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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
tm:ML33:BB/l
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
tm:ML33:BB/2
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
tm:ML27:D 1-2
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.
tm:ML27:D 1-3
---------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,
tm:ML27:E 2-1
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.
tm:ML27:E 2-2
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
tm:ML27:E 2-3
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.
tm:ML27:E 2-4
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.
tm:ML27:E 2-5
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.
tm:ML27:E 2-6
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
tm :r~L27: E 2-7
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.
tm:ML27:E 2-8
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).
tm:ML27:E 2-9
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,
tm:ML27:E 2-10
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)
tm:Ml27:E 2-11
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.
tm:ML27:E 2-12
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.
tm:ML27:E 2-13
--------- (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
tm:ML25:U/3 3-1
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.
tm: ML25: U/3 3-2
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.
tm:ML25:U/3 3-3
---------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.
tm:ML24:X 4-1
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
tm:ML24:X 4-2
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.
tm:ML24:Y
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.
tm:ML24:X 4-4
---------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 ~~ .. ---- __ _... .-. :.~;..: .... :- :..-~ ... =-~-··~ ....
SARASOTA CITY LIMITS
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,
major ditch and culvert lengths and the number of system problems. Figure 6-6
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,
major ditch and culvert lengths and the number of system problems. Figure 6-9
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
PHILLIPPI CREEK 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
SARASOTA CITY LIMITS
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
NO RPPRRENT OUTFRLL FOR RUNOFF
NO RPPRRENT OUTFRLL FOR RUNOFF
NO RPPRRENT OUTFRLL FOR RUNOFF
INLETS PLUGGED WITH DEBRIS UNDERSIZED CONVEYRNCE
POORLY GRRDED STREET
INLET PLUGGED WITH OEBRIS
UNDERSIZED CONVEYRNCE
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 RND RDJRCENT LOTS
PONDING IN STREET RND RDJRCENT LOTS
PONDING IN STREET
PONDING RT INTERSECTION
PONDING IN STREET
PONDING IN STREET
PONDING IN STREET
PROBLEM CflUSE
UNDERSIZED CONVEYflNCE
UNDERSIZED CONVEYRNCE
UNDERSIZED CONVEYRNCE
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
lengths and the number of system problems. Figure 6-15 provides a schematic
diagram of the drainage basin and receiving waters. Table 6-11 identifies
flood problems within the basin giving location, type of problem, problem
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
PHILLIPPI CREEK BASIN
SARASOTA CITY LIMITS
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
UNDERSIZED CONVEYANCE
INLETS PARTUlLL 'l PLUGGED WITH DEBRIS
UNDERSIZED OUTFALL PIPE
UNDERSIZED CONVE'lANCE
UNDERSIZED CONVE'lANCE
UNDERSIZED CONVE'lANCE
UNDERSIZED CONVEYANCE
UNDERSIZED CONVEYANCE
----------------------------------------------------------------------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
UNDERSIZED CONVEYANCE
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
lengths and the number of system problems. Figure 6-17 provides a schematic
diagram of the drainage basin and receiving waters. Table 6-13 identifies
flood problems within the basin giving location, type of problem, problem
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
PHILLIPPI CREEK BASIN
--
--
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 RT INTERSECTION
PONDING IN STREET
PONDING IN STREET
PONDING IN STREET
PONDING IN STREET
PONDING IN STREET
PROBLEN CfiUSE
UNDERSIZED RND POORLY NRINTAINED DUTFfiLL DiTCH
UNDERSIZED CONVEYRNCE
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 DESCRIPTION
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
FACILITY DESCRIPTION
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
FACILITY DESCRIPTION
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
TABLE 7-1 (Continued)
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 DESCRIPTION
FACILITY LOCATION
PHILLIPPI CREEK BASIN
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 DESCRIPTION
TABLE 7-1 (Continued)
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 DESCRIPTION
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
TABLE 7-2 (Continued)
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
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 -------------------------------------------------------------------------------------
',>',
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>
5-YEAR 10-YEAR 25-YEAR
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>
5-YEAR 10-YEAR 25-YEAR
-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 ---------------------------
5-YEAR 10-YEAR 25-YEAR
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
TABLE 7-3 (Continued)
FUTURE CONDITIONS FACILITY FACILITY DEMAND <CFS> NUMBER ---------------------------
5-YEAR 10-YEAR 25-YEAR
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
TABLE 7-3 (Continued)
FACILITY NUMBER
FUTURE CONDITIONS FACILITY DEMAND <CFS>
5-YEAR 10-YEAR 25-YEAR
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>
5-YEAR 10-YEAR 25-YEAR
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%
of estimated capacity
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%
of estimated capacity
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
FACILITY DESCRIPTION
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
FACILITY DESCRIPTION
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
FACILITY DESCRIPTION
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
FACILITY DESCRIPTION
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
TABLE 7-4 (Continued)
--~------------------------
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
TABLE 7-4 (Continued)
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)
Whitaker Bayou (Percent of Basin)
Bayfront Coastal (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: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)
Whitaker Bayou (Percent of Basin)
Bayfront Coastal (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: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
TABLE 8-1 (Continued)
---- --------- -----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
TABLE 8-1 (Continued)
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