city wide master drainag,e plan · 1.1 background section 1 introduction the city of sarasota has...

CITY WIDE MASTER DRAINAG,E PLAN CITY OF SARA SOT A

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""'""'"""-'""""""' ENGINEERING • PLANNING • ARCHITECTURE • LANDSCAPE ARCHITECTURE

CITYWIDE DRAINAGE MASTER PLAN

For

CITY OF SARASOTA

September, 1987

Prepared by :

POST, BUCKLEY, SCHUH & JERNIGAN, INC. Urban Water Resource Division

5300 West Cypress Street, Suite 300 Tampa, Florida 33607

I ,

SECTION

1.0

2.0

3.0

4.0

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Table of Contents

Citywide Drainage Master Plan For

City of Sarasota

TITLE

Introduction

1. 1 Background 1.2 Purpose and Scope 1.3 Project Authorization

Background and Data Collection

2.1 Introduction 2.2 Published Data

2.2.1 2.2.2 2.2.3 2.2.4 2.2.5

·2.2.6

Precipitation and Temperature Groundwater and Surface Water Topographic Mapping Aerial Photography Land Use Data Soils Mapping

2.3 City Working Documents

2.3.1 2.3.2

Engineering Department Planning Department

2.4 Previous Plans and Studies

2.5 Current City Development Projects

2.6 Stormwater Regulations

Drainage System Inventory

3.1 General 3.2 Atlas Update 3.3 Future Updating and Improvements

Land Use Assessment

4.1 General 4.2 Existing Land Use 4.3 Future Land Use

PAGE

1-1 1-2 1-3

2-1 2-1

2-1 2-3 2-4 2-5 2-5 2-7

2-7

2-7 2-8

2-9

2-10

2-12

3-1 3-1 3-2

4-1 4-1 4-2

SECTION

5.0

6.0

7.0

8.0

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TITLE

Table of Contents (Continued)

Development of Design Storm

5.1 General 5. 2 Rain fa 11 Frequency 5.3 Rainfall Duration 5.4 Rainfall Volume 5.5 Rainfall Distribution

Basin Characterization and Problem Identification

6.1 Basin Delineation 6.2 Problem Identification 6.3 Coastal Basins

6.3.1 6.3.2 6.3.3

North Trail Coastal Basin Bayfront Coastal Basin Osprey Coastal Basin

6.4 Inland Basins

6.4.1 6.4.2 6.4.3 6.4.4

Whitaker Bayou Basin Business District Basin Hudson Bayou Basin Phillippi Creek Basin

Stormwater Service Level

7.1 General 7.2 Service Level Definitions 7.3 Capacity and Demand Calculations

7.3.1 7.3.2

Facility Capacity Analysis Facility Demand and Residual Capacity Analysis

7.4 Service Level Attainment 7.5 Analysis of Basin Performance

Funding Needs and Implementation Program

8.1 General 8.2 Capital Needs Assessment 8.3 O&M Needs Assessment 8.4 Implementation Program

PAGE

5-1 5-2 5-5 5-6 5-7

6-1 6-3 6-7

6-9 6-14 6-18

6-23

6-24 6-30 6-31 6-42

7-1 7-1 7-3

7-4

7-9

7-10 7-20

8-1 8-1 3-6 8-9

SECTION TITLE

8.4.1 8.4.2 8.4.3 8.4.4

8.5 Program

8.5.1 8.5.2 8.5.3

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Table of Contents (Continued)

Capital Expenditures Strategic Basin Studies O&M Strategy Implementation Plan

Financing

The Stormwater Utility Bonding Summary

PAGE

8-9 Strategy 8-10

8-11 8-12

8-13

8-18 8-23

SECTION ONE

1.1 BACKGROUND

Section 1

INTRODUCTION

The City of Sarasota has retained Post, Buckley, Schuh & Jernigan to prepare a

city-wide Drainage Master Plan with funding being provided by the State of

Florida through the Department of Community Affairs, Division of Resource

Planning and Management.

The City of Sarasota is located in northwestern Sarasota County, in

southwestern Florida. The community occupies an area of almost 24 square

miles, of which approximately 10 square miles is water. In 1902, the Town of

Sarasota came into being. Large land purchases and investments were followed

by rapid development. In 1914, Sarasota was incorporated as a city. The

population of the city increased from 8,398 in 1930 to 40,237 in 1970.

Since 1930, the City's largest growth occurred between 1950 and 1960, when the

population increased by more than 80 percent. During this last decade, the

population growth of the city was 14 percent based on permanent residency.

Sarasota, as do most coastal communities in Florida, experiences a significant

increase in population during the winter months. A study by the Florida

Department of Commerce estimated that 590,000 out-of-state tourists visited

the study area in 1970. The City is expected to grow about 16 percent to

approximately 59,130 persons by the year 2000.

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With all of this growth has come a growth in stormwater management

responsibility. Analysis of problems and funding of remedial facilities

lagged behind development and simple problems began to compound into major

problems as growth continued.

Chapter 9J-5 F.A.C. outlines the minimum criteria for review of the Local

Government Comprehensive Plans and Determination of Compliance Act's

(Chapter 163, F.S.) requirements. The act generally requires, with respect to

stormwater, that an appraisal of a municipal entity's existing system be made

and, based upon projections of future land use, an assessment of future needs.

In conjunction with this assessment, Chapter 9J-5 requires that a capital

improvement plan be devised with funding means for the necessary stormwater

construction improvements.

1.2 PURPOSE AND SCOPE

Work to be accomplished in this study is confined within the City limits,

excluding the barrier and other islands, although other mainland areas may be

studied as they affect this study, either upstream or downstream of the City.

The specific objectives of this study are to:

1. Establish service levels for stormwater management facilities within the

City.

2. Update the City's Drainage Atlas to reflect changes in drainage patterns

and newer facilities including limited bench mark identification.

3. Analyze from a planning perspective the capacity of the existing drainage

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system to accommodate present and future stormwater flows.

4. Assess for planning purposes the magnitude of existing and anticipated

future stormwater problems within the City•s systems.

5. Develop planning level cost estimates for needed improvements and provide

a financing strategy to implement the stormwater management program.

6. Evaluate the long-term future demands on the drainage systems within the

City and recommend programs for satisfying those demands.

This analysis will provide the City with a framework for managing its

stormwater flows to solve current drainage problems and prevent future

problems.

1.3 PROJECT AUTHORIZATION

Post, Buckley, Schuh & Jernigan, Inc. signed a contract for this project in

March 1987. The City Council of Sarasota, Florida approved and signed this

contract on March 4, 1987 and the City of Sarasota issued a notice to proceed

in t~arch, 1987.

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---------c SECTION TWO) --

2.1 INTRODUCTION

SECTION 2

BACKGROUND DATA COLLECTION

The Scope of Work for Task 1.1 provides for a review of pertinent reports and

data that will establish the basis for future work efforts on the City-Wide

Drainage ~~aster Plan. This section provides an annotated description of all

documents received from the City as well as relevant specific plans and

general data from PBS&J 1 s plan files and technical library.

2.2 PUBLISHED DATA

As part of this study, the City of Sarasota furnished existing data, plans,

reports and other engineering information for review. Some of the data is

used directly in later sections and other information is summarized in this

subsection.

2.2.1 Precipitation and Temperature

One of the major factors responsible for the growth of the City is the

climate. The study area is located in the subtropical climatic zone, which is

characterized by mild, dry winters and warm, wet summers. The average annual

temperature as shown in Tabl.e 2-1 is approximately 740F, with the summer heat

being tempered by sea breezes and the winter temperature being moderated by

the Gulf of Mexico. The rainy season, extending from June through September,

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January

February

March

April

May

June

July

August

September

October

November

December

Annual

TABLE 2-1

DATA AVERAGE MONTHLY CLIMATE

Precipitation (Inches)

2.66

3.06

2.87

2.09

3.54

8.11

8.62

9.47

8. 52

3.24

2.03

2.27

56.48

Source: National Oceanic and Atmospheric Administration, CLIMATOLOGICAL DATA ANNUAL SUMMARY FLORIDA, 1986.

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Temperature (OF)

60.9

63.6

66.3

66.6

76.3

79.6

81.1

81.5

80.9

75.6

71.5

74.7

72.4

coincides 1-Jith the hurricane season. During this period, as shown in Table

2-1, the study area receives approximately two-thirds of its current annual

56.5 inch rainfall. This amount is about 20 percent higher than the 48.3 inch

values published in the Sarasota City Plan (1986) for the period 1965-1975.

The primary monitor of precipitation and temperature data in Florida is the

National Weather Service in cooperation with the National Oceanic and

Atmospheric Administration. Data available for Bradenton, Myakka State Park

and Venice stations include monthly precipitation volumes with departures from

normal, average monthly temperatures with departures from normal, evaporation

and extreme value variations.

2.2.2 Groundwater and Surface Water

Groundwater in Sarasota County is associ a ted with the Hawthorne formation.

Composed primarily of clay, sand, 1 imestone, and marl, this formation ranges

from 300 to 600 feet in thickness. Overlying surface materials consist

primarily of sands and shells, along with some clay.

Seasonal surficial groundwater levels vary from 3 to 4 feet below ground

surface to conicide with land surface in response to seasonal rainfall

patterns. Floridan aquifer potentiometric surface levels vary throughout the

year in response to both local and regional pumping.

The United States Geological Survey (USGS) records water resource data for

southwest Florida which is published annually. Six groundwater wells are

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monitored within the City, mostly in conjunction with water and wastewater

treatment plants. Since the City is located within several coastal (drainage)

basins with no first order inland watercourses, stream gauges are not

currently monitored by USGS. The USGS has previously monitored Whitaker Bayou

and Phillippi Creek for total stage and discharge. Specific groundwater

information is published in USGS's Water Resources Data for Florida, Volume

3B: Groundwater.

2.2.3 Topographic Mapping

Physiographically, Sarasota lies in the coastal lowlands. This region is

characterized by level to nearly level plains where hardly any stream

dissertion has taken place. Although a few small, narrow ridges are situated

throughout the City, their crest elevations are only approximately 30 to 35

feet.

Predominantly flat terrain characterizes the study area. The land rises

gradually from near sea level at the shore of Sarasota Bay to a crest of

approximately 40 feet in the central portion of the City. From there, the

elevation slowly decreases to approximately 15 feet at the eastern corporate

limits of the City adjacent to Phillippi Creek.

USGS quadrangle maps are available for the City. The three maps that cover

the City are the Sarasota (1973), Bee Ridge (1973) and Bradenton (1964)

quadrangles. All are 7.5 minute series at a scale of 1" = 2000'. The

Bradenton quad was photo-revised in 1971.

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Also obtained for this study were the FEMA Flood Insurance Rate Maps which

consist of eleven panels dated February 15, 1984. These maps delineate the

100-year flood plain as well as velocity and flood hazard areas. The Flood

Hazard Study, City of Sarasota, Florida (1983) was published in conjunction

with the maps and contains 1 imited stream flood profiles for the two major

watercourses which effect the City 1 s drainage, Phillippi Creek and Whitaker

Bayou.

The Southwest Florida Water Management District (SWFWMD) typically is the

primary source for local aerial contour mapping. However, since the City is

predominately developed, aerials were not flown by SWFWMD. Consequently, the

USGS quad maps with 5 1 contours, constitute the best available topographic

mapping.

2.2.4 Aerial Photography

Sarasota County flew 111 = 200 1 aerials in January, 1986, for the entire county

including the City. These aerial maps show current development trends but,

unfortunately, do not include any topography.

2.2.5 Land Use Data

The City has published its 1985 Land Use Map (!" = 1600 1) which indicates

current and intended land uses for the entire city. This document will be

used to assess future runoff volumes. Additionally, the City has quantified

current land use patterns which are summarized in the Table 2-2.

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Residential

0 Single Family 0 Mobile Home 0 Multi-Family 0 Group Quarters 0 Hotel/Motel

Commercial

0 Office/Professional 0 Ret a i 1 Sales/Service

Industrial

0 Wholesale/Warehouse 0 Light Industry 0 Heavy Industry

Other

0 Utilities 0 Institutional/Public 0 Vacant 0 Miscellaneous

TOTAL

TABLE 2-2

LAND USE DATA

Total Gross Area (Acres)

2.937 153 718

19 74

141 529

182 24 0

36 1,932

725 21

7,491

*These four land uses total 1.5%.

Percent of City Area

39% 2% 9% 1%* 1 OL ,o

2% 7%

2% 1%* 0%

1%* 26% 10%

1%*

100%

Source: Parcel Information System- 1986 Tax Roll, City of Sarasota Planning Department.

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2.2.6 Soils Mapping

The Soil Conservation Service (SCS) published a comprehensive soil survey for

Sarasota County in November, 1959. This survey is useful for determining soil

runoff coefficients to predict stormwater runoff volumes. An updated edition

of the survey should be published within the year but the soil classifications

should remain essentially the same.

2.3 CITY WORKING DOCUMENTS

In addition to the foregoing published reports, a number of published and

unpublished (working) City documents were reviewed in conjunction with this

study.

2.3.1 Engineering Department

The principal working document is the City's Stormwater Atlas (Drainage Detail

r~aps) originally developed in 1955 at a scale of 1" = 100' and updated as

required thereafter. The Atlas includes all public stormwater conveyances and

has been updated as part of this study. The Atlas was then used, in part, to

help delineate drainage basins prior to evaluation of system capacity and

development of facilities demand calculations.

The City's Engineering Department has updated the text of its Storm Drainage

Design Criteria which has yet to be adopted as official guidance or formally

published. This document addresses both design criteria and necessary

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approval procedures in a more comprehensive and detailed way than in the past.

The storm criteria used in this draft document will be reviewed as part of the

development of a design storm during this current study.

The City•s Engineering Department does not maintain a formal flooding

complaint tracking system. The City has, however, recorded city-wide flooding

in the past during unusual rainfall conditions. Two record maps exist

documenting flooding in August/September 1981 and March 1963.

2.3.2 Planning Department

The most notable document, in addition to the Land Use Map cited previously,

is the Sarasota City Plan: Potable Water, Sanitary Sewer, Solid Waste and

Drainage (Ord. 86-3007, July, 1986). This plan addresses comprehensive

planning measures required of the City to ensure adequate drainage services

and includes an analysis of demands for drainage services, a set of

performance standards and an assessment of the requirements for adequate

performance.

Additional documents provided by the Planning Department for review are the

Land Use Element, Land Development Regulations, Bay Water Quality Standards,

relevant City ordinances which deal directly with flooding and/or stormwater

management, the goals, objectives and policies of the 1986 City Plan and

preliminary goals, objectives and policies of the 1988 City Plan Update.

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2.4 PREVIOUS PLANS AND STUDIES

Over the years a number of studies, investigations and reports were made with

regard to stormwater both in the City and County. A goodly number are in the

City's possession and have been reviewed as part of this study. A listing of

those documents in chronological order follows:

o Phillippi Creek Basin Flood Control Study, Smally, Welford and

Na l ven ( 4/57).

o Whitaker Bayou Canal Drainage, Smally, Welford and Nalven (11/58).

o Phillippi Creek Flood Profile Study, Smally, Welford and Nalven

( 10/59).

0 Phillippi Creek Basin Drainage District Delineation,

Public Works Department, (4/61)

Sarasota

o Comprehensive Drainage Plan, Smally, Welford and Nalven (9/61).

o Proposed Drainage Improvements for Whitaker Bayou and Hudson Bayou

Basins, Smally, Welford and Nalven (2/62).

o Hyde Park Drainage District Delineation, Sarasota Public Works

Department (2/64).

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o Sarasota - Fruitville Drainage District Delineation, Sarasota Public

Works Department (9/64).

o Canal No. 18 Drainage Plans, Mosby Engineering Assoc. (12/71)

o Record Flood Map, Sarasota Public Works Department, (8181).

o Northwest Ora i nage Basin C. I. P. - 1Oth Street to North City limits

(8/82).

o Delineation of Drainage Basins - Sarasota County, Florida, Camp,

Dresser & McKee, Inc. (1983)

0 Sarasota Bradenton Airport New Terminal Complex

DR! Drainage Element, (1/85)

2.5 CURRENT CITY DEVEL~PMENT PROJECTS

land development is taking place in two distinct ways. Development of the

outlying undeveloped areas and the renewal and redevelopment of developed

areas, primarily the downtown area. Additionally, the City, County and State

are restoring or upgrading road facilities which include drainage structures

and conveyances as affected by that work.

A number of private consultants are preparing construction plans for local

roads, including 3rd Street, 17th Street, Bahia Vista Street, Beneva Road,

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Tuttle Avenue, Webber Street and Lemon Avenue. The State has recently

completed the western portion of Fruitville Road in the City. Following is a

listing of all road and drainage projects reviewed to date.

o Plans of Proposed Highway 780 (Fruitville Road), FOOT (2/85).

o lOth & 12th Street Drainage Map, Flood (3/87).

o 17th Street Drainage Map, Flood (3/87).

o Bahia Vista Street, DSA Group (2/87).

o Harbor Acres Drainage, Smally, Wellford and Nalven (9186).

o Norsota Way Drainage, Smally, Wellford and Nalven (5/86).

o lorna Linda Drainage, Smally, Wellford and Nalven (5186).

o LPmon Avenue Streets and Drainage

o Plans of Proposed Webber Street, Craven, Thompson & Associates

(5'86).

o 17th Street Improvements, Smally, Wellford and Nalven (3/86)

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o Construction Plans for Beneva Road, Glace & Radcliffe (4/87).

o 3rd Street, Post, Buckley, Schuh & Jernigan, Inc. (10/86).

2.6 STORMWATER REGULATIONS

Stormwater is regulated on the City, County, State and Federal levels. The

two reviewing agencies most directly affecting new stormwater discharges are

the City's Engineering Department and the SWFWMD. The City should shortly

have its Storm Drain Design Criteria adopted and SWFWMD has its own surface

water management rules, 400-4 and 400-40, in addition to the delegated

responsibility to administer DER's Stormwater Rule, Chapter 17-25 F.A.C.,

which addresses water quality.

The County uses a standard similar to the SWFWMD which requires attenuation

design based on a 25-year/24-hour storm using either the rational method or

SCS TR-55, depending on drainage area size. The City's stormwater regulation

is set forth in the Land Development Regulations (6/30/81).

The Florida Department of Transportation (FOOT) regulates stormwater discharge

to systems that it has constructed and maintains in conjunction with

transportation projects. FOOT has recently promulgated a four volume set of

policies, facilities design criteria and procedures, and hydraulic design

theory which is used for the standardization of basin analysis and regulation

of facility design for off-site systems which discharge to FOOT stormwater

systems.

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The United States Environmental Protection Agency (EPA) has general regulatory

purvue for water quality in streams, lakes and estuaries throughout the State.

EPA has developed the National Pollutant Discharge Elimination System (NPDES)

for regulating point source discharges through monitoring and permitting. In

the 1 ast few years EPA has been bringing the NPDES permitting process to bear

on stormwater discharges and, in the future, this program may well dictate the

extent of attenuation and treatment required from stormwater discharges in

Sarasota.

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--------- (sECTION THREE) --

Section 3

DRAINAGE SYSTEM INVENTORY

3.1 GENERAL

The principal working document in the City's Engineering Department is the

Stormwater Atlas which is a collection of Drainage Detail Maps at an

approximate scale of 1" = 100'. The Atlas Maps were originally developed in

1955 and have been updated as required since then. The Atlas Maps are an

invaluable guide to the public stormwater conveyances and structures in

Sarasota.

3.2 ATLAS UPDATE

The City of Sarasota Drainage Map Atlas atlas includes most public stormwater

conveyances and was updated as a part of this study. The Atlas updating was

conducted from two primary sources. The first was by obtaining plans for

recently completed improvement projects and significant proposed projects.

The plans consulted were previously listed in Section 2.5.

In many cases, drainage improvements resulted from road construction or

improvement and not as a direct result of remedial drainage activities. Some

of the projects that were included in the update have not been constructed but

were imminent so were included to help make a more accurate assessment of

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system capacities. This decision was made due to the large number of such

projects which could significantly effect the study's analyses.

It should be realized then that a significant amount of the updated

information was drawn from construction plans and not "as-built" information.

Additionally, the plans that were used were only those the consultant was

provided by the City engineering staff.

The other source of information was field data obtained directly by PSS&J.

Analysis of the updated atlas revealed areas of concern or question that

required closer scrutiny. In addition, certain areas of concern revealed by

City engineering staff and approximately forty areas prone to flooding were

examined through field inspection.

Three new information items were added to the atlas. They are the FEMA 100-

year flood plain delineation, the drainage basin and subbasin boundaries and

City selected bench marks.

3.3 FUTURE UPDATING AND IMPROVEMENTS

The City's Drainage Detail Maps are a very important tool, both for

maintenance of the drainage system and for assessing future development

impacts on inadequate drainage facilities. It can also be useful in

developing a drainage utility or locating regional detention facilities. It

is therefore imperative that the maps be updated on a regular basis.

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Any public or private development constructed in public right-of-way or

conveying drainage to the public stormwater management system should be added

to the maps immediately after construction. Similarly, maintenance activities

such as pipe replacement or rerouting, often done without construction plans,

should be as-built and included in the Atlas. A single person should be

designated to have this responsibility.

The City should undertake a five-year inventory of its current drainage

facilities in order to determine strategic invert elevations, document pipe

condition and O&M status, to measure primary ditch cross-sections and bridge

openings, and to monitor system flow rates and rainfall volumes. This basic

data should be stored on a relational data base to be used for ongoing

stormwater management planning, required facility design activities, and for

scheduling and prioritizing annual O&M activities.

The City should contract with a qualified aerial cartographer to map city

topography at one-foot intervals when the next set of city-wide aerial

photographs are flown. This data will provide extensive information for

verifying basin/subbasin boundaries, establishing directions of flow, and

facilitating analysis and design of stormwater facilities.

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---------c SECTION FOUR) --

Section 4

LAND USE ASSESSMENT

4.1 GENERAL

The City of Sarasota is located in the northwest section of Sarasota County.

It is part of the developing coastal corridor which extends north from

Sarasota County (Venice) to Pasco County (New Port Richey).

Development has occurred along the U.S. 41 (Tamiami Trail) corridor to such an

extent that the limit of the Bradenton/Sarasota interface is no longer

distinguishable. The two primary areas that yet remain to be developed are

pockets within both the north, east of U.S. 41, and the west, east of Tuttle

Avenue, sections of the City.

4.2 EXISTING LAND USE

The City of Sarasota, on a whole, is a rather stable, mature community

comprised of well defined neighborhoods. The City is primarily residential,

but does include significant industrial areas and many cultural/educational

properties. The only land use conspicuously absent is agricultural/pasture

which is not necessarily unexpected for a city such as Sarasota. This point

is made only in terms of imperviousness of land use with regard to runoff and

pollutant loadings.

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The City has published a Land Use Map (1985) which generally indicates all

existing land uses. t~ith few exceptions, these uses of developed parcels are

expected to change very little over the next twenty years.

4.3 FUTURE LAND USE

Land Development is taking place in two distinct ways. Development of the

outlying areas previously mentioned and the renewal and redevelopment of

developed areas, primarily the downtown area.

The Land Use Element of the 1985 Comprehensive Plan presents a compilation of

current and vacant land uses by census tracts. There are approximately 770

acres vacant within the City, not including the islands, repres~nting 11.8% of

the mainland. Table 4-1 summarizes the vacant acres by zoning and gives a

fair indication of potential (percent) impervious land at total buildout.

The majority (77%) of vacant land is to be developed as residential use which

is second only to park/recreational as low intensity zoning. Industria 1,

institutional, commercial and office comprise the other zoned uses.

The City of Sarasota has designated certain areas as Impact Management Areas

(IMAs). "Impact Management Areas are dynamic areas where development changes

can be reasonably anticipated. Accordingly, it is also anticipated that

properties located within IMAs will be the subject of petitions to rezone more

frequently than properties outside designated IMAs. Outside of the designated

IMAs, existing development and established land use patterns are considered to

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NEIGHBORHOOD DESIGNATION

1

2

3

4

5

6

9

10

TOTAL

NOTE:

VACANT SIZE % VACANT LAND

(ACRES) LAND (ACRES)

758.0 10.1 76.6

640.1 16.1 103.1

373.0 14.6 54.5

2076.1 17.6 365.4

984.5 3.9 38.4

612.6 3.8 23.3

551.8 5.2 28.7

494.5 15.7 77.6

6490.6 - 767.6*

TABLE 4-1

CITY OF SARASOTA VACANT LAND INFORMATION

RES I DENT! AL INSTITUTIONAL % ACRES % ACRES

49.1 37.6 2.8 2.1

55.1 56.8 3.2 3.3

67.7 36.9 0.0 0.0

83.8 306.2 5.3 19.4

94.0 36.0 0.8 0.3

83.1 19.3 0.0 0.0

87.5 25.1 0.0 0.0

96.0 74.5 0.0 _Q.J!

592.4 25.1

NEIGHBORHOODS 7, 8 & 19.01 NOT INCLUDED IN STUDY

*11.8% of Mainland

SOURCE: Land Use Element Sarasota City Plan Adopted July 17, 1986.

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VACANT LAND BY ZONING

INDUSTRIAL COMMERCIAL OFFICE % ACRES % ACRES % ACRES

9.0 6.9 34.7 26.6 4.4 3.4

31.1 32.1 9.3 9.6 1.3 1.3

22.4 12.2 9.9 5.4 0.0 0.0

6.0 21.9 2.7 9.9 2.2 8.0

0.0 0.0 0.8 0.3 4.4 1.8

0.0 0.0 12.2 2.9 4.6 1.1

0.0 0.0 12.5 3.6 0.0 0.0

0.0 _Q.J! 4.0 3.1 0.0 _Q.J!

73.1 61.4 15.6

be relatively stable. For the most part, in areas outside designated IMAs,

current zoning should be appropriate for the foreseeable future." The City's

goal in this regard is to "encourage quality development and redevelopment

within the designed IMAs."

Population projections indicate an increase of approximately 16% over the 15-

year period from 1985 through 2000. This is a substantial increase which may

tax many public utilities but will not have as profound an effect upon

stormwater quantity and quality because the City is largely developed. Future

stormwater capacity demand is addressed in Section 7 of this report.

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---------c SECTION FIVE) --

5.1 GENERAL

Section 5

DE-VELOPMENT OF DESIGN STOR~~

The usual analytical methodology adopted for the design of stormwater

management facilities is to evaluate the flooding conditions that would be

caused by selected cri ti ca 1 rainstorms. The same criti ca 1 rainstorms are used

to evaluate land use changes due to development within a basin. Because it

serves as one of the major yardsticks for quantifying runoff rates and

volumes, the rainstorm database is one of the most important factors in a

stormwater master planning program. Consequently, selection of the critical

design storm(s) requires careful evaluation.

A synthetic design storm consists of a rainfall hyetograph (plot of rainfall

intensity vs. time) which is based upon the characteristics of a number of

historical rainstorms. The key assumption of the design storm approach is

that the frequency of occurrence of the design storm and the calculated runoff

peak are identical. For example, it is assumed that a 25-year design storm

will produce a 25-year peak runoff event. This assumption is critical because

of the difficulty in ascribing a frequency of occurrence to a rainstorm

synthesized from portions of several historical storms, the importance of

antecedent soil moisture conditions and initial lake levels in determining

watershed response to a given rainfall event, and the statistical non

homogeneity of rainfall and runoff data. However, the synthetic design storm

tm:ML27:F 5-1

concept is a theoretical method that continues to be the most widely used

approach to stormwater management planning and drainage facility design.

The four facets which define a particular design storm are (1) the frequency

of occurrence, (2) the storm duration, (3) the total volume of rainfall for

the particular frequency and duration; and (4) the temporal distribution of

that amount over the storm duration.

5.2 RAINFALL FREQUENCY

Stormwater planning studies have relied upon a range of design storm return

periods (recurrence intervals), depending upon the area and the nature of the

stormwater problem. For example, alternatives used within this region include

design storms with 2-year, 5-year, 10-year, 25-year, 50-year, and 100-year

return periods.

The 100-year flood event, which is the standard for FEMA's Federal Flood

Insurance Program, is normally too stringent for a stormwater management

master plan. Because it is such an infrequent and extreme event, the 100-year

flood usually cannot be managed with traditional urban runoff controls. In

the City of Sarasota, it is likely that the majority of the streamflow peak

and streamflow volume during the 100-year flood event are contributed by both

urban and non-urban land uses during the frontal-type storms (i.e., long

duration and moderate rainfall intensity) which produce most 100-year events.

Consequently, it is recommended that the stormwater master planning study

tm:ML27:F 5-2

should not rely upon a 100-year design storm as a performance standard for

structural stormwater management facilities.

Nonstructura 1 stormwater management alternatives such as floodplain management

and regulatory policies should be evaluated on the basis of 100-year flood

flows and it is recommended that the runoff control facilities designed for

less extreme rainstorms should be tested with the 100-year design storm to

ensure that the recommended runoff control plan does not aggravate the 100-

year flood conditions. Presently, Sarasota uses the 100-year flood elevation

to determine minimum acceptable floor elevations for new development.

Floodplain development regulations should also require that loss of storage

and conveyance capacity within the 100-year floodplain, as the result of

development activities, be compensated for by providing off-setting storage

within the floodplain.

Similarly, the 50-year flood is also a rather extreme event which is likely to

require extremely expensive control measures. The only facilities which are

typically designed for a 50-year event are the Sarasota County and FOOT

bridges and stream crossings. The 50-year high-water mark for small land

locked lakes may also be used as a sound standard for defining the floodplain

in these basins.

The 25-year design storm tends to

for stormwater facility design

be the most commonly used "extreme" event

in Florida. City of Sarasota drainage

regulations should stipulate its use in design of external subdivision

drainage facilities and detention basins. SWFWMD also requires this storm

tm:ML27:F 5-3

frequency evaluation for its Surface Water Management Permit applications.

The justification typically given for selecting the 25-year event for

stormwater facility design is that it is more conservative than the 10-year

design storm typically used for local storm sewer design, but less

conservative than the 50- and 100-year events which would require more

expensive runoff control measures that would be used infrequently. Based upon

a recent Army Corps of Engineers study of nation-wide flood damage data

compiled by the Federal Insurance Administration (FIA), additional

justification for selecting the 25-year flood event is now available. Using

generalized relationships between flood depth and damages for different types

of property and generalized elevation-frequency relationships for different

severities of flood hazard, the significance of different flood return periods

was evaluated. This study concluded that the average annual flood damages

within the 25-year floodplain are very high, typically up to ten times greater

than the damages associated with the incremental area between the 25-year and

100-year floodplains. This conclusion suggests that a 25-year design event is

both a reasonable and defensible upper limit for a stormwater management

facility design.

The 5- and 10-year storm events are appropriate design events for the design

of closed storm sewer systems in urbanized drainage basins and subdivisions.

It is recommended that the stormwater regulations for the City of Sarasota

stipulate use of the 5-year design storm for both evaluation and design of

these type of urban stormwater management facilities.

tm:ML27:F 5-4

The 2-year flood event, generally described as the "mean annual flood", is

typically equivalent to an· open channel bankfull flow condition which will

govern the cross-sectional area of the incised channel. If future development

increases the 2-year flow, the stream channel will eventually be eroded until

it reaches an equilibrium condition with a conveyance capacity equivalent to

the 2-year flow. Thus, comparisons of pre-and post-development 2-year flows

can be used to evaluate potential stream channel erosion impacts of future

development.

5.3 RAINFALL DURATION

From various studies of past major rainfall events that have occurred in the -

southeastern portion of the United States, and in the western central portion

of Florida in particular, it is apparent that a large portion of the total

rainfall of most major storms occurs within a 24-hour period. SWFWMD

regulations stipulate the use of a 25-year/24-hour duration design storm event

for the design of stormwater detention ponds for new development. This

requirement is dictated by the need to address the total volume of runoff from

a design storm event of given frequency in the design of such facilities.

City of Sarasota stormwater regulations should be consistent with SWFWMD

regulations in this aspect.

From the design perspective for stormwater conveyances such as ditches,

inlets, storm sewers, and culverts, it is the peak rate of runoff that is the

critical design factor, not the total volume of runoff. Hence a shorter

tm:ML27:F 5-5

duration storm event can be utilized in the evaluation and design of these

facilities.

A 6-hour duration design rainfall is recommended for the City of Sarasota. In

accordance with the design criteria for hydrologic studies which mandates that

the duration of the design rainfall should be approximately equal to or

greater than the time of concentration of the basin, a 6-hour duration should

be sufficient for any application within the City for determination of design

peak flow rates.

5.4 RAINFALL VOLUME

SWFWMD approves the use of the Department of Commerce•s Technical Paper No. 40

and the Soil Conservation Service•s 11 Rainfall Frequency Atlas of Alabama,

Florida, Georgia, South Carolina for Durations from 30 Minutes to 24 Hours and

Return Periods from 1 to 100 Years 11 (USDA, SCS) for the determination of

design storm volumes in the Southwest Florida region. FDOT•s new Drainage

Manual (1987) utilizes this reference in addition to the more recent NOAA

Technical Memorandum NWS HYDR0-35 11 five to 50-Minute Precipitation Frequency

for the Eastern and Central United States 11 publication to develop its set of

rainfall intensity-duration-frequency (!OF) curves. Table 5-1 presents an

appropriate set of !OF curves and design rainfall volumes for use within the

City. These IDF curves were derived from these sources specifically for the

City of Sarasota.

tm:ML27:F 5-6

5.5 RAINFALL DISTRIBUTION

Peak runoff rates for a small (less than 100 acres in size and less than 30-

minute time-of-concentration) urban drainage basin can be determined using the

Rational Method. This method requires only a design rainfall intensity which

corresponds to the time-of-concentration at the design point for the specified

design return period. Table 5-1 presents a set of rainfall intensity

duration-frequency (IDF) relationships for the City of Sarasota to be used in

the Rational Method.

Since the Rational Method generates design peak flow rates, it is

inappropriate to develop design storm hydrographs or determine runoff volumes.

For these purposes, or for 1 arge basins (greater than 100 acres in size or

longer than 30-minute time-of-concentration) an alternate methodology which

uses unit hydrograph theory must be used. This method requires a design storm

hyetograph which distributes a design storm rainfall volume over its duration

at discrete time steps. Tables 5-2 and 5-3 present dimensionless design storm

distributions for the design 24-hour and 6-hour duration storm events,

respectively.

The 24-hour storm distribution, listed in 30-minute increments, is called the

SCS Type II Florida - Modified Distribution and is required for the design of

stormwater detention and retention ponds as per SWFWMD regulations. The 6-

hour storm distribution is broken down into smaller, 10-minute time

tm:ML27:F 5-7

TABLE 5-1

CITY OF SARASOTA STORMWATER MANAGEMENT PLAN DESIGN STORM(S)

I. RAINFALL INTENSITY - DURATION - FREQUENCY

DURATION

5-Min. 10-Min. 15-Min. 20-Min. 30-Min. 45-Min.

1-HR 1.5-HR

2-HR 3-HR 4-HR 6-HR 9-HR

12-HR 18-HR 24-HR

SOURCES:

tm:HL27:G

2-YR

7. 20 ( 0. 60) 6. 05 ( 1. 01) 5.20 (1.30) 4.45 (1.48) 3. 50 ( 1. 74) 2.70 (2.02) 2. 20 ( 2. 20) 1.70 (2.55) 1.40 ( 2.80) 1. 05 ( 3.15) 0.85 (3.40) 0.64 (3.85) 0.48 (4.30) 0.38 (4.50) 0. 28 ( 5. 05) 0.23 (5.50)

RAINFALL INTENSITY, IN/HR (VOLUME, IN.)

RETURN PERIOD, YEARS

5-YR 10-YR 25-YR

7.80 (0.65) 8.40 (0.70) 9.40 (0.78) 6.80 (1.13) 7. 40 ( 1. 23) 8.30 (1.38) 5.85 (1.46) 6.35 (1.59) 7.15 (1.79) 5.10 (1.70) 5.65 (1.88) 6. 40 ( 2. 13) 4. 20 ( 2. 09) 4.65 (2.33) 5.40 (2.70) 3.30 (2.48) 3.75 (2.81) 4.30 (3.22) 2.75 (2.75) 3.10 (3.10) 3. 65 ( 3. 65) 2.15 (3.25) 2.45 (3.65) 2. 85 ( 4. 25) 1. 80 ( 3. 60) 2. 05 ( 4.10) 2.35 (4.70) 1.30 (3.90) 1.50 (4.50) 1.75 (5.30) 1.08 (4.30) 1. 24 ( 4. 95) 1.45 (5.80) 0.82 ( 4. 90) 0.94 (5.65) 1.10 (6.60) 0.61 (5.50) 0.71 (6.40) 0.83 (7.45) 0.50 (6.00) 0.58 (7.00) 0.68 (8.20) 0.37 (6.65) 0.44 (7.90) 0.51 (9.20) 0.30 (7.20) 0.36 (8.65) 0.42 (10.00)

50-YR 100-YR

1 0. 1 0 ( 0. 84) 10.80 ( 0. 90) 8. 95 ( 1.49) 9.65 (1.61) 7. 75 ( 1. 94) .8. 40 ( 2.10) 7.00 (2.33) 7.60 (2.53) 6.00 (3.00) 6.55 (3.28) 4.80 (3.60) 5. 20 ( 3. 90) 4.10 (4.10) 4.50 (4.50) 3.15 (4.75) 3.45 (5.20) 2.60 (5.20) 2.90 (5.75) 1. 95 ( 5 .80) 2.15 (6.45) 1. 60 ( 6.40) 1. 80 ( 7. 20) 1. 20 ( 7. 20) 1.35 (8.10) 0.92 (8.30) 1.04 (9.35) 0. 77 ( 9. 25) 0.85 (10.20) 0. 57 (10. 25) 0.64 (11.50) 0.46 (11.00) 0. 52 (12. 50)

(1) NOAA Technical Memorandum NWS HYDR0-35, FIVE TO 60 MINUTE PRECIPITATION FREQUENCY FOR THE EASTERN AND CENTRAL UNITED STATES, 1977.

(2) Technical Paper No. 40, RAINFALL FREQUENCY ATLAS OF THE UNITED STATES FOR DURATIONS FROM 30 MINUTES TO 24 HOURS AND RETURN PERIODS FROM 1 TO 100 YEARS, 1961.

(3) STATE OF FLORIDA DEPARTMENT OF TRANSPORTATION, DRAINAGE MANUAL, VOLUME 2, PROCEDURES, 1987.

TIME, HRS.

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5

8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5

12.0 12. 5 13.0 13.5 14.0 14.5 15.0 15.5

16.0 16.5 17.0

tm:ML27:F

TABLE 5-2

DESIGN STORM RAINFALL DISTRIBUTION 24-HOUR DURATION STORM WITH 30-MINUTE TIME INCREMENT USING

SCS TYPE II FLORIDA - MODIFIED DISTRIBUTION

ACCUMULATED INCREMENTAL FRACTION OF TOTAL FRACTION OF TOTAL 24-HOUR RAINFALL 24-HOUR RAINFALL

0.000 0.000 0.006 0.006 0. 012 0.006 0.018 0.006 0.025 0.007 0.032 0.007 0.039 0.007 0.046 0.007

0.054 0.008 0.062 0.008 0. 071 0.009 0.080 0.009 0.089 0.009 0.099 0.010 0.110 0.011 0.122 0. 012

0.134 0. 012 0.148 0. 014 0.164 0.016 0.181 0.017 0. 201 0.020 0.226 0.025 0. 258 0.032 0.308 0.050

0.607 0.299 0.719 0.112 0.757 0.038 0.785 0.028 0.807 0.022 0.826 0.019 0.842 0.016 0.857 0.015

0.870 0.013 0.882 0. 012 0.893 0.011

5-9

TIME, HRS.

17.5 18.0 18.5 19.0 19.5

20.0 20.5 21.0 21.5 22.0 22.5 23.0 23.5

24.0

tm:ML27:F

TABLE 5-2 (Continued)

ACCUMULATED FRACTION OF TOTAL 24-HOUR RAINFALL

0.904 0.914 0.923 0. 932 0.940

0.948 0.955 0. 962 0.969 0.976 0.983 0. 989 0.995

1.000

5-10

INCREMENTAL FRACTION OF TOTAL 24-HOUR RAINFALL

0.011 o. 010 0.009 0.009 0.008

0.008 0.007 0.007 0.007 0.007 0.007 0.006 0.006

0.005 TOTAL 1.000

TABLE 5-3

6-HOUR DURATION STORM USING 10-MINUTE TIME INCREMENT

ACCUMULATED INCREMENTAL FRACTION OF TOTAL FRACTION OF TOTAL

TIME, HRS .. 6-HOUR RAINFALL 6-HOUR RAINFALL

0 0 0 0.17 0.009 0.009 0.33 0. 019 0. 010 0.50 0.029 0.010 0.67 0.040 0. 011 0.83 0.051 0. 011

1. 00 0.062 0. 011 1.17 0.074 0. 012 1. 33 0.086 0. 012 1. 50 0.099 0. 013 1. 67 0.112 0.013 1.83 0.127 0.015

2.00 0.145 0.018 2.17 0.167 0.022 2.33 0.195 0.028 2.50 0.230 0.035 2.67 0.276 0. 046 2.83 0.363 0.087

3.00 0. 572 0.209 3.17 0.687 0.115 3.33 0.745 0.058 3.50 0.785 0.040 3.67 0.816 0.031 3.83 0.841 0.025

4.00 0.861 0.020 4.17 0.877 0.016 4.33 0.891 0.014 4.50 0.904 0.013 4.67 0. 916 0. 012 4.83 0.928 o. 012

5.00 0. 940 0. 012 5.17 0.951 0.011 5.33 0.962 0. 011 5.50 o. 972 0.010 5.67 0.982 0.010 5.83 0.991 0.009 6.00 1.000 0.009

TOTAL 1.000

tm:ML27:F 5-11

increments, and should be used to generate design peak flows and hydrographs

for applications on which the smallest drainage subbasin being analyzed has a

time-of-concentration less than 30 minutes. The 6-hour duration design storm

distribution was derived by the methodology originally employed by the SCS to

derive the Type II Florida-Modified distribution. This procedure, as

documented in 11 Interim Runoff Procedure for Florida 11, SCS Florida Bulletin

Number 210-1-2, utilizes the rainfall volumes 1 isted in NWS publications

HYDR0-35 and TP-40 to obtain a set of design storm rainfall increments for a

storm of given recurrence interval and duration. These discrete rainfall

increments are arranged in the design storm by placing the largest increment

in the middle of the storm event distribution. The second largest increment

is placed after the first and the third largest is placed before the first.

Alternating the remaining rainfall amounts continues in the same manner until

the entire storm distribution is completed.

tm:ML27:F 5-12

SECTION SIX

Section 6

BASIN CHARACTERIZATION AND PROBLEM IDENTIFICATION

6.1 BASIN DELINEATION

The City of Sarasota, has a total of twelve drainage basins within its

corporate limits. This study covers the seven mainland basins which are shown

on Figure 6-1 along with their subbasins. Of the seven drainage basins

located on the mainland portion of the City of Sarasota, three are coastal

basins. Flow originating in Sarasota County to the west and Manatee County to

the north passes through the City. A significant portion of the City drains

to the Phillippi Creek Basin which is primarily located in the unincorporated

County.

The primary features that characterize the coastal basins is that they have

multiple direct discharges into Sarasota Bay and being coastal, tidal

fluctuations can have a major influence on tailwater conditions. The tidal

influence on these coastal basins distinguishes them from their upland,

interior counterparts.

Individual basins were delineated using the best available topographic

mapping, USGS 7.5' quadrangle maps, and the City's updated Drainage Atlas.

After basin delineation was completed, subbasins were delineated based on

existing drainage system configuration and basin flow regimes. The general

area variation of the delineation process is summarized in the following

table:

tm:ML27:A 6-1

t.. ...... I

' \

SARASOTA CITY LIMITS

05

' N

-DRAINAGE BASIN KEY

01 NORTH TRAIL COASTAL BASIN

02 WHITAKER BAYOU BASIN

03 BA YFRONT COASTAL BASIN

04 BUSINESS DISTRICT BASIN

05 PHILLIPPI CREEK BASIN

06 HUDSON BAYOU BASIN

07 OSPREY COASTAL BASIN

08 LIDO KEY BASIN

09 ST. ARMANDS KEY BASIN

10 COON KEY BASIN

11 BIRD KEY BASIN

12 SIESTA KEY BASIN

GENERAL BASIN MAP

FIGURE 6-1

Number

01 02

03

04

05

06

07

08

09

10

11

12

Name

North Trail

Whitaker Bayou

Bayfront

Business District

Phillippi Creek

Hudson Bayou

Osprey

Lido

St. Armands Key

Coon Key

Bird Key

Siesta Key

Coastal

Inland

Coasta 1

Inland

Inland

Inland

Coastal

Island

Island

Island

Island

Island

Area (Acres)

757

1717

374

600

2496_

1598 '

542

548

149

30

237

139

9187

Subbasins

7

20

7

7

20

19

7

9

4

2

7

5

114

These basins have been studied by the Federal Government, the County and the

City. It is the intent of this study is to draw upon previous work, rather

than replicate it. What follows are brief overviews of the basin

characteristics and their associated problems.

6.2 PROBLEM IDENTIFICATION

Flooding results from two major sources in the City of Sarasota. Coasta 1

areas are subject to inundation from surges from the Gulf of Mexico and

associated coastal waves. Inland areas become· flooded when rainfall

accumulates in low, flat areas which have inadequate or poorly maintained

drainage systems. Rainfall occurs primarily due to thunderstorm activity in

the summer months, with additional rainfall occurring with the passage of

tm:ML27:A 6-3

hurricanes. A transition region near the coast is vulnerable to both rainfall

and gulf surge flooding.

Hurricanes cause the most severe flooding problems in the City and it should

be noted that most hurricanes occur in the latter portion of the rainy season.

Thus, rain associated with hurricanes commonly falls when conditions are most

critical for runoff. A brief description of the five most significant

hurricanes provides historic information which indicate the level of coastal

flood hazard experienced in the City of Sarasota.

o October 24, 1921

Flooding conditions were prolonged due to the slow forward movement

of the storm. A combination of high tides (above 7 feet) with wave

action resulted in heavy damage in Sarasota County. Total loss in

the City of Sarasota estimated at $200,000.

o September 19, 1926

In the Sarasota area, flooding caused damage estimated at $1

million. In addition, wave action resulted in considerable erosion

along the coast in Sarasota County.

o September 10, 1960

tm:ML27:A

Hurricane Donna, one of the great storms of this century, resulted

in tidal heights of approximately 3 feet above normal in Sarasota.

Precipitation from the storm averaged from 5 to 7 inches in the

county, but a heavy prestorm rainfall of almost 10 inches saturated

6-4

the ground.

flooding.

Consequently, this hurricane produced considerable

o October 18, 1968

Tides of up to five feet above normal produced considerable damage

in Sarasota County.

o June 18, 1972 (Hurricane Agnes)

Although the center of this storm passed approximately 150 miles

west of the south Florida peninsula, it produced high tides of three

feet above normal and precipitation of five inches in Sarasota

County. The high tides caused damage to many homes, seawalls,

revetments, and roads along the Sarasota County coastline. In

addition, wave action produced considerable erosion throughout the

County.

Recent studies by the Federal Emergency Management Agency (FEMA) have

identified the probable extent of coastal and inland flooding due to gulf

surge tides, hurricanes and significant tropical storms. Areas impacted by

this type of flooding, as generally shown in Figure 6-2, are typically 400 to

1200 feet inland from the coast of Robert • s Bay and Sarasota Bay and 1. 6 to

2.0 miles upstream in significant coastal creeks.

The second major stormwater concern is inland flooding caused by inadequate or

poorly maintained drainage systems. In this case, land development activities

have significantly increased runoff volumes and exceeded the existing capacity

tm:Ml27:A .6-5

Sarasota City Limits

Sarasota Bay

•

12--J "-"'A""- ....

' ' I

r-'~ L

~~.-A-~]

PBSJ

-l I

' N

-LEGEND

100 YEAR FLOOD ZONE

500 YEAR FLOOD ZONE

EXTENT OF POTENTIAL COASTAL FLOODING

FIGURE 6-2

of natural or manmade drainage systems. This type of flooding is more

frequent and more easily controlled. The City staff ha,s identified a number

of i so 1 a ted sma 11 problems throughout the City and a 1 arge area of concern

along Phillippi Creek in the eastern portion of the City.

The following sections address identified flooding problems in terms of

location, cause and indicated solution. Fifty-two individual problems ~'/ere

identified through limited field inspection of existing facilities,

investigation of documented drainage complaints, review of previous

engineering and bond covenants reports and through staff interviews as

indicated in Figure 6-3. These problems are discussed in the following

sections.

6.3 COASTAL BASINS

The three coastal basins in the City of Sarasota are the North Trail Coastal

basin, Bayfront Coastal basin, and Osprey Coastal Basin. These three coastal

basins each contains seven subbasins and are not particularly unique from each

other with the possible exception of the Bayfront Coastal Basin. This basin

does have one defined, all but minor, conveyance called Hog Creek which does

not show on all published maps.

tm:t~l27:A 6-7

-----NOCRTH TRAIL I -1 OASTAL .;

BASIN I

""" t . ' \ -. \"~· (

\

'L WHITAKER BAYOU \

BASIN --

PBSJ

l

PHILLIPPI CREEK BASIN

i N

-LEGEND

• FLOOD PROBLEM AREA

LOCATION OF FLOODING PROBLEMS

FIGURE 6-3

They all share the same soil classification of fine sand which is predominate

throughout the City of Sarasota. This soil type, an SCS 11 C11 type, has a slow

infiltration rate when thoroughly wetted and typically has a layer which

impedes downward water movement. Because of unavailable pore space, 11 C11 type

soil has a slow water transmission rate. The following is a brief discussion

of each of the three coastal basins.

6.3.1 North Trail Coastal Basin

The North Trail Coastal Basin consists of 757 acres within the City of

Sarasota. An undefined area outside the city limits in unincorporated

Sarasota in Manatee Counties also drains through this basin. The northwest

portion of the basin has large areas of open space, primarily on the grounds

of the Ringling Museum, Ringling Mansion, Bay Haven School, the New

Co 11 ege/USF Campus and a portion of the Sarasota-Bradenton Airport. These

open areas will mostly, in all likelihood, remain open. The balance of the

basin is mostly residential with attendant commercial and very little

undeveloped land.

Figure 6-4 shows the general basin boundaries and the attendant subbasins of

which there are seven. Table 6-1 provides a summary of the characteristics of

the basin and subbasins which includes subbasin number, area, cumulative area,

major ditch and culvert lengths and the number of system problems. Figure 6-5

provides a schematic diagram of the flow patterns within the drainage basin

and receiving waters. Table 6-2 identifies flood problems within the basin

giving location, type of problem, problem cause and problem solution. Upon

tm:NL27:A 6-9

••••••••••••••••••••••••••••••

••••••••••••••••••••••• ::::;::::::::::::::;.;:

MANA TEE COUNTY ~~ .. ---- __ _... .-. :.~;..: .... :- :..-~ ... =-~-··~ ....


01-03

SARASOTA BAY

01-04

01-05

01-06

L WHITAKER BAYOU 7 BASIN

NORTH TRAIL COASTAL BASIN FIGURE 6-4

TABLE 6-1

SUMMARY OF BASIN AND SUBBASIN CHARACTERISTICS FOR NORTH TRAIL COASTAL BASIN

SUBBRSIN NUMBER

SUBBitSIN RRER

fRCRES>

NORTH TRRIL CORSTRL BRSIN -------------------------01-01 275 !ll1-!ll2 57 01-03 101 01-04 57 01-05 109

01-06 98 01-07 60

SUBTOTRLS 757

CUMULRTIVE MRJOR DITCH NRJOR CULVERT RRER LENGTH LENGTH

fRCRES> <FEET> fFEET>

275 4,260 2,300 57 ill 1, 740

101 440 0 57 0 700

109 580 1 ,20/ll

98 0 0 60 0 0

5,280 5,940

NUMBER OF PROBLEMS

1 0 1 1 0

0 0

3

s A R A s 0 T A

B A y

NORTH TRAIL DRAINAGE BASIN

01-01

01-02

01-03

01-04

01-05

01-06

01-07

FIGURE 6-5

PROBLEM B~SINI

NUMBER SUBB~SIN

TABLE 6-2

PROBLEM IDENTIFICATION IN THE NORTH TRAIL COASTAL BASIN

STREET LOC~TION

PROBLEM DESCRIPTION

PROBLEM CJ/USE

NORTH TR~IL CO~ST~L B~SIN

1

..... .::

3

01-01

01-03

01-04

47TH ST. BETWEEN N. mMI~MI PONDING IN STREET TR~IL & ROY~L P~LM ~VE.

BRYWILL CL. PONDING IN STREET

45TH S~ BETWEEN B~YSHORE & CORWOOD PL.

PONDING IN STREET

UNDERSIZED RO~DSIDE DITCH

UNDERSIZED CONVEYRNCE CONSTRICTED CHRNNEL

INLETS PLUGGED WITH DEBRIS ~ND SILT

reviewing these flooding problems, 1>1e find that two of the three problems

noted are caused by undersized systems while the third problem is maintenance

related. From Figure 6-5 it can be seen that this basin has multiple direct

discharges to Sarasota Bay.

6.3.2 Bayfront coastal Basin

The Bayfront Coastal Basin is composed of 870 acres located in the west

central portion of the City on Sarasota Bay. The north boundary is the

Whitaker Bayou and the south boundary is the Hudson Bayou. The northern and

southern-most portions of this basin have some single-family. residential

development with the balance of the basin being developed in multi-family and

commercial properties. Some of the main cultural attractions in Sarasota are

located in this basin and include: Municipal Civic Center Park, Florida West

Coast Symphony Music Center, Van Wezel Performing Arts Hall, County Historical

Archives, Public Library, and Selby Botanical Gardens. The area along

Bayfront Drive adjacent to the Bay is primarily recreation and open space and

includes Island Park.

Figure 6-5 shows the basin boundaries and the attendant subbasins of which

there are seven. Table 6-3 provides a summary of the characteristics of the

basin and subbasins which includes subbasin number, area, cumulative area,


provides a schematic diagram of the drainage basin and receiving waters. The

Bayfront Coastal Basin has no identified flooding problems. Figure 6-7

indicates that the basin has multiple direct discharges to Sarasota Bay with

tm:t1L27:A 6-14

.. ·.· ... ·.~. ·.·. ·.

................. ················· ................

SARASOTA BAY

WHITAKER BAYOU BASIN i N

-10TH STREET

BUSINESS DISTRICT BASIN

HUDSON BAYOU BASIN

,.. HUDSON oot BAYOU en BASIN ::)

PBSJ BAYFRONT COASTAL BASIN FIGURE 6-6

TABLE 6-3

SUMMARY OF BASIN AND SUBBASIN CHARACTERISTICS FOR BAYFRONT COASTAL BASIN

SUBBRSIN NUNBER

SUBBI:JSIN RRER

(/:JCRESJ

BR YFRONT COf:lSTRL Bf:lS IN

03-01 03-02 03-03 03-04 03-'-7!5

l,:l]-I,..7f6

03-07

SUBTOTRLS

46 68 41 50 50

58 6 . .., .::

374

CUMULRTIVE MRJOR DITC!-1 RRER

(RCRESJ

46 68 41 50 50

12fl 62

LENGTH (FEE TJ

0 0

160 0 0

tZ'I

~1

160

NRJOR CULVERT

LENGTH (FEETJ

0 1' 120 1,500

460 2,840

861Z! 6, 421i1

13,200

NUMBER OF PROBLENS

0 0 0 0 0

0 ~1

0

03-01

03-02

s A 03-03 R A s 0 T 03-04 A

B A y

03-05

03-06

03-07

BAYFRONT COASTAL BASIN FIGURE 6-7

subbasins 03-01 through 03-06 discharging directly and subbasin 03-07

discharging into Subbasin 03-06.

6.3.3 Osprey Coastal Basin

This basin totals 542 acres within the City. The north basin boundary is

formed by the Hudson Bayou outfall and the south basin boundary is formed by

the Sarasota City Limits. The basin is primarily residential with some

commercial use along the south end of Osprey Avenue adjacent to the City

limits. Again, this basin has multiple direct discharges to Sarasota Bay.

Figure 6-8 shows the basin boundaries and the attendant subbasins of which

there are seven. Table 6-4 provides a summary of the characteristics of the

basin and subbasins which includes subbasin number, area, cumulative area,


provides a schematic diagram of the drainage basin and receiving waters.

Table 6-5 identifies flood problems within the basin giving location, type of

problem, problem cause and problem solution. When reviewing the flooding

problems from Table 6-5, we find that one problem is maintenance related and

the other three are system size related. These four problems were the only

ones noted. It can be seen from Figure 6-9 that the basin has multiple direct

discharges to Sarasota Bay with the exception of subbasin 07-05 which

discharges to subbasin 07-04.

All three coastal basin are composed primarily of Leon fine sand which is

shallow, somewhat poorly drained soil, over an organic hardpan. The North

tm:ML27:A 6-18

•••••••••••••••••••••••

<: ... ):\ 07-03 SARA SOT A BAY ::iiiil:·i:

<-o7.:o_4_ .. ::::::::::::;::::::::::::

••••••••••••••••••••••••••••••••••••••••••••• SESTA DRIVE /U/U!t\ / - - - ... \ 07-07

•••••••••••••••••••••••••

... .... 0 :)

! N

-HUDSON BAYOU BASIN


OSPREY COASTAL BASIN FIGURE 6-8

TABLE 6-4

SUMMARY OF BASIN AND SUBBASIN CHARACTERISTICS FOR OSPREY BASIN

SUBB~SIN SUBB~SIN CUNUL~TIVE N~JOR DITCH N~JOR CULVERT NUNBER OF NUN FER ~RE!l !lRE!l LENGTH LENGTII PROBLENS

(f:lCRES) (f1CRE5) (FEETJ <FEET) ' ----------

OSPREY B!lSIN

------------07-01 78 78 0 0 1 07-02 83 83 0 3,100 1 11.17-03 93 93 0 0 0 07-04 34 76 0 0 0 07-05 4"""' .:: 4"""' .:: 0 0 0

07-06 146 146 0 60 1 07-07 67 67 340 1,640 1 -------------------------------------------------------------------------------SUBTOT!lLS 542 340 4,800 4

07-01

07-02

s A

07-03 R A s 0 T 07-04 A

B A y

!Hill

07-06

07-07

OSPREY COASTAL BASIN FIGURE 6-9

TABLE 6-5

PROBLEM IDENTIFICATION IN THE OSPREY COASTAL BASIN

PROBLEN B~SIN/

NUNBER SUBB~SIN

STREET LOC~riON

OSPREY CO~STRL B~SIN

49 07-01 B~HIR VISTR RT ORRNGE RVE.

50 07-02 H~RBOR DRIVE RT FLOWER DRIVE

51 07-06 INTERSECTION OF OLD ORK DRIVE ~ND WISCONSIN LN.

52 07-07 FLORES ~VE. SOUTH OF SIESTR DRIVE

PROf/LEN VESCh'lPIIUN

PONDING IN STREET

PONDING IN STREET

PONDING RT INTERSECTION

PONDING IN STREET

PROf/LEN CI/USE

UNDERSIZED CONVEY~NCE

UNDERSIZED CONVEY~NCE

INLETS RT HIGHER ELEVRTION TH~N RORD

INLETS PLUGGED WITH DEBRIS UNDERSIZED CONVEYRNCE

Trail Coastal Basin has some small quantities of Pomello fine sands which are

in the same association as Leon.

There are a 1 so sma 11 areas of Plummer and Rutl ege fine sands. The Bayfront

Coastal Basin has a large area of Lakewood fine sand also, and some Pomello

fine sand located in its central interior. Blanton fine sand, a somewhat

excessively to moderately well drained deep soil and Delray fine sand, a

poorly to very poorly drained soil which is shallow and found over alkaline

materials.

6.4 INLAND BASINS

There are four basins which outfall to Sarasota Bay that are not coastal

basins but interior basins by nature. Starting at the north end of the city

and going south they are Whitaker Bayou Basin, Business District Basin, Hudson

Bayou Basin and Phillippi Creek Basin. These four basins run the full range

of development from residential to heavy commercial to nearly undeveloped

rural. There sizes range from 653 acres to 2496 acres. The primary soil,

found in these basins is SCS 11 C11 type, in the form of Leon fine sand. As

discussed previously this soil has a slow infiltration rate when thoroughly

wetted and typically has a layer which impedes downward water movement. Due

to unavailable pore space this 11 C11 type soil has a slow water transmission

rate. When discussing the basin soi 1 s we 1-1i 11 be concerned with these soils

as they exist within the city limits of Sarasota.

tm :t~L27 :A 6-23

6.4.1 Whitaker Bayou Basin

Whitaker Bayou is located in the northwest section of the County and drains a

total area of approximately 8,200 acres of which 1,717 are within the City.

The balance of 6,483 acres is divided between Manatee and Sarasota Counties.

This basin's outfall also drains a portion of southwestern Manatee County that

is composed of undeveloped commercial/industrial zoned areas. Generally, the

basin's primary drainage channel is via an improved natural channel. The area

drained within Sarasota County is highly urbanized and many of the area's

developments occurred some time ago. Development regulations of this period

provided for only minimal stormwater retention and detention. Within the City

portion of this basin there are some undeveloped parcels of vacant land.

Figure 6-10 shows the basin boundaries and its twenty subbasins which range in

size from 31 to 179 acres. Table 6-6 provides a summary of the

characteristics of the basin and subbasins which includes subbasin number,

area, cumulative area, major ditch and culvert lengths and the number of

system problems. Figure 6-11 provides a schematic diagram of the drainage

basin and receiving waters. Table 6-7 identifies flood problems within the

basin giving location, type of problem, problem cause and problem solution.

There are eighteen flooding problem areas noted in Table 6-7. The causes of

flooding in the basin range from maintenance of the conveyance size which

would require construction, to a combination of both.

tm:ML27:A 6-24

...J < 1-(/)

< 0 0

02-20

-...oi-1~ '-"""""-

02-18 ........

.......... 02-17 - .........

/ oe-_, / J ... _..,. __ .....

02-12

BUSINESS DISTRICT ASIN


02-11

HUDSON BAYOU BASIN

z c;,; -c I:D ~ w w a: 0

WHITAKER BAYOU BASIN FIGURE 6-10

TABLE 6-6

SUMMARY OF BASIN AND SUBBASIN CHARACTERISTICS FOR WHITAKER BAYOU BASIN

SUf/f/{lSJN

NUN FER

SUflfl{lSIN

RRER (f:lCRESJ

WHimKER BRYOU BRSIN --------------------82-81 47 02-02 85 02-83 77 02-84 34 82-05 41

02-06 24 02-07 152 02-08 56 02-09 33 02-10 110

02-11 216 02-12 158 02-13 57 02-14 167 02-15 77

02-16 20 02-17 118 02-18 97 02-19 22 02-20 128

CUNULRTIVE ftf{lJOR DITCH f>l{lJOR CULVERT t:lREt:l LENGTH LENGTH

(RCRESJ <FEETJ <FEETJ

1, 719 0 0 85 0 660 77 0 5,600

878 0 1' 180 632 1,100 40

591 400 1,660 567 2,900 1' 300

56 0 1,540 359 2,620 100 326 2,800 1,200

216 3,100 2,800 844 4,800 1,300

57 800 100 167 1,060 4,080

77 9, 740 1,560

385 1,100 740 118 3,660 4, 960 247 3,20/t."'t 980

EC 300 21t.10 128 4,340 1' 84Jt.1

NUNBER OF

PROf/LENS

1 4 0 0 0

0 .... .::

0 0 0

1 ·::> ,_

0 4 .... .::

0 0 1 1 0

-------------------------------------------------------------------------------SUBTOmLS 1, 717 41,920 31, 760 18

S. A R A s 0 T A

8 A y

FIGURE 6-11

TABLE 6-7

PROBLEM IDENTIFICATION IN THE WHITAKER BAYOU BASIN

PROBLEM BilSIN/ NUMBER SUBBilSIN

STREET LOCilTION

WHITilKER BilYOU BilSIN

4

5

6

7

8

9

10

11

1 .-, c

13

02-01

02-02

02-02

02-02

02-02

02-07

02-07

02-11

02-12

02-12

SYLVilN DRIVE

15TH ST. BETWEEN CENTRilL ilVE. ilND RiliLROilD

16TH ST. BETWEEN CENTRilL ilVE. ilND RiliLRO!lD

1 7TH ST. BETWEEN CENTRilL ilVE. ilND RiliLROilD

18TH ST. BETWEEN CENTRilL ilVE. ilND RiliLROilD

INTERSECTION OF OR!lNGE ilVE. ilND 18TH ST.

LEON ilVE.BETWEEN 24TH ilND 22ND STREETS

INTERSECTION OF 10TH ST. ilND TUTTLE ilVE.

CENTRilL ilVE. NORTH OF 27TH STREET

LEMON I:WE. NORTH OF 27TH STREET

PROBLEM DESCRIPTION

PONDING IN STREET

PONDING IN STREET

PONDING IN STREET

PONDING IN STREET

PONDING IN STREET

PONDING ilT INTERSECTION

PONDING IN STREET

PONniNG ~T TNTERSECTTON

PONDING IN STREET RND ilDJilCENT LOTS

PONDING IN STREET RND ilDJRCENT LOTS

PROBLEM CRUSE

OUTFRLL PLUGGED OR SUBMERGED

NO RPPRRENT OUTFRLL FOR RUNOFF




INLETS PLUGGED WITH DEBRIS UNDERSIZED CONVEYRNCE

POORLY GRRDED STREET

INLET PLUGGED WITH OEBRIS

UNDERSIZED CONVEYRNCE


-------------------------------------------------------------------------------------------------------PROBLEM BRSINI NUMBER SUBBRSIN

14 f'2-14

15 02-14

16 f'2-14

17 f'2-14

18 02-15

19 t12-15

211.1 t12-18

21 f'2-19

STREET LOCRTION

LEON RVE. NORTH OF 27TH ST.

NOBLE RVE. NORTH OF 27TH STREET

ORRNGE RVE. NORTH OF 27TH STREET

GILLESPIE RVE. BETWEEN 27TH RND 29TH STREETS

28TH STREET, ERST OF WRSHINGTON BLVD.

MRBLE LONG WRY (31ST ST. ) ERST OF WRSHINGTON BLVD.

47TH S~ BETWEEN ROYRL PRLM RVE. RND OLD BR!JDENTON RD.

DRVID !JVENUE SOUTH OF MECCR DRIVE

PROBLEM DESCRIPTION

PONDING IN STREET RND RDJRCENT LOTS



PONDING IN STREET


PONDING IN STREET

PONDING IN STREET

PONDING IN STREET

PROBLEM CflUSE

UNDERSIZED CONVEYflNCE



IMPROPER LOCRTION OF INLETS

INLET PLUGGED WITH DEBRIS RND SILT

INLET PRRTIRLLY PLUGGED WITH DEBRIS

UNDERSIZED RORDSIDE DITCH

UNDERSIZED SW!JLE

As can be seen from the schematic of the drainage flows, all twenty subbasins

have an ultimate discharge into Sarasota Bay via Whitaker Bayou. Subbasin 02-

01 has a direct discharge to the Bay while subbasins 02-02, 02-03, 02-04 and

02-05 discharge into the Whitaker Bayou Channel. The rest of the subbasins

discharge to either Subbasins 02-04 or 02-05. Subbasins 02-15, 02-16 and 02-

20 have flows from unincorporated Sarasota County.

The primary soil found in the Whitaker Bayou Basin is Leon fine sand. The

balance of the soils found here in any quantity are Ona fine sand, a somewhat

poorly drained deep soil, Lakeland fine sand, a somewhat excessively to

moderately drained deep soil and some Adamsville find sand, somewhat poorly

drained soil that is shallow and found over alkaline materials.

6.4.2 Business District Basin

This basin contains approximately 600 acres and has been divided into seven

subbasins which range in size from 49 to 135 acres. The basin contains both

residential and commercial development with most of the residential being

located in the northwest and west portion of the basin and the southeastern

corner. The balance is composed of commercial and light industrial

development and this basin also contains the City of Sarasota Sewage Treatment

Plant. As it • s name implies, the older portion of the downtown business

district is also located within the bounds of this basin.

The primary soil of this basin is Leon fine sand and the balance is composed

of fine sands which are somewhat poorly to very poorly drained. The basin

tm:ML27:A 6-30

has some undeveloped land mostly in the commercial/light industrial areas in

the northeast and eastern portions.

Figure 6-12 shows the basin boundaries and the attendant subbasins. Table 6-8

provides a summary of the characteristics of the basin and subbasins which

includes subbasin nmumber, area, cumulative area, major ditch and culvert

lengths and the number of system problems. Figure 6-13 provides a schematic

diagram of the drainage basin and receiving waters. Table 6-9 identifies

flood problems within the basin giving location, type of problem, problem

cause and problem solution. In the Business District Basin there were six

flooding problems identified. Three of the problems involved a combination of

maintenance and a need for additional inlets. The other three problems

involved a collapsing conveyance system in one case, lack of system altogether

in another case and poorly graded street which made additional inlets.

The basin drainage schematic, Figure 6-13, shows two direct discharges from

04-01 and 04-02 into the bay. The ba 1 ance of the subbasins, 04-03, 04-04, 04-

05, 04-06 and 04-07 discharge into Hog Creek and then into Sarasota Bay.

6.4.3 Hudson Bayou 8asin

The Hudson Bayou Basin is located just south of the Bayfront Coastal Basin and

encompasses 1,598 acres of the City of Sarasota and is composed of nineteen

subbasins.

and natural

commercial.

tm:ML27:A

Stormwater is collected utilizing a combination of storm sewers

channels. This basin has a mix of both residential and

The commercial development is concentrated along U.S. 41 and U.S.

6-31

WHITAKER BAYOU BASIN

04-01 J ,/ ____ ...

..__ I .- - ..... ,. - - - ~ 0 4 .._ ' 10TH STREET

04-oa '--" , ............ __ I 1 I 04-05~ ..... J I I

~,1 J \ I \

BA YFRONT COASTAL BASIN

MAIN STREET

HUDSON BAYOU BASIN

BUSINESS DISTRICT BASIN FIGURE 6-12

TABLE 6-8

SUMMARY OF BASIN AND SUBBASIN CHARACTERISTICS FOR BUSINESS DISTRICT BASIN

SUBBf:JSIN NUMBER

SUBBf:lSIN f:JREf:l

(f:JCRES.I

BUSINESS DISTRICT BRSIN

-------------------------04-01 135 04-02 56 04-03 114 04-04 53 04-05 49

04-06 98 04-07 95

CUMULf:JTIVE Mf:l~TOR DITCH Mf:JJOR CULVERT f:lREf:l

ff:JCRESJ

135 465 114 295

49

193 95

LENGTH fFEETJ

3300 460

0 1660

0

2520 1140

LENGTH fFEET.J

2700 1740

10100 1500 1500

1360 1920

NUMBER OF PROBLEMS

2 0 1 1 2

0 it

-------------------------------------------------------------------------------SUBTOTf:JLS 600 9080 20820 6

04-01

04-05

04-02 04-04

04-03

PBS) BUSINESS DISTRICT BASIN FIGURE 6-13

TABLE 6-9

PROBLEM IDENTIFICATION IN THE BUSINESS DISTRICT BASIN

----------------------------------------------------------------------------------------------·---------PROBLEM BRSIN/ NUMBER SUBBRSIN

STREET LOCRTION

PRO ElLEN DESCRIPTION

PROBLEN GIUSE

--------------------------------------------------------------------------------------------

BUSINESS DISTRICT BRSIN

EE 04-01

23 04-01

24 04-03

25 04-04

26 04-05

27 04-05

INTERSECTION OF ORRNGE I:WE. RND 11TH ST.

OHIO PLRCE RT MORRILL STREET

INTERSECTION OF 4TH ST. t:WD KUMflURT CT.

GOODRICH RVE. BETWEEN 5TH RND 10TH STREETS

GILLESPIE RVE. BETWEEN 7TH ST. RND 10TH ST. DITCH

OSPREY RVE. BETWEEN 6TH RND 10TH STREETS

PONDING IN STREET

PIPE FRILURE

PONDING IN STREET

PONDING IN STREET

PONDING IN STREET

PONDING IN STREET

IMPROPER LOCRTION OF INLETS POORLY GRRDED STREET

COLLRPSE OF CITY PIPE IN ERSEMENT

FLRT SLOPE, NO INLETS

INLETS PLUGGED WITH DEBRIS

SOME INLETS PLUGGED WITH DEBRIS

SOME INLETS PLUGGED WITH DEBRIS

301, both of which run north-south through the basin. The northern end of the

basin forms the approximate southern half of the downtown business district.

The balance of the basin is composed of single family and some multi-family

residential neighborhoods. The vacant land found in this basin is primarily

park and/or recreational in nature and under normal conditions would remain

vacant.

Figure 6-14 shows the basin boundaries and the nineteen subbasins. Table 6-

10 provides a summary of the characteristics of the basin and subbasins which

includes subbasin number, area, cumulative area, major ditch and culvert




cause and problem solution. The vast majority of the flooding problems in

this basin (eleven areas) were caused from an undersized conveyance. One area

has a poorly graded street and two areas require replacing culverts and

bridges. In only one case was maintenance found to be the cause of flooding.

The schematic for Hudson Bayou basin is somewhat complex and is best

understood by reviewing Figure 6-15. As can be seen, the basin has three

primary collector systems which combine prior to discharge through Hudson

Bayou.

Soils found in this basin are composed primarily of Leon fine sand which is

somewhat poorly drained, shallow over an organic hardpan. There are some

large areas of Immokalee fine sand which is in the same association as Leon

tm:ML27:A 6-36

SARASOTA BAY

j N

-BUSINESS DISTRICT BASIN

06-16

06-17

06-18



HUDSON BAYOU BASIN FIGURE 6-14

TABLE 6-10

SUMMARY OF BASIN AND SUBBASIN CHARACTERISTICS FOR HUDSON BAYOU BASIN

SUBBt:JSIN NUMBER

SUBBt:JSIN t:JREt:J

ft:JCRESJ

HUDSON Bt:JYOU Bt:JSIN

------------------06-01 49 06-02 31 06-03 110 06-04 34 06-05 35

06-06 93 06-07 87 06-08 86 06-09 96 06-10 29

06-11 109 06-12 67 06-13 61 06-14 85 06-15 105

06-16 144 06-17 179 06-18 145

CUMULt:JTIVE /IIIUOR DITCH t:JREt:J LENGTH

(11CRESJ fFEETJ

1598 0 210 0 179 920 69 0 35 0

233 3180 87 360

1106 0 96 0

924 1120

571 2560 67 0

395 1280 85 2400

249 1820

144 2700 324 1700 145 3840

MI:UOR CULVERT LENGTH fFEETJ

0 940

6440 2920 1920

2520 960 760

3280 0

50 920

0 2060 2000

2980 2300

20

Ni.J/1/BER OF PROBLEMS

0 0 1 0 0

1 0 0 1 0

0 0 0 6 2

1 3 0

-------------------------------------------------------------------------------SUB TO TilLS 1598 21880 31770 15

s A R A s 0 T A

8 A y

06- 05

06-04

06-03 06-07

HUDSON BAYOU BASIN

06- 16

06- 15

06- 13

06- II

06.;.. 09

FIGURE-- 6-15

PROBLEM BASIN/ NUNBER SUBBASIN

TABLE 6-11

PROBLEM IDENTIFICATION IN THE HUDSON BAYOU BASIN

STREET LOCATION

PRUBLEN DESCRIPTION

PROFLEN CfJUSE

HUDSON BAYOU BASIN

34

35

36

37

38

39

40

41

, . ., ... .::

06-03

06-06

06-t19

06-14

06-14

06-14

06-14

06-14

06-14

INTERSECTION OF ALDERMAN S~ PONDING IN STREET AND OSPREY AVENUE

INTERSECTION OF ALDERMAN PONDING IN INTERSECTION ST. AND US 301

INTERSECTION OF LAURENT PL. AND HILLVIEW ST.

POPLAR ST. EAST OF TUTTLE AVENUE

PONDING IN INTERSECTION

PONDING IN STREET

OAK ST. EAST OF TUTTLE AVE. PONDING IN GUTTERS, DRIVEWAYS AND YARDS

MICHIGAN ST. EAST OF TUTTLE PONDING IN GUTTERS, AVENUE DRIVEWAYS AND 'lARDS

LOUISE ST. EAST OF TUTTLE PONDING IN GUTTERS, AVENUE DRIVEWAYS AND 'r'ARDS

SEflUOIA LANE EAST OF PONDING IN GUTTERS, TUTTLE AVENUE DRIVEWAYS AND 'lARDS

DAVIS BLVD. EAST OF TUTTLE PONDING IN GUTTERS, AVENUE DR I VEWA 'lS AND YARDS

UNDERSIZED CONVEYANCE


INLETS PARTUlLL 'l PLUGGED WITH DEBRIS

UNDERSIZED OUTFALL PIPE

UNDERSIZED CONVE'lANCE





----------------------------------------------------------------------PROBLEM Br:JSJNI NUNBER SUBBr:JSJN

43 06-15

44 06-15

45 06-16

46 06-17

47 06-17

48 06-17

STREET LOCflTJON

EUCLID Cf/NflL f/ND BELVOIR ST.

EUCLID CflNflL f/ND SYDELLE ST.

INTERSECTION OF JEFFERSON flVE. flND 6TH ST.

TflMI-SOLfl ST. BETWEEN SCHOOL flVE. flND SHflDE flVE.

LOMfl LINDfl CT.

INTERSECTION OF flRLINGTON ST. flND SHflDE AVENUE

PRUBLEN DESCRIPTION

PONDING IN STREETS

PONDING IN STREETS

PONDING IN INTERSECTION flND YflRDS

PONDING IN STREET

PONDING IN STREET

PONDING IN STREET

PROBLEN CRUSE

CONSTRICTED CHflNNEL

CONSTRICTED CHflNNEL

UNDERSIZED CONVEYflNCE

POORLY GRflDED STREET flDJACENT TO WETLflNDS

NO INLETS FOUND


fine sand. There are areas of other soils but in quantities which would have

little or no effect on the overall drainage of the basin.

6.4.4 Phillippi Creek Basin

T~e Phillippi Creek basin is the largest basin within Sarasota County and

drains approximately 57 square miles of northwest Sarasota County and a small

portion of lower Manatee County. Approximately 2,496 acres of the basin is

within the city limits and the reach of the main channel through the City is

approximately 5.2 miles long and is fed at its upstgream by two major canals,

~ain A and Main B. These canals are in turn fed by smaller branch canals and

tributaries. The portion of the avera 11 basin within the City has been

divided into 20 subbasins which range in size from 23 to 283 acres.

The entire watershed consists of gently sloping terrain which rises from sea

level at the outflow in Roberts Bay to just over 40 feet (NGVD) at the

headwaters. The surface of the basin has an average slope of just over 0. 2

percent or a 1-foot drop for every 500 feet of distance. The slope of the

stream bed varies from about 4 feet per mile at its upper reaches to less than

1 foot per mile.

There are a number of bridges crossing the creek throughout its 1 ength. The

largest bridge across the main channel is at the intersection of the creek and

Tamiami Trail (U.S. 41), approximately one-half mile above the mouth of the

creek. There is one major flow control structure within the creek which is a

tm :t1L27 :A 6-42

spillway located on the main channel approximately 3.4 miles above the outlet

that once was used as a salinity barrier.

The main channel below the confluence of Main A and Main B lies almost

entirely within the boundaries of the City of Sarasota. This highly urbanized

area is laced with small tributary channels flowing from the City into the

creek. Historical flooding of this area has at time been rather severe.

The portion of the basin in the City is largely residential with light

commercial along the main roads. There is one area with a large sports

complex and camper parking located in the north-central part of this basin

which is not representative of the overall basin. This basin contains some

large parcels of undeveloped land which, when developed, could significantly

effect the overall drainage patterns.

Figure 6-16 shows the basin boundaries and its twenty subbasins. Table 6-12

provides a summary of the characteristics of the basin and subbasins which

includes subbasin number, area, cumulative area, major ditch and culvert




cause and problem solution. The flooding in this basin is caused by a

combination of things. One problem was caused by an undersized and poorly

maintained outfall ditch while another area had an undersized conveyance. One

area had a poorly graded street and maintenance problems while two other areas

had poorly graded streets only. In one case the problem was lacking a system.

tm:t1L27:A 6-43

> w a: a. C/)

0

HI"J:AKER BAYOU . BASIN

BUStNE s OISTRIC BASIN

gl u;· ::)

u.s. 41

HUDSON BAYOU BAS IN

~ z w > ~

w ..J .... .... ::;) ....

\ -- ... 05-16 ' ' , _____

05-11 ' -------~ ' I

' I \ I \ 05-15 \ \ \

05-10

05-09

J


--

--

05-19

05-20

l N

-

FIGURE 6-16

TABLE 6-12

SUMMARY OF BASIN AND SUBBASIN CHARACTERISTICS FOR PHILLIPPI CREEK BASIN

SUBFRSIN NUNBER

SUBBRSIN RRER

<RCRESJ

PHILLIPPI CREEK Bf1SIN

---------------------05-01 107 05-02 66 05-03 166 05-04 24 05-05 39

05-06 6".., c

05-07 137 05-08 6".., c

05-09 316 05-10 181

05-11 265 05-12 45 05-13 24 05-14 74 05-15 157

05-16 263 05-17 75 05-18 23 05-19 283 05-20 128

CUNULRTIVE NRJOR DITCH f1REf1 LENGTH

lr?CRESJ (FEET)

464 1,400 66 1' 540

166 0 125 1,280 39 100

62 0 137 0

6"""' c 0 1,325 7,620

181 0

310 5,160 45 0 24 0

494 2,560 157 1' 900

263 8, 780 381 2,700

23 0 283 9, 80/ll 128 3,400

NfUOR CULVER r "-ENGT/1 CFEETJ

0 100

5,020 (!1

1.420

1' 720 2,260

0 300

1' 800

1' 040 2,120 1, 000

60 900

5,440 0

960 300 540

NUNFER OF PROBLENS

1 1 t1

0 0

0 0 0 0 3

1 0

'-"" 0 0

0 0 0 0 0

-------------------------------------------------------------------------------SUBT0Tf1LS 2,496 46,240 24,980 6

05- 15

05 - 12 I

L I T 05-05 05-04 05-06 05 - II 05-13 05- 19 T L E

s A R 05-02 05-03 05-07 05-08 05-09 05- 10 05- 18 A s 0 T A

B A

05- 01

y

PHILLIPPI CREEK BASIN FIGURE 6-17

TABLE 6-13

PROBLEM IDENTIFICATION IN THE PHILLIPPI CREEK BASIN

PROBLEM B!1SIN/ NUMBER SUBBRSIN

STREET LOCRTION

PHILLIPPI CREEK BRSIN ---------------------

28 05-01 INTERSECTION OF PROSPECT RND BRINK

29 05-02 ERST RVENUE SOUTH OF CLEMRTIS ST.

30 05-10 BRINK RVE. (FRUITVILLE RD. TO RSPINWRLL STREETJ

31 05-10 CONRRD RVE. ( FRUITVILLE RD. TO RSPINWRLL STREETJ

-.-, ,j,:: 05-10 POMPRNO ST. (FRUITVILLE RD.

TO RSPINWRLL STREETJ

33 05-11 TUTTLE RVE. SOUTH OF 1 7TH STREET

PROFLEN DESCRIP710N


PONDING IN STREET

PONDING IN STREET

PONDING IN STREET

PONDING IN STREET

PONDING IN STREET

PROBLEN CfiUSE

UNDERSIZED RND POORLY NRINTAINED DUTFfiLL DiTCH


INLETS PLUGGED WITH DEBRIS POORLY GRRDED STREET

' POORLY GRRDED STREET /

POORLY GRRDED STREET /

NO INLETS FOUND J

The schematic for the Phillippi Creek Basin is somewhat complex and Figure 6-

17 should be reviewed for a clear understanding of the subbasin's relationship

to each other. The creeks main channel system is fed by three primary

collector systems which route urban flows to the creek.

This basin has large areas of Leon fine sand but also has numerous other soil

types. The other significant soils in the basin are Delray fine sand (shallow

phase) Pompany fine sand, Manatee loamy fine sand, Immokalee fine sand and

Pomello fine sand. All of these soils fall into associations described as

"somewhat poorly drained soils, shallow over organic hardpans" or "poorly to

very poorly drained soils. The remaining soil types are in small quantities

which would have little overall effect on the drainage basin.

tm:ML27:A 6-48

SECTION SEVEN

7.1 GENERAL

Section 7

STORMWATER SERVICE LEVEL

Only in the recent past has stormwater service been likened to highway

capacities by defining levels of service with the performance of stormwater

management systems being ranked on a relative continuum from good to bad for a

given design storm. This section examines the concept of service levels for

stormwater management systems, recommends specific service level definitions

and assesses both existing and anticipated future levels of service attainment

for the City's current system.

7.2 SERVICE LEVEL DEFINITIONS

The selection of appropriate performance criteria is a policy issue which has

significant budget consequences. If criteria are selected which are too

conservative the cost of solutions to existing drainage problems become overly

expensive. Conversely, if the selected criteria are too lax, the resultant

system does not meet the intended level of service. Clearly a policy issue

which must be resolved is the appropriate level of service.

Good performance for an urban system might be defined as flow contained within

the gutter with no system surcharging or street flooding while bad performance

may be defined as structure flooding. It is fair to say that every portion of

every service area does not require the highest level of service at all times

for all events. Many areas can tolerate a 1 imi ted amount of street or yard

flooding if it does not last very long and is not frequently experienced.

tm:ML28:W 7-1

The City of Sarasota experiences flooding from a variety of rainfall events.

The degree of severity of flooding by its impacts: street flooding, yard

flooding or structure flooding. Four service levels were defined based upon

these severity classifications:

0 Service Level A: Gutter Flow Only

0 Service Level B: Street Flooding

0 Service Level C: Street and Yard Flooding

0 Service Level D: Street, Yard and Structure Flooding

While these definitions seem rather simplistic, they represent a

classification system that facilitates evaluation of overall system

performance and the prioritization of funding for stormwater management system

construction, 0 & M and development.

The individual service levels are defined functionally in terms of the

performance criteria for the stormwater management system. The development of

service level criteria involves a compromise between an academic approach and

the availability of usable data for cross-section profiles of the roadway,

right-of-way, yard and finish fl oar of structures. The proposed performance

criteria for each service level utilize available topographic and aerial

photographic information in conjunction with functional criteria definitions

which are valid in most instances:

o Service Level A: Water Contained Within The Gutters

tm:ML28:W

No flooding of major roadways, minor roadways, yards or structures. The hydraulic grade line (free water surface) is generally at or below the inlet throat.

7-2

o Service Level B: Water Contained Within Right-of-Way

Flooding of major roadways is limited to the outer lane but does not prevent travel, i.e., limited duration flooding of minor streets, flooding of yards generally limited to the right-of-way but no flooding of structures. The hydraulic grade line is at or slightly above the inlet throat.

o Service Level C: Water contained Within the Front Yard

Flooding of major roadways precludes the use of outer 1 ane and travel in inner lanes is possible but difficult, prolonged flooding of minor streets which precludes travel, flooding of front yards up to the front face of the structure but no flooding of the structure. The hydraulic grade line is significantly above the inlet.

o Service Level D: Structure Flooding

Extensive flooding of streets, yards and structures for prolonged periods.

Clearly, the existence of Service Level D conditions represent a stormwater

manager's nightmare and is never an acceptable design condition. However,

virtually any system may suffer Service Level D performance if subjected to a

severe enough rainfall event.

It is recommended that these definitions be reviewed by the City staff and

then formally adopted as a basis for setting stormwater service levels,

throughout the city.

7.3 CAPACITY AND DEMAND CALCULATIONS

The assessment of the ability of stormwater facilities ability to meet the

defined service levels, as previously discussed, requires an analysis of the

facility capacity and an estimation of peak flow (demand) for the primary

drainage systems within the City of Sarasota. By a comparison of the two, it

tm:ML28:W 7-3

can be determined whether specific drainage facilities are of sufficient

capacity to meet the designated service level or whether an upgrade is

necessary to satisfy the expected demand.

7.3.1 Facility Capacity Analysis

Storm drainag~ facility capacity is a complicated technical parameter that is .,

difficult to ~'assess at a planning level. An accurate engineering

determination! requires a detailed hydraulic analys1s .of each element of the

stormwater conveyance system including physical parameters of size, slope,

elevation, roughness, and cross section area. For the analysis here, many of

these physical parameters were unknown and required estimation from City's

Drainage Atlas maps and USGS 1 11 = 2000' topographic quadrangle maps.

For the purpose of this analysis, key primary drainage facilities within the

City were identified and capacities were calculated by one of two different

means. Within a closed storm sewer system, capacity was defined as the ability

of the conveyance system to carry flow under a full flow regime with a

hydraulic gradeline slope which conformed to the average land slope along the

path of the storm sewer 1 i ne. The capacity of a culvert in an open channel

system was calculated assuming a headwater depth of 2 feet and a full-flow

condition. Nomographs published in FHWA's Hydraulic Design series No. 5,

Hydraulic Design of Highway Culverts, were utilized to estimate the culvert

capacity under these conditions. The resulting capacity estimate for each

drainage facility is summarized in Table 7-1 by basin.

tm:ML28:W 7-4

FACILITY NUMBER

TABLE 7-1

SUMMARY Of STORMWATER MANAGEMENT FACILITY CHARACTERISTICS AND CAPACITIES

FACILITY DESCRIPTION

FACILITY LOCATION

ESTIMATED CAPACITY

<CFS> -----------------------------------------------------------------------------------NORTH TRAIL COASTAL BASIN

01-01-01 01-02-01 01-03-02 01-04-01 01-05-01 01-06-01 01-06-02 01-07-01

FACILITY NUMBER

42" ss 36" ss 18" ss 36" ss 24" ss (48" 30" RCP SS 24" RCP SS 24" RCP SS

N. TAMIAMI TRAIL &CITY LIMIT SUN CIRCLE & SAPPHIRE DRIVE BRYWILL CIRCLE TO SUN CIRCLE BAY SHORE ROAD & 45th STREET

ELLIPTICAl>BAY SHORE ROAD & 40th STREET BAY SHORE ROAD & VIRGINIA DRIVE BAY SHORE ROAD & VIRGINIA DRIVE ALAMEDA AVENUE & 22r•d STREET


FACILITY LOCATION

WHITAKER BAYOU BASIN

02-02-02 02-03-01 02-03-02 02-04-01 02-06-01 02-06-02 02-07-01 02-07-02 02-08-01 02-09-01 02-10-01 02-10-02 02-10-03 02-11-01 02-11-02 02-11-03 02-12-03 02-12-06 02-12-08 02-13-01 02-14-01 02-14-02 02-14-03 02-14-04 02-14-05 02-15-01 02-16-02 02-17-01 02-17-02 02-18-02 02-18-03 02-18-04 02-19-01 02-20-03 02-20-04

36" RCP SS 42" RCP SS 42" RCP SS 42" RCP SS 2-6. 5' X 8' BC 36" RCP SS 78" RCP SS 72" RCP SS 48" RCP SS 5' X 10' BC 7' X 7' BC 43" X 68" CULVERT 5' X 10' BC 43" X 68" RCP CULV 30" RCP SS 30" RCP CULVERT 60" RCP SS 30" RCP SS 60" RCP CULVERT 22" X 36" CMP CULV 36" RCP SS 48" RCP SS 48" RCP SS 54" RCP CULVERT 60" RCP CULVERT 36" RCP SS 30" RCP SS 48" RCP SS 48" RCP SS 36" RCP SS 30" RCP SS 30" RCP SS 30" RCP SS 42" RCP SS 36" RCP SS

TAMIAMI TRAIL S.OF HUDSON BAYOU TAMIAMI TRAIL & SYLVAN DRIVE 27th STREET & TAMIAMI TRAIL 27th ST, E OF OLD BRADENTON RD CENTRAL AVENUE & 23rd CENTRAL AVENUE & 23rd LEON AVENUE & 24th 23rd & PALMA DELLA 23rd & MAPLE AVENUE 21st & MAPLE AVENUE 20th & WASHINGTON 17th & EAST 17th & SHADE AVENUE 17th & SHADE AVENUE 12th & SHADE AVENUE 12th & SHADE AVENUE CENTRAL AVENUE & 29th STREET MYRTLE & COCOANUT AVENUE LEMON AVENUE, NORTH OF 27th 29th STREET & LEON AVENUE 29th STREET & GOODRICH AVENUE 29th STREET & MAPLE AVENUE ORANGE AVENUE NORTH OF 27th NOBLE AVENUE NORTH OF 27th LEON AVENUE NORTH OF 27th MYRTLE & GILLESPIE AVENUE 40th STREET AND COCOANUT AVENUE GARY STREET & TAMIAMI TRAIL 42th STREET AND COCOANUT AVENUE 48th & OLD BRADENTON ROAD 47th & OLD BRADENTON ROAD 47th & OLD BRADENTON ROAD OLD BRADENTON ROAD AT 50th DESOTO ROAD & OLD BRADENTON ROAD DESOTO ROAD & OLD BRADENTON ROAD

7-5

lil18 7'3 14 72 35

. 44 30 3IZI

ESTIMATED CAPACITY

<CFS)

65 110 6'3 6'3

760 51

402 325 11 ill 410 400 140 410 165 3'3 42

155 31

175 23 51 '38 85

145 175

51 28

110 98 56 28 28 35 84 28

FACILITY NUMBER


BAYFRONT COASTAL BASIN

03-02-01 03-03-01 03-03-02 03-04-01 03-04-02 03-05-01 03-05-02 03-06-01 03-07-01 03-07-02 03-07-03

FACILITY NUMBER

38" X 60" RCP SS 29' X 45" RCP SS 19" X 30" RCP SS 30" RCP SS 30" RCP SS 42" RCP SS 36" RCP SS 30" RCP SS 4' X 7' BC SS 48" RCP SS 54" RCP SS


BUSINESS DISTRICT BASIN

04-01-01 04-01-02 04-01-03 04-01-04 04-02-01 04-02-02 04-03-01 04-04-01 04-04-02 04-05-01 04-06-01 04-06-02 04-06-03 04-06-04 04-07-01

30" RCP SS 60" RCP SS 36" RCP SS 4' X 10' BOX CULVERT 72" RCP LO-HED SS 72" RCP LO-HED SS 54" RCP SS 5' X 10' BOX CULVERT 36" RCP SS 36" RCP SS 48" RCP CULVERT 30" RCP SS 48" RCP CULVERT

· 42" RCP CULVERT 36" RCP SS


FACILITY LOCATION

BLVD OF THE ARTS TAMIAMI TRAIL & 3rd STREET TAMIAMI TRAIL & 2nd STREET GULF STREAM AVE & GOLDEN GATE PT GULF STREAM AVE & GOLDEN GATE PT BAYFRONT DRIVE & MARINA PLAZA BAYFRONT DRIVE & MARINA PLAZA BAYFRONT DRIVE & ISLAND PARK BAYFRONT DRIVE & RINGLING BLVO PALM AVENUE & RINGLING BLVD PALM AVENUE & RINGLING BLVU

FACILITY LOCATION

N. TAMIAMI TRAIL & WHITAKER LN 11th & COCOANUT 11th & ORANGE TAMIAMI TRAiL & 11th 10th & TAMIAMI TRAIL 10th & CENTRAL 10th &. LEMON 10th & ORANGE 10th & GOODRICH 10th & OSPREY 10th & OSPREY 10th & us 301 10th & us 301 10th & EAST AVENUE 7th & SCL RR

7-6

ESTIMATED CAPACITY

<CFS)

110 7'3 27 4121 40 '37 65 4'3

286 156 1b5

ESTfMHTED CAPACITY

<CFS>

31 17'3 56

330 355 2~1 135 440

46 46

105 28

1(1)5 78 51

FACILITY NUMBER

TABlE 7-1 (Continued)


FACILITY LOCATION


05-01-02 05-02-01 05-02-02 05-02-03 05-03-01 05-03-02 05-03-03 05-04-01 05-05-01 05-06-01 05-07-01 05-09-01 05-09-02 05-10-01 05-10-02 05-11-01 05-11-02 05-11-03 05-12-01 05-13-01 05-14-01 05-15-01 05-15-02 05-16-01 05-16-02 05-16-03 05-16-04 05-16-05 05-17-01 05-17-02 05-18-01 05-19-01 05-19-02 05-19-03 05-20-01

36" CMP CULVERT 44" X 72" CMP CULV 48" RCP CULVERT 18" RCP SS 84" CMP SS 3-30" RCP SS 36" RCP SS 2-42" RCP CULVERTS 42" RCP SS 54" RCP SS 48" RCP SS 30" RCP SS 48" RCP SS 30" RCP SS 24" RCP SS 30" RCP SS 5' X 10' BC 38" X 60" RCP SS 42" RCP SS 30" RCP SS 14' X 14' BC 54" RCP CULVERT 36" RCP SS<LO-HED> 36" RCP SS 2-43" X 68" CULVS 48" RCP CULVERT 43" X 68" RCP SS 42" RCP SS 24" CMP SS 24" CMP SS 30" CMP SS 30" CMP SS

HYDE PARK STREET & TUTTLE AVENUE SUNNYSIDE PLACE HIBISCUS STREET EAST AVENUE & CLEMATIS STREET SCHOOL AVENUE & GROVE STREET SCHOOL AVENUE & SIESTA DRIVE SCHOOL AVENUE & SIESTA DRIVE GROVE STREET & EAST AVENUE GROVE STREET & TAMIAMI TRAIL GROVE STREET & TAMIAMI TRAIL BAHIA VISTA STREET BENEVA ROAD & SCL RR LOCKWOOD RIDGE RD & FRUITVILLE RD LOCKWOOD RIDGE RD & FRUITVILLE RD LOCKWOOD RIDGE RD & FRUITVILLE RD MELODY STREET LOCKWOOD RIDGE ROAD 17th STREET & TUTTLE AVENUE 12th STREET & TUTTLE AVENUE BENEVA & FRUITVILLE RD BENEVA & FRUITVILLE RD CIRCUS BLVD BREEZEMONT DR 17th STREET & CIRCUS BLVD 17th STREET & BENEVA ROAD 17th STREET & LOCKWOOD RIDGE ROAD 17th STREET & LOCKWOOD RIDGE ROAD CIRCUS BLVD & CALLIANDRA DRIVE MIDWEST PARK & HAWKEYE MIDWEST PARK & BUCKEYE MIDWEST PARK & DAVIS BLVD MIDWEST PARK & GOPHER MIDWEST PARK & WOLVERINE 30" CMP SS

2-6'X 8.5' CMP 4' X 4' BC

CULV FRUITVILLE ROAD & BOBBY JONES ROAD FRUITVILLE ROAD & DADE AVENUE

7-7

ESTIMATED CAPACITY

<CFS>

42 11 ill lic:J5

':3 155 84 4b

160 6':3

117 110 33 '38 28 16 28

410 85 60 28

1200 132 56 33

28tll 105

'36 51

8 8

17 12 12

510 124

FACILITY NUMBER



FACILITY LOCATION

HUDSON BAYOU BASIN

06-01-01 06-02-01 06-02-02 06-03-01 06-03-02

,,~~06-03-03_

,.06-03-04 06-04-01 06-05-01 06::-:06:-01 06-06-02 06-06-03 06-07-01 06-08-01 06-09-01 06-09-02 06-09-03 06-12-01 06-13-01 06-14-01 06-14-02 06-15-01 06-15-02 06-15-03 06-15-04 06-16-01 06-17-01 06-17-02 06-17-03 06-17-04 06-18-01

18" RCP SS 36" RCP SS 30" RCP SS 48"& 60" RCP CULVS 60" RCP SS 42" RCP SS 60" RCP SS 36" RCP SS 34" X 53" RCP SS 48" RCP SS _, 48" RCP CULVERT 36" RCP SS 36" RCP SS 18" RCP SS 48" RCP SS 36" RCP SS 18" RCP SS 42" RCP SS 2-42" CMP CULVERTS 36" X 58" CMP CULV 31" X 50" CMP SS 2-36" RCP CULVERTS 36" CMP SS 2-36" RCP CULVERTS 2-36" RCP CULVERTS 2-36" RCP CULVERTS 6' X 10' BC 66" CMPAC 60" LO-H CULVERT 29" X 45" RCP SS 48" CMP CULVERT

POMELO AVENUE AT HUDSON BAYOU BAYFRONT DR & N BRANCH HUDSON BAYOU BAYFRONT DR & N BRANCH HUDSON BAYOU ALDERMAN ST AT N BRANCH HUDSON BAYOU NOVUS STREET AT N BRANCH HUDSON BAYOU LAUREL STREET & OHIO PLACE ALDERMAN STREET & OSPREY AVENUE RINGLING BLVD & WASHINGTON BLVD SCHOOL AVENUE & RINGLING BLVD BAYFRONT DRIVE .& .. US 301 BAYFRONT DRIVE & US 301 ALDERMAN STREET & US 301 ALDERMAN STREET & SCHOOL AVENUE OSPREY AVENUE & LINCOLN DRIVE US 301 & LINCOLN DRIVE US 301 & HAWTHORNE HILLVIEW STREET & LAURENT PLACE EUCLID & HATTON STREET EUCLID AVENUE & BROWNING STREET TUTTLE AVENUE & NOVIS STREET EAST OF TUTTLE AVE & SCL RR SCL RR & EUCLID AVENUE x DAVIS BLVD & EUCLID BELVOIR BLVD & EUCLID EUCLID AVENUE & SYDELLE EUCLID & ASPINWALL STREET BAHIA VISTA & HUDSON BAYOU SCHOOL AVENUE & FLOYD STREET ARLINGTON STREET & SHADE AVENUE LOMA LINDA CT JEFFERSON & HILLVIEW

FACILITY NUMBER


FACILITY LOCATION

OSPREY BASIN -------------07-01-01 24" RCP SS BAHIA VISTA STREET & ORANGE AVENUE 07-02-01 48" RCP SS FLOWER DRIVE & HARBOR DRIVE 07-02-02 30" RCP SS ORANGE AVENUE & WALDMERE STREET 07-02-03 30" RCP SS FLOWER DRIVE & HARBOR DRIVE 07-03-01 18" RCP SS ORIOLE DRIVE & SANDPIPER LANE 07-04-01 24" RCP SS HARMONY LANE & CARDINAL PLACE 07-05-01 18" RCP SS OSPREY AVENUE & GROVE STREET 07-06-01 18" RCP SS SIESTA DRIVE & TANGIER TERRACE 07-07-01 36" CMP CULVERT TANGIER TERRACE & BEE RIDGE RuAD

7-8

ESTIMATED CAPACITY

<CFS>

11 51 31

285 218

'38 218

56 5'3

140 '32 55 E)j 16

13'3 56

'3 l36

115 b6 34

120 32

120 120 104 540 21'3 160 56 90

ESTIMATED CAPACITY

<CFS>

1'3 llld 44 34 12 25 14 14 4b

7.3.2 Facility Demand and Residual Capacity Analysis

The estimation of a design peak flow (demand) at a given storm drainage

facility was calculated by one of two methods. For a contributing drainage

basin of 300 acres or less, the Rational Method was utilized. This method

requires, (1) a contributing drainage area, estimated from measuremenents of

city drainage atlas sheets, (2) a composite runoff coefficient estimated

according to land use patterns and degree of imperviousness within the

contributing drainage area is determined from City aerial photographhs, and

(3) a design rainfall intensity corresponding to the time-of-concentration for

the contributing drainage area, estimated according to basin slope, hydraulic

length, and land use.

The second method of peak flow calculations, for contributing drainage basins

greater than 300 acres, utilized the basin regression method documented in the

USGS publication, Magnitude and Frequency of Flooding on Small Urban

Watersheds in the Tampa Bay Area West-Central-Florida. This method of

analysis utilizes the basin drainage area, channel slope, basin development

factor, and surface areas of lakes, ponds, and detention basins, all of which

were measured from the City-wide Drainage Atlas sheets.

The residual facility capacity is calculated by subtracting the estimated

demand (peak flow) from the estimated capacity for each facility. A positive

residual value indicates that the facility has adequate capacity while a

tm:~~L28:W 7-9

negative value indicates that the facility is unable to pass the

basin/subbasin demand.

Table 7-2 presents the estimated demands and residual capacities for

individual facilities for current conditions by basin for the 5-, 10- and 25-

year design storms.

future conditions.

Table 7-3 presents the same information estimated for

7.4 SERVICE LEVEL ATTAINMENT

Specific quantitative levels of service have not been adopted for drainage

facilities in the City of Sarasota. Consequently, it is not possible to

evaluate performance of individual facilities against specific quantitative

standards. The foregoing service level definitions for Service Level A-D are

recommended for adoption by the city. However, until they are formally

adopted, the definitions will be used for discussion purposes.

Analysis of reported flooding problems and projected problems for the design

storm event indicate that the City's existing facilities are generally of

providing Level C or better service. This minimum level of service, flooding

in yards but not in structures, is fairly consistent with many coastal

communities with Sarasota's level and general age of stormwater infrastructure

systems.

tm:ML28:W 7-10

/ l J I I /

TABLE 7-2 \ ) SUMMARY OF STORMWATER SERVICE

DEMAND AND RESIDUAL FACILITY CAPACITY FOR CURRENT CONDITIONS

FACILITY NUMBER

CURRENT CONDITIONS FACILITY DEMAND <CFS>

5-YEAR 10-YEAR 25-YEAR

NORTH TRAIL COASTAL BASIN --------------------------01-01-01 20.32 23.21 26.'32 01-02-01 . 3'3.35 44.82 51.71 01-03-02 31.47 35.52 40.85 01-04-01 33.2'3 37.'31 43.74 01-05-01 100.05 114. 14 132.05 01-05-01 51.7'3 58.85 67.72 01-06-02 51.42 58.32 67.00 01-07-01 13.86 15.77 18. 17

CURRENT CONDITIONS FACILITY FACILITY DEMAND <CFS> NUMBER --------------------------5-YEAR 10-YEAR 25-YEAR

ESTIMATED CAPACITY

(CFS>

108 7'3 14 72 35 44 30 30

ESTIMATED CAPACITY

<CFS>

CURRENT CONDITIONS RESIDUAL CAPACITY <CFS>

5-YEAR 10-YEAR 25-YEHR

87.58 84.7'3 81.08 3'3.55 34. 18 27. 2'3

-17.47 -21.52 -25.86 38.71 34.0'3 28.25

-55.05 -7'3. 14 -'37.0b -7.7'3 -14.85 -23.72

-21.42 -28.32 -37.id0 15. 14 14.2.3 11.8.3

CURRENT CONDITIONS RESIDUAL CAPACITY <CFS)

--------------------------5-YEAR llcl-YEAR 25-YEAR

-------------------------------------------------------------------------------------WHITAKER BAYOU BASIN ---------------------02-02-02 57.0'3 65.18 76.71 65 7.'31 -0. 18 -11.71 02-03-01 66.55 75.83 8'3.84 110 43.45 34.17 20. 15 02-03-02 6'3.78 7'3.75 '33.32 6'3 -0.78 -10.75 -24.32 02-04-01 38. 18 4.3.58 50.48 6'3 30.82 25.42 18.52 02-06-01 351.63 400.86 477.31 750 408.37 35'3. 14 282.5'3 02-06-02 12.75 14.52 16.75 51 38.25 36.48 34.25 02-07-01 302. 10 344.04 40'3.07 402 '3'3.'30 57.'36 -7.07 02-07-02 25'3.65 2'35.72 351. 11 325 65.35 2'3.28 -26.11 02-08-01 80.03 '31. 34 105.78 110 2'3.'37 18.66 4.22 02-0'3-01 316.58 360.'33 426.82 410 '33.42 4'3.07 -16.82 02-10-01 382.6'3 436.68 514.8'3 400 17.31 -36.58 -114.8'3 02-10-02 77.08 87.3'3 100.35 140 62.'32 52.51 .3'3.65 02-10-03 296.76 338.85 3'38.52 410 113.24 71. 15 11.48 02-11-01 130.45 148.80 175.66 165 34.55 16.20 -1~.55 02-11-02 38.40 43.88 51.08 39 0.6(!) -4.88 -12.08 02-11-03 67.73 77.20 '31.36 42 -25.73 -.35.20 -4'3.36 02-12-03 12.58 14.37 16.83 155 142.42 140.63 138. n 02-12-06 27.21 31.10 36.20 31 3.7'3 -0. 10 -:i.20 02-12-08 58.05 5&.33 77.&7 175 116.'35 108.67 97.33 02-13-01 36.05 41. 1 '3 47.8'3 23 -13.05 -18.1'3 -24.8'3 02-14-01 43.83 50. 10 58.4'3 51 7.17 0.'30 -7.49 02-14-02 30.77 35.0'3 40.58 '38 &7.23 62.'31 57.42 02-14-03 58.48 66.82 77.68 85 26.52 18. 18 7.32 02-14-04 60.7o &'3.44 80.83 145 84.24 75.55 64.17 02-14-05 o2.Bo 71.86 83.84 175 112. 14 103. 14 '31. 16 02-15-01 35.75 40.85 47.44 51 15.25 1~. 15 .3.55 02-lo-02 25.35 28.'38 33.75 28 2.o4 -0.'31:1 -5.75 02-17-01 57.64 o5.88 77.05 110 52.35 44. 12 .32. ':;15 02-17-02 7&.65 87.50 103.01 '38 21.35 10.50 -5.01 02-18-02 45.41 53.02 51.54 5o '3.5'3 2.'38 -5.54 02-18-03 11. 58 13. 10 15.02 28 1b.42 14.'30 12.98 02-18-04 25.5'3 2'3.34 34.03 28 2.31 -1.34 -5.il)3 02-1'3-01 25.53 30.40 35.20 35 8.37 4.60 -0.21l) 02-20-03 22.78 25.'36 2'3.'3'3 84 51.22 58.04 54.01 02-20-04 '3.05 10.34 11. '37 28 18.'34 17.5o lb.03

7-11

j

TABLE 7-2 (Continued(,

CURRENT CONDITIONS CURRENT CONDITIONS FACILITY FACILITY DEMAND <CFS> ESTIMATED RESIDUAL CAPACITY <CFS> NUMBER -------------------------- CAPACITY --------------------------

5-YEAR 10-YEAR 25-YEAR <CFS> 5-YEAR 10-YEAR 25-YEAR -------------------------------------------------------------------------------------BAYFRONT COASTAL BASIN ------------------------03-02-01 75.86 85.24 97.37 110 34.14 24.76 12.63 03-03-01 85.52 96.39 110.27 79 -6.52 -17.39 -31.27 03-03-02 28.60 32.00 36.49 27 -1.60 -5.00 -9.49 03-04-01 31.07 34.93 39.91 40 8.93 5.07 0.09 03-04-02 34.00 37.87 43.11 40 6.00 2.13 -3.11 03-05-01 91.08 103.06 118.18 97 5.92 -6.06 -21.18 03-05-02 36.77 41.23 47.07 65 28.23 23.77 17.93 03-06-01 75.59 85.13 97.36 49 -26.59 -36.13 -48.36 03-07-01 137.50 156.71 180.98 286 148.50 129.29 105.02 03-07-02 154.24 175.34 201.86 156 1. 76 -19.34 -45.86 03-07-03 97.60 110.82 127.43 165 67.40 54.18 37.57

CURRENT CONDITIONS CURRENT CONDITIONS FACILITY FACILITY DEMAND <CFS> ESTIMATED RESIDUAL CAPACITY <CFS> NUMBER -------------------------- CAPACITY --------------------------5-YEAR 10-YEAR 25-YEAR <CFS> 5-YEAR 10-YEAR 25-YEAR -------------------------------------------------------------------------------------BUSINESS DISTRICT BASIN ------------------------04-01-01 22.77 25.91 29.86 31 8.23 5.09 1.14 04-01-02 72.96 83.23 98.21 179 106.04 95.77 80.79 04-01-03 66.59 76.11 88.86 56 -10.59 -20.11 -32.86 04-01-04 101.49 115.72 136.77 330 228.51 214.28 193.23 04-02-01 199.20 226.86 269.42 355 155.80 128.14 85.58 04-02-02 205.71 234.43 277.62 291 85.29 56.57 13.38 04-03-01 79.62 90.98 106.62 135 55.38 44.02 28.38 04-04-01 154.93 . 176.68 208.74 440 285.07 263.32 231.26 04-04-02 30.48 34.83 40.49 46 15.52 11.17 5.51 04-05-01 21.50 24.55 28.86 46 24.50 21.45 17.14 04-06-01 109.37 124.79 147.18 105 -4.37 -19.79 -42.18 04-06-02 15.79 18.04 20.95 28 12.21 9.96 7.05 04-06-03 96.37 110.06 129.32 lOS 8.63 -5.06 -24.32 04-06-04 75.97 86.81 101.68 78 2.03 -8.81 -23.68 04-07-01 48.29 55.17 64.10 51 2. 71 -4.17 -13.10

7-12


CURRENT CONDITIONS CURRENT CONDITiONS FACILITY FACILITY DEMAND (CFS> ESTIMATED RESIDUAL CAPACITY (LFSl NUMBER -------------------------- CAPACITY --------------------------

5-YEAR 10-YEAR 25-YEAR (CFS) 5-YEAR 1~-YEAR 25-YEAR --------------------------------------------------------------------------------------PHILLIPPI CREEK BASIN ----------------------05-01-02 20.17 23.05 25.'35 42.00 21.83 18.'35 15.04 05-02-01 55.57 74.84 85.44 110.00 44.33 35. 15 23.55 05-02-02 44.25 50.38 58.0'3 105.00 50.74 54.52 4b.91 05-02-03 15.2'3 17.38 20.01 '3.1Z10 -5.29 -8.38 -11.1£11 05-03-01 133.35 152.31 178.88 155.01ll 21.55 2.5'3 -23.88 05-03-02 55.31 54.28 74.47 84.00 27.5'3 1'3. 72 '3. 53 05-03-03 40.7'3 45.25 53. 11 45.00 5.21 -0.25 -7. 11 05-04-01 53.26 72.27 84.74 150.00 '35.74 87.73 75.26 05-05-01 32.34 35.'35 43.00 5'3.00 3b.bb 32.04 25.00 05-06-01 60. 15 58.5'3 7'3.70 117.00 56.85 48.31 3l.30 05-07-01 100.74 115. 13 134.00 110.00 '3.26 -5. 13 -24.00 05-0'3-01 24.33 27.55 31.83 33.00 8.67 5.35 1. 17 05-09-02 78.59 8'3.77 105.93 '38.00 1'3.31 8.23 -7.93 05-10-01 31.65 36.17 42.05 28.00 -3.55 -8.17 -14. l£15 05-10-02 14.75 15.85 1'3.53 15.00 1. 25 -0.85 -3.53 05-11-01 19.58 22.44 25.'33 28.00 8.32 5.56 2.07 05-11-02 58.'38 78.70 '32.87 410.00 341.02 331. 3~ 317.13 05-11-03 42.58 48.26 55.32 85.00 42.32 36.74 2'3.68 05-12-01 28.50 32.57 37.85 50.00 31.50 27.43 22. 15 05-13-01 16.45 18.80 21.86 28.00 11.::i5 '3.20 6. 14 05-14-01 756.53 857. 13 1031. 14 1200.00 443.37 332.8/ 1b8.8b 05-15-01 72.'30 83.27 97.76 132.00 5'3. 10 4~.73 34.24 05-15-02 3'3.09 44.25 50.77 55.00 1 b. '31 11. 75 5.2.3 05-16-01 16.6'3 1'3.08 22.26 33.00 16.31 13. ':12 10.74 05-15-02 147.'38 158.67 1'39.62 280.00 132.02 111.33 8~.38 05-16-03 '34.21 107.67 125.37 105.00 10.79 -2.67 -20.37 05-16-04 84.03 '36.03 111. 70 '36.00 11. '37 -0.03 -15.7~ 05-16-05 35.03 40.04 46.62 51.00 15.'37 10.'36 4.38 05-17-01 6.20 7.06 a. 14 8.00 1. Bill 0.'34 -0. 14 05-17-02 8.46 '3.63 11. 10 8.00 -0.46 -1.53 -3. 10 05-18-01 12.7'3 14.60 17.16 17.00 4.21 2.41ll -0. 1b 05-1'3-01 5. 11 5.84 6.80 12.00 6.8'3 6.16 5.2tll 05-1'3-02 7.47 8.53 '3.'34 12.00 4.53 3.47 2.0b 05-1'3-03 151.42 173.3'3 206.26 510.00 358.58 336.61 303.74 05-20-01 67.'3'3 77.45 '31. 89 124.00 55.01 46.55 32. 11

7-13


CURRENT CONDITIONS CURRENT CONDITIONS FACILITY FACILITY DEMAND <CFS> ESTIMATED RESIDUAL CAPACITY <CFS> NUMBER -------------------------- CAPACITY --------------------------5-YEAR 10-YEAR 25-YEAR <CFS> 5-YEAR 10-YEAR 25-YEAR -------------------------------------------------------------------------------------

',>',

06-01-01 06-02-01 06-02-02 06-03-01 06-03-02 06-03-03 06-03-04 06-04-01 06-05-01 06-06-01 06-06-02 06-06-03 06-07-01 06-08-01 06-09-01 06-09-02 06-09-03 06-12-01 06-13-01 06-14-01 06-14-02 06-15-01 06-15-02 06-15-03 06-15-04 06-16-01 06-17-01 06-17-02 06-17-03 06-17-04 06-18-01 06-19-01

FACILITY NUMBER

OSPREY BASIN -------------07-01-01 07-02-01 07-02-02 07-02-03 07-03-01 07-04-01 07-05-01 07-06-01 07-07-01

13.75 15.71 18.25 13.96 15.86 18.24 10.20 11.56 13.27

164.98 186.49 213.71 209.40 238.10 274.18

90.39 102.47 117.67 138.30 158.01 183.60 72.94 83.36 97.53 30.62 34.98 40.64

169.07 193.17 224.49 69.07 78.92 92.50 58.15 66.32 76.70 55.57 63.47 74.52 28.67 32.54 37.42 93.28 106.57 124.99 49.41 56.42 65.43 19.55 22.15 25.43 74.30 84.93 99.11

105.48 120.12 142.85 49.19 56.20 65.96 36.40 41.58 48.77

126.29 144.01 170.18 24.34 27.81 32.33

109.77 125.36 147.35 130.69 149.11 175.85

95.21 108.78 127.53 213.98 244.58 285.56 200.77 229.42 266.82 130.67 149.06 172.41

54.19 60.34 68.70 89.32 102.04 118.50 55.11 62.95 72.92

CURRENT CONDITIONS FACILITY DEMAND <CFS>


20.32 23.21 26.93 76.34 87.18 101.09 48.98 55.91 64.75 26.58 30.23 34.81 33.26 37.70 43.28 23.97 27.33 31.58 33.29 38.03 44.16 13.48 15.37 17.78

106.93 121.69 140.27

11 51 31

285 218

98 218

56 69

140 92 65 65 16

139 56 9

86 116

66 34

120 32

120 120 104 540 219 160

56 90

140

ESTIMATED CAPACITY

CCFS>

19 110

44 34 12 25 14 14 46

7-14

-2.75 -4.71 -7.25 37.04 35.14 32.76 20.80 19.44 17.73

120.02 98.51 71.29 8.60 -20.10 -56.18 7.61 -4.47 -19.67

79.70 59.99 34.40 -16.94 -27.36 -41.53 38.38 34.02 28.36

-29.07 -53.17 -84.49 22.93 13.08 -0.50

6.85 -1.32 -11.70 9.43 1. 53 -9.52

-12.67 -16.54 -21.42 45.72 32.43 14.01

6.59 -0.42 -9.43 -10.55 -13.15 -16.43

11.70 1.07 -13.11 10.52 -4.12 -26.85 16.81 9.80 0.04 -2.40 -7.58 -14.77 -6.29 -24.01 -50.18 7.66 4.19 -0.33

10.23 -5.36 -27.35 -10.69 -29.11 -55.85

8.79 -4.78 -23.53 326.02 295.42 254.44

18.23 -10.42 -47.82 29.33 10.94 -12.41 1.81 -4.34 -12.70 0.68 -12.04 -28.50

84.89 77.05 67.08

CURRENT CONDITIONS RESIDUAL CAPACITY <CFS>


-1.32 -4.21 -7.93 33.66 22.82 8.91 -4.98 -11.91 -20.75 7.42 3.77 -0.81

-21.26 -25.70 -31.28 1.03 -2.33 -6.58

-19.29 -24.03 -30.16 0.52 -1.37 -3.78

-60.93 -75.69 -94.27

TABLE 7-3 SUMMARY OF STORMWATER SERVICE

DEMAND AND RESIDUAL FACILITY CAPACITY FOR FUTURE DESIGN CONDITIONS

FUTURE CONDITIONS FACILITY FACILITY DEMAND <CFS) NUMBER ---------------------------


ESTIMATED CAPACITY

<CFS>

FUTURE CONDITIONS RESIDUAL CAPACITY <CFS>

5-YEAR 10-YEAR 25-YEAR ------------------------------------------------------------------------------------------NORTH TRAIL COASTAL BASIN --------------------------01-01-01 20.32 23.21 26.'32 108 87.68 84.7'3 81.08 01-02-01 3'3.35 44.82 51.71 7'3 3'3.65 34. 18 27.2'3 01-03-02 31.47 35.62 40.86 14 -17.47 -21.62 -26.86 01-04-01 33.2'3 37.'31 43.74 72 38.71 34.0'3 28.26 01-05-01 100.05 114. 14 132.06 35 -65.05 -7'3. 14 -'37.06 01-06-01 51. 7'3 58.85 67.72 44 -7.7'3 -14.85 -23.72 01-06-02 51.42 58.32 67.00 30 -21. 42 -28.32 -37.0~ 01-07-01 13.86 15.77 18. 17 30 16. 14 14.23 11.83

FUTURE CONDITIONS FUTURE CONDITIONS FACILITY FACILITY DEMAND (CFS> ESTIMATED RESIDUAL CAPACITY <CFS> NUMBER --------------------------- CAPACITY ---------------------------

5-YEAR 10-YEAR 25-YEAR <CFS> 5-YEAR 10-YEAR 25-YEAR ------------------------------------------------------------------------------------------WHITAKER BAYOU BASIN ---------------------02-02-02 '3'3.'31 114. 06 134.24 65 -34.'31 -49.06 -6'3.24 02-03-01 76.06 86.67 102.67 110 33.'34 23.33 7.33 02-03-02 7'3.75 '31. 15 106.65 69 -10.75 -22. 15 -37.65 02-04-01 44.54 50.84 58.8'3 69 24.46 18. 16 10. 11 02-06-01 410.24 467.67 556.87 760 349.76 292.33 2~3. 13 02-06-02 22.31 25.41 2'3.31 51 28.69 25.59 21. 6'3 02-07-01 377.63 430.04 511. 34 402 24.37 -28.04 -10'3.34 02-07-02 259.65 2'35.72 351. 11 325 65.35 29.28 -26. 11 02-08-01 80.03 '31.34 105.78 110 2'3.97 18.66 4.22 02-09-01 316.58 360.93 426.82 410 93.42 4'3.07 -16.82 02-10-01 382.69 436.68 514.89 400 17.31 -36.68 -114.89 02-10-02 81.90 '32.85 106.63 140 58. 10 47. 15 33.37 02-10-03 315.31 360.03 423.43 410 94.69 49.'37 -13.43 02-11-01 182.63 208.32 245.93 165 -17.63 -43.32 -80.93 02-11-02 38.40 43.88 51.08 39 0.60 -4.88 -12.08 02-11-03 118.52 135.10 159.88 42 -76.52 -93.10 -117.88 02-12-03 22.01 25. 15 29.45 155 132.99 129.85 125.55 02-12-06 50.13 57.29 66.68 31 -19.13 -26.29 -35.68 02-12-08 101. 58 116. 08 135.92 175 73.42 58.92 39.08 02-13-01 84.12 96.11 111.73 23 -61.12 -73.11 -88.73 02-14-01 75. 14 85.88 100.27 51 -24.14 -34.88 -49.27 02-14-02 46.15 52.64 60.88 98 51.85 45.36 37.12 02-14-03 87.72 100.24 116.52 85 -2.72 -15.24 -31.52 02-14-04 91. 14 104.16 121.24 145 53.86 40.84 23."/6 02-14-05 94.30 107.78 125.76 175 80.70 67.22 49.24 02-15-01 51.64 59.00 68.53 51 -0.64 -8.00 -17.53 02-16-02 50.72 57.96 67.49 28 -22.72 -29.96 -39. 4':3 02-17-01 49.41 56.47 66.04 110 60.59 53.53 43. ':to 02-17-02 114.97 131.24 154.51 98 -16.'37 -33.24 -56.51 02-18-02 72.20 82.47 '35.73 56 -16.20 -26.47 -39.73 02-18-03 18.02 20.38 23.37 28 9.98 7.62 4.63 02-18-04 59.'35 68.46 79.3'3 28 -31.95 -40.46 -51.39 02-19-01 39.95 45.59 52.79 35 -4.95 -10. 5'::3 -17.79 02-20-03 53.15 60.58 6'3.'37 84 30.85 23.42 14.03 02-20-04 21. 13 24. 12 27.'33 28 6.87 3.8d 0.0/

7-15


FUTURE CONDITIONS FACILITY FACILITY DEMAND <CFS> NUMBER ---------------------------


BAYFRONT COASTAL BASIN ------------------------.03-02-01 75.8E. 85.24 97.37 03-03-01 85.52 9E..3'3 110.27 03-03-02 28.E.0 32.00 3E..49 03-04-01 31.07 34.'33 39.'31 03-04-02 34.00 37.87 43. 11 03-05-01 91.08 103.0E. 118. 18 03-05-02 3E..77 41.23 47.07 03-06-01 75.5'3 85.13 '37.3E. 03-07-01 137.50 156.71 180.98 03-07-02 154.24 175.34 201.8E. 03-07-03 97.E.0 110.82 127.43

FUTURE CONDITIONS FACILITY FACILITY DEMAND <CFS> NUMBER ---------------------------5-YEAR 10-YEAR 25-YEAR

ESTIMATED CAPACITY

<CFS>

110 7'3 27 40 40 97 E.5 4'3

28E. 156 1E.5

ESTIMATED CAPACITY

<CFS>

FUTURE CONDITIONS R~SlDUAL CAPACITY CCFSI

5-YEAR 1~-YEAH 25-YEAR

34.14 24.7& 12.&3 -6.~2 -17.3'3 -31.27 -1.60 -5.0~ -9.4'3

8.'33 5.07 0.0'3 6.00 2. 13 -3. 11 5.92 -G.t{)G -21. 18

28.23 23.77 17.93 -2E..59 -36.13 -48.3E. 148.50 129.29 105.02

1. 76 -19.34 -45.86 E.7.40 54. 18 37.57

FUTUkE CONDITIONS RESIDUAL CAPACITY CCFS>

---------------------------5-YEAR 10-YEAR 25-YEAR ------------------------------------------------------------------------------------------BUSINESS DISTRICT BASIN ------------------------04-01-01 34. 1 e. 38.87 44.80 31 -3. 16 -7.87 -13.80 04-01-02 83.38 95.12 112.24 17'3 '35.E.2 83.88 66.7E. 04-01-03 83.23 95.13 111.08 5E. -27.23 -39. 13 -55.08 04-01-04 126.8E. 144.65 170.9E. 330 203.14 185.35 159.04 04-02-01 349.60 396.21 472.79 355 5.40 -41.21 -117.79 04-02-02 360.64 409.54 485.94 291 -69.64 -118.54 -194.94 04-03-01 139. 34 159.22 186.59 135 -4.34 -24.22 -51.59 04-04-01 270.78 308.86 3E.5.97 440 169.22 131.14 74.03 04-04-02 53.34 E.0.95 70.86 4E. -7.34 -14.95 -24.86 04-05-01 37.68 42.92 50.40 4E. 8.32 3.08 -4.40 04-0E.-01 191. 40 218.39 257.5E. 105 -8&.40 -113.39 -152.56 04-0E.-02 27.E.4 31.57. 3E..67 28 1{).36 -3.57 -8.67 04-0E.-03 1E.8.E.5 192.E.1 22E..31 105 -&3.65 -87.E.1 -121. 31 04-0E.-04 132.'35 151.92 177.93 78 -54. ':15 -73.'32 -9'3.'33 04-07-01 84.51 9E..55 112. 18 51 -33.51 -45.55 -Gl. 18

7-16

TABLE 7-3 {Continued)

FUTURE CONDITIONS FUTUkE CONDITIONS FACILITY FACILITY DEMAND <CFS> ESTIMATED RESIDUAL CAPACITY <CFS> NUMBER --------------------------- CAPACITY ---------------------------

5-YEAR 10-YEAR 25-YEAR <CFS> 5-YEAR H~l-YEAR 25-YEAR ------------------------------------------------------------------------------------------PHILLIPPI CREEK BASIN ----------------------05-01-02 28.81 32.93 38.51 42.00 13. 19 9.07 3. 4':1 05-02-01 93.82 106.92 123.48 110. 00 16. 18 3.1£18 -13. '+8 05-02-02 75.88 86.37 99.58 105. 00. 29. 12 18.63 5.42 05-02-03 26.21 29.80 34.30 9.00 -17.21 -20.80 -25.30 05-03-01 160.02 182.77 214.66 155.00 -5.02 -27.77 -59.66 05-03-02 75.08 85.70 99.29 84.00 8.92 -1.70 -15.29 05-03-03 40.79 46.25 53.11 46.00 5.21 -0.25 -7. 11 05-04-01 108.44 123.89 145.28 160.00 51.56 36. 11 14.72 05-05-01 43. 12 49.27 57.34 69.00 25.88 19.73 11. 66 05-06-01 90.22 103.04 119. 55 117.00 26.78 13. '::16 -2.55 05-07-01 172.70 197.37 229.71 110. 00 -62.70 -87.37 -119.71 05-09-01 41.70 47.40 54.57 33.00 -8.70 -14.40 -21.57 05-09-02 134.89 153.89 181.59 98.00 -3(:).89 -55.89 -83.59 05-10-01 58.03 66.31 77. 10 28.00 -30.03 -38.31 -4'3. 10 05-10-02 27.05 30.88 35.80 16.00 -11. 05 -14.88 -19.81'.1 05-11-01 33.73 38.46 44.45 28.00 -5.73 -1tll.46 -16.45 05-11-02 126.47 144.28 170.25 410.00 283.53 2(:)5.72 239.7'6 05-11-03 66.40 75.07 86.05 85.00 18.60 '3.93 -1.05 05-12-01 57.00 65.13 75.71 60.00 3.01'.1 -5. 13 -15.71 05-13-01 32.90 37.59 43.72 28.00 -4.'::1121 -'3. :i'3 -15.72 05-14-01 1891.58 2167.83 2577.85 1200.00 -6'31.58 -967.83 -1377.85 05-15-01 145.7'3 166.53 195.53 132.00 -13.79 -34.53 -63.53 05-15-02 78. 18 88.51 101.53 56.00 -22. 18 -32.51 -4:,.53 05-16-01 22.26 25.44 29.68 33.00 10.74 7.56 3.32 05-16-02 147.98 168.67 19'3.62 280.00 132.02 111.33 8tl1.38 05-16-03 94.21 107.67 125.37 105.00 1tll.79 -2.67 -21£1.37 05-16-04 117.65 134.44 156.37 96.00 -21.65 -38.44 -60.37 05-16-05 46.71 53.38 62. 16 51.00 4.29 -2.38 -11. 16 05-17-01 12.41 14. 12 16.28 8.00 -4.41 -6.12 -8.28 05-17-02 15. 51 17.65 20.35 8.00 -7.51 -9.(:)5 -12.35 05-18-01 21.92 25.03 2'3.41 17.00 -4.92 -8.03 -12.41 05-19-01 '3.37 10.71 12.47 12.00 2.63 1. 29 -0.47 05-19-02 13.69 15.65 18.22 12.00 -1.69 -3.65 -6.22 05-19-03 277.60 317.88 378. 14 510.00 232.40 192.12 131.86 05-20-01 124.65 141.'38 168.46 124.00 -0.65 -17.'38 -44.4(:)

7-17


FACILITY NUMBER

FUTURE CONDITIONS FACILITY DEMAND <CFS>


HUDSON BAYOU BASIN

05-01-01 05-02-01 05-02-02 05-03-01 05-03-02 05-03-03 0-e.-:.:03-04 05-04-01 05-05-01 05-05-01 -06:..;05-02 05-05-03 05-07-01 05-08-01 05-0'3-01 05-0'3-02 05-0'3-03 05-12-01 05-13-01 06-14-01 05-14-02 06-15-01 05-15-02 05-15-03 06-15-04 05-lo-01 05-17-01 06-17-02 06-17-03 06-17-04 05-18-01 16-1'3-01

FACILITY NUMBER

23.58 23.'33 15.30

154.'38 20'3.40

'30.3'3 138.30

72.'34 57.40

211.41 85.34

10'3.03 83.35 43.00

115.5'3 74. 11 25.88 74.30

155.75 57.54 50.05

173.55 33.45

150.'34 17'3.5'3 130.'31 335.25 372.85 242.58

54. 1'3 153.13 103.33

25.'33 27. 18 17.34

185.4'3 238.10 102.47 158.01 83.35 55.58

241. 2e '38.55

124.35 '35.21 48.82

133.21 84.53 30.45 84.'33

188.75 77.27 57. 18

1'38.01 38.24

172.37 205.03 14'3.58 384.34 425.07 275.82

50.34 174.'33 118.04

31.2'3 31.27 1'3.'30

213.71 274. 18 117.57 183.50

'37.53 75.20

280.68 115. 52 143.82 111. 78 56.13

155.24 '38. 15 34.'35 '3'3. 11

224.48 '30.70 57.05

234.00 44.45

202.51 241.7'3 175.35 448.74 4'35.53 320.18 58.70

203.14 136.72

FUTURE CONDITIONS FACILITY DEMAND <CFS>


ESTIMATED CAPACITY

<CFS>

11 51 31

285 218

'38 218

5o 59

140 '32 55 55 1o

13'3 5o

'3 ao

115 00 34

120 32

120 120 104 540 21'3 150 so '30

140

ESTIMATED CAPACITY

<CFS>

FUTURE CONDITIONS RESIDUAL CAPACITY <CFS>

5-YEAR

-12.58 27.1/J? 15.70

120.02 8.5~ 7.51

7'3.70 -15.94

11. 50 -71.41

5.55 -44.03 -18.35 -27.00

22.41 -18. 11 -17.88

11.70 -4'3.75 -1.54

-15.05 -53.55 -1.46

-30.'34 -5'3.5'3 -25.'31 21.:.13.75

-153.85 -82.58

1. 81 -53. 13 36.67

1~-YEAR 25-YEAR

-15.'33 23.82 13.oo 98.51

-20. 11.:.1 -4.47 5'3.'3'3

-27 • .:.5 3.42

-1e1.20 -5.65

-5'3. 35 -30.21 -32.82

5.79 -28.63 -21.46

1. 07 -72.76 -11.27 -23.18 -78.01 -6.24

-52.37 -85.03 -45.58 155.55

-207.07 -115.82

-4.34 -84.'33 21.96

-20.29 1 ':l. 7 3 11. 10 71. 2'3

-55.18 -1':l. 67

34.41£\ -41.53 -7.20

-t4e.e;e -23.6.:: -78.82 -46.78 -412J. 13 -17.24 -42. 15 -25.9b -13. 11

-108.48 -24.712J -33.06

-114.00 -12.46 -82.61

-121.79 -71. 35 91.26

-275.53 -160. 18

-12.70 -113. 14

3.28

FUTURE CONDITIONS RESIDUAL CAPACITY CCFS>

5-YEAR h~•-YEAR 25-YEAR ------------------------------------------------------------------------------------------OSPREY BASIN -------------07-01-01 20.32 23.21 25.'33 19 -1.32 -4.21 -7.93 07-02-01 75.34 87.18 101. 0'3 110 33.55 22.82 8.'31 07-02-02 48.'38 55.'31 54.75 44 -4.98 -11.91 -20.75 07-02-03 25.58 30.23 34.81 34 7. 42 3. 77 -0.81 07-03-01 33.25 37.70 43.28 12 -21.25 -25.70 -31.28 07-04-01 23.97 27.33 31.58 25 1. 03 -2.33 -6.58 07-05-01 33.2'3 38.03 44.15 14 -19.2'3 -24.03 -30.16 07-05-01 25.03 28.55 33.01 14 -11. 03 -14.55 -1 '3. 01 07-07-01 154.45 175.77 202.51 45 -108.45 -129.77 -156.61

7-18

Qualitatively, many of the catchments within the City, particularly those in

the upper reaches of the basins, meet the criteria of Service Level A or

Service Level B depending upon whether the roadway segments have curbs.

Unfortunately, many of the catchments in the lower reaches of the basins

experience Service Level C performance for events of less consequence than the

current design storm.

Service Level attainment was estimated for each facility based on the residual

capacity estimated in Section 7.3 for both current and future conditions.

Criteria used in this assessment are briefly summarized as follows:

Major Facilities

Service Level A:

Service Level B:

Service Level C:

Service Level 0:

Minor Facilities

Service Level A:

Service Level B:

tm:t1L28:W

Passes the 10-year peak flow

Capacity shortfall for the 10-year storm is within

10% of estimated capacity

Capacity shortfall for the 10-year storm is between

10% and 50% of estimated capacity

Capacity shortfall for the 10-year storm exceeds 50%

of estimated capacity

Passes 5-year peak flow

Capacity shortfall for the 5-year storm is within 20%


7-19

Service Level C:

Service Level D:

Capacity shortfall for the 5-year storm is between

20% and 50% of estimated capacity

Capacity shortfall for the 5-year storm exceeds 50%


Estimated service level attainment is summarized in Table 7-4 for both current

and future conditions for each facility evaluated.

7.5 ANALYSIS OF BASIN PERFORMANCE

The evaluation of estimated service levels for current conditions indicates

that the City can expect to attain Service Level A in approximately 76% of its

primary facilities with only about 8% of the facilities falling below

Service Level C. Table 7-5 summarizes service level attainment for current

conditions by basin.

Table 7-6 presents service level attainment results by basin for future

conditions. The City should expect to obtain Service Level A in about 45% of

its fac i 1 i ties which represents a 30% decrease due to growth. Service wi 11

drop below Service Level C for approximately 24% of its facilities which is

three times as many as for current conditions.

Comparison of Tables 7-5 and 7-6 indicates that about 39% of the facilities

will experience service level degradation as growth continues in Sarasota. It

is estimated that about 60% of the basins attaining Service Level A and B

under current conditions wi 11 experience degradation whi 1 e 25% of today• s

tm : M L 2 8 I A 7- 2 0

\ ~ \ ) TABLE 7-4

ESTH1ATES OF STORmJATER SERVICE LEVELS FOR CURRENT AND FUTURE CONDITIONS


NORTH TRAIL COASTAL BASIN --------------------------01-01-01 01-02-01 01-03-02 01-04-01 01-05-01 01-06-01 01-06-02 01-07-01

FACILITY NUMBER

42" 36" 18" 36" 24" 30" 24" 24"

ss ss ss ss ss (48" ELLIPTICAl> RCP SS RCP SS RCP SS


ESTIMATED SERVICE LEVEL ESTIMATE CAPACITY ---------------------------

<CFS> CURRENT FUTURE

1ill8 A A 7'3 A A 14 D D 72 A A 35 D D 44 B B 3ill D D 30 A A

---------------------------ESTIMATED SERVICE LEVEL ESTIMATE CAPACITY ---------------------------

<CFS> CURRENT FUTURE ----------------------------------------------------------------------------WHITAKER BAYOU BASIN

02-02-02 02-03-01 02-03-02 02-04-01 02-06-01 02-06-02 02-07-01 02-07-02 02-08-01 02-0'3-01 02-10-01 02-10-02 02-10-03 02-11-01 02-11-02 02-11-03 02-12-03 02-12-06 02-12-08 02-13-01 02-14-01 02-14-02 02-14-03 02-14-04 02-14-05 02-15-01 02-16-02 02-17-01 02-17-02 02-18-02 02-18-03 02-18-04 02-19-01 02-20-03 02-20-04

36" RCP SS 42" RCP SS 42" RCP SS 42" RCP SS 2-6.5' X 8' BC 36" RCP SS 78" RCP 55 72" RCP SS 48" RCP SS 51 X 10' BC 7' X 7' BC 43" X 68" CULVERT 5' X 10' BC 43" X 68" RCP CULV 30" RCP 55 30" RCP CULVERT 60" RCP 55 30" RCP SS 60" RCP CULVERT 22" X 36" CMP CULV 36" RCP SS 48" RCP SS 48" RCP SS 54" RCP CULVERT 60" RCP CULVERT 36" RCP SS 30" RCP SS 48" RCP SS 48" RCP SS 36" RCP SS 30" RCP SS 30" RCP SS 30" RCP SS 42" RCP SS 36" RCP SS

7-21

65 110 69 6'3

760 51

4ill2 325 110 410 400 140 410 165 39 42

155 31

175 23 51 '38 85

145 175 51 28

110 98 56 28 28 35 b4 28

A A c A A A A A A A B A A A A D A A A D A A A A A A A A A A A D A A A

D A c A A A A A A A B A A c A D A D A D c A B A A c D A B c A D B A A

\ TABLE 7~4 (Continued)

z. ,;:&'

FACILITY NUMBER


BAYFRONT COASTAL BASIN ------------------------03-02-01 03-03-01 03-03-02 03-04-01 03-04-02 03-05-01 03-05-02 03-06-01 03-07-01 03-07-02 03-07-03

FACILITY NUMBER

38" X 60" RCP 55 29' X 45" RCP 55 19" X 30" RCP 55 30" RCP 55 30" RCP 55 42" RCP 55 36" RCP 55 30" RCP 55 4' X 7' BC 55 48" RCP 55 54" RCP 55


ESTIMATED SERVICE LEVEL ESTIMATE CAPACITY ---------------------------<CFS> CURRENT FUTURE

110 A A 7'3 c c 27 c c 40 A A 40 A A '37 B B 65 A A 4'3 D D

286 A A 156 c c lb5 A A

EST!MHTED SERVICE LEVEL ESTIMATE CAPACITY ---------------------------<CFS> CURRENT FUTURE

-------------------------------------------------------------------------BUSINESS DISTRICT BASIN ------------------------04-01-01 30" RCP SS 31 A c 04-01-02 60" RCP SS 17'3 A A 04-01-03 36" RCP SS 56 B B 04-01-04 4' X 10' BOX CULVERT 330 A A 04-02-01 72" RCP LO-HED SS 355 A c 04-02-02 72" RCP LO-HED SS 2'31 A c 04-03-01 54" RCP SS 1.35 A B 04-04-01 5' X 10' BOX CULVERT 440 A A 04-04-02 36" RCP 55 46 A B 04-05-01 36" RCP 55 46 A A 04-06-01 48" RCP CULVERT 105 A D 04-06-02 30" RCP SS 28 A A 04-06-03 48" RCP CULVERT 1_,5 B D 04-06-04 42" RCP CULVERT -/8 A 0 04-07-01 36" RCP SS 51 A D

7-22


--~------------------------

FACIL.ITY FACILITY ESTIMATED SERVICE LEVEL ESTIMATE NUMBER DESCRIPTION CAPACITY ---------------------------

<CFS> CURRENT FUTURE ---------------------------------------------------------------------------PHILLIPPI CREEK BASIN ----------------------05-01-02 36" CMP CULVERT 42 A A 05-02-01 44" X 72" CMP CULV 110 A A 05-02-02 48" RCP CULVERT 11.15 A A 05-02-03 18" RCP SS '3 D D 05-03-01 84" CMP SS 155 A B 05-03-02 3-30" RCP SS 84 A A 05-03-03 36" RCP SS 4b A A 05-04-01 2-42" RCP CULVERTS 161£1 A A 05-05-01 42" RCP SS 6'3 A A 05-06-01 54" RCP SS 117 A A 05-07-01 48" RCP SS 110 B D 05-0'3-01 30" RCP SS j3 A c 05-0'3-02 48" RCP SS '38 A D 05-10-01 30" RCP SS 28 B D 05-10-02 24" RCP SS 16 A D 05-11-01 30" RCP SS 28 A B 05-11-02 5' X 10' BC 410 A A 05-11-03 38" X 60" RCP SS 85 A A 05-12-01 42" RCP SS 60 A B 05-13-01 30" RCP SS 28 A c 05-14-01 14' X 14' BC 1200 A D 05-15-01 54" RCP CULVERT 132 A B 05-15-02 36" RCP SS<LD-HED> 56 A c 05-16-01 36" RCP SS 33 A A 05-16-02 2-43" X 68" CULVS 280 A A 05-16-03 48" RCP CULVERT 105 B B 05-16-04 43" X 68" RCP SS '36 A c 05-16-05 42" RCP SS 51 A A 05-17-01 24" CMP SS 8 A D 05-17-02 24" CMP SS 8 B D 05-18-01 30" CMP SS 17 A c 05-1'3-01 30" CMP SS 12 A A 05-1'3-02 30" CMP SS 12 A B 05-1'3-03 2-6' X 8. 5' CMP CULV 510 A A 05-20-01 4' X 4' BC 124 A B

7-23


FACILITY NUMBER

FACILITY ESTIMATED SERVICE LEVEL ESTIMATE DESCRIPTION CAPACITY ---------------------------

<CFS> CURRENT FUTURE ----------------------------------------------------------------------HUDSON BAYOU BASIN ------------------06-01-01 18" RCP SS 11 c D 06-02-01 36" RCP SS 51 A A 06-02-02 30" RCP SS 31 A A 06-03-01 48"& 60" RCP CULVS 285 A A 06-03-02 60" RCP SS ·218 A A 06-03-03 42" RCP SS ·;,a A A 06-03-04 60" RCP SS 218 A A 06-04-01 36" RCP SS 56 c c 06-05-01 34" X 53" RCP SS 6'3 A A 06-06-01 48" RCP SS 140 c D 06-06-02 48" RCP CULVERT '32 A B 06-06-03 36" RCP SS 65 A D 06-07-01 36" RCP SS 6j A c 06-08-01 18" RCP SS 16 D D 06-09-01 48" RCP SS 139 A A 06-09-02 36" RCP SS 56 B c 06-09-03 18" RCP SS '3 D D 06-12-01 42" RCP SS ~6 A A 06-13-01 2-42" CMP CULVERTS 116 A c 06-14-01 36" X 58" CMP CULV b6 A c 06-14-02 31" X 50" CMP SS 34 c D 06-15-01 2-36" RCP CULVERTS 12\ll c D 06-15-02 36" CMP SS 32 A B 06-15-03 2-36" RCP CULVERTS 120 A c 06-15-04 2-36" RCP CULVERTS 120 B c 06-16-01 2-36" RCP CULVERTS 104 A c 06-17-01 6' X 10' BC 540 A A 06-17-02 66" CMPAC 219 A D 06-17-03 60" LO-H CULVERT 160 A D 06-17-04 29" X 45" RCP SS 56 A A 06-18-01 48" CMP CULVERT 90 A D 06-19-01 48" RCP SS 140 A A

---------------------------FACILITY FACILITY ESTIMATED SERVICE LEVEL ESTIMATE NUMBER DESCRIPTION CAPACITY ---------------------------<CFS> CURRENT FUTURE

OSPREY BASIN -------------07-01-01 24" RCP SS 1'3 c c 07-02-01 48" RCP SS 1116 A A 07-02-02 30" RCP SS 44 B B 07-02-03 30" RCP SS 34 A A 07-03-01 18" RCP SS 12 D D 07-04-01 24" RCP SS 25 A B 07-05-01 18" RCP SS 14 D D 07-06-01 18" RCP SS 14 B D 07-07-01 36" CMP CULVERT 4b D D

7-24

i

\

\

i \

TABLE 7-5

FACILITIES ATTAINING SERVICE LEVELS FOR CURRENT CONDITIONS

Bas ;·n

North Trail Coastal (Percent of Basin)

Whitaker Bayou (Percent of Basin)

Bayfront Co as ta 1 (Percent of Basin)

Business District (Percent of Basin)

Phillippi Creek (Percent of Basin)

Hudson Bayou (Percent of Basin)

Osprey Coastal (Percent of Basin)

City-Wide Performance (Percent of All Basins)

tm:t~L27:H

A

4 50

31 88

6 55

13 87

30 86

23 72

3 33

110 76

Service Level

B

1 12

1 3

1 9

2 13

4 11

2 6

2 22

13 9

7-25

Attained

c

0 0

1 3

3 27

0 0

0 0

5 16

1 11

10 7

D

3 38

2 6

1 9

0 0

1 3

2 6

3 33

12 8

Total Systems

8

35

11

15

35

32

9

145

TABLE 7-6

FACILITIES ATTAINING SERVICE LEVELS FOR FUTURE CONDITIONS

Basin

North Trail Coastal (Percent of Basin)


Bayfront Coastal (Percent of Basin)






tm:t1L27 :H

A

4 50

20 58

6 55

5 33

15 43

12 38

2 22

64 44

Service

B

1 12

4 11

1 9

3 20

7 20

2 6

2 22

20 14

Level

7-26

Attained

c

0 0

5 14

3 27

3 20

5 14

8 25

1 11

25 17

D

3 38

6 17

1 9

4 27

8 23

10 31

4 45

36 25

Tota 1 Systems

8

35

11

15

35

32

9

145

Service Level C basins will fall to Service Level D. The results of this

analysis are summarized in Table 7-7.

tm:ML28/A 7-27

Basin

North Trail Basin (Percent of Basin)


Bayfront Coastal (Percent of Basin)






tm:ML27:H

A TO B

0 0

3 8.5

0 0

2 13.3

6 17.1

2 6.2

1 11.1

14 9.7

TABLE 7-7

FACILITIES EXPERIENCING SERVICE LEVEL DEGRADATION FOR FUTURE CONDITIONS

A TO c

0 0

4 11.4

0 0

3 20.0

5 14.3

5 15.6

0 0

17 11.7

Service Level

A TO

D

0 0

4 11.4

0 0

3 20.0

4 11.4

3 9.4

0 0

14 9.7

7-28

Degradation

B TO c

0 0

0 0

0 0

0 0

0 0

2 6.3

0 0

2 1.4

B TO D

0 0

0 0

0 0

1 6.7

3 8.8

0 0

1 11.1

5 3.4

c TO

D

0 0

0 0

0 0

0 0

0 0

4 12.5

0 0

4 2.7

Total

0 0

11 31.4

0 0

9 60.0

18 51.4

16 50.0

2 22.2

56 38.6

SECTION EIGHT

Section 8

FUNDING NEEDS AND IMPLEMENTATION PROGRAM

3.1 GENERAL

This section evaluates the City•s overall funding needs, develops a plan to

implement the program over the next 20 years, and evaluates funding mechanisms

needed to provide the funds for the program.

8.2 CAPITAL NEEDS ASSESSMENT

The results of the City-wide drainage planning study has been the

identification of a number of specific Capital Improvements Program (CIP)

projects and the need to conduct basin specific studies to identify the cause

of and solution for future problems indicated by the facilities analysis.

A total of fifty-four individual activities were identified to solve recurring

problems which require approximately $3,234,000 of capital expenditure for new

or upgraded facilities and $29,000 in annual system maintenance. The

individual activities are summarized in Table 8-1 and are summarized by

basins. The largest expenditure, $1,501,000, is required in the Business

District Basin while the Phillippi Creek Basin requires no immediate

expenditure. The location of the individual problems and their corresponding

remedial activities are presented in Figure 8-1. To date, only four projects

have been funded.

tm:ML27:J 8-1

TABLE 8-1

COST AND PRIORITY OF SOLUTIONS TO EXISTING PROBLEMS

---------PROaal BASIN/ PROBLEM SEVERITY PRIORITY Fl.N)INS lUBER SUBBASIN Sll..UTI~ RATINS RATINS STATUS COST ---------------------------------- ---------------------------------NORTH TRAIL COASTAL BASIN --------------------------

01-01 COOTRI..CT PII=1:S AND HUTS B 3 UN $34,006

2 01-03 COOTRI..CT ADDITiotR HUTS ClEAR AND GRADE DRAI~ DITCH

B 3 UN $183,000

3 01-04 MAINTAIN EXISTINS STRI..CTURES B 3 UN u,000

-------SUBTOTAL $218,000

lliiTAKER BAYOO BASIN --------

4 1.\:-81 It«:REASE OOTFALL PII=1: SIZE B 3 UN $13,000

5 l.\:-e2 REGRADE AND CLEAR RAILR!Wl B 2 UN $15,000 DITCH

6 1.\:-1.\: REGRADE AND CLEAR RAILR!Wl B 2 UN $15,006 DITCH

7 l.\:-e2 REGRADE AND CLEAR RAILR!Wl B 2 UN t15,0ee DITCH

8 l.\:-e2 REGRADE 1M> CLEAR RAILR£W> B 2 lJf $15,0ee DITCH

'3 1.\:-87 It£~ EXISTINS PI~ B 2 lJf S29,0ee TO 2-24" RCP'S

10 1.\:-87 RECOOTRLCT STREET B 3 lJf t33,0ee

11 92-11 MAINTAIN EXISTINS I~ B 3 F3 t1,0ee

12 1.\:-12 It£~ EXIST. PI~ TO 2-72" B 3 lJf $13,006 ReP'S, GRADE ~¥om CLEAR DITCH

13 1.\:-12 It£~ EXIST. PIPE TO 2-72" B 3 UN $1'3,006 RCP' S, GRADE ~ CLEAR DITCH

14 02-14 It«:REASE EXIST. PIPE TO 72" B 3 lJf f16,008

15 02-14 It«:REASE EXIST. PIPE TO 72• B 3 lJf t16,008

16 92-14 It£~ EXIST. PIPE TO 72" B 3 lJf t16,008

17 02-14 COOTRLCT ADDITIIJR I~S B 3 UN $5,008

18 02-15 COOTRLCT ADDITIIJR HUTS B 3 UN ss,008 MAINTAIN I~S B 3 UN $1,008

1'3 1.\:-15 MAINTAIN EXISTINS STRLCTURES B 3 lJf S2'5,008

29 02-18 COOTRLCT PIPES ~¥om I~S B 3 lJf $34,008

21 1.\:-19 COOTRLCT PIPE ~ HUTS B 3 lJf $16,008

SliBTOTil. t388,Ne

8-2


---- --------- -----pROJU)il BASIN/ PROBLEM SEVERITY PRIORITY F\JIDING II.MBER SUBBASIN S(l.UTH~ RATING RATING STATUS COST ------- ----------------

BUSIIESS DISTRICT BASIN

22 &4-tl aJISTRltT ADDITIIJA... HUTS B 2 ~ S13,M8

23 M-tl RECOOTROCT PIPE B 2 l.fi S161,M

24 M-t3 COOTRLCT PIPES AND HUTS B 3 l.fi S1,324,eet

25 1!4-iM C!JETROCT ADDITIIJR Itt.ETS B 3 l.fi $1,.

2Ei 04-tS C!JETROCT ADDITIIJR Itt.ETS B 3 l.fi $1,.

27 1!4-tS CIJETROCT ADDITIIJR Itt.ETS B 3 l.fi S1,.

SUBTOTil. S1,5e1,.

PHILLIPPI CREEK MSIN

28 05-01 a:JETRLCT PIPES AND Itt.ETS B 3 l.fi S23,.

29 \JS-02 Ilf:REASE EXIST. PIPE TO 24" B 3 l.fi m,•

3t 1}5-10 RECIJETROCT STREET 8 3 l.fi S38,.,

31 1}5-18 RECIJETROCT STREET 8 3 l.fi S38,.

32 05-11 REWISTROCT STREET 8 3 lM S38,.

33 85-11 CIJETRLCT PIPES AND Itt.ETS B 3 lM S31,eet /

-----SUBTOT~ S254,eet

~ BAYOO BASIN

34 86-tJ IP«:REASE EXIST. PIPE TO 54" 8 3 lM st7,a

35 86-e& Ilf:REASE EXIST. PIPE TO 54" 8 l.fi S2'3,Ne

36 86-t9 ~INTAIN EXISTING STil£TURES 8 3 lJI Sl,Ne RECIJETRI..CT 1 Itt.ET B 3 lJI S3,NI

37 86-14 IPI:REASE EXIST. PIPE TO 72" 8 3 lM S43,Ne

38 86-14 II£1£ASE EXIST. PIPE TO 72" B 2 lJI $43,8

8-3

PROILEM BASIN/ ~R SUBBASIN

3'1 86-14

~ 86-14

41 86-14

42 86-14

43 86-15

" 86-15

45 86-16

46 86-17

lt7 86-17

;,a 86-17


PROBLEM Sll.UTII~

SEVERITY PRIORITY FUNDING RATING RATING STATUS

·------------COST

------------------

INCREASE EXIST. PIPE TO f18• 8 2 lM t67,M

INCREASE EXIST. PIPE TO f18• 8 2 lM .07,~

INCREASE EXIST. PIPE TO oe• 8 2 lM t67,8e&

INCRB& EXIST. PIPE TO 54• 8 2 lM t51,~

RmJlCE Cll.VERTS WITH BRIDGE 8 2 lM t114,8N

RmJlCE Cll.VERTS WITH BRIDGE 8 2 ~ S114,~

INCIBSE EXIST. PIPE TO f18• c 2 lM S9,8N

REaJETRLCT STREET c ~ S17,8N

aJETRLCT PIPES IH> IIUTS B 3 F3 S75,8N

Ir«:REASE EXIST. PIPE TO 2-68• 8 3 ~ S33,M

------SUBTOTil. t7'51,8N

OSPREY aJISTil. BASIN

49 87-81 Ir«:REASE EXISTING PIPE 8 F3 S9e,8N

5e 87-82 CREATE llJTFil.L 8 F3 S..?S,~

51 07-06 ADD ADDITIIJR. IIUT B 3 ~ S3,8N

52 87-87 Ir«:REASE EXIST. PIPE TO Je• 8 3 ~ S114,~

-------SUBTOTil. S232,~

KEY TO ~DING ~=INlJIDED CITYWIDE TOTil. S3,2e3,8N F 1 = FLtiDED llJT lilT DESI 6rED F2 = FLtiDED AND IN DESI~PE"'ITIING PROCESS F3 = FUNDED AWAITING BID

8-4

PBS)

' N

-

LOCATION ·OF NEEDED CAPITAL IMPROVEMENTS

FIGURE 8-1

The individual projects were evaluated in terms of their severity and

corresponding funding priorities. Of the total $3,263,000 funding need

identified, only 5% of the funds are associated with Priority 1 projects and

24% was associated with Priority 2 projects. Consequently, 71% of the funds

were required by Priority 3 projects which, in many cases, are projects

designated to solve recurring cases of nuissance flooding which temporarily

retards travel but eventually dissolves road base materials and undermines

other public facilities in the rights-of-way throughout the City. Table 8-2

presents the funding priorities by basins and summarizes the City-wide need.

8.3 O&M NEEDS ASSESSMENT

Proper O&M is the keystone to keeping existing facilities in their peak

operational condition. Unfortunately the City's budget for stormwater related

O&M activities is only approximately $35,000 annually and the results of this

limited budget are readily apparent.

A very brief analysis of the City's 23.7 miles of major ditches, 25.3 miles of

major culverts and key structure in the seven mainland basins suggests a

recurring need for programmed maintenance. Based on typical unit production

rates and the City's actual manpower and equipment costs, it would an O&M

budget allocation of $482,600 annually to maintain these facilities once a

year. Individual basin costs vary from $6,100 to $151,000 as summarized in

Table 8-3.

tm:r~L27:J 8-6

Basin

TABLE 8-2

SUMMARY OF BASIN CAPITAL CONSTRUCTION FUNDING REQUIREMENTS BY PRIORITY LEVEL

Funding B,t Priorit.z: Level

1 2 3

North Trail Capital $ 0 $ 0 $ 218,000

Whitaker Bayou 0 89,000 219,000

Bay front Co as ta 1 0 0 0

Business District 0 174,000 1,327,000

Phillippi 0 0 254,000

Hudson Bayou 46,000 532,000 172,000

Osprey Coastal 115,000 0 117,000

CITY-WIDE NEED $161,000 $795,000 $2,307,000

Priority Funding Distribution 5% 24% 71%

tm:ML27:K 8-7

Total Funding

$ 218,000

308,000

0

1,501,000

254,000

750,000

232,000

$3,263,000

100%

TABLE 8-3

SUMMARY OF RECURRING 0 & M FUNDING REQUIREMENT

Major Major Key Culverts ( LF) Ditches ( LF~ Structures

North Trail Coastal 5,940 5, 280 0 Whitaker Bayou 31,760 46,620 8 Bayfront Coastal 13,200 160 0 Business District 22,660 9,000 3 Phillippi Creek 24,980 46,240 7 Hudson Bayou 30,070 28,080 4 Osprey Coastal 4,800 340 0

Citywide 133,410 135,720 22

CITY-WI DE

Major Major Kev Total Culverts Ditches Structures Cost

North Trail Coastal 6,500 12,000 0 18,500 Whitaker Bayou 35,000 108,000 8,000 151,000 Bay front Co as ta 1 15,000 1,000 0 16,000 Business District 25,000 20,000 3,000 48,000 Phillippi Creek 28,000 104,000 7,000 139,000 Hudson Bayou 33,000 67,000 4,000 104,000 Osprey Coastal 5,100 1,000 0 6,100

$147,600 $313,000 $22,000 $482,600

tm:ML27:L 8-8

8.4 IMPLEMENTATION PROGRAM

The implementation program developed for the City consists of strategies for

capital expenditures, annual O&M funding, continuing R&R expenditures and

strategic basin-wide studies as well as an integrated funding needs assessment

and a 20-year plan to solve the City•s problems.

8.4.1 Capital Expenditures Strategy

The expenditure program established for capital construction projects focuses

on prioritized projects and seeks to complete all of the identified projects

within a ten year period. Allowing 10% of the construction cost for survey,

studies and designs, the annual expenditure required to achieve this program

is $360,000 per year. The order of projects within each priority level is

arbitrary and an mixture of Priority 1 and Priority 2 projects would be

scheduled during the first three years.

/: \ 'c,,

A second and major capital expenditure consideration is !thee\ repair and/or \ I \

replacement (R&R) of existing facilities as they reach the end of their f>

service life and begin to fail. The average service life of concrete and

corrugated metal culverts has been estimated at 30-60 years depending upon

their method of manufacture, protective coatings, installation procedures and

service environment.

Recognizing that some of the facilities in Sarasota have been in service since

the 194o•s, the City must be prepared to begin replacing and repairing these

tm:ML27:J 8-9

facilities as they fail. The recent collapse of the storm sewer in Ohio Place

in the Business District Basin which will cost about $161,000 to reconstruct

is an example of this type of capital construction need.

The City should conduct a conditions survey in 1988 and 1989 to ascertain the

general condition and remaining service life of its primary and secondary

drainage facilities. Based upon this survey, the City should prioritize

replacement and repair projects to prevent catastrophic system failures.

Funding at $135,000 should be developed for the survey during the first two

years. Upon completion of survey, appropriate funding should be allocated for

system. For the purposes this study , the initial R&R funding in year 3 has

been established as the $123,000 presently allocated from the 6th cent gas tax

revenues and allowed to grow, of an annual rate of 4.25% to $250,000 by the

year 2007. This growth rate seeks to compensate for the increasing rate of

pipe facilities as the City•s systems age.

8.4.2 Strategic Basin Studies Strategy /

/

Evaluation of service level degradation due to the impact of growth on

undersized and inadequate indicates that the number of major facilities

falling below Service Level C standards will triple from 21 to 60. This fact

indicates that the City should initiate a series of comprehensive basin

modelling studies to identify problems and select the best and most cost

effective basin with solutions. These studies should begin in the third year

of the program and should be undertaken in the following basin order:

tm:ML27:J 8-10

Priorit~ Basin Stud~ Date Stud~ Cost tA /pi I

1 Hudson Bayou 1990,,1991 $193,100 \

2 Phillippi Creek 1992, 1994 $312,000

3 Whitaker Bayou 1995,1996 $214,600 :J (

4 Osprey Coastal 1997 $ 40,700

5 Business District 1997 $ 81,700

6 Bayfront Coastal 1998 $ 28,100

7 North Trail Coastal 1990 $ 56,800

Also indicated is the year(s) the study should be undertaken and an estimated

current cost to evaluate the basin using hydraulic simulation procedures.

Some studies, due to the size and complexity of the basins, will be very

expensive and complicated and will take two to three years to complete. The

City should monitor in each basin the year before the studies are conducted in

order to have appropriate rainfall and runoff data to conduct the hydrologic

and hydraulic simulations.

8.4.3 O&M Strategy

Assuming that major facilities are maintained on a five year cycle and that

the maintenance of minor systems is approximately twice as expensive but

accomplished on a 10 year cycle, the City's annual O&r~ expenditure would be

approximately $193,000 which is about 5.5 times the current annual expenditure

of $35,000.

tm:ML27:J 8-11

In order to achieve an adequate O&M funding program, the strategy used in this

study is to gradually raise the annual 0&~1 funding level from its current

$35,000 to the needed level of about $193,000 over the next 5 years.

Thereafter, the O&M funding level would be maintained at the $193,000 level

for five years and the \gradually raised over the next 10 years at 2% per year

to $235,000 to refiect the increasing O&M funding required to maintain the new

facilities which are being constructed through the CIP construction projects.

8.4.4 Implementation Plan

As discussed in the foregoing sections, the capital construction fundinq for

both identified current CIP projects and unidentified future CIP projects,

combined with the continuing need for annual O&M activities and an increasing

need for R&R projects must be scheduled over a reasonable program

implementation period.

implementation plan.

The results of this scheduling effort is the

This study has evaluated the City•s current and anticipated future needs for

the next 20 years in an effort to develop a viable program. Utilizing the

strategies in Sections 8.4.1 through 8.4.3 as the basis, three long-term

implementation plans were developed for Sarasota. All three plans are

identical for the plan years. 1-10 which cover the period 1988-1997. However,

the programs differ in terms of real program growth for the years 1998-2007.

The financial differences of the three plans programs is summarized in the

following table:

tm:t~L27:J 8-12

Post-1997 Alternative Growth Rate

1 1%

2 2%

3 3%

Unidentified CIP Funding

$4,552,000

$5,056,000

$5,593,000

Total Program Cost

$15,987,000

$16,491,000

$17,028,000

The fundamental difference in the three plans is the post-1997 growth rate

\'lhich is reflected in the level of funding planned for currently unidentified

CIP projects that will be identified in the strategic basin studies. The

individual programs are summarized by year by individual expenditure category

in Tables 8-4, 8-5 and 8-6.

These projections do not consider many of the daily activities already

accomplished by the City's current stormwater management program. Overa 11 ,

the City should try to pursue a real growth rate in its stormwater program of

2% as represented by Alternative 2. Inflation has not been considered in the

foregoing analysis or in Table 8-5 for Alternative 2. Table 8-7 summarizes

the difference in costs for Alternative 2 if a 5% continuous inflation rate is

applied over the 20 years of the program.

8.5 PROGRAM FINANCING

The City• s stormwater management program must develop a stable and reliable

financing program if it is to be successful and solve Sarasota's current and

future stormwater problems. There are several alternatives that are available

to cities and counties in Florida to fund a stormwater management program.

These include:

tm:ML27:J 8-13

PROGRAM YEAR

1 ':J ._ 3 4

5 6 7 8

9 10 11 12

13 14 15 16

17 18 19 20

TOTAL FUNDS REQUIRED

CALENDAR YEAR

1988 1989 1990 1991

1992 1993 1994 1995

1996 1997 1998 1999

2000 2001 2002 2003

2004 2005 2006 2007

PERCENT OF TOTAL NEED

IDENTIFIED CIP

PROJECTS

$360 $360 $360 $360

$360 $360 $360 $360

$360 $360

$0 $0

$0 $0 $0 $0

$0 $0 $0 $0

$3,600

22.5%

R & R COSTS

$35 $35

$123 $128

$134 $139 $145~

$151

$158 $165 $172 $179

$186 $194 $203 $211

$220 $230 $240 $250

$3,298

20.6~

STRATEGIC STUDIES

$0 $0

$97 $97

$104 $104 $104 $107

$107 $122

$85 $0

$0 $0 $0 $0

$0 $0 $0 $0

$927

5.8~

0 & M COSTS

$35 $54 $82

$126

$193 $193 $193 $193

$193 $193 $197 $201

$205 $209 $213 $217

$222 $226 $230 $235

$3,610

22.6~

UNIDENTIFIED CIP

PROJECTS

$0 $0 $0 $0

$0 $0 $0 $0

$0 $0

$394 $477

$474 $471 $467 $464

$459 $454 $449 $443

$4,552

28.5~

TABLE 8-4

SUMMARY OF STORMWATER EXPENDITURES FOR ALTERNATIVE 1 (1% REAL GROWTH AFTER 1997]

TOTAL FUNDING

REQUIRED

$430 $449 $662 $711

$791 $796 $802 $811

$818 $840 $848 $857

$865 $874 $883 $892

$901 $910 $919 $928

$15,987

100.0~

8-14

PROGRAM YEAR

1 2 3 4

5 6 7 8

9 10 11 12

13 14 15 16

17 18 19 20

CALENDAR YEAR

1988 1989 1990 1991

1992 1993 1994 1995

1996 1997 1998 1999

2000 2001 2002 2003

2004 2005 2006 2007

IDENTIFIED CIP

·PROJECTS

$360 $360 $360 $360

$360 $360 $360 $360

$360 $360

$0 $0

$0 $0 $0 $0

$0 $0 $0 $0

R & R COSTS

;135~ ~3~/\

$12.51 $128\)

$134 $139 $145 $151

$158 $165 $172 $179

$186 $194 $203 $211

$220 $230 $240 $250

STRATEGIC STUDIES

$0 $0

$97 $97

$104 $104 $104 $107

~H07 ~fi122

$85 $0

$0 $0 $0 $0

$0 $0 $0 $0

0 & M COSTS

$35 $54 t8~,

·$126 .,_.....-

$193 C/

$193 $193 $193

$193 $193 $197 $201

$205 $209 $213 $217

$222 $226 $230 $235

UNIDENTIFIED CIP

PROJECTS

$0 $0 $0 $0

$0 $0 $0 $0

$0 $0

$403 $494

$500 $506 $511 $518

$523 $528 $534 $539

TABLE 8-5

SUMMARY OF STORMWATER EXPENDITURES FOR ALTERNATIVE 2 (2% REAL GROWTH AFTER 1997)

CITY OF SAR~SOTA

CITY WIDE MASTER DRAINAGE PLAN

September 1987 PBS&J

TOTAL FUNDING

REQUIRED

$430 $449 $662 $711

$791 $796 $802 $811

$818 $840 $857 $874

$891 $909 $927 $946

$965 $984

$1,004 $1,024

'')

----------------------------------------------------------------------------------------------------------------------------------------------TOTAL FUNDS REQUIRED $3,600 $3,298 $927 $3,610 $5,056 $16,491

PERCENT OF TOTAL NEED 100.0"

8-15

---------------------------------------------------------------------------------------------------------------------------------------------PROGRAM

YEAR CALENDAR

YEAR IDENTIFIED

CIP PROJECTS

R & R COSTS

STRATEGIC STUDIES

0 & M ·COSTS

UNIDENTIFIED CIP

PROJECTS

TOTAL FUNDING

REQUIRED ---------------------------------------------------------------------------------------------------------------------------------------------

1 1988 $360 $35 $0 $35 $0 $430 2 1989 $360 $35 $0 $54 $0 $449 3 1990 $360 $123 $97 $82 $0 $662 4 1991 $360 $128 $97 $126 $0 $711

5 1992 $360 $134 $104 $193 $0 $791 6 1993 $360 $139 $104 $193 $0 $796 7 1994 $360 $145 $104 $193 $0 $802 8 1995 $360 $151 $107 $193 $0 $811

9 1996 $360 $158 $107 $193 $0 $818 10 1997 $360 $165 $122 $193 $0 $840 11 1998 $0 $172 $85 $197 $411 $865 12 1999 $0 $179 $0 $201 $511 $891

13 2000 $0 $186 $0 $205 $527 $918 14 2001 $0 $194 $0 $209 $542 $945 15 2002 $0 $203 $0 $213 $558 $974 16 2003 $0 $211 $0 $217 $575 $1,003

17 2004 $0 $220 $0 $222 $591 $1,033 18 2005 $0 $230 $0 $226 $608 $1,064 19 2006 $0 $240 $0 $230 $626 $1,096 20 2007 $0 $250 $0 $235 $644 $1, 129

TOTAL FUNDS REQUIRED $3,600 $3,298 $927 $3,610 $5,593 $17,028

PERCENT OF TOTAL NEED 21.1';{ 19.4';{ 5.4';{ 21. 2';{ 32.8';{ 100.0';{

TABLE 8-6

SUMMARY OF STORMWATER EXPENDITURES FOR AlTERNATIVE 3 (3% REAl GROWTH AFTER 1997)

8-16

TABLE 8-7

SUMMARY OF STORMWATER EXPENDITURES FOR 2% REAl GROWTH AFTER 1997 WITH A CONSTANT 5% INFLATION RATE

2% REAL GROWTH WITH 5% ANNUAL INFLATION

-------------------------------------------------------------------------------·--------------------------------------------PROGRAM

YEAR CALENDAR

YEAR IDENTIFIED

CIP PROJECTS

R & R COSTS

STRATEGIC STUDIES

0 & I'IJ COSTS

UNIDENTIFIED CIP

PROJECTS

TOTAL FUNDING

REQUIRED -------------------------------------------------------------------------------·--------------------------------------------

1 1988 $360 $35 $0 $35 $0 $430 2 1989 $378 $37 $0 $5'7 $0 $471 3 1990 $397 $136 $107 $90 $0 $730 4 1991 $417 $148 $112 $14(; $0 $823

5 1992 $438 $163 $126 $23:5 $0 $961 6 1993 $459 $177 $133 $246 $0 $1, 016 7 1994 $482 $194 $139 $25':3 $0 $1,075 8 1995 $507 $212 $151 $2n $0 $1, 141

9 1996 $532 $233 $158 $28:5 $0 $1,209 10 1997 $558 $256 $189 $299 $0 $1,303 11 1998 $0 $280 $138 $321 $656 $1,396 12 1999 $0 $306 $0 $34't $845 $1,495

13 2000 $0 $334 $0 $368 $898 $1,600 14 2001 $0 $366 $0 $39it $954 $1,714 15 2002 $0 $402 $0 $422 $1,012 $1,835 16 2003 $0 $439 $0 $451 $1,077 $1,967

17 2004 $0 $480 $0 $485 $1, 142 $2, 106 18 2005 $0 $527 $0 $518 $1,210 $2,255 19 2006 $0 $578 $0 $55~. $1,285 $2,416 20 2007 $0 $632 $0 $594 $1,362 $2,588

TOTAL FUNDS REQUIRED $4,528 $5,935 $1,254 $6,373 $10,441 $28,532

PERCENT OF TOTAL NEED 15.9% 20.8% 4.4% 22.3% 36.6" 100.0"

8-17

Revenue for Annual Operation Expenses

o General Fund o Drainage UtiTity Service Charges

Fundings for Major Capital Improvements

o General Obligation Bonds Repaid by Property Taxes o Revenue Bonds Repaid by Utility Service Charges o Utility Tax Revenues o Community Development Block Grant Funds

Fundings for New Development Services

o Plan Review Fees o On-site System Inspection Fees o Impact Fees o System Development Charges o In-lieu of Construction Charges o Latecomer Fees

Funding for Special Services

o Loca 1 Improvement Districts o Utility Local Improvement Districts o Special-Purpose Taxing Districts

Unfortunately, only the stormwater utility and bonding programs are capable of

providing adequate funding to completely meet the City's long-term needs for

stormwater facilities.

8.5.1 The Stormwater Utility

The stormwater utility concept is still fairly new, with most stormwater

utilities having been established within the past 10 years. One of the

purposes of utility user charges and rate structures is to equitably

distribute the costs of the utility program. (it has been recognized that

charging in relationship to each property's role in contributing stormwater

runoff is at least as equitable as charging for service or benefit. By

instituting user fees, individuals pay according to the service/benefit that

tm:ML27:J 8-18

is used/received. Parcels of properties are frequently charged according to

their runoff characteri sties. Charges are most often based on the percent of

impervious area and on the parcel size. Adjustments can be built into the

system for those properties who use appropriate stormwater management control

practices that may change the runoff characteristics of the property

(detention/retention practices) and reduce downstream impacts.

User charges can provide a true alternative to general fund financing for

drainage rather than just a supplement to it. Revenues derived from service

charges can be used to pay for administration, planning, design, operations

and maintenance, revenue bonds for new construction and replacement of old

systems, support services, regulatory functions and virtually anything else

required in a comprehensive stormwater management program. Rate structures

are flexible mechanisms which enable a local government to tailor the cost

distribution to fit the local program and be consistent with other local

policies. Finally, drainage utility revenues remain in the utility fund if

not spent rather than reverting for redistribution in the next year•s budget,

an important factor in long-term program stability.

Considering the establishment of a stormwater utility for Sarasota requires a

thoughtful evaluation of the program steps. Typical steps which should be

considered in setting up a utility are as follows:

o Identify Functional Requirements

o Understand Legal Framework

o Determine Organizational Structure

tm:ML27:J 8-19

o Prepare O&M/CIP Program (short and long range)

o Review Finance Options

o Establish Utility Rate Policy/Model

o Implement Billing System

o Conduct Public Awareness Program

As applied to Sarasota, the land use mix of the city must be considered as

well as runoff generation characteristics. For purposes of illustration, a

very preliminary analysis of land uses suggests that the current level of

development within the city would generate a runoff volume equal to the runoff

generated by about 35,200 average residential parcels. The Equivalent

Residential Unit (ERU) is a common unit of measurement used in assessing land

use mixes, the effect of various percentages of impervious surface, and the

stormwater rundff potential within a city.

The calculation of an ERU for Sarasota is based on typical single family lot

size (0.22 acres) and a typical level of impervious surface on the single

family lot (45%) which results in a:~ ERU value of about 0.10 acres of

impervious surface. Similar calculations for other land uses within the City

are summarized in Table 8-8.

qased on the estimated annual revenue need previously presented in Table 8-5

for 2% real growth in the stormwater program, an estimated monthly charge per

ERU was calculated. This average residential charge, as summarized in Table ''

8-9, varies from about $1.02 in 1987 to $1,.83 in the year 2oo7. This charge

would probably be closer to $1.50 per month in 1987, if implemented, in order

tm:ML27:J 8-20

TABLE 8-8

SUMMARY OF ERUs BY LAND USE

Total Number Gross Intensity of Total Number

of Parcels Area Development Impervious of ERU or Units {Acres} Factor Area { AC} ~uivalents

Residential

0 Single Family 13,115 2,937 0.45 1,322 13,115 0 Mobile Home 1,752 153 0.65 99 995 0 Multi-Family 11,423 718 0.80 574 5,744 0 Group Quarters 984 19 0.75 15 143 0 Hotel/Motel 2,409 74 0.90 46 550':

Subtotal 29,683 3,901 0.53 2,066 20,547

Conrnercial

0 Office/Professional 141 0.80 113 1,128 0 Retail Sales/Service 529 0.90 487 4,761

Subtota 1 670 0.88 589 5,889 c;g

Industrial I N .....

0 Wholesale/Warehouse 182 0.80 146 1,456 0 Light Industry 24 0.90 22 216 0 Heavy Industry 0 0.95 0 0

Subtotal 206 0.82 168 1,672

Other

0 Util Hies 36 0.80 29 0 0 Industrial/Public 1,932 0.65 1, 255 6,300 0 Vacant 725 0.20 145 660 0 Miscellaneous 21 0.40 9 100

Subtotal 2, 714 0.52 1,408 7,060

TOTAL 7,491 0.56 4,231 35,168

TOTAL ANNUAL CITY APPROXIMATE UTILITY ESTIMATED PROGRAM CALENDAR FUNDING TOTAL COST RECOVERY CHARGE ANNUAL

YEAR YEAR REQUIRED ERUs RATE RATE UTILITY

---------------------------------------------------------------------~!:=~~~1~~--------~!:=~~~~-----~=~=~~=-1 2 3 4

5 6 7 8

9 10 11 12

13 14 15 16

17 18 19 20

1988 1989 1990 1991

1992 1993 1994 1995

1996 1997 1998 1999

2000 2001 2002 2003

2004 2005 2006 2007

$430,000 $449,000 $662,000 $711,000

$791,000 $796,000 $802,000 $811,000

$818,000 $840,000 $857,000 $874,000

$891,000 $909,000 $927,000 $946,000

$965,000 $984,000

$1,004,000 $1,024,000

35,168 35,700 36,200 36,800

37,300 3..7,900 38,500 39,000

39,600 40,200 40,800 41,400

42,000 42,700 43,300 44,000

44,600 45,300 46,000 46,700

$1.02 $1.05 $1.52 $1.61

$1.77 $1.75 $1.74 $1.73

$1.72 $1.74 $1.75 $1.76

$1.77 $1.77 $1.78 $1.79

$1.80 $1.81 $1.82 $1.83

1. 50 1. 50 2.00 2.00

2.25 2.25 2.25 2.25

2.50 2.50 2.50 2.50

2.75 2.75 2.75 2.75

3.00 3.00 3.00 3.00

$633,024 $642,600 $868,800 $883,200

$1,007,100 $1,023,300 $1,039,500 $1,053,000

$1,188,000 $1,206,000 $1,224,000 $1,242,000

$1,386,000 $1,409,100 $1,428,900 $1,452,000

$1,605,600 $1,630,800 $1,656,000 $1,681,200

-----------------------------------------------------------------·-------------------------------------------TOTALS $16,491,000 $24,260,124

8-22

TABLE 8-9

SUMMARY OF POTENTIAL CHARGES AND REVENUES FOR A CITY STORMWATER UTILITY

to cover billing and other administrative costs and and would likely rise to

$3.00 over the 20-year program period. Surplus revenues can be used for other

stormwa ter program efforts or the rate could be reduced if genera 1 funds from

ad valoren taxes will continue to be used. These average monthly rates are

very reasonable when compared to current rates and projected rates across the

country.

8.5.2 Bonding

A bonding program is the other method of providing financing for the proposed

1 ong-term stormwa ter management program. Whether a general obligation or

revenue bond, the city would have to utilize ad valorem taxes or other utility

revenues to repay the debt service.

For purposes of illustration, the proposed capital construction and R&R

program has been divided into four bond issues and an 8.00% interest rate has

been assumed for analytical purposes. If the projects identified in the first

15 years of the program are funded in three bond issues which have a 10-, 15-,

and 20-year debt service, the City would find the first 10 years of the

program to be relatively painless while the last 10 years would be very

expensive.

The debt service has been conservatively calculated on the three bond issues

and combined with O&M and strategic basin studies to arrive at the annual cost

of the .. deferred financing .. strategy. Initial annual funding needs would only

be $290,000 and rise significantly after the tenth year eventually reaching

tm :t~L27: J 8-23

PROGRAM YEAR

1 2 3 4

5 6 7 8

9 10 11 12

13 14 15 16

17 18 19 20

TOTAL FUNDS REQUIRED

CALENDAR YEAR

1988 1989 1990 1991

1992 1993 1994 1995

1996 1997 1998 1999

2000 2001 2002 2003

2004 2005 2006 2007

UNBONDED R & R COSTS

$0 $0 $0 $0

$0 $0 $0 $0

$0 $0 $0 $0

$0 $0

$203 $211

$220 $230 $240 $250

$1,354

STRATEGIC STUDIES

$0 $0

$97 $97

$104 $104 $104 $107

$107 $122

$85 $0

$0 $0 $0 $0

$0 $0 $0 $0

$927

0 & M COSTS

$35 $54 $82

$126

$193 $193 $193 $193

$193 $193 $197 $201

$205 $209 $213 $217

$222 $226 $230 $235

$3,610

UNBONDED . UNIDENTIFIED

CIP PROJECTS

$0 $0 $0 $0

$0 $0 $0 $0

$0 $0 $0 $0

$0 $0

$511 $518

$523 $528 $534 $539

$3,153

DEBT SERVICE PAYMENT

$255 $255 $255 $255

$255 $582 $582 $582

$582 $582

$1,014 $1,014

$1,014 $1,014 $1,014 $1,014

$1,014 $1,014 $1,014 $1,014

$14,325

TOTAL FUNDING

REQUIRED

$290 $309 $434 $478

$552 $879 $879 $882

$882 $897

$1,296 $1,215

$1' 219 $1,223 $1' 941 $1,960

u, 979 $1,998 $2,018 $2,038

$23,369

TABLE 8-10

SUMMARY OF STORMWATER EXPENDITURES USING A BONDING PROGRAM AND A DEFERRED fiNANCING STRATEGY FOR CIP CONSTRUCTION PROJECTS

8-24

$2,038,000 in the twentieth year. The annual costs estimated under this

"deferred bond financing" scenario are summarized in Table 8-10.

8.5.3 Summary

Stormwater management wi 11 continue to receive increased emphasis throughout

Florida as a major element in the State•s plan to management growth. The

requirements of the 1985 Growth Management Legislation have r~g~l~~d that each

community establish a stormwater program that addresses new growth by

establishing goals and identifying needs. The success of the City• s program

will depend on it to fund the stormwater management program. In general,

traditional financing methods have not generated sufficient revenue to fund

comprehensive stormwater programs that address flooding, water quality

enhancements, replacing decaying infrastructure, meeting the demands of ne\'1

development and performing the important maintenance and operating activities.

The most promising revenue source appears to be the creation of an enterprise

funded stormwater utility.

Now is the time for Sarasota to review the objectives of its stormwater

management programs. The future is near and the city can plan and be prepared

or chose not to plan and take its chances.

tm:t~L27:J 8-25