85;80 5.199 0.32 1.094 20.51 4.872 2.123 -1.006 0.424 1.144;90 5.198 0.32 1.288 16.83 5.939 2.455 -1.162 0.549 1.509;

100 5.197 0.32 1.503 13.8 7.239 2.817 -1.321 0.703 1.961;110 5.196 0.32 1.738 11.32 8.824 3.219 -1.482 0.892 2.521;120 5.194 0.32 1.992 9.289 10.76 3.68 -1.649 1.126 3.225;124 5.193 0.32 2.092 8.632 11.58 3.889 -1.72 1.241 3.57; merging;128 5.191 0.32 2.226 8.013 12.47 4.255 -1.909 1.568 4.56; bottom hit;130 5.189 0.32 2.318 7.702 12.97 4.498 -2.025 1.78 5.2;140 5.177 0.32 2.974 6.318 15.81 6.548 -2.59 2.935 8.709;150 5.16 0.32 3.984 5.183 19.28 9.348 -3.109 4.222 12.64;160 5.138 0.32 5.42 4.252 23.5 11.17 -3.575 5.623 16.93;165 5.127 0.32 6.329 3.851 25.94 12.23 -3.789 6.367 19.22; acute zone;170 5.114 0.32 7.386 3.488 28.64 13.41 -3.992 7.146 21.62;180 5.086 0.32 10.01 2.862 34.92 16.17 -4.371 8.833 26.82;190 5.054 0.32 13.47 2.347 42.56 19.56 -4.725 10.75 32.73;192 5.047 0.32 14.28 2.256 44.28 20.32 -4.793 11.16 34.02; matched energy radial vel = 0.232m/s;200 5.011 0.32 17.3 1.926 51.88 23.7 -5.106 13.28 40.58;210 4.938 0.32 21.2 1.58 63.25 28.77 -5.62 17.4 53.38; surface;


1.57412 63.47 25.5 20 0.00149 0 0 0.32 6.80E-041.5768 63.36 25.87 25 0.00583 0 0 0.32 6.80E-04

1.57775 63.33 26.23 30 0.0102 0 0 0.32 6.80E-041.57827 63.31 26.59 35 0.0145 0 0 0.32 6.80E-041.57862 63.29 26.95 40 0.0188 0 0 0.32 6.80E-041.57886 63.28 27.3 45 0.0232 0 0 0.32 6.80E-041.57898 63.28 27.64 50 0.0275 0 0 0.32 6.80E-041.57893 63.28 27.98 55 0.0319 0 0 0.32 6.80E-041.57863 63.29 28.32 60 0.0362 0 0 0.32 6.80E-041.57798 63.32 28.65 65 0.0405 0 0 0.32 6.80E-041.5769 63.36 28.98 70 0.0449 0 0 0.32 6.80E-04

1.57532 63.42 29.31 75 0.0492 0 0 0.32 6.80E-04count: 12

;7:45:37 AM. amb fills: 2

Attachment 2 Dissolved Oxygen Calculations

pwspread_v20101108\idod2, Printed 8/3/2017

Dissolved oxygen concentration following initial dilution.References: EPA/600/6-85/002b and EPA/430/9-82-011

Based on Lotus File IDOD2.WK1 Revised 19-Oct-93

INPUT

1. Dilution Factor at Mixing Zone Boundary: 54

2. Ambient Dissolved Oxygen Concentration (mg/L): 6.6

3. Effluent Dissolved Oxygen Concentration (mg/L): 3

4. Effluent Immediate Dissolved Oxygen Demand (mg/L): 2

OUTPUT

Dissolved Oxygen at Mixing Zone Boundary (mg/L): 6.50

pwspread_v20101108\idod2 (2), Printed 8/3/2017

Dissolved oxygen concentration following initial dilution.References: EPA/600/6-85/002b and EPA/430/9-82-011

Based on Lotus File IDOD2.WK1 Revised 19-Oct-93

INPUT

1. Dilution Factor at Mixing Zone Boundary: 54

2. Ambient Dissolved Oxygen Concentration (mg/L): 8.1

3. Effluent Dissolved Oxygen Concentration (mg/L): 3

4. Effluent Immediate Dissolved Oxygen Demand (mg/L): 2

OUTPUT

Dissolved Oxygen at Mixing Zone Boundary (mg/L): 7.97