Stevenson Creek Watershed Management Plan Final Report

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### EXECUTIVE SUMMARY

Watershed Description
The Stevenson Creek Watershed, the largest and most urbanized watershed within the City of Clearwater, drains 6,286 acres in west central Pinellas County. Of this area, 4,057 acres (65 percent) are within the Clearwater city limits. The remaining 35 percent of the basin is within the City of Dunedin (1,287 acres or 20%), unincorporated Pinellas County (859 acres or 14%) and the City of Largo (83 acres or about 1%).
Stevenson Creek discharges to Clearwater Harbor. The majority of the creek has been channelized or otherwise altered, and little of the historic floodplain remains intact. Land uses within the basin are predominantly medium- and high-density residential, commercial, and open space. Approximately 90 percent of the watershed has been developed, and the vast majority of the development occurred prior to the implementation of regulatory requirements for floodplain preservation, environmental protection, stormwater treatment and attenuation. Several developments have been constructed within the creek’s floodplain and have experienced severe flooding. In addition, the creek and its tributaries experience moderate to severe erosion problems due to steep embankments, improper maintenance, highly erodable soils, and inadequate right-of-way.
The majority of the land use changes within the watershed have been detrimental to water quality, flood protection, and wildlife habitat. Urban development has resulted in greater stormwater runoff volumes and peak flow rates, as well as the transport of sediments and pollutants into the creek.
Purpose and Objectives
The Stevenson Creek Watershed Management Plan has been initiated as the result of a cooperative agreement between the City of Clearwater and the Southwest Florida Water Management District (SWFWMD). Stormwater quality and quantity are identified within the City of Clearwater Comprehensive Plan as areas of service deficiencies which
must be addressed.Stevenson Creek Watershed Management Plan Final Report

1.1-2 J:\DATA\737626\EXECUTIVE SUMMARY.doc The basic purpose of the management plan is to identify the causes and sources of problems such as flooding, water quality degradation, excessive channel erosion, and loss of riparian habitat. Once these problems were identified, recommendations were made to solve or alleviate the problems. Recommendations include capital improvement projects (i.e. stormwater infrastructure improvements), creation and restoration of habitat, maintenance strategies, pollution reduction programs, and public involvement and awareness. This management plan will be used as a tool in the planning, regulation, and management of natural resources and future development, and as a basis for determining and prioritizing capital improvements by the City of Clearwater and SWFWMD.

Data Collection
The information-gathering process included such activities as a literature search and review of existing data, field reconnaissance and ground-truthing of aerial photography, ground surveying, streamflow monitoring, surface water sampling and testing, habitat assessment, interviews with City operations personnel, and input from residents of the
watershed.

Flood Protection Level of Service
In order to assess the current flood protection level of service and to determine the most effective means of alleviating the identified flooding problems, a hydrologic and hydraulic model of the watershed was prepared.
The Advanced Interconnected Channel and Pond Routing Model, Version 2.2 (AdICPR) was chosen for the hydrologic and hydraulic modeling analysis. To provide the necessary level of detail, the basin was divided into a total of 307 discrete subbasins averaging 20.5 acres in size. The delineation of subbasins was dictated to a large extent by the complexity of the drainage network itself and the need to define the contributing drainage area to modeled elements of the conveyance system.

The AdICPR model was calibrated to measured rainfall and streamflow data collected for this project. The large storm of July 15, 2000 was used as the calibration event. Once calibrated, the model was used to simulate the 5, 10, 25, 50, 100, and 500- year design flood events. Floodplain mapping and flood profiles were prepared in orderStevenson Creek Watershed Management Plan Final Report

1.1-3 J:\DATA\737626\EXECUTIVE SUMMARY.doc to identify flooding problem areas. This information will be used to support a request for revision of the applicable FEMA flood insurance rate maps.
Design 100 year flood elevations were compared with surveyed finished floor elevations of homes and businesses within the 100-year floodplain. Of the 470 structures entered into the database, 263 structures were found to have finished floor elevations below the 100-year flood level. This is, by definition, a structure flooding level of service deficiency. The majority of these structures are located within the primary floodplains of the Stevenson Creek and Spring Branch main channels. However, many of the identified FPLOS deficiencies result from inadequate secondary drainage systems
that feed into the main channels.
Natural Systems
The entire watershed was investigated for undeveloped land, wetlands, natural areas, and potential restoration or preservation areas. The boundaries of the natural areas were identified and mapped on aerial photography. These areas were characterized using the Florida Land Use Cover and Forms Classification System (FLUCCS) (FDOT, 1985).
The Stevenson Creek Watershed is a highly urbanized, densely populated area with little to offer in the way of natural systems. With one exception, the only undeveloped areas are golf courses and city parks. Wetlands are predominantly small isolated stormwater retention ponds or natural lakes that have been altered to such a degree that their origin can only be determined from historic aerial photography. The waterways are predominantly channelized with little riparian habitat. The intense development has also altered the estuarine system so that little habitat is provided at the mouth of Stevenson
Creek.
Water Quality Assessment
Low dissolved oxygen levels, fecal contamination, and excessive nutrient concentrations are the primary water quality issues that have been identified in the watershed, and as such, water quality in Stevenson Creek is rated as “poor” by the state. The state’s rating is based on sampling conducted by the Pinellas County Department ofStevenson Creek Watershed Management Plan Final Report

1.1-4 J:\DATA\737626\EXECUTIVE SUMMARY.doc Environmental Management (PDEM). The city’s ambient monitoring program as well as monitoring conducted for this study affirms these water quality issues.
Stevenson Creek is included on Florida’s impaired waters list {303(d) List} due to concerns over dissolved oxygen, fecal coliform bacteria, and nutrients. The FDEP has given Stevenson Creek a priority rating of “High”. Stevenson Creek is located in the “Crystal River to St. Petersburg Beach Basin” which is in Group 5 of the basin rotation cycle. TMDL development activity is expected to begin in 2004.
Water quality assessments conducted for this study included the following elements:

• Review of Existing Data,

• Base flow and storm event monitoring program,

• Water quality data interpretation,

• Nonpoint source loading assessment, and

• Fecal contamination source tracking study. Capital Improvement Projects The relative scarcity of publicly-owned and vacant land within the watershed limited the range of available alternatives and posed a unique challenge in meeting all the goals of the Watershed Management Plan in a cost effective manner. For this reason,acquisition of private property, including 33 flood-prone or flood-susceptible singlefamily residential homes, is recommended in order to provide the necessary land for various infrastructure improvement projects that will benefit the watershed as a whole.
In most, but not all cases, it was considered feasible and cost-effective to achieve the adopted flood protection level of service goals. A total of 26 individual capital projects are recommended, consisting of a combination new stormwater management facilities and retrofits to existing facilities and infrastructure. If all recommended projects are implemented, 243 of the identified 334 structure FPLOS deficiencies (73%) will be remedied. Many (28) of the remaining FPLOS deficiencies are located within the coastal high hazard area of Lower Stevenson Creek and are susceptible to flooding from storm surge. Reductions in the riverine floodplain (flooding due to rainfall and runoff) will therefore not remedy these FPLOS deficiencies. The combined projects would removeStevenson Creek Watershed Management Plan Final Report

1.1-5 J:\DATA\737626\EXECUTIVE SUMMARY.doc FPLOS deficiencies at 33 locations on residential streets, 16 locations on collector roads,
and on one arterial road.
Water quality, habitat, erosion and sedimentation projects were developed individually and in conjunction with the recommended flood protection projects wherever feasible. Alternative projects were evaluated with respect to water quality improvement
benefits.
Other Improvements/Recommendations
In addition to the capital improvement projects, the WMP includes recommendations for watershed maintenance activities, exotic plant eradication, public education and involvement, and legal and regulatory framework. A more detailed and comprehensive study to pinpoint the source(s) of the fecal coliform bacteria is also recommended. The study would serve as the basis for developing an effective strategy to address the fecal contamination problem.
Capital Costs
For purposes of budgetary planning, cost estimates were made of each recommended capital improvement project. The cost estimates are based on the conceptual design and are subject to change pending completion of a more detailed design process. The total estimated cost of the recommended projects is approximately $27 million, in 2001 dollars, including property acquisition design, and permitting. The magnitude and scope of the recommended improvements, coupled with budgetary constraints, will require phased implementation of the plan over a number of years.
Project Prioritization
Capital projects that can be expected to provide the greatest overall benefit in the most cost effective manner were identified using a project ranking procedure. This management tool is a convenient and effective method of recommending priorities for the allocation of available funding. To help identify the priority projects in the Stevenson Creek Watershed Management Plan, a set of comparative evaluation criteria were identified, and a project ranking matrix was developed. Within each category, individual projects were graded on a scale from 0 to 10, with the lowest score indicating no realStevenson Creek Watershed Management Plan Final Report

1.1-6 J:\DATA\737626\EXECUTIVE SUMMARY.doc benefit and the highest indicating a high beneficial value. The categories considered in the ranking analysis included the following:

• flood control benefits,

• water quality benefits,

• ecological benefits,

• channel erosion and sedimentation control benefits,

• Recreational and Educational Benefits,

• Implementability, and

• Relative Benefits to Cost. Those projects which serve multiple purposes rank the highest when compared to those with singular objectives. Also apparent is the observation that the projects that rank the highest generally have the highest scores in the relative benefits to cost category.
Through the public meetings, workshops, and meetings among members of the project team, five projects were identified as potentially controversial. These include the highest-ranked project, the Glen Oaks stormwater detention facility. Winning public support for these projects through the City’s public information initiatives will be crucial to successful implementation of these projects. The final design and implementation of these projects must be sensitive to resident’s potential concerns regarding alternative recreational opportunities, the environment, safety, aesthetics, and property values.i J:\DATA\737626\REPORTS\MGTPLAN\FINAL\TOC.DOC 

### TABLE OF CONTENTS
STEVENSON CREEK WATERSHED MANAGEMENT PLAN
FINAL REPORT
SECTION Page

SECTION 1.0 INTRODUCTION ............................................................................................... 1.1-1
1.1 What is a Watershed Management Plan? ................................................. 1.1-1
1.2 The Benefits of a Watershed Management Approach.............................. 1.1-2

1.3 The Stevenson Creek Watershed .............................................................. 1.1-2 1.3.1 Watershed Location and Description ......................................... 1.1-2 1.3.2 Basin History.............................................................................. 1.1-4
1.4 Project Objectives..................................................................................... 1.1-6

SECTION 2.0 EXISTING CONDITIONS ANALYSIS AND PROBLEM IDENTIFICATION ............................................................................................. 2.1-1
2.1 Flooding Conditions Assessment and Problem Identification .................. 2.1-1 2.1.1 Watershed Model Selection ....................................................... 2.1-1 2.1.2 Hydrologic Model Development................................................ 2.1-2 2.1.2.1 Subbasin Delineations ................................................ 2.1-3 2.1.2.2 Land Use..................................................................... 2.1-5 2.1.2.3 Impervious Areas........................................................ 2.1-9 2.1.2.4 Runoff Curve Number ................................................ 2.1-9 2.1.2.5 Time of Concentration.............................................. 2.1-15 2.1.3 Hydraulic Model Development ................................................ 2.1-15 2.1.3.1 Drainage Facility Inventory ...................................... 2.1-16 2.1.3.2 Channel Cross-Section and Floodplain Definition.................................................................. 2.1-20 2.1.3.3 Storage Node Stage-Area Relationships................... 2.1-21 2.1.3.4 Model Schematic ...................................................... 2.1-22 2.1.3.5 Boundary Conditions ................................................ 2.1-24 2.1.4 Model Calibration and Verification ......................................... 2.1-25 2.1.4.1 Introduction............................................................... 2.1-25 2.1.4.2 Streamflow and Precipitation Gaging Data .............. 2.1-25 2.1.4.3 Selection of Calibration/Verification Storm Events............................................................. 2.1-27 2.1.4.4 Calibration Parameters and Results.......................... 2.1-29ii J:\DATA\737626\REPORTS\MGTPLAN\FINAL\TOC.DOC 

### TABLE OF CONTENTS (CONTINUED)

SECTION Page

2.1.5 Flooding Conditions Assessment ............................................. 2.1-37 2.1.5.1 Design Storm Events................................................. 2.1-39 2.1.5.2 Existing Flooding Conditions ................................... 2.1-39 2.1.5.3 Flooding Level of Service Criteria ........................... 2.1-41 2.1.5.4 Flooding Problem Identification............................... 2.1-43

2.2 Natural Resources Assessment and Problem Identification ..................... 2.2-1 2.2.1 Introduction ................................................................................ 2.2-1 2.2.2 Existing Conditions .................................................................... 2.2-2 2.2.3 Wildlife..................................................................................... 2.2-12 2.2.4 Endangered and Threatened Species........................................ 2.2-12
2.3 Water Quality Assessment and Problem Identification ............................ 2.3-1 2.3.1 Existing Data .............................................................................. 2.3-2 2.3.1.1 Existing Monitoring Programs.................................... 2.3-4 2.3.1.2 Other Existing Data .................................................... 2.3-6 2.3.2 Monitoring Program ................................................................... 2.3-9 2.3.2.1 Monitored Basins........................................................ 2.3-9 2.3.2.2 Hydrologic Monitoring............................................. 2.3-10 2.3.2.2.1 Water Quality .................................... 2.3-17 2.3.3 Water Quality Characteristics .................................................. 2.3-17 2.3.3.1 Petroleum Hydrocarbons .......................................... 2.3-24 2.3.3.2 Oxygen Demand ....................................................... 2.3-25 2.3.3.3 Solids ........................................................................ 2.3-28 2.3.3.4 Metals ....................................................................... 2.3-28 2.3.3.5 Nutrients ................................................................... 2.3-33 2.3.3.6 Bacteria ..................................................................... 2.3-34 2.3.4 Nonpoint Source Loading......................................................... 2.3-34 2.3.4.1 Runoff Coefficients.................................................. 2.3-37 2.3.4.2 Event Mean Concentrations ..................................... 2.3-40 2.3.4.2.1 In-Stream EMCs................................ 2.3-40 2.3.4.2.2 Exisitng Stormwater Runoff Treatment .......................................... 2.3-41 2.3.4.2.3 Landuse-Based EMCs ....................... 2.3-43 2.3.4.3 Results...................................................................... 2.3-46

SECTION 3.0 RECOMMENDED MASTER PLAN IMPROVEMENTS ................................... 3.1-1
3.1 Flood Protection, Water Quality, Habitat, Erosion and Sedimentation Improvements ................................................................... 3.1-1 3.1.1 Subwatershed 1: Spring Branch ................................................. 3.1-5iii J:\DATA\737626\REPORTS\MGTPLAN\FINAL\TOC.DOC 

### TABLE OF CONTENTS (CONTINUED)

SECTION Page

3.1.2 Subwatershed 2: Lower Stevenson Creek ................................ 3.1-22 3.1.3 Subwatershed 3: Middle Stevenson Creek............................... 3.1-30 3.1.4 Subwatershed 4: Upper Stevenson Creek................................. 3.1-35 3.1.5 Subwatershed 5: Hammond Branch ......................................... 3.1-43 3.1.6 Subwatershed 6: Lake Bellevue Branch................................... 3.1-52 3.1.7 Subwatershed 7: Jeffords Street Branch................................... 3.1-58
3.2 Human-Sourced Fecal Contamination Study ............................................ 3.2-1 3.2.1 Purpose of Further Study............................................................ 3.2-1 3.2.2 Plan of Study .............................................................................. 3.2-2 3.2.3 Dissemination of Results to End Users ...................................... 3.2-3

3.3 Recommended Watershed Maintenance Plan ........................................... 3.3-1
3.4 Public Awareness and Involvement Programs .......................................... 3.4-1 3.4.1 Adopt-a-Creek Program for Stevenson Creek............................ 3.4-1 3.4.2 Proper Use of Pesticides and Fertilizers..................................... 3.4-2 3.4.2.1 Pesticide Use........................................................... 3.4-2 3.4.2.2 Fertilizers ................................................................ 3.4-3 3.4.3 “Green” Thumb Landscaping Practices ..................................... 3.4-3 3.4.4 Florida Yards and Neighborhoods Program............................... 3.4-4 3.4.5 Storm Drain Marking Program................................................... 3.4-5
3.5 Exotic Plant Eradication Program ............................................................ 3.5-1 3.5.1 Brazilian Pepper ......................................................................... 3.5-2 3.5.2 Australian pine ........................................................................... 3.5-3 3.5.3 Melaleuca ................................................................................... 3.5-3 3.5.4 Other Exotics.............................................................................. 3.5-4 3.5.5 Estuary Restoration Plan ............................................................ 3.5-4 3.5.6 Summary and Recommendations ............................................... 3.5-5
3.6 Legal and Regulatory Framework ............................................................ 3.6-1 3.6.1 U.S. Army Corps of Engineers................................................... 3.6-1 3.6.2 U.S. Environmental Protection Agency ..................................... 3.6-2 3.6.3 Federal Emergency Management Agency .................................. 3.6-2 3.6.4 Southwest Florida Water Management District Florida Department of Environmental Protection...................... 3.6-4 3.6.5 City of Clearwater....................................................................... 3.6-4
3.7 Capital Improvement Cost Estimates ........................................................ 3.7-1iv J:\DATA\737626\REPORTS\MGTPLAN\FINAL\TOC.DOC 

### TABLE OF CONTENTS (CONTINUED)

SECTION Page

SECTION 4.0 WATERSHED MANAGEMENT PLAN PROJECT PRIORITIZATION ............................................................................................... 4.1-1

SECTION 5.0 REFERENCES AND BIBLIOGRAPHY .............................................................. 5.1-1

5.1 Drainage, Hydrology, and Flood Protection............................................. 5.1-1 5.2 Water and Sediment Quality..................................................................... 5.1-3 5.3 Natural Resources..................................................................................... 5.1-4v J:\DATA\737626\REPORTS\MGTPLAN\FINAL\TOC.DOC 

### LIST OF TABLES

Table 2.1-1 Node and Subbasin Numbering Scheme Table 2.1-2 Basin Land Use Percentages Table 2.1-3 Hydrologic Soil Group Acreages and Percentages Table 2.1-4 Runoff Curve Number Computation Matrix Table 2.1-5 Comparison of Measured and Simulated High Water Elevations Table 2.1.6 Comparison of Simulated 100-Year Peak Flows and Flood Stages Table 2.1-7 Proposed Flood Control Level of Service Criteria for Stevenson Creek Table 2.1-8 Summary of Structure Flood Protection Level of Service Deficiencies Table 2.2-1 Land Use Classification by Major Subbasin Table 2.2-2 Wildlife Observed or Expected Within the Stevenson Creek Watershed Table 2.2-3 Endangered, Threatened, or Special Concern Species Present or Potentially Present in the Stevenson Creek Watershed Table 2.3-1 Loads During Monitoring Period Table 2.3-2 Water Quality Sampling Parameters Table 2.3-3 Overall Hydrologic Conditions at Monitoring Stations Table 2.3-4 Laboratory Results Table 2.3-5 Water Quality Indices Table 2.3-6 Base Flow Oxygen Demand Table 2.3-7 Storm Event Oxygen Demand Table 2.3-8 Base Flow Solids Table 2.3-9 Storm Event Solids Table 2.3-10 Metals Table 2.3-11 Base Flow Nutrients Table 2.3-12 Storm Event Nutrients Table 2.3-13 Runoff Coefficients Table 2.3-14 In-Stream EMCs Table 2.3-15 BMP Maximum Efficiencies Table 2.3-16 Landuse-Based EMCs Table 2.3-17 Landuse-Based EMCs – Selected Literature Value Table 2.3-18 Major Basin Loads

Table 3.1-1 Maximum BMP Removal Efficiencies Table 3.1-2 Alternative Projects Water Quality Improvement Benefits Table 3.1-3 Vegetation Recommended for Planting in Varying Water Depths Table 3.3-1 Recommended Channel Maintenance Plan Table 3.5-1 Exotic Plant Species Within the Stevenson Creek Watershed Table 3.6-1 Proposed Flood Protection Level of Service (FPLOS) Criteria Table 3.7-1 Capital Improvement Project Cost Estimates
Table 4-1 Stevenson Creek Watershed Management Plan Improvement Project Ranking Matrix Table 4-2 Project Precedencevi J:\DATA\737626\REPORTS\MGTPLAN\FINAL\TOC.DOC 

### LIST OF FIGURES

Figure 1.3-1 Stevenson Creek Watershed Location Map Figure 1.3.2 Stevenson Creek Bridge Near Clearwater, Fla, 1890
Figure 2.1-1 Stevenson Creek Watershed Drainage Map and Model Schematic Figure 2.1-2 Stevenson Creek Watershed Land Use Map Figure 2.1-3 Stevenson Creek Watershed Hydrologic Soil Group Classification Map Figure 2.1-4 AdICPR Node-Reach Schematic Existing Conditions Figure 2.1-5 Locations of Monitoring Stations Figure 2.1-6 July 15, 2000 Storm Event Figure 2.1-7 Box Culverts Downstream of Kings Highway Monitoring Station Figure 2.1-8 Vegetation in Channel Downstream of Drew Street Monitoring Station Figure 2.1-9 Rating Curve for Stevenson Creek at Drew Street Figure 2.1-10 Rating Curve for Spring Branch at Kings Highway Figure 2.1-11 Stevenson Creek July 15, 2000 Calibration Storm Comparison Figure 2.1-12 Spring Branch July 15, 2000 Calibration Storm Comparison Figure 2.1-13 Stevenson Creek June 12, 2000 Verification Storm Comparison Figure 2.1-14 Spring Branch June 12, 2000 Verification Storm Comparison Figure 2.1-15 Stevenson Creek Watershed Existing Conditions 100-and 500-Year Floodplain Map Figure 2.1-16 Existing Conditions Flood Profiles Key Map Figure 2.1-17 Stevenson Creek Flood Profile, Existing Conditions Figure 2.1-18 Stevenson Creek Flood Profile, Existing Conditions Figure 2.1-19 Stevenson Creek Flood Profile, Existing Conditions Figure 2.1-20 Stevenson Creek Flood Profile, Existing Conditions Figure 2.1-21 Stevenson Creek Flood Profile, Existing Conditions Figure 2.1-22 Stevenson Creek Flood Profile, Existing Conditions Figure 2.1-23 Spring Branch Flood Profile, Existing Conditions Figure 2.1-24 Spring Branch Flood Profile, Existing Conditions Figure 2.1-25 Flooding on Hillcrest Avenue, South of Lakeview Road
Figure 2.3-1 Water Quality Monitoring Stations Figure 2.3-2 Marshall Street WWTP Location Figure 2.3-3 Septic Tank Densities Figure 2.3-4 Monitoring Stations Location and Coverage Figure 2.3-5 Land Use by Monitoring Station Figure 2.3-6 Rainfall Conditions Figure 2.3-7 Stevenson Creek Hydrologic Record Figure 2.3-8 Stevenson Creek Hydrologic Record – Low Flow Detail Figure 2.3-9 Spring Branch Hydrologic Record Figure 2.3-10 Spring Branch Hydrologic Record – Low Flow Detail Figure 2.3-11 Existing Stormwater Treatment Areas Figure 2.3-12 Existing Stormwater Treatment Coveragevii J:\DATA\737626\REPORTS\MGTPLAN\FINAL\TOC.DOC 

### LIST OF FIGURES (CONTINUED)

Figure 2.3-13 BOD Loading Rates by Subwatershed Figure 2.3-14 TSS Loading Rates by Subwatershed Figure 2.3-15 Nitrogen Loading Rates by Subwatershed Figure 2.3-16 Phosphorus Loading Rates by Subwatershed
Figure 3.1-1 Improvement Projects Location Map Figure 3.1-2 Private Crossing of Spring Branch Near Betty Lane, to be Removed Figure 3.1-3 Conceptual Plan of Project 1A.1 Figure 3.1-4 Conceptual Plan of Project 1A.2 Figure 3.1-5 Conceptual Plan of Project 1B Figure 3.1-6 Conceptual Plan of Project 1C Figure 3.1-7 Photograph of site of Project 1C Figure 3.1-8 Conceptual Plan of Project 1D Figure 3.1-9 Conceptual Plan of Project 1E Figure 3.1-10 Conceptual Plan of Project 1F Figure 3.1-11 Conceptual Plan of Project 1G Figure 3.1-12 Conceptual Plan of Project 1H Figure 3.1-13 Conceptual Plan of Project 2A Figure 3.1-14 Conceptual Plan of Project 2B Figure 3.1-15 Conceptual Plan of Project 2D Figure 3.1-16 Photograph of site adjacent to Project 2D Figure 3.1-17 Conceptual Plan of Project 3A Figure 3.1-18 Project 3A, Conceptual Plan Detail Figure 3.1-19 Stevenson Creek Channel and Trees to Remain Along Hillcrest Avenue, Between Jeffords Street and Browning Street (Project 4A) Figure 3.1-20 Failing Retaining Wall Upstream of Browning Street to be Replaced and Vegetation to be Removed (Project 4A) Figure 3.1-21 Conceptual Plan of Project 4A Figure 3.1-22 Conceptual Plan of Project 4B Figure 3.1-23 Conceptual Plan of Project 4C Figure 3.1-24 Conceptual Plan of Project 5A Figure 3.1-25 Conceptual Plan of Project 5B Figure 3.1-26 Conceptual Plan of Project 5C Figure 3.1-27 Conceptual Plan of Project 5D Figure 3.1-28 Conceptual Plan of Project 5E Figure 3.1-29 Wetland Planting Illustration Figure 3.1-30 Conceptual Plan of Project 6A.1 Figure 3.1-31 Conceptual Plan of Project 6A.2 Figure 3.1-32 Conceptual Plan of Project 6B Figure 3.1-33 Conceptual Plan of Project 7A Figure 3.1-34 Conceptual Plan of Project 7B Figure 3.1-35 Conceptual Plan of Project 7Cviii J:\DATA\737626\REPORTS\MGTPLAN\FINAL\TOC.DOC 

### LIST OF FIGURES (CONTINUED)

Figure 3.1-36 Project Conditions Flood Profiles Key Map Figure 3.1-37 Stevenson Creek Flood Profile, Project Conditions Figure 3.1-38 Stevenson Creek Flood Profile, Project Conditions Figure 3.1-39 Stevenson Creek Flood Profile, Project Conditions Figure 3.1-40 Stevenson Creek Flood Profile, Project Conditions Figure 3.1-41 Stevenson Creek Flood Profile, Project Conditions Figure 3.1-42 Stevenson Creek Flood Profile, Project Conditions Figure 3.1-43 Spring Branch Flood Profile, Project Conditions Figure 3.1-44 Spring Branch Flood Profile, Project Conditions Figure 3.1-45 Project Conditions 100-Year Floodplain Comparison
Figure 3.6-1 Yard Waste on the Banks of Upper Stevenson Creekix J:\DATA\737626\REPORTS\MGTPLAN\FINAL\TOC.DOC 

### TECHNICAL APPENDICES

VOLUME I

APPENDIX A ADICPR HYDROLOGIC INPUT DATA SUMMARY

APPENDIX B ADICPR HYDROLOGIC AND HYDRAULIC MODEL INPUT AND OUTPUT DATA FILES, CALIBRATION STORM EVENTS

APPENDIX C ADICPR HYDROLOGIC AND HYDRAULIC MODEL INPUT AND OUTPUT DATA FILES, EXISTING CONDITIONS

VOLUME II

APPENDIX D EXISTING CONDITIONS LEVEL OF SERVICE EVALUATION

APPENDIX E ADICPR HYDROLOGIC AND HYDRAULIC MODEL INPUT AND OUTPUT DATA FILES, PROPOSED CONDITIONS

APPENDIX F PROPOSED CONDITIONS LEVEL OF SERVICE EVALUATION

VOLUME III
APPENDIX G URBAN HYDROLOGY FOR SMALL WATERSHEDS (TR-55) CHAPTERS 1-3

APPENDIX H CAPITAL COST ESTIMATES
APPENDIX I WATER QUALITY MONITORING DATA

APPENDIX J BACTERIAL SOURCE TRACKING STUDY

APPENDIX K POLLUTANT LOADING MODEL INPUT AND OUTPUT DATA

Subbasin Loading – BOD Subbasin Loading – Nitrogen Subbasin Loading – TSS Subbasin Loading - Phosporusx J:\DATA\737626\REPORTS\MGTPLAN\FINAL\TOC.DOC APPENDIX L PUBLIC MEETING QUESTIONNAIRESStevenson Creek Watershed Management Plan Final Report

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### SECTION 1.0
INTRODUCTION

1.1 WHAT IS A WATERSHED MANAGEMENT PLAN?
Significant improvements in the protection and restoration of the physical, chemical, and biological integrity of the nation’s waters have been made in the last 25 years. The passage of the Clean Water Act and Safe Drinking Water Act has resulted in the control of pollution from “point sources” such as industrial waste and sewage treatment plants. However, until recently the federal laws have tended to focus on particular sources, pollutants, or water uses, and have not resulted in an integrated environmental management approach. Problems resulting from nonpoint pollution sources, habitat degradation, flooding, and wastewater overflows have not been resolved. These problems necessitate a comprehensive understanding of a complex system, and solutions that integrate disciplines and overlap political boundaries. This holistic, comprehensive approach is called a watershed management plan. The watershed management plan approach to improving the physical, chemical, and biological integrity of surface water is a three-part process. These three components include identifying the watershed’s natural boundaries, applying the latest scientific methods to identify problems, and coordinating the improvements within social, political, and economic constraints.

• A watershed boundary incorporates all the land area that contributes stormwater runoff to a particular surface water body.

• In order to identify, characterize, and evaluate the problems within a watershed, the latest scientific tools, techniques, and theory must be utilized. The proposed
solutions must include the latest and most cost-effective methods of watershed rehabilitation, integrating various scientific disciplines and expertise.

• Watersheds are seldom contained within a single political boundary. This necessitates a team approach, incorporating local, state, and federal agencies, asStevenson Creek Watershed Management Plan Final Report

1.1-2 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Final_links\SEC1.DOC well as the concerned public. Team members form a partnership and work together toward a common goal based on shared information, and an understanding of the priorities and responsibilities of all parties.

1.2 THE BENEFITS OF A WATERSHED MANAGEMENT APPROACH
Coordination of a watershed management plan is beneficial for environmental, financial, social, and administrative reasons. Managers from all levels of government
will be better able to understand and reduce the cumulative effects of human activities in a watershed on pollution control, increased surface water runoff, fish and wildlife protection, drinking water protection, and other water resource programs when allowed to view the “big picture,” rather than just their portion of the watershed. The most critical problems are identified, and priorities can then be set to allocate the available financial
and human resources.

The watershed management approach also can result in significant savings by improving communication and coordination, which will in turn reduce costly duplication of efforts and conflicting actions. This cooperation gives an active voice in resource management to the people who depend on the area resources for their recreation, health, and overall quality of life.

1.3 THE STEVENSON CREEK WATERSHED
1.3.1 Watershed Location And Description
The Stevenson Creek Watershed, the largest and most urbanized watershed within the City of Clearwater, drains 6,286 acres in west central Pinellas County (refer to Figure
1.3-1 ). Of this area, 4,057 acres (65 percent) are within the Clearwater city limits. The remaining 35 percent of the basin is within the City of Dunedin (1,287 acres or 20%), unincorporated Pinellas County (859 acres or 14%) and the City of Largo (83 acres or about 1%).Stevenson Creek Watershed Management Plan Final Report

1.1-3 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Final_links\SEC1.DOC ( FIGURE 1.3-1 )Stevenson Creek Watershed Management Plan Final Report

1.1-4 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Final_links\SEC1.DOC Stevenson Creek discharges to Clearwater Harbor. The majority of the creek has been channelized or otherwise altered, and little of the historic floodplain remains intact. Land uses within the basin are predominantly medium- and high-density residential, commercial, and open space. Approximately 90 percent of the watershed has been developed, and the vast majority of the development occurred prior to the implementation of regulatory requirements for floodplain preservation, environmental protection, stormwater treatment and attenuation. Several developments have been constructed within the creek’s floodplain and have experienced severe flooding. In addition, the creek and its tributaries experience moderate to severe erosion problems due to steep embankments, improper maintenance, highly erodable soils, and inadequate right-of-way.

1.3.2 Basin History
Land use changes within the Stevenson Creek Watershed over the last 100 years have been significant. A cursory history of the changes within the basin can be determined from a review of historic archives and aerial photography. Aerial photography dated

Figure 1.3-2 Stevenson Creek Bridge, near Clearwater, Fla., 1890. (Photo courtesy of City of Clearwater Public Library)Stevenson Creek Watershed Management Plan Final Report

1.1-5 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Final_links\SEC1.DOC 1926 shows the Stevenson Creek Estuary to be much wider than it is now, approximately 1,000’ wide at the mouth, compared to only 700’ today. Prior to 1926, the original 19 th Century wooden bridge connecting Clearwater to Dunedin, which spanned the entire estuary (Figure 1.3.2), was replaced with an earthen causway with a much narrower open span for Edgewater drive. The 1926 photography depicts a relatively intact floodplain and associated wetlands, with adjacent land uses predominantly agricultural, under development, or undeveloped. Some channelization had occurred within Spring Branch,
and within Stevenson Creek between Drew Street and Druid Road. The east-west
railroad that bisects the basin as well as the coastal railroad that borders the basin to the east had already been constructed. Most of the population at the time was concentrated within a 1⁄2-mile strip of land bordering Clearwater Harbor. Effects of the 1920’s land boom are evidenced by the numerous subdivision streets with sidewalks constructed throughout the interior portions of the watershed. However, by 1942, only a few homes had been built within these interior subdivisions. During the post-war boom of the 1950’s and 1960’s, the majority of the watershed was built out within these medium density residential subdivisions and commercial developments. Also during this period, portions of the Stevenson Creek estuary were filled in along its southern banks.

By 1974, over 95% of the developable area in the watershed had been developed or set aside as parks and golf courses, and the full length of Stevenson Creek and its tributaries had been channelized. Very little of the creek’s floodplain and associated wetlands remained intact. With the exception of the two golf courses bordering the creek, almost the entire floodplain of Stevenson Creek had been developed.

The majority of the land use changes within the watershed have been detrimental to water quality, flood protection, and wildlife habitat. Urban development has resulted in greater stormwater runoff volumes and peak flow rates, as well as the transport of sediments and pollutants into the creek. The effects of land use changes within the
watershed on wildlife habitat are described in Section 2.2.Stevenson Creek Watershed Management Plan Final Report

1.1-6 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Final_links\SEC1.DOC In response to severe flooding experienced within the watershed as a result of a storm event in July of 1987, a flood control study was commissioned by the City of Clearwater in April of 1988. In the study, a three-phase flood control project was developed for the main channel of Stevenson Creek. To date, two of the three phases of the project have been constructed, consisting of the main channel segments between Betty Lane and Jeffords Streets. The third phase, which included segments upstream of Jeffords Street, has not been constructed, primarily because of environmental concerns. Because the objective of the original study was focused on flood control on the main stem of Stevenson Creek, water quality and environmental enhancement/ protection needs and problems were not addressed. The tributaries and secondary drainage systems were not analyzed in detail, and the Spring Branch portion of the watershed was excluded from the original study.

1.4 PROJECT OBJECTIVES

The Stevenson Creek Watershed Management Plan has been initiated as the result of a cooperative agreement between the City of Clearwater and the Southwest Florida Water Management District (SWFWMD). Drainage improvements for enhanced stormwater quality and quantity are identified within the City of Clearwater Comprehensive Plan as
areas of service deficiencies which must be addressed. Section 16.2 of the Plan states:

Objective – The City of Clearwater shall continue to develop watershed management plans which should seek to identify, evaluate, and implement the most cost effective and cost efficient programs for stormwater management, including stormwater quantity and quality... In addition to the municipal and regulatory involvement, the residents within the watershed have had an active role in the shaping of the watershed plan. Numerous suggestions and comments concerning management actions have been received from residents and other property owners in the area through documented reports and through the public meeting process. Public involvement is a very important component of thisStevenson Creek Watershed Management Plan Final Report

1.1-7 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Final_links\SEC1.DOC plan; watershed improvements cannot be realized without the willingness and cooperation
of residents within the watershed boundaries.

The basic purpose of the management plan is to identify the causes and sources of problems such as flooding, water quality degradation, excessive channel erosion, and loss of riparian habitat. Once these problems were identified, recommendations were made to solve or alleviate the problems. Recommendations include capital improvement projects (i.e. stormwater infrastructure improvements), creation and restoration of habitat, maintenance strategies, pollution reduction programs, and public involvement and awareness. This management plan will be used as a tool in the planning, regulation, and management of natural resources and future development, and as a basis for determining and prioritizing capital improvements by the City of Clearwater and SWFWMD. The initial phase to meet this objective included a comprehensive analysis of the watershed in order to identify the problems to be addressed.

The first task in the analysis process was to collect, record, and organize all potentially useful existing information relevant to the watershed. Once the data were collected and analyzed, any data deficiencies were noted and the missing data were gathered. The information-gathering process included such activities as a literature search and review of existing data, field reconaissance and ground-truthing of aerial photography, ground surveying, streamflow monitoring, surface water sampling and testing, habitat assessment, interviews with City operations personnel, and input from
residents of the watershed.

The second task included a comprehensive stormwater quantity and quality modeling analysis of the watershed. The model was used to develop a comprehensive watershed management plan with recommendations for site-specific physical improvements for flood protection, habitat improvement, and water quality improvement. This planning phase included a conceptual design sufficient to determine permit and construction feasibility, cost effectiveness, and property acquisition requirements. At the end of theStevenson Creek Watershed Management Plan Final Report

1.1-8 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Final_links\SEC1.DOC planning phase, meetings of the Management Plan participants will be held to discuss a course of action for proceeding to the implementation phase.

The following sections describe the methods used to gather the necessary data, how the data were applied in the development of the watershed plan, and the recommended improvements produced through the cooperative efforts of the project team.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC 

### SECTION 2.0
WATERSHED ASSESSMENT AND PROBLEM IDENTIFICATION

This section of the Watershed Management Plan describes the existing flooding, natural resources, and water quality conditions within the Stevenson Creek Watershed, and the watershed assessment methods used. The first portion of the section addresses the primary concern of those living within the watershed; the periodic flooding of roads and buildings. The second portion describes the natural resources available within the watershed, such as the location and quality of wildlife habitat. The third portion details the water quality assessment, including the results of the water quality sampling program and pollutant loading modeling.

2.1 FLOODING CONDITIONS ASSESSMENT 2.1.1 Watershed Model Selection
This section details the methods and procedures used to perform the assessments of watershed hydrologic and hydraulic conditions. An important component of this Watershed Management Plan for Stevenson Creek is an assessment of the current flood protection level of service provided throughout the watershed. A thorough understanding of basinwide hydrologic and hydraulic processes is necessary to determine the most effective means of alleviating the identified flooding problems. The watershed model prepared for this Management Plan was used as a planning tool to assess the existing flooding problems and susequently, to optimize the flood protection benefits of the proposed improvements.

The Advanced Interconnected Channel and Pond Routing Model, Version 2.2 (AdICPR) was chosen for the hydrologic and hydraulic modeling analysis, in part because of its ability to mathematically represent the time-dependent processes that govern flow and stage in low-relief coastal watersheds such as Stevenson Creek. Furthermore, it wasStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC necessary to select a model which has been accepted by the Federal Emergency Management Agency (FEMA) for flood insurance studies, since the results of the analysis will be used to support a request for revision of the applicable FEMA flood insurance rate

maps.
2.1.2 Hydrologic Model Development
The hydrologic model used for this study is the SCS Runoff Curve Number (CN) and Unit Hydrograph Method contained within AdICPR. This method computes a runoff (flow) versus time relationship (hydrograph) for each subbasin, given a set of hydrologic input parameters.

Hydrologic parameters required for the SCS Runoff CN and Unit Hydrograph Method include the following:

• Subbasin drainage area

• Subbasin time of concentration (TC)

• Subbasin percent directly connected impervious area (DCIA)

• Subbasin weighted runoff curve number (CN) for areas outside of DCIA

• Unit hydrograph shape factor

• Rainfall data
A description of the methodologies used to derive each of these hydrologic parameters follows in the remainder of this section.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC 2.1.2.1 Subbasin Delineations

The Stevenson Creek watershed drainage area consists of approximately 9.82 square miles (6,286 acres) of moderately sloping terrain in west central Pinellas County that discharges to Clearwater Harbor. To provide the level of detail that was deemed necessary to analyze the primary drainage facilities within the heavily urbanized Stevenson Creek watershed, the basin was divided into a total of 307 discrete subbasins that range in size from 1 to 197 acres. The average subbasin size is 20.5 acres. The delineation of individual subbasins was dictated to a large extent by the complexity of the drainage network itself and the need to define the contributing drainage area to modeled elements of the conveyance system.

Approximately 20% and 14% of the watershed area lies within the City of Dunedin and unincorporated Pinellas County, respectively. Although these governmental bodies are not official participants in the Management Plan, approximately the same level of hydrologic and hydraulic model detail was applied in these areas. This was deemed necessary in order to accurately quantify the volumes and peak rates of runoff contributed to Stevenson Creek and its tributaries by these areas.

Figure 2.1-1 in the attached map pocket shows the delineation of the Stevenson
Creek watershed into its 307 individual subbasins. Subbasin ID numbers consist of the letter “B” followed by a four-digit number. The four-digit number generally coincides
with the ID number of the node at the outlet of the subbasin. In cases where two subbasins drain to the same node, the second subbasin has an ID number equal to the node number plus one. Nodes and subbasins were generally numbered in order increasing in the upstream direction. For convenience, the 307 individual subbasins were aggregated into eight major subbasins, or “subwatersheds”. Subbasin and node numbers are grouped according to the subwatershed in which they lie, as follows:Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC Table 2.1-1 Node / Subbasin Numbering Scheme

Subwatershed Node / Subbasin ID Range
Lower Stevenson Cree k 0000 – 0499

Lower Spring Branch 0500 – 0999 Upper Spring Branch 1000 – 1999

Hammond Branch 2000 – 2999 Middle Stevenson Creek 3000 – 3499 Lake Belleview Branch 3500 – 3999 Upper Stevenson Creek 4000 – 4139 Jeffords Street Branch 4140 – 4999

The means of defining subbasin boundaries employed a number of sources of information and methods. The principle source was 1”=200’ topographic aerial photographic mapping of the watershed provided by SWFWMD. This mapping shows overland topography, thus indicating direction of overland flow. However, because much of the watershed is developed, with a variety of residential, commercial, industrial, and institutional developments, man-made secondary drainage systems comprising swales, gutters, storm sewer systems, ditches, and detention ponds have interrupted the natural overland flow patterns within the basin and, in many cases, diverted storm runoff in directions that are not readily apparent from inspection of the topographic mapping. It is also important to note that the SWFWMD mapping within the basin is, for the most part, over 20 years old. Therefore, new development that has occurred within the watershed since that time does not appear on these maps, and drainage patterns and grades in certain areas have been altered since that time due to this new development.

The City of Clearwater drainage atlas maps provided detailed layouts of the secondary drainage systems within the incorporated city portions of the watershed and proved to be of immense value for assisting in the delineation of the subbasins. In addition, record drawings of permitted stormwater management facilities within the basin
on file with the SWFWMD were reviewed and referenced in the subbasin delineationStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC process as a means of defining the drainage systems and drainage areas for newer developments that did not show up on any of the previously listed information sources.

The final check of subbasin delineations was field reconnaissance of the watershed to confirm the initial boundaries and to inspect the drainage facilities and conditions in the basin firsthand, to investigate areas where there was no information available from the previously listed sources, and to resolve discrepancies where there was a conflict between different sources of information regarding drainage facilities.

2.1.2.2 Land Use
Existing land use conditions within the Stevenson Creek watershed were defined with the aid of a Geographic Information System (GIS) land use coverage data file provided by SWFWMD. For convenience, the 26 different land use classifications that were defined in the SWFWMD land use coverage of the basin were consolidated into the following 13 categories:

• Commercial

• Cropland and Pastureland

• Forest

• Low Density Residential

• Medium Density Residential

• High Density Residential

• Industrial

• Institutional

• Open Land and Range Land

• Specialty Farms

• Transportation, Communications and Utilities

• Water

• Wetlands

For the purposes of this study, the medium density residential classification was redefined to include residential areas containing between 2 and 5 dwelling units per acre. In the SWFWMD classification system, this was considered to be high density. It was deemed necessary to reclassify these areas, because the actual (measured) impervious areaStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC percentages in these areas are more consistent with literature values cited for medium density residential. The significance and determination of impervious area is described in the next section. This change increased the percentage of the basin classified as medium density residential from none to the majority of the basin. Areas of multi-family developments (i.e., apartment and condominium complexes) remained classified as high density residential.

These land use coverages were then field-truthed by examination of recent aerial photography of the basin and comparing to the map to confirm that both the classifications and the areal extent are properly represented. Many adjustments were required. The majority involved the delineation of the developed portions of areas that were designated as institutional or transportation/utilities in the SWFWMD land use coverage to separate them from open land areas that occurred within these parcels to various degrees. The institutional land use classification includes parcels such as nursing homes, schools, churches, hospitals, auditoriums, and cemeteries, which can vary over a wide range in their degree of imperviousness. For the same reasons, significant open land areas within industrial and commercial tracts were delineated to segregate them from the actual developed portions of the parcels. Other changes were required in order to update the mapping to account for recent development. The resultant hydrologic land use classification map of the Stevenson Creek watershed that was used for model development purposes is shown in Figure 2.1-2 . Table 2.1-2 presents a composite breakdown of land use acreages and percentages in the Stevenson Creek Watershed.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC Table 2.1-2 Basin Land Use Percentages

Land Use Classification Total Area (acres) Percentage of Basin (%) Commercial 610 9.7 Cropland and Pastureland 5 0.1 Forest 50 0.8 Low Density Residential 56 0.9 Medium Density Residential 3861 61.4 High Density Residential 459 7.3 Industrial 42 0.7 Institutional 182 2.9 Open Land and Range Land 573 9.1 Specialty Farms 10 0.2 Transportation, Communications, and Utilities 170 2.7 Water 205 3.3 Wetlands 63 1.0 Total 6286 100.0Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC ( Figure 2.1-2 )Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC 2.1.2.3 Impervious Areas

Impervious areas are those surfaces such as rooftops and pavement, which impede the infiltration of runoff into the soil. Directly connected impervious area (DCIA) is defined as those impervious areas that are connected directly to the subbasin outfall (i.e., node) without flow occurring over a pervious surface. In the AdICPR model, DCIA is an optional parameter which, if used, is treated as a separate subarea within each subbasin. A separate hydrograph is computed for the DCIA, which is not subject to any initial abstraction (i.e., infiltration). Any impervious area which is not directly connected to the subbasin outfall is then used in computing a weighted curve number (CN) as described in
the next section.

For the Stevenson Creek watershed model, literature values of total percent imperviousness for the different land use classifications were utilized. Measurements of impervious coverage within representative samples of each land use classification were conducted using aerial photography, in order to confirm the literature values. The split between DCIA and non-directly connected impervious areas was determined through the model calibration process, as discussed in subsequent sections.

2.1.2.4 Runoff Curve Number
By superposition, the hydrograph computed using the DCIA is added by AdICPR to the hydrograph computed using a weighted runoff curve number (CN). This results in a single composite hydrograph, which is then input into the corresponding node of the hydraulic model.

In the SCS method, the CN is a function of S, the potential maximum infiltration after runoff begins (in inches):

CN = 1000 S+10 The standard SCS method uses the following empirical relationship:
I a = 0.2SStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC Where I a is the initial abstraction, which includes all losses before runoff begins. It includes water intercepted by vegetation, shallow depression storage, evaporation, and infiltration. For design storm conditions in watersheds containing sandy soils, experience and literature on the subject indicate that infiltration losses comprise the majority of the
initial abstraction.
The weighted CN is therefore primarily a function of the non-directly connected impervious coverages (based on land use), and the infiltration capacity of the soils. For this study, a land use/ hydrologic soils group intersection analysis was performed using the ArcView/ArcInfo Geographic Information Systems (GIS) software.

The Soil Conservation Service (SCS) (now the Natural Resources Conservation Service) of the U.S. Department of Agriculture has mapped soils in Pinellas County in its publication “Soil Survey of Pinellas County, Florida” (1972). This soil survey also provides generalized information on the hydrologic properties of the soil classifications.

A standard method of soils classification is the hydrologic soils group. Soils are grouped into four hydrologic soil groups A through D. These groups are commonly used in hydrologic analyses to estimate infiltration rates and soil moisture capacities. Descriptions of these soil groups are:
Hydrologic Soil Group A (low runoff potential): Soils that have high infiltration rates even when thoroughly wetted and a high rate of water transmission. Typical maximum infiltration rate of 10 inches per hour when dry and 0.5 in/hr when
saturated.
Hydrologic Soil Group B (moderately low runoff potential): Soils that have moderate infiltration rates when thoroughly wetted and a moderate rate of water transmission. Typical maximum infiltration rate of 8 in/hr when dry and 0.4 in/hr
when saturated.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC Hydrologic Soil Group C (moderately high runoff potential): Soils that have a slow infiltration rate when thoroughly wetted and a slow rate of water transmission. Typical maximum infiltration rate of 5 in/hr when dry and 0.25 in/hr when saturated.
Hydrologic Soil Group D (high runoff potential): Soils having very slow infiltration rates when thoroughly wetted and a very slow rate of water transmission. Typical infiltration rate of 3 in/hr when dry and 0.10 in/hr when saturated.
In many cases in Florida, dual hydrologic soil group classifications (A/D or B/D) are assigned to soils that, during the wet season, are saturated throughout much of the soil column due to a high surficial water table. Thus, during this time of year, infiltration is impeded and the soil acts as a D soil. However, during the rest of the year, when the water table is lower, the soil acts as an A or B soil.

Figure 2.1-3 presents a composite hydrologic soil group classification map of the Stevenson Creek watershed. It can be seen from the map that soils within the basin are predominantly classified as A and B/D. Group A soils occur on upland sand ridges and group B/D soils occur on low lying areas and flat areas with poor natural drainage around natural waterbodies and wetlands. A composite breakdown of the hydrologic soil group acreage and percentages for the basin is as follows:

Table 2.1-3 Hydrologic Soil Group Acreages and Percentages

Hydrologic Soil Group Total Area (acres) Percentage of Basin (%)
A 2424 38.6 B 21 0.3 B/D 2158 34.3

C 1114 17.7 D 370 5.9 Water 199 3.2 Total 6286 100.0Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC (Figure 2.1-3 )Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC The following table presents the Runoff Curve Number Computation Matrix used by the ArcView/ArcInfo Geographic Information Systems (GIS) software to compute the overall area-weighted curve number for each subbasin. In this method, a unique curve number is assigned to each possible combination of hydrologic soil group and land use category. The computer program then computes an area-weighted value based on the percentages of these soil/land use combinations found within the particular subbasin.

Table 2.1-4 Runoff Curve Number Computation Matrix

Land Use Classification Hydrologic Soil Group Runoff Curve Number

Commercial A 89 Commercial B 92 Commercial C 94 Com m ercial D 95 Commercial B/D 94 Cro p land and Pastureland A 49 Cro p land and Pastureland B 69 Cro p land and Pastureland C 79 Cro p land and Pastureland D 84 Cro p land and Pastureland B/D 79 Fores t A 36 Fores t B 60 Fores t C 73 Fores t D 79 Fores t B/D 73 Hi g h Densit y Residential A 77 Hi g h Densit y Residential B 85 Hi g h Densit y Residential C 90 Hi g h Densit y Residential D 92 Hi g h Densit y Residential B/D 90 Industrial A 81 Industrial B 88 Industrial C 91 Industrial D 93 Industrial B/D 91 Institutional A 81 Institutional B 87 Institutional C 91Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC Table 2.1-4 (Continued) Runoff Curve Number Computation Matrix

Land Use Classification Hydrologic Soil Group Runoff Curve Number

Institutional D 93 Institutional B/D 91 Low Densit y Residential A 50 Low Densit y Residential B 65 Low Densit y Residential C 76 Low Densit y Residential D 87 Low Densit y Residential B/D 76 Medium Densit y Residential A 61 Medium Densit y Residential B 75 Medium Densit y Residential C 83 Medium Densit y Residential D 86 Medium Densit y Residential B/D 83 O p en Land and Ran g eland A 39 O p en Land and Ran g eland B 61 O p en Land and Ran g eland C 74 O p en Land and Ran g eland D 80 O p en Land and Ran g eland B/D 74 S p ecialt y Farms A 59 S p ecialt y Farms B 74 S p ecialt y Farms C 82 S p ecialt y Farms D 86 S p ecialt y Farms B/D 82 Trans p ortation, Communications, and Utilities A 78 Trans p ortation, Communications, and Utilities B 83 Trans p ortation, Communications, and Utilities C 88 Trans p ortation, Communications, and Utilities D 90 Trans p ortation, Communications, and Utilities B/D 88 Wate r W 100 Wetland A -D 98 Wetland W 100 Overall CN values were calculated for each subbasin using the above matrix and GIS intersection analysis. In order to derive the percent impervious area for each subbasin, a “pervious area” CN was created for each subbasin based only on its soil type and its pervious area land use. For example, medium density residential was shown as open land and range land to represent the lawns and open space. By comparing the overall CN toStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOCthe pervious area CN, a total percent impervious area for each subbasin was backcalculated using using an excel spreadsheet. Then, based on the percent of total impervious as DCIA (derived through the calibration process), the curve numbers were recomputed using only the unconnected impervious area. The excel spreadsheet used for this analysis is included in Appendix A.

2.1.2.5 Time of Concentration
The time of concentration (TC) is a measure of the time scale of the runoff hydrograph and is a function of subbasin slope and surface roughness. Conceptually, it is the time required for the hydrologically most distant point in the subbasin to begin contributing flow to the subbasin outlet, following the commencement of rainfall. The
time of concentration for each subbasin within the Stevenson Creek watershed was computed using the Kinematic Wave approach as outlined in SCS Technical Release 55. In this method, the TC is computed as the sum of travel times for sheet flow, shallow concentrated flow, and open channel flow. The reader is referred to chapter 3 of SCS Technical Release 55 in Appendix E for further details on this method.

2.1.3 Hydraulic Model Development
The hydraulic model used for this study was AdICPR, which contains a onedimensional unsteady flow hydraulic routing model. This model uses a node-reach representation of the drainage system. AdICPR receives hydrograph input at specific nodes by file transfer from the hydrologic model. The model performs dynamic routing of stormwater flows through the defined storm drainage system to the points of outfall in the receiving waterbody. The program will simulate branched or looped networks; backwater due to tidal or non-tidal conditions; free-surface flow; pressure flow or surcharge; flow reversals; flow transfer by weirs, orifices, and pumping facilities; and storage. Types of reaches that can be simulated include pipes, weirs, open channels of regular or irregular cross section, bridges, and drop structures (weir and pipe in series).Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC Simulation output takes the form of water surface elevations and discharges at each node and reach within the model network, reported at user-specified time intervals.

2.1.3.1 Drainage Facility Inventory
The initial and most important step in the development of the hydraulic model of the Stevenson Creek watershed was the inventory of the drainage structures along the primary drainage system. This information provides the foundation for the model representation of the hydraulic system. The drainage facility inventory of the study area was compiled from an array of sources and methods. Hydraulic data for culverts, storm sewers, bridges, control structures, and watercourse cross sections were obtained from city drainage atlas mapping, development plans, roadway plans, previous studies, and field surveys. Data collected included elevations, lengths, dimensions, construction materials, channel vegetation, structure entrance and exit conditions, and other pertinent features. The following is a discussion of the sources and methods used to collect this
information:

Existing Maps, Plans and As-Builts

The City of Clearwater maintains 1”=100’ scale drainage atlas maps that include considerable detail of locations, dimensions, and invert elevations of drainage facilities located within the incorporated city limits. These maps are periodically updated as new development occurs or new information is obtained, and provide a great deal of detail within the areas they cover, including secondary storm sewer systems. Invert elevations are not always indicated, however, and there is no information shown for the unincorporated areas within the basin. The City of Dunedin storm atlas provides a similar degree of mapping of drainage facilities.

It was previously noted that the SWFWMD stormwater management facility permit
files were researched to collect information on facilities constructed within the Stevenson Creek watershed since the inception of the permit regulations in 1984. The City of Clearwater, Pinellas County, and the City of Dunedin also provided record drawings ofStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC drainage and flood control works that have been constructed within the basin. In addition, the Stevenson Creek Sediment Evaluation with Cross Sections completed by the City of Clearwater in August 1999 provided many of the irregular cross sections used in the model. The following list contains the most noteworthy plans, maps and as-builts used as sources of existing hydraulic model input data used in the development of the Stevenson Creek hydraulic model:

• Pinellas-Anclote Basin Aerial Photography with Contours. March 1977, May 1979, and December 1985, Southwest Florida Water Management District.

• City of Clearwater Stormwater Atlas. 1996-1999, City of Clearwater Public Works Administration, Engineering.

• City of Dunedin Stormwater Atlas. 1999, City of Dunedin Engineering Section

• Stevenson Creek Sediment Evaluation with Cross Sections. August 1999, City of Clearwater Public Works Administration, Engineering.

• Spring Branch of Stevenson’s Creek Drainage Basin Field Survey Notes. March 1979, Pinellas County Engineering Department.

• Stevenson’s Creek Watershed Channel Improvements, Phase 1 As-Built Plans. February 1993, W.K. Daughtery Consulting Engineers, Inc.

• Stevenson Creek – Channel Improvements – Phase II Plans. March 1995, Camp, Dresser and McKee.

• Highland Avenue Stormwater Improvements As-Built Plans. November 1998, HDR Engineering, Inc.

• The Mall From Union Street to the South Terminus Record Drawings. July 1994, Seminole Engineering.

• 3 rd Avenue Drainage Improvements Record Drawings. March 2000, City of Dunedin Department of Public Works and Utilities.

• Villas at Renaissance Square (Old Sunshine Mall) Construction Plans. January 1999. Florida Design Consultants, Inc.

• Various MSSW and ERP permit information on file with the Southwest Florida Water Management District.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC Previous Studies
The Stevenson Creek watershed has been the subject of several stormwater management studies in the last 20 years that served as valuable sources of information on the existing structures and channels along the primary drainage system of the basin. These sources were used to varying degrees to supplement and/or confirm other sources to provide the required AdICPR model input data to describe the primary drainage system
and facilities in the watershed.

The first of these studies was a storm drainage basin study conducted in 1981 by Henningson, Durham, and Richardson, Inc. (HDR) for Pinellas County. This study was a part of the countywide comprehensive stormwater drainage master plan, which has since been adopted within the Pinellas County Comprehensive Plan in its Drainage Element (1989). To conduct its study of the Stevenson Creek basin, HDR used the SCS TR-20 computer model for hydrologic analysis. Runoff hydrographs were developed for each subbasin in the watershed, using existing and comprehensive future land use, with the 25- year, 6-hour duration storm event of 5.5 inches total precipitation used as the basis for design. The U.S. Army Corps of Engineers HEC-2 model was used to perform backwater analyses to determine flood profiles for each of the design storm events. The Pinellas County Study also served as the basis for a Master Drainage Plan for the Spring Branch Watershed, prepared in 1983 by the City of Dunedin Public Works Department. For this study, Parsons ES used selected information from the original Pinellas County field survey notes as needed to augment the structure and cross section information within the City of Dunedin portion of Spring Branch.

In 1988, a Preliminary Master Plan for Stevenson Creek was prepared by W.K. Daughtery, Inc. for the City of Clearwater. In the 1988 study, a three-phase channel improvement project was recommended for the main channel of Stevenson Creek. The modeling methodology employed TR-20 to generate runoff hydrographs for the 5-, 10-, 25-, 50-, and 100-year, 24 hour duration storm events. The hydrographs were then input to a one-dimensional, steady-flow water surface profile model (WSP-2) to calculate theStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC flood elevations. In 1990-1991, Camp, Dresser, and McKee, Inc. (CDM) prepared a limited re-study of Stevenson Creek under which the TR-20/WSP-2 model was converted to AdICPR, Version 1.4. The AdICPR model was then used to support the detailed design of portions of the preliminary master plan project, as well as a FEMA Letter of Map Revision (LOMR). This re-study by CDM also included analysis of alternatives for floodplain enhancements within the Glen Oaks Golf Course. To date, two of the three phases of the original project have been constructed, consisting of the channel segments between Betty Lane and Jeffords Streets. The previously referenced as-built plans for these channel improvements were relied upon extensively in the development of the
model.

The following list summarizes the previous and on-going studies of the Stevenson Creek Watershed which were consulted in the development of this watershed management plan:

• Summary Report for Stevenson’s Creek Preliminary Master Plan. August, 1988, W.K. Daughtery Consulting Engineers, Inc.

• City of Clearwater 1997 Watershed Management Plan, Volume II. Post, Buckley, Schuh & Jernigan

• Stevenson Creek Channel Improvements, Phase 2 – Joint Dredge and Fill Permit Application. April 1992, Camp, Dresser, and McKee

• Technical information submitted to FEMA in support of request for Stevenson Creek Letter of Map Revision. May 1998, Camp, Dresser and McKee.

• Pinellas County Storm Drainage Basin Study Technical Appendix – Spring Branch of Stevenson Creek Basin and Coastal Zone 4 Basin. October 1981, Henningson, Durham & Richardson, Inc.

• Repetitive Loss Report – City of Clearwater, FL. October 1998, FEMA

• Master Drainage Plan: Spring Branch Watershed. September, 1983, City of Dunedin Public Works Department, Water Resources.

• Stevenson Creek Sediment Characterization and Removal Feasibility Study - Final Report. August 1998, BCI, Inc.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC • Stevenson Creek Estuary – Preliminary Restoration Plan. October 2000, U.S. Army Corps of Engineers, Jacksonville District Field Reconnaissance and Field Survey Field reconnaissance of the Stevenson Creek watershed was conducted by driving and walking the basin to determine drainage patterns, map drainage facilities, measure facility dimensions inspect the condition of the drainage facilities in the field, assemble a photographic log of drainage facilities, and to confirm information collected from the previously discussed sources and/or resolve differences between different sources.

Following completion of the field reconnaissance, Parsons ES developed a field survey plan to establish the size, location, dimensions and inverts of drainage structures, and to define current stream channel and floodplain cross sections within the Stevenson Creek watershed based on the specific needs of the hydraulic model. The emphasis of this survey was placed on areas within the basin where there were no available sources of as-built record drawings and surveys. The survey program was conducted by Harry Marlow, Inc., under the direction of Parsons ES. In addition, the City of Dunedin conducted limited surveys of selected structures and cross sections for use in the portion of the model that lies within the limits of the City of Dunedin.

2.1.3.2 Channel Cross Section and Floodplain Definition
A variety of sources of channel cross section and drainage structure data were utilized in the formulation of the AdICPR model. Parsons ES used what was judged to be the most current, detailed, and representative source of information available for anyparticular reach of the open channel system. In addition, the extension of channel crosssections into the floodplain regions of the Stevenson Creek floodway was necessary for many of the surveyed cross-sections obtained from the various sources. In these instances, the SWFWMD one-foot contour topographic maps were used to scale off the floodplain extensions.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC One of the most important requirements of the hydraulic model representation of open channel reaches is the selection of an appropriate channel roughness coefficient, or Manning’s n, value. This is an index of the resistance to flow, primarily due to friction, that is dependent upon factors such as the extent and type of channel vegetation, channel bottom material, channel irregularity, channel alignment, obstructions, and depth of flow. Selection of an appropriate Manning’s n value for a particular channel reach is a subjective procedure that is facilitated by past experience. As a first step in this procedure, Parsons ES personnel took color photographs of all open channel reaches within the model. Published guides and past modeling experience were then applied in the selection of channel and floodplain Manning’s n values. These values were either confirmed or adjusted during the model calibration process using the rating curves of the streamflow gaging stations and the measured high water elevations.

2.1.3.3 Storage Node Stage-Area Relationships
In order to represent the attenuating effects of storage on the hydrographs computed by the hydrologic model, it is important that all significant stormwater storage areas and their hydraulic controls features be well defined within the model. This is especially important in the Stevenson Creek watershed where much of the drainage throughout the basin is controlled by lakes (man-made and natural) and natural depression areas. The AdICPR model allows the user to specify a variable stage-area relationship at any model node that defines the storage properties at that point, be it a pond, lake, wetland, or other water body.

In the development of the Stevenson Creek watershed hydraulic model, Parsons ES used, where available, record drawings and permits as a means of establishing stage-area relationships of constructed stormwater management facilities. For all others, including the natural lakes, ponds, and wetlands within the watershed, the stage-area relationships were determined by direct measurement of SWFWMD one-foot topographic maps with a planimeter.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC 2.1.3.4 Model Schematic
The hydraulic model (AdICPR) of the Stevenson Creek watershed consists of a network of open channel segments, culverts, bridges, storm sewers, weirs, lakes, ponds, and wetlands that compose the primary drainage system within the basin. AdICPR uses a link-node concept to idealize the “real world” drainage system. A node is a discrete location in the drainage system where conservation of mass (continuity) is maintained. Links, or “reaches” are the connections between nodes and are used to convey water through the system. The entire network of nodes and reaches forms the hydraulic model network and serves as the computational framework for AdICPR.

The first step in development of a model schematic was to identify the primary drainage system and all drainage facilities within it. This task was accomplished through the research and review of all available sources of information that have been previously described, and through field reconnaissance of the entire watershed. All such information was compiled and a watershed drainage map developed which depicts the primary drainage system. Figure 2.1-1 , included in the attached map pocket, presents the drainage map of the Stevenson Creek watershed and the model node locations which were used to define the primary conveyance network of the basin. General guidelines which were followed in development of the model schematic are:

• Nodes are required at the upstream and downstream ends of any structure (e.g. culvert, bridge, weir, etc.).

• Storage elements (ponds, lakes, wetlands, etc.) are specified as nodes.

• Nodes are located at tributary confluence locations.

• Nodes are placed at locations where there is a major surface water inflow to the conveyance system.

• Points of change in channel geometry and/or slope are specified as node
locations.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC • Nodes are added at locations within the network to define the hydraulic gradeline in greater detail.
When constructing a model network, unique identifiers must be assigned to all nodes and reaches. The node-numbering scheme is the same as the subbasin numbering scheme previously described, except that node identifiers begin with the letter “N”. By convention, the identification of a reach between two nodes is the same as the name of the upstream node. Reach identifiers begin with a letter prefix pertaining to the type of
reach as follows:

Reach Type Prefix
Channel C

Pipe P
Weir W Drop Structure DS Bridge BR
Overland Flow Channel COF

Overland Flow Weir WOF

A node-reach schematic of the AdICPR model of the Stevenson Creek watershed is provided in Figure 2.1-4 , contained within the attached map pocket. This schematic represents the hydraulic network as it is modeled. Storage nodes and type of reaches are indicated as they are represented within the AdICPR model. The schematic includes “overflow” reaches which model the overland flow paths that floodwaters can follow when flow rates exceed the capacities of the primary drainage system. In all, the model includes 383 nodes, 252 pipe reaches, 176 open channel reaches, 171 irregular cross sections, 98 weir reaches, 39 drop structure reaches, and 6 bridge reaches.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC 2.1.3.5 Boundary Conditions
The AdICPR model requires specification of hydraulic boundary conditions at all outfall points of the model schematic. In the Stevenson Creek watershed application, the primary basin outlet is located at the downstream face of the most downstream bridge at Edgewater Drive (Alt. US 19). A constant tailwater boundary condition representing the water elevation of Clearwater Harbor, a tidal waterbody, was specified at elevation 2.5 feet above mean sea level, 1929 National Geodetic Vertical Datum (NGVD) for all model simulations. This elevation was intended to approximate a “spring tide” condition within the harbor. It should be noted that for flow rates above approximately 3,000 cfs (which applies to the peak rates of flow for all design storms), the existing conditions stages within the Stevenson Creek estuary were not found to be sensitive to changes in the tidal boundary condition over a range of 0 to 3 feet NGVD.

An “overflow” boundary node exists at the northern end of the Jeffords Street Branch where floodwaters can “pop off” to the Allens Creek Basin when the flows exceed the capacity of the storm sewers. A third boundary node exists at the Clearwater Executive Airport, where a 36” diameter CMP culvert under the runways diverts a portion of the flow from the headwaters of Hammond Branch east into the Alligator Creek Basin. The tailwater elevations at these overflow boundary nodes are allowed to fluctuate with normal depth in the boundary link. Modeling results from the completed Allens Creek and Alligator Creek Watershed Plans were consulted to determine whether flooding was predicted in those watersheds which would influence stages in the corresponding Stevenson Creek boundary nodes. These model results indicated that the design flood elevations are well below the Stevenson Creek “pop-off” elevations, therefore it was not necessary to code in the time/stage boundary conditions based on
these other models.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC 2.1.4 Model Calibration and Verification

2.1.4.1 Introduction
Model calibration refers to the adjustment of model parameters within reasonable limitations so that the model results (i.e., streamflows and water elevations) are in reasonable agreement with a set of measured data. A reasonable range of values for the adjustment of model parameters is established through the review of literature references, and adjustments outside of those ranges are made only if some unusual hydrologic or hydraulic condition exists. Ideally, the model is calibrated to more than one different storm event in order to represent a variety of volumes, intensities, and distributions. It is also desirable to calibrate to recorded flow and stage information at different locations
within the watershed.

The two primary data requirements for model calibration and verification are gaged rainfall and streamflow for the study area. When selecting a calibration storm event, the rainfall and streamflow data must be sufficiently documented in appropriate time intervals so that variations in rainfall intensity and the associated runoff can be accurately simulated. Data should be recently acquired so that the current land use and hydraulic conditions existing in the study area are accurately represented. Additionally, because of the non-uniform spatial distribution inherent in Florida rainfall patterns, it is desirable that precipitation data be collected at more than one location within a large study area.

2.1.4.2 Streamflow and Precipitation Gaging Data
Prior to the initiation of this watershed management plan, no known measured streamflow data existed for Stevenson Creek. Therefore, it was necessary to collect streamflow data for calibration of the hydrologic/hydraulic computer model. This was accomplished by establishing two streamflow gaging stations within the Watershed. Continuous rainfall, stage, and streamflow data were collected under the direction of Parsons ES by Hydrogage, Inc. at Stevenson Creek near Drew Street and at Spring Branch near King’s Highway. The locations of the stations are shown on Figure 2.1.5

.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC ( Figure 2.1-5 )Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC The streamflow data was collected in digital format from May 12, 2000 to October 12, 2000. Stream stage (water level) was recorded at 15-minute intervals using a calibrated pressure transducer. Rainfall amounts were recorded at 15-minute intervals using a standard tipping-bucket rain gage. The rainfall data recorder utilized a telemetry system to alert Hydrogage of storm events in progress. Streamflow measurements were made over a wide range of flow conditions using standard USGS stream gaging procedures. These measurements were then correlated to recorded stage elevations to establish a flow versus stage rating curve at each location.

In addition to the precipitation and streamflow data, storm event flow-weighted composite water samples were collected with the aid of automatic samplers at each station. The water quality monitoring program is described in detail in Section 2.3.2.

2.1.4.3 Selection of Calibration/Verification Storm Events
July 15, 2000 Due to the relatively short period of record, only a handful of storm events was available for calibration of the model. Fortunately for this analysis, the period of record captured a large storm that occurred on July 15, 2000. This storm produced 7.60” and 5.21” of total rainfall within a ten-hour period at the Drew Street and King’s Highway sites, respectively. As evident from Figure 2.1-6 , this storm consisted of two separate rainfall events occurring approximately 6 to 7 hours apart. The first event occurred from about 7:00 AM to 10:00 AM and produced 3.23” at the Drew Street site and 1.69” at the King’s Highway site. At 2:00 PM, the second event occurred, producing 4.37” at the Drew Street site and 3.52” at the King’s Highway site. All of the rainfall in the afternoon event fell within a 2-hour period from 2:00 PM to 4:00 PM. The peak 15-minute intensity occurred at about 2:30, averaging 7.44 and 4.04 inches per hour at the Drew Street and King’s Highway sites, respectively. This storm produced widespread flooding throughout Stevenson Creek and the City of Clearwater. Following this event, staff fromStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC ( Figure 2.1-6 )Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC Parsons ES and the City marked visible high water elevations at 21 locations throughout the basin, which City survey personnel later surveyed (three of the elevations marked in the field as “questionable” were later discarded).

Because the hydrologic model chosen for the analysis is intended to be used strictly as a single-event model, the larger, afternoon rainfall event was chosen as a calibration event. By inspection of Figure 2.1-6 , it is evident that both Stevenson Creek and Spring Branch responded to the two storms as separate and distinct events. It should be noted, however, that the first event served to substantially increase the soil moisture leading into the second event. Prior to the morning of July 15, hydrologic conditions within the watershed were still extremely dry due to the several months of drought during the spring
of 2000.

June 12, 2000 In order to compliment and verify the large storm event of July 15, a smaller storm was chosen in order to verify the calibration parameters, and to “fine-tune” the DCIA percentages. For these purposes, the storm of June 12, 2000 was chosen, which produced 0.85 and 0.54 inches of rainfall at the Drew Street and King’s Highway stations, respectively. The antecedent moisture conditions preceding this event were extremely dry. The total rainfall amounts were therefore small enough to make the assumption that all runoff due to this storm was contributed by the DCIA, and thus all rainfall in areas
outside the DCIA was lost to infiltration.

2.1.4.4 Calibration Parameters and Results
When calibrating a computer model, certain model input parameters are held constant while others are adjusted in attempt to produce reasonable agreement with measured data. Those parameters that are adjusted are referred to as calibration parameters. Since it is desirable to limit the number of calibration parameters to the fewest possible, those parameters that can be easily measured or calculated normally are not adjusted. Calibration parameters are typically those coefficients and or indexes thatStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC are not easily determined from known quantities and/or established procedures. The two primary calibration parameters chosen for the Stevenson Creek model are runoff peak rate factor for the hydrologic component, and channel Manning’s roughness for the hydraulic component of the model.

When calibrating a model which uses the SCS unit hydrograph and runoff curve number method, it is often necessary to adjust the runoff curve number (CN) in order for the model to match the measured runoff volume. This is primarily due to the fact that the selected calibration storm events may have antecedent moisture conditions which differ significantly from typical design values found in the literature, which are conventionally based on either average, or average wet season, conditions. Runoff volumes can be very sensitive to CN, especially in southwest Florida where the sandy soils and seasonally high water table can result in a wide range of CN values depending on the time of year (i.e, wet season versus dry season). However, no CN adjustment was necessary for the Stevenson Creek calibration since the runoff volumes predicted for the July 15 th storm using CN’s corresponding to average antecedent moisture conditions matched the observed volumes fairly well. This is due to the likelihood that the first of the two rainfall events on July 15 th served to increase the soil moisture conditions from dry conditions to something closer to typical design conditions.

Channel Mannings Roughness

The primary means of calibrating the AdICPR hydraulic model was through adjustment of the Mannings Roughness Coefficient, or Mannings “n”. This is an index of the resistance to flow through a channel, primarily due to friction, that is dependent upon factors such as the extent and type of channel vegetation, channel bottom material, channel irregularity, channel alignment, obstructions, and depth of flow. Adjustments to the channel Mannings “n” were made to the cross sections in the vicinity of the streamflow gages until the simulated flow versus stage rating curve provided a reasonable match with streamflow measurements made during a number of different storm eventsStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC and flow conditions. No adjustments were made to the Manning’s roughness in the vicinity of the Spring Branch at King’s Highway station however, since within the range of the measurements, the flow appears to be controlled by the box culverts under King’s Highway (refer to Figure 2.1-7). The simulated rating curve at this location provided a reasonable fit to the measured data without any adjustment to the Mannings “n” values.

Figure 2.1-7 Box Culverts Downstream of King’s Highway Monitoring Station

At the Drew Street gage in Stevenson Creek, it was necessary to increase the in-bank Mannings “n” from the initial estimate of 0.07, to 0.09 for the cross section immediately downstream of the gage in order to match the measured data. In a field visit in March of 2000, this section was observed to be heavily vegetated (refer to Figure 2.1-8), although the degree of vegetation in the channel generally decreased in the sections further downstream through the golf course. Of course, the degree of vegetation varies not only with location, but also with time of year and point in the maintenance cycle.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC Figure 2.1-8 Vegetation in Channel Downstream of Drew Street Monitoring Station Figures 2.1-9 and 2.1-10 illustrate the simulated flow versus stage rating curves at Drew Street and King’s Highway, respectively. Note that the dependant variable (flow) is plotted on the X-axis. The measured values are plotted for comparison.

Following calibration of the Peak Rate Factor (described below), the channel Mannings “n” values were adjusted at several other locations in the watershed in order to match the surveyed high water elevations of the July 15 th flood event.

Peak Rate Factor
In the SCS Unit Hydrograph Method, a composite unit hydrograph is constructed of several incremental triangular unit hydrographs that adhere to the basic SCS triangular unit hydrograph equation:

q p = K’AQ T pStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC ( Figure 2.1-9 and 2.1-10 )Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC Where q p = peak runoff rate in cfs, A = area in square miles, Q = rainfall excess depth in inches, K’ = runoff peak rate factor The runoff peak rate factor, K’, includes a unit conversion and a hydrograph shape factor which determines the respective fractions of the runoff volume occurring under the rising and falling limbs of the hydrograph. The value of K’ has been shown to vary widely, from 100 in extremely flat basins in South Florida, up to 600 in steep, mountainous terrain. It has been suggested that K’ varies with watershed surface storage and/or average watershed slope. However, since no definitive relationship between subbasin slope and K’ has been proposed, it is often used as a calibration parameter. In the absence of gage data, the SCS recommends using a value of 256 for Florida, and 484 for most of the rest of the country. It can be shown that a K’ of 484 corresponds to 3/8 and 5/8 of the runoff volume occurring on the rising and falling limbs of the hydrograph, respectively. A K’ of 256 corresponds to 1/5 and 4/5 of the runoff volume occurring on the rising and falling limbs, respectively. The lower peak rate factors produce longer recession limbs with a smaller peak discharge rate for the same unit volume of runoff. It should be noted that these empirical values were derived from regional studies of small groups of similar watersheds, and are not necessarily applicable when applied outside their experimental ranges.

For the Stevenson Creek watershed, a value of 256 was used as the initial estimate of K’ for all subbasins, in accordance with the SCS recommendation for Florida. However, this value tended to produce simulated hydrograph shapes that suggested that the K’ value was too low. The K’ was increased to 484 for several of the steeper subbasins throughout the watershed, including several along the main channel of Stevenson creek which had average slopes exceeding 3%. Those subbasins with average slopes of less than about 1% were left with their original K’ of 256. This adjustment produced better agreement with the observed hydrograph shapes. Figures 2.1-11 and 2.1-12 provide a comparison between the simulated and measured hydrographs for the storm of July 15, 2000.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC ( Figure 2.1-11 and 2.1-12 )Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC Once the model was calibrated to match the observed hydrograph shape, the Mannings “n” was adjusted for the remaining cross sections throughout the watershed, in order to provide a closer match to the surveyed high water elevations. The following table compares the simulated and the measured high water elevations of the flood of July 15, 2000:

Table 2.1-5 Comparison of Measured and Simulated High Water Elevations Storm of July 15, 2000 Peak Stage (ft NGVD '29) Difference Node ID Node Location Measured Simulated (ft) 1000 Spring Branch at King’s Highway gage 12.51 12.48 -0.03 1040 Spring Branch at Union Street (u/s) 16.45 16.36 -0.09 2030 Hammond Branch Pond at King’s Highway 13.16 13.47 0.31 2130 Flagler Ditch at Saturn Avenue 61.10 61.11 0.01 2300 Smallwood Circle and Rosewood Road 45.98 46.08 0.10 3000 Stevenson Creek at Drew Street gage 14.12 14.14 0.02 3040 Stevenson Creek at Cleveland Street (u/s) 18.04 17.81 -0.23 3090 Stevenson Creek at Court Street (d/s) 18.61 18.83 0.22 3100 Stevenson Creek at Court Street (u/s) 18.97 18.88 -0.09 3120 Stevenson Creek at Druid Road (d/s) 20.76 20.60 -0.16 3125 Stevenson Creek at Druid Road (u/s) 20.67 20.82 0.15 3700 Lake Belleview outfall structure at Lakeview 40.22 40.13 -0.09 4020 Stevenson Creek at Browning Street (u/s) 30.05 30.21 0.16 4040 Stevenson Creek at Lakeview Road (u/s) 31.16 31.14 -0.02 4080 Stevenson Creek at St. Thomas Drive (u/s) 39.53 39.52 -0.01 4090 Stevenson Creek at Belleair Road (d/s) 39.80 39.58 -0.22 4100 Stevenson Creek at Belleair Road (u/s) 40.08 40.12 0.04 4140 Jeffords Street Branch at Highland Avenue 28.73 28.73 0.00 4160 Jeffords St Branch at Skyview and Jeffords 31.14 30.70 -0.44 4190 Jeffords Street Branch at Barry and Tuscola 30.80 30.67 -0.13Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC All of the simulated high water elevations were within 0.50 feet of the measured values, which is within the accuracy of computation for this type of analysis, and exceeds FEMA’s minimum requirements for flood insurance studies. All except two of the values
were with 0.25 feet of the measurements.
Model Verification and DCIA
The storm of June 12, 2000 was simulated in order to verify the calibration parameters and to fine-tune estimates of DCIA as a percentage of total impervious area. As mentioned in previous sections, total impervious area within each subbasin was estimated based on land use and aerial photography. A 50/50 split between directly and non-directly connected impervious areas was initially assumed. Since runoff volumes resulting from high intensity, large volume storm events normally are not sensitive to the percentage of total impervious as DCIA, a small, less intense storm event was chosen for DCIA determination. Since the storm of June 12 was a low volume, low intensity storm that had extremely dry antecedent moisture conditions, all runoff from this storm can reasonably be attributed to DCIA. The initial model simulation slightly under predicted the volume from this storm. The percentage of total impervious as DCIA was then raised from 50% to 65%, which resulted in a better fit with the measured hydrographs (refer to Figures 2.1-13 and 2.1-14 ). The 15% impervious area that was transferred into DCIA was subtracted from the calculations of weighted CN, resulting in slightly lower CN values. Then, the calibration storm of July 15 was simulated with the new CN and DCIA values. As expected, the results from the larger storm event did not change significantly.
2.1.5 Flooding Conditions Assessment
Upon the successful completion of the development and calibration of the detailed hydrologic and hydraulic model, the next step of the watershed management planning process was to apply the model to assess the performance of the basin drainage network for a given set of design storm events. Results of these simulations were then analyzed with respect to the flooding level of service criteria, in order to identify the locations and the severity of potential flooding problems.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC ( Figure 2.1-13 and 2.1-14 )Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC 2.1.5.1 Design Storm Events

The basis for the evaluation of flooding conditions in the watershed were the 10, 25, 50, and 100-year return period, 24-hour duration design storm events. The total rainfall for these events are 7.5, 9.0, 10.5, and 12.0 inches, respectively, as determined from the SWFWMD Environmental Resource Permitting (ERP) Information Manual (February 1996). The 500-year, 24-hour storm was also simulated in order to be consistent with FEMA mapping guidelines. The rainfall of 14.8 inches for the 500-year storm was determined through a probability analysis of the more frequent design storm events. The SCS Type II Florida-Modified rainfall distribution was used to develop the design storm hyetographs for the all return periods.

2.1.5.2 Existing Flooding Conditions
Using the described design storm events as the basis for simulations, the AdICPR model was run to generate predictions of basinwide flooding conditions for the existing conditions throughout the Stevenson Creek watershed. The results of these model simulations are summarized in Appendix D, Table D.1. This table lists the model nodes in sequence starting from the downstream end and the corresponding model predictions of 10-, 25-, and 100-year flood elevation at those locations. Also listed are the locations and descriptions of the adjacent roadways and the low road elevation at each structure. Note that the low road elevation does not necessarily occur at the exact location of the structure itself, since sags along the road profile, as determined from SWFWMD topographic mapping and/or roadway construction drawings, may occur several hundred feet away in certain instances. When a peak flood elevation exceeds the low road elevation, it indicates that the roadway will be inundated at that location by a depth corresponding to the difference in elevations.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC Comparison with Previous Studies

The following table compares the simulated 100-year flood elevations and peak discharge rates at five key locations within Stevenson Creek to the previous analyses of
the watershed:

Table 2.1-6 Comparison of 100-year Peak Discharge Rates and Flood Stages

Location W.K. Daugherty 1988 Preliminary Master Plan, Future Conditions CDM 1997 FEMA Submittal Parsons ES Existing Conditions

100-yr Flow (cfs) 100-yr Stage (ft, NGVD) 100-yr Flow (cfs) 100-yr Stage (ft, NGVD) 100-yr Flow (cfs) 100-yr Stage (ft, NGVD) Douglass Avenue 5,859 4.6 n/a n/a 4,697 7.73
Palmetto Street 4,603 11.0 2,190 8.67 3,300 10.14
Drew Street Gage 3,718 15.5 2,030 12.75 2,848 15.70
S. of Court Street 3,075 22.8 1,280 19.58 2,588 22.89
Jeffords Street 2,574 28.0 1,724 25.00 1,998 28.24

Because the modeling completed for this study was calibrated to measured stage and flow data, and the level of detail in the model network is an order of magnitude higher than the modeling completed for the previous studies, differences in the results are to be expected. Comparison of the peak discharge rates shows that those predicted by the Watershed Management Plan model consistently fall between those predicted by the other two studies. Upstream of Palmetto Street, the flood elevations predicted by the Parsons ES model generally compare closely with the W.K. Daugherty future conditions model, which includes the phase 1, 2, and 3 improvements (of which only phases 1 and 2 were constructed). In these same locations, the flood elevations predicted both in this study and in the W. K. Daugherty study are approximately three feet higher than those reportedStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC in the 1997 CDM study. While the reason for this large difference was not readily discernable, it should be mentioned that the 100-year project conditions flood levels reported in the 1997 CDM FEMA submittal are 0.5’ to 2.5’ lower than the 25-year project conditions flood levels reported in the 1992 CDM dredge and fill permit application (not shown). In addition, when comparing flood elevations at Douglass Avenue and Palmetto Street, it should be noted that neither of the two previous studies included the modeling of bridges at Edgewater Drive and the Pinellas Trail. In addition, the CDM study did not include the bridge at Douglass Avenue.

2.1.5.3 Flooding Level of Service Criteria
For the development of the comprehensive watershed management plan for the Stevenson Creek watershed, it was necessary to establish flood protection level of service (FPLOS) criteria by which flooding problems can be identified and alternatives for flood control can be evaluated. Determination of appropriate FPLOS criteria is therefore a very important part of the watershed planning process. Once the design storm flood elevations have been determined through the comprehensive modeling procedures, the FPLOS criteria then become the primary factor in determining the cost taxpayers must bear in order to remedy the existing flooding problems. Thus, the FPLOS criteria become the point at which the cost of infrastructure improvements is balanced against the public’s desire to further reduce the flooding in the watershed.

The primary FPLOS criterion is that there is to be no structural flooding (i.e., homes and businesses) for events up to and including the 100-year flood. This criterion refers to the low floor slab elevation (lowest inhabited floor) as the point of structural flooding. This is consistent with FEMA guidelines, and has been widely adopted by counties and municipalities across the state and the country.

The secondary set of FPLOS criteria specifies allowable thresholds for street flooding. The criteria is based upon residential, collector, and arterial roadways being passable for the 10, 25, and 100-year flood events, respectively. For the purposes of thisStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC study, “passable” is defined as 6” of flooding or less at the lowest edge of pavement in a travel lane. No flooding is allowable on hurricane evacuation routes for events up to and including the 100-year flood. The following table summarizes the proposed FPLOS
criteria for Stevenson Creek:

Table 2.1-7 -- Proposed Flood Protection Level of Service (FPLOS) Criteria for the
Stevenson Creek Basin

FPLOS Category Allowable Flooding Depths
1. Residential Streets, 2 lanes Up to 6” Allowed for 10-year flood
2. Collector Roads, 2-4 lanes Up to 6” Allowed for 25-year flood
3. Arterial Roads, 4 or more lanes Up to 6” Allowed for 100-year flood
4. Hurricane Evacuation Routes No flooding up to 100-year flood
5. Habitable Structures No flooding up to 100-year flood

In the next section, the above FPLOS criteria is used to identify and develop potential projects to reduce the design flood elevations to within the allowable flooding depths. However, experience shows that improving infrastructrue to reduce flood depths to meet a desired level of service is not always cost effective. For this reason, project costs must be weighed against the relative benefits. Of course, multiple-use facilities provide benefits in addition to flood control which must also be considered, as will be discussed in subsequent sections. Projects which do not provide benefits commensurate with the costs will not be recommended for funding.

Furthermore, it is not always technically feasable to reduce flood depths to meet a desired level of service. For example, many structures in low-lying areas near the coast in Clearwater were erected prior to the community’s participation in the National Flood Insurance Program, which first began in 1968. Many of these structures are subject toStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC saltwater inundation from the 100-year storm (hurricane) surge from the Gulf of Mexico. Although beyond the scope of this Watershed Management Plan, it is highly unlikely that an infrastructure project designed to protect against the 100-year storm surge in this area would be technically feasable.

In instances such as these where it is not cost effective or technically feasable to lower the floodplain, alternatives to flood level reduction should be considered. One such alternative would be a program which allows the city, in cooperation with FEMA, to assist willing property owners in the floodproofing, elevating, or purchase of flood prone

structures.

2.1.5.4 Flooding Problem Identification
The limits of the 100-year floodplain were generated by delineating the predicted flood elevations on SWFWMD 1”=200’ one foot contour aerial maps. Within the lower tidal portions of Stevenson Creek, the mapped floodplain limits are governed by FEMA’s computed storm surge elevations, as they are higher than those predicted to occur from riverine (freshwater) flooding due to rainfall and runoff. The storm surge floodplain intersects with the riverine floodplain near the Palmetto Street crossing of Stevenson
Creek.

The floodplain limits were digitized for incorporation into the GIS, as illustrated in Figure 2.1-15 in the rear map pocket. The 500-year floodplain was mapped per FEMA requirements and is shown for informational purposes only. Although the hydrologic and hydraulic modeling necessarily included the entire watershed, including areas outside the corporate limits of the City of Clearwater, floodplain limits within the City of Dunedin were not mapped. Riverine flood profiles were plotted for the 10, 25, 50, 100, and 500- year design storm events for Stevenson Creek and Spring Branch, as shown on Figures
2.1-16 through 2.1-24 at the end of this section.

Flood protection level of service deficiencies were identified in the watershed area within the corporate limits of the City of Clearwater. The street flooding level of serviceStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC deficiencies for the basin are tabulated in Appendix D, Table D.1. Shaded cells indicate locations that currently do not meet the proposed FPLOS criteria. The locations of the street FPLOS deficiencies are shown graphically on Figure 2.1-15

.
In order to determine the number and location of structure FPLOS deficiencies, habitable structures within the limits of the 100-year floodplain were identified. A determination was then made as to which homes and businesses were likely to be susceptible to flooding for the 100-year event. This determination was based on the assumption that the floor elevations for slab-on-grade type structures are at least 6 inches above adjacent ground as shown on the SWFWMD aerials. Using this proceedure, 470 structures were identified as potentially flood susceptible. In order to more accurately approximate the actual number of structure FPLOS deficiencies, surveyed finished floor information was compiled for the majority of these structures. Surveyed elevations for approximately 75 of the structures were obtained as part of the 1988 W.K. Daugherty study. An additional 272 structures were surveyed by Harry Marlow, Inc., as part of this study. The remaining 123 structure elevations were estimated from the SWFWMD topography and the surveyed elevations of nearby structures.

Of the 470 structures entered into the database, 263 structures were found to have finished floor elevations below the 100-year flood level. This is, by definition, a structure flooding level of service deficiency. As indicated on Figure 2.1-15 , the majority of these structures are located within the primary floodplains of the Stevenson Creek and Spring Branch main channels. However, many of the identified FPLOS deficiencies result from inadequate secondary drainage systems that feed into the main channels.

Table D.2 in Appendix D provides a complete listing of the structure flooding level of service evaluation for the Stevenson Creek Watershed. A summary of the identified structure FPLOS deficiencies in terms of both structures and total dwelling units is provided below as Table 2.1-8. Because many of the structures are multi-familyStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC buildings (duplexes, apartment buildings, etc), the number of flood-susceptible dwelling units is larger than the number of flood susceptible structures.

Table 2.1-8 Summary of Structure Flooding Level of Service Deficiencies

Subwatershed Identified 100-year FloodSusceptible Structures Identified 100-year FloodSusceptible Dwelling Units
Spring Branch 32 32

Lower Stevenson Creek 32 32

Middle Stevenson Creek 49 105
Upper Stevenson Creek 85 85

Hammond Branch 6 6

Lake Bellevue Branch 14 23

Jeffords Street Branch 45 51

Total 263 334

Subwatershed 1: Spring Branch

The Spring Branch Subwatershed was found to contain 32 structure FPLOS deficiencies. The majority of these (27) are in the area of Byram Drive and Flora Drive between King’s Highway and Highland Avenue, and along Huntington Lane, east of King’s Highway. These FPLOS deficiencies are located in a depressional area bordering the historical Spring Branch channel. At Woodlawn Terrace, east of Douglass Avenue,
an additional four structure FPLOS deficiencies were identified in an isolated depressional area drained by an inadequate secondary storm sewer system. These two areas were identified in the 1997 City of Clearwater Watershed Management Plan, through interviews with City staff in the Engineering Department, as “areas of concern for flooding”. Sunset Point Baptist Church was also identified as a level of serviceStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC deficiency. Four residential street FPLOS deficiencies and eight collector road FPLOS deficiencies were identified, including Douglass Avenue, King’s Highway, Sunset Point Road (two locations) and Highland Avenue. Although not FPLOS deficiencies of the City of Clearwater, there are estimated to be 10-15 flood-susceptible homes along Betty Lane and Macomber Avenue, north of Sunset Point Road within unincorporated Pinellas County. The locations of the City of Clearwater FPLOS deficiencies are shown on Figure
2.1-15

.

Subwatershed 2: Lower Stevenson Creek

In the Lower Stevenson Creek Subwatershed, 32 structure FPLOS deficiencies were identified. The majority of these (27) are located along the main channel of Stevenson Creek between Douglass Avenue and Palmetto Street. These homes and businesses all have floor elevations below 9.5 feet NGVD, and are susceptible to flooding from both riverine flooding (rainfall and runoff) and storm (hurricane) surge. The 100-year storm surge elevation, as determined from the FEMA Flood Insurance Rate Maps, is elevation 11.0, NGVD. In addition to the structures susceptible to both flooding sources, there are several additional structures between Edgewater Drive and Palmetto Street which are susceptible to storm surge flooding only, which were not included. Other structure FPLOS deficiencies in Lower Stevenson Creek include two utility buildings adjacent to the Creek in the Clearwater Country Club. Also identified were two relatively isolated
structure FPLOS deficiencies in the North Greenwood area and one near the intersection of Palmetto Street and King’s Highway. The latter three FPLOS deficiencies are far removed from the creek, and are the result of inadequate secondary drainage systems. Residential street FPLOS deficiencies were identified at seven locations, and collector road FPLOS deficiencies were identified at six locations, including Douglass Avenue, Fairmont Avenue (two locations), Palmetto Street (two locations), and North Greenwood Avenue (refer to Figure 2.1-15 ).Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC Subwatershed 3: Middle Stevenson Creek

In terms of the concentration of flood-susceptible dwelling units, the most severe flooding problems in the watershed occur within the Middle Stevenson Creek subwatershed. Approximately 49 structures consisting of 105 ground-floor dwelling units along the banks of Middle Stevenson Creek were identified that are subject to inundation from the 100-year design flood. Many of the structures are multi-family buildings. All of the FPLOS deficiencies identified in this subwatershed are adjacent to the main channel of the Creek between Drew Street and Jeffords Street. The majority (60) of these structure FPLOS deficiencies occur in the area immediately to the west of Glen Oaks Golf Course. To provide an idea of the magnitude of the flood problem in this area, 24 dwelling units were also found to be vulnerable to the 25-year flood. In addition, three homes were found susceptible to the 10-year flood, including two homes in the 600 block of Betty Lane, which have been the subject of documented structure flooding. The most notable street FPLOS deficiency occurs at Cleveland Street, a hurricane evacuation route, at its crossing of Stevenson Creek. The predicted flood depths are more than two feet above the roadway for the 100-year flood. The roadway would also be impassable for a 25-year flood, and minor flooding is predicted for a 10-year flood. Residential street FPLOS deficiencies were identified at five locations, including Pierce Street, Franklin Street, Betty Lane (2 locations), and Mark Drive.

Although the construction of the Phase 1 and Phase 2 improvements in the 1990’s significantly improved the conveyance capacity of Stevenson Creek from Drew Street to Court Street, floodplain enhancements within the Glen Oaks Golf Course were never constructed to the level originally envisioned in the 1990-1991 re-study of Stevenson Creek by CDM. In addition, the effectiveness of the constructed conveyance improvements has been greatly diminished due to a lack of adequate maintenance. Layers of sediment, and at times dense vegetation, have occupied portions of the improved channel. This problem was observed to be most severe between Drew Street and
Cleveland Street.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC Subwatershed 4: Upper Stevenson Creek

Upper Stevenson Creek encompasses the portion of the Creek targeted for conveyance improvements in Phase 3 of the 1988 W.K. Daugherty study. This phase was never constructed, primarily due to environmental concerns over the proposed improvement method of hardlining (paving) the channel with concrete. In the current analysis, the Upper Stevenson Creek subwatershed was found to contain 85 structure FPLOS deficiencies. All of these lie within the floodplain of the main channel of Stevenson Creek, with the largest concentration of them occuring on both sides of the Creek between Jeffords Street and Lakeview Avenue, and along Hillcrest Avenue south of Lakeview Road (see Figure 2.1-25).

Figure 2.1-25 Flooding on Hillcrest Avenue, South of Lakeview Road Storm of July 15 , 2000

However, the most severe and frequent flooding in the subwatershed occurs along Evergreen Avenue between Bellevue Boulevard and St. Thomas Drive, where sevenStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC homes were found susceptible to the 10-year flood. According to the City’s complaint logs, at least two of these structures flooded during the recent storm of July 15, 2000. The flooding problem at this location is due to a 54” CMP culvert placed within the Stevenson Creek Channel that lacks the capacity to convey even the mean annual storm event. Residential street FPLOS deficiencies were identified at seven locations, and collector road FPLOS deficiencies were identified on Belleair Rd and Highlands Avenue.

Subwatershed 5: Hammond Branch

Hammond Branch was found to contain six structure FPLOS deficiencies, the fewest of all the subwatersheds. All of the FPLOS deficiencies are a result of inadequate secondary drainage systems. A single structure FPLOS deficiency on Hibiscus Street near King’s Highway occurs when the storage capacity of the Hibiscus Pond is exceeded due to inflows from a 54” RCP culvert from the Highland Avenue drainage system. The existing outfall of Hibiscus Pond, consisting of a gunited 30” CMP, is not adequate to handle the inflows from the Highland’s Avenue culvert. An unrelated problem occurs on Smallwood Circle (southeast of Highland and Palmetto), where two structure FPLOS deficiencies were identified. These homes were built in a depressional area surrounding a small city park, which floods frequently during moderate to heavy rains. The depression is drained by an undersized, failing 24” CMP culvert which runs under existing homes on Elmwood Street and Smallwood Circle. In addition, three FPLOS deficiencies were identified on Linwood Drive near Sharondale Drive, on the north side of the CSX railroad that runs parallel to Flagler Drive. This problem area is the result of floodwaters from the Flagler Drive ditch backing up through twin 48” RCP culverts under the CSX railroad. The 48” culverts were intended to convey runoff from the subbasin to the north into the Flagler ditch. During flood events, however, the culverts flow in the opposite direction, directing floodwaters from the south side of the railroad, across the flood susceptible properties bordering Linwood Drive. The problem is exacerbated by the fact that the floor elevations of the homes are only two to three feet above the invert of the Flagler
Drive Ditch.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC Residential street FPLOS deficiencies were identified at twelve locations in the
Hammond Branch Subwatershed. Collector road FPLOS deficiencies were identified at nine locations, including three locations on King’s Highway, four locations on Highland Avenue, and two locations on Palmetto Street.

Subwatershed 6: Lake Bellevue Branch

Incrementally over past several decades, the Lake Bellevue Branch has been almost completely enclosed in storm sewer. Unfortunately, little of the storm piping was designed to adequately handle major a storm event. In the Lake Bellevue Branch Subwatershed, 14 structures consisting of 23 ground-floor dwelling units were found susceptible to inundation from the 100-year design flood. Of this total, five are businesses located on Missouri Avenue immediately south of Turner Street. Missouri Avenue itself constitutes an arterial road FPLOS deficiency at this location. This flooding problem is due to the fact that upstream of Missouri Avenue, the Lake Bellevue Branch flows into a 54” diameter culvert which lacks the capacity to convey the flow resulting from even a mean-annual storm event. Further upstream in the subwatershed, four structure FPLOS deficiencies occur at Pinellas Street, east of Greenwood Avenue, and one on Tuskawilla Street, west of Greenwood Avenue. These FPLOS deficiencies are also the result of undersized culverts placed within the historic channel of the Lake Bellevue Branch. Upstream of Lake Bellevue, four flood-susceptible structures containing a total of 13 dwelling units were identified on Wildwood Way, west of the
CSX railroad. These structures were built in a low area southwest of the Lake. The drainage for this area is towards Lake Bellevue, but flows are restricted by undersized culverts beneath the CSX railroad tracks. In addition to the single arterial road FPLOS deficiency on Missouri Avenue, the Lake Bellevue Branch contains five collector road FPLOS deficiencies on Druid Road, South Greenwood Avenue (two locations), Lakeview Road, and Belleair Road, and six residential street FPLOS deficiencies.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC Subwatershed 7: Jeffords Street Branch

Within the Jeffords Street Branch Subwatershed, 45 structures containing 51 dwelling units were found susceptible to the 100-year flood. The majority of these structures (35 of 45) are located within a contiguous floodplain area that encompasses the Jeffords Street ditch and the three interconnected lakes in the vicinity of Duncan Avenue and Jeffords Street. Historical 1926 aerial photography shows a wetland existed where these structures and lakes are today. It is likely that material dredged to form the three lakes was used as fill to form the building lots and roadways in the former wetland. However, the area is still extremely floodprone, as evidenced by the numerous documented complaints of flooding, and the mapped extent of the 100-year floodplain. The remaining structure FPLOS deficiencies (10 structures/16 dwelling units) were also constructed in a former wetland, in the area now bounded by Spencer Avenue, Turner Street, Duncan Avenue, and Druid Road. These structures flood on a very frequent basis, as seven are below the 10-year flood level and nine of the ten are below the 25-year flood level. According to the City’s complaint logs, at least two of these structures flooded during the recent storm of July 15, 2000. Collector road FPLOS deficiencies were identified on Highland Avenue, Lake Avenue (two locations), and Cleveland Street at Duncan Avenue. In addition, seven residential street FPLOS deficiencies were identified, most of which lie within the large contiguous floodplain area that encompasses the
Jeffords Street Ditch.

• Figure 2.1-17 Stevenson Creek Flood Profile, Existing Conditions

• Figure 2.1-18 Stevenson Creek Flood Profile, Existing Conditions

• Figure 2.1-19 Stevenson Creek Flood Profile, Existing Conditions

• Figure 2.1-20 Stevenson Creek Flood Profile, Existing Conditions

• Figure 2.1-21 Stevenson Creek Flood Profile, Existing Conditions

• Figure 2.1-22 Stevenson Creek Flood Profile, Existing Conditions

• Figure 2.1-23 Spring Branch Flood Profile, Existing ConditionsStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\SEC2-1.DOC • Figure 2.1-24 Spring Branch Flood Profile, Existing ConditionsStevenson Creek Watershed Management Plan Final Report

2.2-1

J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC2-2.DOC 2.2 NATURAL RESOURCES ASSESSMENT AND PROBLEM IDENTIFICATION

2.2.1 Introduction In order to prepare the Watershed Management Plan for the Stevenson Creek Watershed, the entire watershed was investigated for undeveloped land, wetlands, natural areas, and potential restoration or preservation areas. The boundaries of the natural areas were identified and mapped on aerial photography (scale: 1” = 200’). These areas were characterized using the Florida Land Use Cover and Forms Classification System (FLUCCS) (FDOT, 1985).
The Stevenson Creek Watershed is a highly urbanized, densely populated area with little to offer in the way of natural systems. With one exception, the only undeveloped areas are golf courses and city parks. Wetlands are predominantly small isolated stormwater retention ponds or natural lakes that have been altered to such a degree that their origin can only be determined from historic aerial photography. The waterways are predominantly channelized with little riparian habitat. The intense development has also altered the estuarine system so that little habitat is provided at the mouth of Stevenson
Creek.

Despite the intense urbanization of the watershed, improvements that do not require large expanses of open land and large expenditures of public funds can be made to increase the wildlife habitat and improve water quality. Studies have shown that golf courses can be managed to improve the water quality and wildlife habitat provided by the expanses of open space without negatively impacting the recreational function. For the purposes of this watershed management plan, a discussion of the existing natural conditions is provided in this section, while improvements that can be accomplished by public entities, private non-profit organizations, and by concerned private citizens are
discussed in Section 3.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC2-2.DOC 2.2.2 Existing Conditions
As can be seen in the land use map (Figure 2.1-2) and Table 2.2-1, the predominant land use within the watershed is residential, comprising approximately 70% of the total land area. Other developed areas such as commercial, industrial, institutional, open land, and transportation/utility land uses combined make up another 19% of the watershed. This leaves only 11% of the watershed in potential natural resource land uses, which includes undeveloped upland areas, recreational areas, open water bodies, or wetlands.

Most of the individual subwatersheds are similar in distribution of land uses. The Upper Spring Subwatershed has more wetlands than any other subwatershed, with 40 acres compared to less than 7 acres for each of the other subwatersheds. This is due to two large forested wetland areas near the intersection of Keene Road and Virginia Street. A 36-acre upland forested area in the Lower Spring Branch Subwatershed is by far the largest available habitat area in the watershed. The other subwatersheds have 0 to 7 acres of undeveloped uplands that may provide habitat. The open water bodies land use, which includes ponds, lakes, and other open water areas, is divided among three subwatersheds that have only 7 acres and four subwatersheds that have between 22 and 56 acres. The following paragraphs provide a subwatershed-by-subwatershed description of the land
uses and available habitat.

Upper Spring Branch Subwatershed The Upper Spring Subwatershed is located in the northernmost portion of the watershed and is the largest in total land area. There are several forested wetland areas within the watershed, as well as a freshwater marsh.

The freshwater marsh (approximately 4 acres) is located west of the forested wetland areas near the intersection of Virginia and Keene. The marsh is highly disturbed and dominated by nuisance vegetation such as primrose willow, cattail, and others. Some open water is present in the center of the marsh, indicating a depth that may be associatedStevenson Creek Watershed Management PlanFinal Report2.2-3J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC2-2.DOCTable 2.2-1LAND USE TYPES PER BASIN IN THE STEVENSON CREEK WATERSHED(Approximate acreages)Land Use HammondBranchJeffordsStreetLakeBelleviewLowerSpringLowerStevensonMiddleStevensonUpperSpringUpperStevensonTOTALResidential (1000-1300)64952934033851628712264914376Commercial(1400)3431178115614511541610Industrial(1500)5413020000042Institutional(1700)2114162331115315182Recreational(1800)964024011645180339Open Land(1900)4121337111110514234Agriculture(2000)10000005.015Upland Forests(4000)20536007050Water Bodies(5000)2722378407567205Wetlands(6000)11775240063Trans./UtilitiesCommunication(8000)2782252727477170Total per Basin91465165546582153516735756286Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC2-2.DOC with historic activities such as peat mining or excavation to increase retention and/or to reduce the ground water levels in adjacent properties. Development is encroaching upon the marsh, with new housing constructed on the east side. In its current state, this marsh still can provide wildlife habitat, although the isolated, fragmented condition of the marsh has greatly reduced the potential.

The 30 acres of forested wetlands appear to be the former headwaters of Spring Branch, which flows from this area south and west to the confluence with Stevenson Creek. These forested wetlands have been substantially altered with dredging, draining, filling, and channelizing. The canopy consists of a mixture of hardwoods and cypress, with slash pine in the drier transitional areas. The vegetation in these wetlands has been impacted by the hydrologic alterations, and nuisance species are now dominant in some

areas.
Lower Spring Branch Subwatershed The Lower Spring Branch Subwatershed is located north and east of the confluence of Stevenson Creek and Clearwater Harbor. This is the smallest of the subwatersheds, at only 465 acres. Although this subwatershed is 80% developed, there are two areas within this subwatershed that offer habitat to wildlife. In addition, portions of the Spring Branch channel still maintain a remnant of riparian habitat in the form of trees and a somewhat
natural streambed. The forested upland area within this watershed is located near the intersection of Sunset Point Road and Betty Lane. This approximately 25-acre parcel has been impacted in the past with clear-cutting and grading. Historic aerial photography (1926) shows that this parcel was cleared and a pond was excavated on the west side, potentially in preparation for development. The southern portion of the parcel supports a stand of second-growth oak and pine with an open understory. Spring Branch borders the east side of this portion of the parcel. The northern, more mesic portion of the parcel supports more nuisance vegetation, especially around the pond and the outer edges of the site. However, there are mature trees in the canopy and native species in the understory andStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC2-2.DOC shrub layer. The vegetation in the pond is dominated by Carolina willow, and appears to be intermittently inundated.

Despite the impacted condition of the parcel, it currently provides the only wildlife habitat of any substantial size within the watershed. Recent survey lines cut through the parcel indicate that it may be too late to preserve it, but it has the potential to become locally significant wildlife habitat, as well as a neighborhood recreational area. This photo was taken facing north from the ditch that drains the small excavated pond within the forested area at Betty Lane and Sunset Point Drive.

This photo was taken in the mesic forested area, in the southern part near State Street. The vegetation in this area includes slash pine, laurel oak, saw palmetto, and cabbage palm.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC2-2.DOC Lower Stevenson Creek Subwatershed This subwatershed is 80% developed in residential, industrial, commercial, and utility/transportation land uses. Fourteen percent of the watershed is identified as recreational, but this includes a ballpark and the Clearwater Country Club. There are no large tracts of undeveloped upland areas that may provide habitat for wildlife, and few areas that would provide wetland habitat. There is a small (approximately 9-acre) parcel of land east of the Douglas Avenue Bridge on the north side of Stevenson Creek that provides the best potential habitat in the subwatershed. The parcel appears to have been a dumping ground for construction material, fill, household waste, and landscape trimmings. The majority of the site is vegetated with nuisance exotic species such as ear tree ( Enterolobium contortisiliquum ), lead tree ( Leucaena leucocephala ), Caesar weed ( Urena lobata ), castor bean ( Ricinus communis ), beggar’s tick ( Bidens pilosa ), Australian pine ( Casuarina equisetifolia ), Brazilian pepper ( Schinus terebinthifolius ), and other noxious weeds. Some remnants of native upland vegetation are present on the eastern boundary, adjacent to the auto-salvage yard along the eastern boundary of the undeveloped parcel. Species present in this area include laurel oak ( Quercus laurifolia ), saw palmetto ( Serenoa repens ), cat briar ( Smilax bona-nox ), and wild grape ( Vitis sp.).

The shoreline of the parcel along Stevenson Creek is vegetated in mangroves, including black ( Avicennia germinans ) and red ( Laguncularia racemosa ). A small mangrove swamp is located on the western side of the property. This swamp is predominantly black mangrove with an open water area in the center. The City is currently in negotiations with the owner to purchase the property containing this parcel.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC2-2.DOC Stevenson Creek meanders through the Clearwater Country Club golf course on asemi–natural streambed. There have been previous attempts to create marsh habitat online with the creek that have been somewhat successful. On-line wetlands are always difficult to create because of the need to accommodate the occasional heavy volumes of water flowing through the stream and the potential for erosion. In addition, maintenance is difficult due to the nuisance exotic vegetation that can be washed in from problem areas upstream. In spite of the drawbacks, the golf course provides one of the best potential areas for habitat improvement, depending upon the available area. The photo to the left was taken on the north bank of Stevenson Creek west of the Douglas Avenue Bridge. The view is to the southeast

This photo shows the mitigation area within the golf course. The low gabion wall was installed to protect the mitigation area from erosion and the influx of exotic vegetation.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC2-2.DOC Middle Stevenson Creek Subwatershed The Middle Stevenson Creek Subwatershed is 90% developed, with golf courses and a few stormwater ponds comprising the remaining ten percent. This subwatershed has the second highest area devoted to commercial enterprises, but no industrial land uses. There are no potential habitat areas with the exception of the golf courses, which provide marginal habitat at best. The creek is armored and channelized through this portion of the watershed, and although these types of improvements may be essential for flood abatement, they do little to enhance water quality and wildlife habitat.

Hammond Branch Subwatershed

This second largest subwatershed is located on the east side of the watershed, with the majority of the subwatershed lying north of Drew Street. This subwatershed is 87% developed, with a golf course and ball fields again comprising the majority of the undeveloped land. There are three fairly large water bodies in the subwatershed totaling 27 acres. These managed water bodies and two very small freshwater marshes provide the best habitat options in the subwatershed. The photo to the left shows a typical section of the creek (Lynn Lake) through the Middle Stevenson Creek Subwatershed. The algal mats on the water surface usually indicate poor water quality.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC2-2.DOC Jeffords Street Subwatershed The Jeffords Street Subwatershed is located in the eastern portion of the watershed, south of the Hammond Branch Subwatershed. This watershed is 91% developed with several water bodies and a golf course making up the remaining land uses. Crest Lake, the 20+-acre lake in the northern portion of the subwatershed, is located within a city park. This lake and the surrounding shoreline could potentially be enhanced to increase the habitat potential without impacting the park significantly. A discussion of these improvements and Best Management Practices for golf courses is provided in Section 3.

There are several small water bodies in the subwatershed ranging in size from 0.5 to 4.0 acres. These ponds are located within dense residential neighborhoods and likely do not provide more than the most minimal habitat for wildlife. Even small ponds can be improved to enhance the wildlife habitat availability by planting the shoreline with native species and improving water quality by reducing the pollutants in stormwater runoff. The photo to the left shows a view of Lake Hobart facing south. This lake is one of the larger water bodies.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC2-2.DOC Lake Bellevue Branch Subwatershed

The Lake Belleview Subwatershed is located in the southwestern portion of the Stevenson Creek Watershed, with Missouri Road roughly forming the eastern boundary. The subwatershed is 89% developed, with the 33-acre Lake Bellevue comprising another 5% and the adjacent park and playgrounds adding another 5%.

This recreational area (Ed Wright Park) is the only potential wildlife habitat in the Subwatershed, but the habitat is marginal at best. The lake is maintained to keep aquatic weeds from overtaking, however on the west side of the lake, the banks are covered with Brazilian pepper and other noxious invasive plants. These weeds do provide some function acting as a buffer from the heavy traffic on Myrtle Avenue. The northeast corner of the park supports a heavy canopy of mature oaks, but the understory is predominantly a parking area.

There are six small water bodies in the subwatershed, excluding Lake Bellevue. As with the majority of the other small water bodies in the watershed, these are highly maintained, isolated, and located within dense residential neighborhoods. These areas provide marginal habitat at best. This photograph is a view of Crest Lake from the northeastern corner. The sparseness of the understory vegetation can contribute to erosion and sedimentation in the lake due to stormwater runoff.Stevenson Creek Watershed Management Plan Final Report

2.2-11

J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC2-2.DOC Upper Stevenson Creek Subwatershed

The Upper Stevenson Creek Subwatershed is located in the southeastern portion of the watershed with Missouri Avenue forming the western boundary. This subwatershed is completely built out, with the exception of four small water bodies totaling 7 acres. The creek is completely lined with houses, leaving no options for habitat improvements without purchasing expensive residential property. This photograph of Lake Bellview shows the bare shorelines and lack of significant littoral vegetation. The littoral vegetation would provide habitat and water quality benefits.

This photograph was taken on the southwestern corner of the lake and shows the nuisance vegetation infestation

. Cleaning up this area would enhance the wildlife habitat provided by this

area
.Stevenson Creek Watershed Management Plan Final Report

2.2-12

J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC2-2.DOC 2.2.3 Wildlife
This highly urbanized area does not provide much habitat for wildlife, other than for generalist species that have adapted to urban environments. Table 2.2-2 provides a list of common faunal species that were observed or are expected to occur in the watershed.

The Backyard Habitat program promoted by the National Wildlife Federation educates citizens on building habitat within their own backyards, which increases the available habitat in urban environments. Details on this program are available on the
National Wildlife Federation website.

2.2.4 Endangered and Threatened Species Endangered and threatened species are those that have been categorized in some way by the respective jurisdictional agencies as meriting special protection or consideration. The state lists of animals are maintained by the Florida Fish and Wildlife Conservation Commission and categorized as endangered, threatened or of special concern. The lists constitute Rules 39-27.003, 39-27.004, and 39-27.005, respectively,
Florida Administrative Code. This is an example of one the culverts within the Upper Stevenson Creek Subwatershed. This culvert is near the intersection of Hillcrest and Browning.Stevenson Creek Watershed Management Plan Final Report

2.2-13

J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC2-2.DOC Table 2.2-2

Wildlife Observed (*) or Expected Within the Stevenson Creek Watershed

Scientific Name Common Name Birds Accipiter cooperii Cooper’s hawk Agelaius phoeniceus* Red-winged blackbird Ajaia ajaja* Roseate spoonbill. Anas fulvigula* Mottled duck Anhinga anhinga* Anhinga Ardea herodias* Great blue heron Aramus guarauna Limpkin Bombycilla cedrorum* Cedar waxwing Botaurus lentiginosus American bittern Bubulcus ibis* Cattle egret Buteo lineatus* Red-shouldered hawk Butorides virescens* Green heron Cardinalis cardinalis* Cardinal Casmerodius albus* Great egret Cathartes aura* Turkey vulture Ceryle alcyon* Belted kingfisher Chadradrius vociferous* Killdeer Colaptes auratus* Northern flicker Columba livia* Rock dove Coragyps atratus* Black vulture Corvus brachyrhynchos* American crow Corvus ossifragus* Fish crow Cyanocitta cristata* Blue jay Dendroica coronata* Yellow-rumped warbler Dendroica palmarum Palm warbler Dryocopus pileatus* Pileated woodpecker Dumetella carolinensis* Catbird Egretta caerula* Little blue heron Egretta thula* Snowy egret Egretta tri-color* Tricolor heron Elanoides forficatus* Swallow-tailed kite Eudocimus albus* White ibis Falco sparverius* American kestral Falco peregrinus Peregrine falconStevenson Creek Watershed Management Plan Final Report

2.2-14

J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC2-2.DOC Fulica americana* American cootStevenson Creek Watershed Management Plan Final Report

2.2-15

J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC2-2.DOC Table 2.2-2 (cont.)

Wildlife Observed (*) or Expected Within the Stevenson Creek Watershed

Scientific Name Common Name Birds (cont.) Gallinula chloropus* Common moorhen Geothlypis trichas* Common yellowthroat Ixobrychus exilis* Least bittern Lanius ludovicianus* Loggerhead shrike Larus argentatus* Herring gull Larus atricilla* Laughing gull Larus delawarensis* Ring-billed gull Larus philadelphi Bonapart’s gull Melanerpes carolinus* Red-bellied woodpecker Mimus polyglottus* Mocking bird Mycteria Americana* Wood stork Nycticorax nycticorax* Black-crowned night heron Nyctanassa violacea* Yellow-crowned night heron Otus asio* Belted kingfisher Pandion haliaetus* Osprey Passer domesticus* House sparrow Parus bicolor* Tufted titmouse Pelecanus occidentalis* Brown pelican Phalacrocorax auritus* Double-crested cormorant Picoides pubescens* Downy woodpecker Plegadis falcinellus Glossy ibis Podilmbus podiceps* Pied-billed grebe Quiscalus major* Boat-tailed grackle Quiscalus quiscula* Common grackle Rallus elegans King rail Rallus limicola Virginia rail Sterna forsteri* Forster’s tern Streptopelia decaocto* Eastern screech owl Strix varia Barred owl Sturnus vulgarus* European starling Tachycineta bicolor* Tree swallow Toxostoma rufum* Brown thrasher Turdus migratorius* American robin Thryothorus ludovicianus Carolina wrenStevenson Creek Watershed Management Plan Final Report

2.2-16

J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC2-2.DOC Zenaida macroura* Mourning doveStevenson Creek Watershed Management Plan Final Report

2.2-17

J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC2-2.DOC Table 2.2-2 (cont.)

Wildlife Observed (*) or Expected Within the Stevenson Creek Watershed

Scientific Name Common Name Mammals Dasypus novemcinctus* Armadillo Didelphis virginiana* Opossum Lasiurus intermedius Northern yellow bat Lontra canadensis River otter Peromyscus gossypinus Cotton mouse Peromyscus polionotus Oldfield mouse Procyon lotor* Raccoon Nycticeius humeralis Evening bat Sciurus carolinensis* Eastern gray squirrel Sciurus niger shermanii Sherman’s fox squirrel Sigmodon hispidus Hispid cotton rat Sylvilagus floridanus Eastern cottontail Sylvilagus palustris Marsh rabbit Tadarida brasiliensis Brazilian free-tail bat Reptiles And Amphibians Anolis carolinensis Green anole Anolis sagrei sagrei Brown anole Acris gryllus Southern cricket frog Rana sphenocephala Southern leopard frog Bufo terrestris Southern toad Coluber constrictor Black racer Diadophis punctatus Ring necked snake Hyla cinerea Green tree frog Hyla gratiosa Barking tree frog Hyla squirella Squirrel tree frog Osteopilus septentrionalis Cuban tree frog Pseudemys floridana floridana Florida cooter Rana sphenocephala Southern leopard frog Sternotherus sp. Common musk turtle Thamnophis sirtalis Common garter snake Trachemys scripta elegans Red-eared turtle Trachemys scripta scripta Yellow bellied turtleStevenson Creek Watershed Management Plan Final Report

2.2-18

J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC2-2.DOC Table 2.2-2 (cont.)

Wildlife Observed (*) or Expected Within the Stevenson Creek Watershed

Common Name Common Name Fish and Shellfish Lane Snapper Spotted Sea trout Mojarra Silver Sea trout Grunt Red Snapper Weakfish Yellowtail Snapper Gray Snapper Scad Atlantic Bumper Silver Perch Mutton Snapper Spot Lookdown Atlantic Croaker Leatherjack Silver Porgy Mahogany Snapper Sand Perch Permit Gag Grouper Black Drum Stone Crab Red Drum Tunicate Sheepshead Burrfish Pinfish Puffer Blue Crab Flounder Toadfish Hogfish Cowfish Wrasse Filefish Spadefish Sole Black Seabass Mullet Glass Slipper Parrotfish Squid Egg Mass Sergeant Major Comb Jelly Snook Sea Urchin Gulf Shrimp Bivalve (U.N.I.D) Grass Shrimp Sea Snail (Banded Tulip) Ghost Shrimp Sea Hare Mud Crab Sea Pork Hermit Crab Trunkfish Arrow Crab Sea Horse Pipefish Spade Crab Sand Dollar Feather Bleeny Lizardfish Scallop Spider Crab SpongeStevenson Creek Watershed Management Plan Final Report

2.2-19

J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC2-2.DOC Table 2.2-2 (cont.)

Wildlife Observed (*) or Expected Within the Stevenson Creek Watershed

Common Name Common Name Seabream Octopus Shade Crab Polychete Worms Scaled Sardine Sea Snail (Moon Snail) Wort Jelly Juv. Flying Gunnard Horshoe Crab Squid Lentil Spider Calico Crab Sea Cucumber Mangrove Snapper Silverside Whelk Egg Brittle Star Sea Snail (Banded Tulip) Source: Clearwater Audubon Society (Ms. Jane Williams), and Clearwater Marine Aquarium (Mr. Geoff Lane), field observations (Parsons ES, May 2000), and Florida Natural Areas Inventory, 1996 The state lists of plants are categorized into endangered and threatened and commercially exploited and are administered and maintained by the Florida Department of Agriculture and Consumer Services via Chapter 5B-40, F.A.C. The federal list of animals and plants is administered by the U.S. Fish and Wildlife Service and are published in 50 CFR 17 (animals) and 50 CFR 23 (plants).

Even the most urban environments can support some endangered species. For instance, during the field reviews for this project, white ibis and little blue heron were observed on one of the golf courses within the watershed. Bald eagles have nested in other watersheds within the City of Clearwater, and could nest in the Stevenson Creek watershed if the appropriate habitat were available. Table 2.2-3 lists the endangered, threatened, or species of special concern that occur or potentially occur in the watershed.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC2-2.DOC Table 2.2-3 Endangered, Threatened, or Special Concern Species Observed (*) or Potentially Present in the Stevenson Creek Watershed
Gopher Tortoise Sherman’s fox squirrel* Florida sandhill crane
Gopher frog Little blue heron* Peregrine falcon*
American alligator* Wood stork* SE American kestrel
Florida mouse Tri-colored heron* Bald eagle*
Eastern indigo snake Snowy egret* Burrowing owl
Limpkin* Roseate spoonbill* White ibis*
The species identified with an asterisk (*) in the table above have been observed in the watershed by members of the Clearwater Audubon Society. It is highly unlikely that any of these species are successfully breeding in or if viable populations of these species
exist within the Stevenson Creek Watershed due to the lack of suitable habitat.Stevenson Creek Watershed Management Plan Final Report

2.3-1

J:\DATA\737626\GIS\FIGURES_PDF\SEC2-3.DOC 2.3 WATER QUALITY ASSESSMENT The Stevenson Creek Watershed is the largest watershed in the City of Clearwater. Residential land uses are dominant in this urban watershed, which provides drainage for the western portion of Clearwater as well as portions of Dunedin and unincorporated Pinellas County. The main stem of the creek originates near Belleair
Road and flows northward to Clearwater Harbor.

The largest tributary is Spring Branch which flows from Dunedin and southward entering Stevenson Creek just upstream of Clearwater Harbor. Other major tributaries include two highly altered streams draining the eastern portion of the watershed. One of these streams drains into Stevenson Creek near Palmetto Street and the other empties into the creek near Jeffords Street. Another major tributary is a remnant stream that drains
Lake Belleview and enters the main channel near Glenn Oaks Golf Course.

Numerous small, natural water storage areas are located throughout the basin as
well as several lakes. Most notable in size is Lake Bellevue which is around 25 acres. The two other largest lakes in the basin are Crest Lake and Lake Hobart which are about half
the size of Lake Bellevue.

These storage areas and lakes provide stormwater runoff treatment. Best management practices (BMPs) for new (post-1982) development are also present; however, stormwater runoff treatment is lacking in many areas. New BMPs can help to improve water quality in the watershed; however, anthropogenic sources other than stormwater runoff appear to influence water quality in the Stevenson Creek Watershed to a significant degree.

Low dissolved oxygen levels, fecal contamination, and excessive nutrient concentrations are the primary water quality issues that have been identified in the watershed, and as such, water quality in Stevenson Creek is rated as “poor” by the state. The state’s rating is based on sampling conducted by the Pinellas County Department ofStevenson Creek Watershed Management Plan Final Report

2.3-2

J:\DATA\737626\GIS\FIGURES_PDF\SEC2-3.DOC Environmental Management (PDEM). The city’s ambient monitoring program as well as monitoring conducted for this study affirms these water quality issues.

Stevenson Creek is included on Florida’s impaired waters list {303(d) List} due to concerns over dissolved oxygen, coliforms, and nutrients. The FDEP has given Stevenson Creek a priority rating of “High”. Stevenson Creek is located in the “Crystal River to St. Petersburg Beach Basin” which is in Group 5 of the basin rotation cycle. TMDL development activity is expected to begin in 2004.

Water quality assessments conducted for this study included a

• Review of Existing Data (Section 2.3.1, Existing Data ),

• Base flow and storm event monitoring program (Section 2.3.2, Monitoring Program ),

• Water quality data interpretation (Section 2.3.3, Water Quality Characteristics ), and

• Nonpoint source loading assessment (Section 2.3.4, Nonpoint Source Loads ).
Each of these four elements is described separately in the following subsections.

2.3.1 Existing Data During the last decade, Pinellas County and the city have conducted and documented water quality monitoring programs within the Stevenson Creek Watershed ( Figure 2.3-1 ); likewise, the Marshall Street Wastewater Treatment plant (MWWTP) maintains operating records, and the Pinellas County Health Department maintains records concerning individual septic tanks. These monitoring programs and records were reviewed and are more specifically described as follows:

• Pinellas County ambient surface water monitoring program -- active Pinellas County monitoring program containing two stations within the Stevenson Creek Watershed (Refer to Existing Water Quality Monitoring Programs , Section 2.3.1.1)Stevenson Creek Watershed Management Plan Final Report

2.3-3

J:\DATA\737626\GIS\FIGURES_PDF\SEC2-3.DOC Figure 2.3-1 Water Quality Monitoring StationsStevenson Creek Watershed Management Plan Final Report

2.3-4

J:\DATA\737626\GIS\FIGURES_PDF\SEC2-3.DOC • City of Clearwater ambient surface water monitoring program -- ambient surface water quality monitoring program from 1992 through 1995 containing ten stations within the Stevenson Creek Watershed (Refer to Existing Water Quality Monitoring Programs , Section 2.3.1.1)

• Southwest Florida Water Management District, Lake Bellevue monitoring program-- short-term program from 1996-1997 (Refer to Existing Water Quality Monitoring Programs , Section 2.3.1.1)

• Marshall Street Wastewater Treatment Plant operating reports -- ten-year record (Refer to Other Existing Data , Section 2.3.1.2)

• Pinellas County Health Department septic tank records-

- Recent septic tank construction and repair applications (Refer to Other Existing Data , Section 2.3.1.2)
2.3.1.1 Existing Monitoring Programs Pinellas County, the Southwest Florida Water Management District (SWFWMD), and the City of Clearwater have conducted monitoring programs within the Stevenson Creek Watershed. Summary results from each of these monitoring programs are provided in Appendix I.

Pinellas County Department of Environmental Management (PDEM) maintains two stations in Stevenson Creek as part of its countywide ambient water quality monitoring program. The data from these two stations is the basis for the state’s inclusion of Stevenson Creek on the impaired waters list, and the county has used these data to implicate Stevenson Creek as having some of the poorest water quality in the county (Myers et al. 2000).

PDEM provided the following description of these two stations to EPA’s
STORET database:

• “Stevenson's Creek off the southeast side of the Douglass Ave bridge just north of the Clearwater WWTP from mid span sampled monthly”Stevenson Creek Watershed Management Plan Final Report

2.3-5

J:\DATA\737626\GIS\FIGURES_PDF\SEC2-3.DOC • “collected from Spring Branch of Stevenson’s Creek off the west side of the Overbrook bridge just west of Douglass Ave at mid span sampled monthly”
Most prominent in each of these data sets are average fecal coliforms counts and ammonia nitrogen levels, which often exceed state standards. Phosphorous is high at the Spring Branch station, and nitrate + nitrite is high at both stations, particularly at the Stevenson Creek Station. The state reports a trophic state index of 65 for the Stevenson Creek estuary indicating that water quality is poor. A review of the nitrogen/phosphorus ratios shows that the estuary is nitrogen-limited.

A short-term monitoring program was conducted by SWFWMD on Lake Belleview (1996-1997). This program consisted of two sampling events- one in each year. The results showed low phosphorous levels for both measurements and high nitrogen levels for the 1996-measurement followed by low nitrogen levels during the 1997-measurement. Accordingly, a sharp drop in lake productivity was observed during the second year. Nitrogen forms were almost entirely organic.

The city conducted an ambient surface water quality monitoring program from years 1992 through 1995. The program included 10 stations in the Stevenson Creek Watershed. The monitoring program included grab samples analyzed for nutrients, oil and grease, suspended solids, coliforms and fecal streptococcus, biochemical oxygen demand (BOD 5 ), chlorides, and field parameters (dissolved oxygen, pH, etc.). Dissolved oxygen and fecal contamination were the most significant concerns identified for the Stevenson Creek Watershed during the city’s monitoring program. Nutrient levels were also often elevated during the monitoring period.

2.3.1.2 Other Existing Data Operating reports for Marshall Street Wastewater Treatment plant (MWWTP) were reviewed along with limited septic tank information made available by the Pinellas County Health Department. These records show that MWWTP (Figure 2.3-2) contributes significant quantities of nutrients, solids, and oxygen-demanding substances to the Stevenson Creek estuary, and, the septic tank information, considered inStevenson Creek Watershed Management Plan Final Report

2.3-6

J:\DATA\737626\GIS\FIGURES_PDF\SEC2-3.DOC Figure 2.3-2 Marshall Street Wastewater Treatment Plant



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Marshall Street WWTP

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H conjunction with coliforms sampling results, provides information concerning potential
sources of fecal contamination in
the basin.

The MWWTP dischargesnutrients, solids, and oxygendemanding substances to
Stevenson Creek. While
concentrations for these constituents in the plant effluents are within appropriate standards, the average 5.55 MGD-flow (6.8 MGD average daily flow minus 1.25 MGD flow to the reclaimed water system) results in masses that make up a significant percentage of total loads to the estuary originating from the Stevenson Creek Watershed. Information from the monthly operating reports for the year 1999 were averaged to produce the table below which compares loads from the treatment plant with loads measured during the 186-day monitoring period, of this study, at the two monitoring stations (Drew Street and Kings Highway). Stevenson Creek at the location of the MWWTP discharge has a much higher

capacity to assimilate pollution than do the upper, freshwater reaches of the creek, and Table 2.3-1 Loads During Monitoring Period

Input Source Volume Discharged
(ac-ft) BOD 5 (Pounds) TSS
(Pounds) TN
(Pounds) TP
(Pounds)
Base and Storm Flow (1) 3,170 101,199 157,406 11,542 3,084
MWWTP 2,587 82,596 128,471 9,420 2,517 Note: Loads measured (based on mean concentration of all samples, this study, and the overall flow) at the Spring Branch (King’s Highway) and Stevenson Creek (Drew Street) Station, Ma y 2000 – November 2000Stevenson Creek Watershed Management Plan Final Report

2.3-7

J:\DATA\737626\GIS\FIGURES_PDF\SEC2-3.DOC these mass loading calculations are provided only to add perspective to overall watershed load estimates presented elsewhere in this report.

Indirect evidence suggests that both the sanitary sewer system (i.e., crossconnections or inflow) and septic tanks may contribute to bacteria and nutrient levels in the Stevenson Creek Watershed. The MWWTP appears to receive a moderate increase in flow during the wet season. In addition, the locations and density of septic tank repair permits seem to coincide with the highest percent of human isolates found in the results of the fecal coliform sampling.

A fourteen-year flow record (January 1985- January 2000) was reviewed for theMWWTP. During this time period the average daily flow during the wet season (JuneSeptember) was 7.06 MGD as compared to 6.65 MGD during the remaining eight months of the year. If this variation is due to increased rainfall during the wet season, then possible explanations for the increase are infiltration, inflow, or cross connections between the sanitary and storm systems. Anecdotal evidence of one possible infiltration or cross connection problem is provided by a resident who reported that a lift station on Sunset Point Road (just west of Stevenson Avenue) overflows during heavy rains “causing the creek to stink like sewage”.

Pinellas County recently began keeping records of applications for septic tanks repairs. The locations of the septic tanks contained in this database were plotted ( Figure
2.3-3 ), and seem to suggest that septic tanks within the city are concentrated between Union Street and Palmetto Street. These locations are near City of Clearwater monitoring Station STC1 and STC2, which happen to be the two stations with the highest percent of human isolates in fecal coliform samples (refer to Appendix J and Figure 2.3-1 ). While this seems to implicate septic tanks as a source of fecal contamination, a direct “cause and effect” statement concerning the use of septic tanks in the Stevenson Creek Watershed cannot be made. Other factors, such as the downstream position of STC1 and STC2, may be the cause of the higher human-source fecal contamination that was observed - in other words, the origin of the human-sourced fecal contamination measured at STC1 and STC2 could potentially be located upstream of the septic tanks.Stevenson Creek Watershed Management Plan Final Report

2.3-8

J:\DATA\737626\GIS\FIGURES_PDF\SEC2-3.DOC Figure 2.3-3 Septic Tank DensitiesStevenson Creek Watershed Management Plan Final Report

2.3-9

J:\DATA\737626\GIS\FIGURES_PDF\SEC2-3.DOC 2.3.2 Monitoring Program A hydrologic and water quality monitoring program was implemented for the Stevenson Creek Watershed project. Two monitoring stations were installed – one station in Stevenson Creek ( Stevenson Creek Station ) just downstream of Drew Street and one station in Spring Branch ( Spring Branch Station ) just downstream of Kings Highway ( Figure 2.3-4 ).

Each station logged rainfall depth and channel stage at 15-minute intervals from May 21,2001 through November 23, 2000. Flow-weighted composite samples were collected for seven (7) separate storm events and grab samples were taken for six (6) base flow events at each station. Savannah Laboratories in Tampa analyzed the samples in accordance with their FDEP-approved quality assurance plan. One equipment blank for each station was collected and analyzed prior to the first storm-sampling event.

Laboratory parameter included solids, oxygen demand, nutrients, metals and petroleum hydrocarbons. These parameters are more specifically described in Table 2.3- 2 along with their corresponding minimum detection limits.

2.3.2.1 Monitored Basins The majority (65%) of the watershed was monitored. Figure 2.3-4 shows the areas that drain to each of the monitoring stations. These areas include a 2400-acre area draining to the Stevenson Creek Station and a 1700-acre area draining to the Spring Branch Station. The unmonitored portion of the basin is approximately 2200 acres.

Both the Stevenson Creek and Spring Branch Stations are similar with respect to land use. The dominant land use is residential. The primary distinguishing factor is the presence of a larger amount of commercial land use in the Stevenson Creek Basin and a larger amount of high-density residential land use in the Spring Branch Basin. The Land uses in the unmonitored portion of the basin are similar to the monitored basins as shown in Figure 2.3-5 – shown as a doughnut graph to emphasize similarity.Stevenson Creek Watershed Management Plan Final Report

2.3-10

J:\DATA\737626\GIS\FIGURES_PDF\SEC2-3.DOC Table 2.3-2 Water Quality Sampling Parameters

1 Minimum Detection Limit Parameter MDL 1 (mg/l ) Hardness as CaC0 3 3.3 Petroleum Hydrocarbons Oil and Grease 5.0 Total Recoverable Petroleum Hydrocarbons, TRPH 0.30 Oxygen Demand Biochemical Oxygen Demand (5 Day), BOD 5 2.0 Chemical Oxygen Demand, COD 20 Total Organic Carbon, TOC 1.0 Solids Total Suspended Solids, TSS 5.0 Total Dissolved Solids, TDS 5.0 Metals Aluminum, Al 0.20 Arsenic, As 0.010 Cadmium, Cd 0.0050 Chromium, Cr 0.010 Copper, Cu 0.020 Lead, Pb 0.0050 Nickel, Ni 0.040 Zinc, Zn 0.020 Nutrients Ortho Phosphate, P 0.050 Total Phosphorus, TP 0.10 Ammonia, NH 3 0.03 Total Kjeldahl Nitrogen, TKN 0.20 Nitrate + Nitrite, NO 3 , NO 2 0.05Stevenson Creek Watershed Management Plan Final Report

2.3-11

J:\DATA\737626\GIS\FIGURES_PDF\SEC2-3.DOC Figure 2.3-4

Monitoring Stations Location and CoverageStevenson Creek Watershed Management PlanFinal Report2.3-12J:\DATA\737626\GIS\FIGURES_PDF\SEC2-3.DOCFigure 2.3-5Land Use by Monitoring StationAgriculturalCommercialHigh Density ResidentialHighway/UtilityIndustrialInstitutionalLow Density ResidentialMedium Density ResidentialOpen LandRecreationalUpland ForestWaterWetland ForestWetland Non-ForestedUnmonitoredDrew StreetStationSpring BranchStationStevenson Creek Watershed Management Plan Final Report

2.3-13

J:\DATA\737626\GIS\FIGURES_PDF\SEC2-3.DOC 2.3.2.2 Hydrologic Monitoring Hydrologic monitoring was conducted from May 21, 2000 through November 23, 2000. Rainfall conditions preceding and during the monitoring period were, in general, drier than normal. Rainfall conditions leading up to and including the monitoring period as compared to normal conditions are shown on Figure 2.3-6. The monitoring period followed an extremely dry “dry season” (5.1 inches of rainfall were received October 1999 to May 2000 at SWFWMD’s Site #15 rain gauge) with monthly rainfall conditions recovering to normal during the second month (June 2000) of monitoring. July 2000 was wetter than normal due chiefly to a large storm event that occurred on July 15 dropping 7.7 inches at the Stevenson Creek Station and 5.7 inches at the Spring Branch Station. Drier-than-normal conditions returned after July.

Towards the end of May 1999 it was discovered that the Stevenson Creek rain gage was receiving inputs from the Clearwater Country Club’s sprinkler system. The rain gauge was moved away from the influence of the sprinklers as far as possible; however, minor inputs were still received from the sprinklers.

Translating the total measured flow during the monitoring period to a depth (flow volume divided by basin area), at the Stevenson Creek station 11.0 inches of rainfall appeared as flow the creek; likewise, 31.16 inches of rainfall at the Spring Branch Station resulted in 6.9 inches of flow. The remaining rainfall was lost to initial abstraction and evapotranspiration or became groundwater - later to appear as base flow of aquifer recharge. A simplified technique of base flow separation was applied to determine the relative magnitude of base flow. This technique uses the minimum daily flow during dryperiods together with professional judgment to separate the flow into two componentsbase flow and storm event runoff. Overall hydrologic conditions for the monitoring period are listed in Table 2.3-3. Daily flow along with rainfall for the two monitoring stations is shown on Figures 2.3-7 and 2.3-9. Figures 2.3-8 and 2.3-10 provide a more
detailed view for low flow conditions.Stevenson Creek Watershed Management PlanFinal Report2.3-14J:\DATA\737626\GIS\FIGURES_PDF\SEC2-3.DOCFigure 2.3-6Rainfall Conditions0.05.010.015.020.025.0Aug99Sep-99Oct-99Nov-99Dec-99Jan-00Feb-00Mar-00Apr-00May-00Jun-00Jul-00Aug-00Sep-00Oct-00Nov-00Pinellas County Long-Term.Average for Month (SCS,1972)City of Clearwater(SWFWMD Pinellas CountySite #15)Stevenson Creek Station(refer to Section 2.3.2.2)Spring Branch StationPinellas County Long-Term. Average for Month (SCS,1972)9.0 8.4 3.9 1.7 2.1 2.5 3.0 3.7 3.2 2.6 6.3 9.2 9.0 8.4 3.9 1.7City of Clearwater (SWFWMD Pinellas County Site #15)6.9 4.4 1.5 0.3 0.0 0.0 1.5 0.8 1.0 0.0 7.7 19.3 6.2 2.1 0.0 1.2Stevenson Creek Station (refer to Section 2.3.2.2)1.54 9.70 17.95 4.46 7.93 1.68 2.34Spring Branch Station0.00 6.74 14.22 3.92 5.20 0.17 0.91Aug99Sep-99Oct-99Nov-99Dec-99Jan-00Feb-00Mar-00Apr-00May-00Jun-00Jul-00Aug-00Sep-00Oct-00Nov-00Stevenson Creek Watershed Management Plan Final Report

2.3-15

J:\DATA\737626\GIS\FIGURES_PDF\SEC2-3.DOC Table 2.3-3 Overall Hydrologic Conditions at Monitoring Stations

Watershed Item Quantity Percent of Rainfall Area (AC) 1,673.50 -- Rainfall Depth (in.) 31.16 100% Volume of Rain (AC-Ft.) 4,345.52 100% Total Flow (AC-Ft.) 960 22% Base Flow (AC-Ft.) 184 4% Spring Branch

Storm Flow (AC-Ft.) 776 18% Area (AC) 2,415.50 Rainfall Depth (in.) (1) 45.61 100% Volume of Rain (AC-Ft.) 9,181.91 100% Total Flow (AC-Ft.) 2210 24% Base Flow (AC-Ft.) 376 4% Stevenson Creek

Storm Flow (AC-Ft.) 1834 20%Note 1 : Rainfall depth reflects inputs from Clearwater Country Club sprinkler systemrefer to Section 2.3.2.2.Stevenson Creek Watershed Management PlanFinal Report2.3-16J:\DATA\737626\GIS\FIGURES_PDF\SEC2-3.DOCFigure 2.3-7Stevenson Creek Hydrologic Record0200400600800100012001400160018002000May-00 Jun-00 Jul-00 Aug-00 Sep-00 Oct-00 Nov-00Date

Daily Flow (cfs)0.001.002.003.004.005.006.007.008.009.00 Rainfall (in.)RainfallMeanMaxStevenson Creek Watershed Management PlanFinal Report2.3-17J:\DATA\737626\GIS\FIGURES_PDF\SEC2-3.DOCFigure 2.3-8Stevenson Creek Hydrologic RecordLow Flow Detail05101520253035May-00 Jun-00 Jul-00 Aug-00 Sep-00 Oct-00 Nov-00Date

Daily Flow (cfs)0.000.100.200.300.400.500.600.700.800.901.00 Rainfall (in.)RainMeanMinBaseStevenson Creek Watershed Management PlanFinal Report2.3-18J:\DATA\737626\GIS\FIGURES_PDF\SEC2-3.DOCFigure 2.3-9Spring Branch Hydrologic Record050100150200250300350400450May-00 Jun-00 Jul-00 Aug-00 Sep-00 Oct-00 Nov-00Date

Daily Flow (cfs)0123456 Rainfall (in.)RainfallMeanMaxStevenson Creek Watershed Management PlanFinal Report2.3-19J:\DATA\737626\GIS\FIGURES_PDF\SEC2-3.DOCFigure 2.3-10Spring Branch Hydrologic RecordLow Flow Detail05101520253035May-00 Jun-00 Jul-00 Aug-00 Sep-00 Oct-00 Nov-00Date

Daily Flow (cfs)00.10.20.30.40.50.60.70.80.91 Rainfall (in.)RainMeanMinBaseStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\gis\figures_pdf\Sec2-3.doc 2.3.2.3 Water Quality Seven (7) storm event samples and six (6) base flow samples were collected at each monitoring station. The laboratory results are provided in Table 2.3-4. Violations of Class III water quality criteria occurred in a number of instances. Details concerning these exceedences as well as other information concerning the findings of the sampling program are described in the following section.

2.3.3 Water Quality Characteristics Water quality in the Stevenson Creek Watershed is described in the following subsections. These descriptions include assessments of base flow and storm flow and identify probable sources of pollution. Water quality parameters measured during this project are compared to Florida water quality criteria ( Chapter 62-302, Florida
Administrative Code - referred to as water quality standards in this report ) , STORET database values (as published in the 2000 state Section 305(b) report), and comparable literature values, as appropriate. More specifically, comparisons are made with state water quality standard where numeric standards exists; otherwise, comparison is made with Florida averages as published in the 305(b) report (for base flow samples) or literature values (for stormwater runoff samples). Water quality indices are calculated for the base flow samples.

The Florida Department of Environmental Protection (FDEP) recommends the use of a Water Quality Index (WQI) to summarize water quality conditions in rivers and streams (Hand et al. 1996). The WQI is based on six categories of water quality indicators (water clarity, dissolved oxygen, oxygen-demanding substances, bacteria, nutrients, and biological diversity). Several categories contain multiple constituents (e.g., total organic carbon and BOD 5 , within the category of oxygen-demanding substances). In such cases, data availability determines constituent(s) used in calculating the WQI. For each measured constituent, the raw data (e.g., monthly or quarterly observations) are converted to annual averages. The annual averages are then converted to percentiles,Stevenson Creek Watershed Management PlanFinal Report2.3-21J:\DATA\737626\gis\figures_pdf\Sec2-3.docTable 2.3-4 – Laboratory ResultsMetals Oxygen Demand Solids Nutrients

Date Log # Time Type Oil and G r ease Hardness as CaC03 Al As Cd Cr Cu Pb Ni Zn BOD5 COD Total Organic Total Suspe n ded Total Dissolved Ortho Phosphate Total Phosphoru Ammonia Total Kjeldahl Nitrate + Nitrite Organic-N Total NitrogenStevenson Creek (Drew Street)"June 20, 2000" 61864-2 10:19 Base Flow #1 <5.0 140 <0.20 <0.010 <0.0050 <0.010 <0.020 <0.0050 <0.040 <0.020 5.9 30 15.0 6.8 200 0.450 0.56 0.088 1.10 <0.050 1.01 1.10"June 30, 2000" 61983-1 14:15 Storm Event #1 <5.0 76 <0.20 <0.010 <0.0050 <0.010 <0.020 <0.0050 <0.040 <0.020 2.1 30 9.3 <5.0 130 0.170 0.22 0.059 0.66 <0.050 0.60 0.66"July 12, 2000" 62071-2 12:08 Base Flow #2 <5.0 210 <0.20 <0.010 <0.0050 <0.010 <0.020 <0.0050 <0.040 <0.020 <2.0 37 12.0 <5.0350 0.370 0.36 0.140 1.80 <0.050 1.66 1.80"July 20, 2000" 62194-1 12:30 Storm Event #2 <5.0 68 <.20 <0.01 <0.005 <0.01 <0.02 <0.005 <0.04 0.029 24 54 15 15.0 110 0.10 0.17 0.12 0.78 <0.050 0.66 0.78"July 24, 2000" 62218-1 11:35 Storm Event #3 <5.0 71 <0.20 <0.010 <0.0050 <0.010 0.02 <0.0050 <0.040 <0.020 7.2 26 8.2 6.0 94 0.110 0.16 0.290 0.88 <0.050 0.59 0.88"July 31, 2000" 62290-1 17:30 Storm Event #4 <5.0 59 0.69 <0.010 <0.0050 <0.010 <0.020 0.0071 <0.040 0.038 8.9 29 7.4 30.0 86 0.140 0.30 0.058 0.65 0.51 0.59 1.16"August 3, 2000" 62336-2 14:34 Base Flow #3 <5.0 140 <0.20 <0.010 <0.0050 <0.010 <0.020 <0.0050 <0.040 <0.020 2.0 45 11.0 8.4 210 0.200 0.27 0.091 0.81 0.18 0.72 0.99"August 23, 2000" 62526-1 10:27 Base Flow #4 <5.0 210 <0.20 <0.010 <0.0050 <0.010 <0.020 <0.0050 <0.0040 0.200 <2.0 <20 11.0 <5.0 300 0.17 0.21 0.088 0.82 0.27 0.73 1.09"September 13, 2000" 62731-1 13:45 Base Flow #5 <5.0 180 <0.20 <0.010 <0.0050 <0.010 <0.020 <0.0050 <0.040 <0.020 19.0 58 24.0<5.0 240 0.12 0.21 0.150 0.89 0.44 0.74 1.33"September 13, 2000" 62737-3 13:30 Storm Event #5 <5.0 140 <0.20 <0.010 <0.0050 <0.010 <0.020 <0.0050 <0.040 <0.020 <2.0 58 11.0 6.0 220 0.20 0.26 0.037 0.87 0.55 0.83 1.42"September 17, 2000" 62758-2 12:45 Storm Event #6 <5.0 89 0.62 <0.010 <0.0050 <0.010 <0.020 <0.0050 <0.040 0.036 60 38 30.0 26140 0.24 0.49 0.054 1.20 0.23 1.15 1.43"October 12, 2000" 62999-2 14:50 Base Flow #6 <5.0 190 0.33 <0.010 <0.0050 <0.010 <0.020 <0.0050 <0.040 0.022 <2.0 22 10.0 18 300 0.18 0.38 0.038 1.10 0.27 1.06 1.37"November 15, 2000" 63376-2 13:30 Storm Event #7 <5.0 140 0.27 <0.010 <0.0050 <0.010 <0.020 0.0054 <0.040 0.066 14 93 27.0 26 240 0.34 0.57 0.031 1.60 0.34 1.57 1.94Spring Branch (Kings Highway)"June 20, 2000" 61864-1 9:10 Base Flow #1 <5.0 150 0.25 <0.010 <0.0050 <0.010 <0.020 <0.0050 <0.040 <0.020 7.8 43 19.0 16.0 2700.560 0.76 0.110 1.90 <0.050 1.79 1.90"June 30, 2000" 61983-2 15:00 Storm Event #1 <5.0 64 <0.20 <0.010 <0.0050 <0.010 <0.020 <0.0050 <0.040 <0.020 3.3 <20 10.0 8.8100 0.290 0.33 0.079 0.80 0.06 0.72 0.86"July 12, 2000" 62071-1 11:17 Base Flow #2 <5.0 130 <0.20 <0.010 <0.0050 <0.010 <0.020 <0.0050 <0.040 <0.020 6.1 62 20.0 15.0 240 0.640 0.73 <0.030 2.10 <0.050 2.10 2.10"July 17, 2000" 62131-1 15:30 Storm Event #2 <5.0 34 0.44 <0.010 <0.0050 <0.010 <0.020 0.0130 <0.040 0.049 2.2 <20 4.6 39.0 410.210 0.45 0.150 1.40 <0.050 1.25 1.40"July 20, 2000" 62194-2 13:25 Storm Event #3 <5.0 58 0.32 <0.01 <0.005 <0.01 <0.02 <0.005 <0.04 <0.020 14 43 12 14.0 120 0.20 0.27 0.110 0.93 <0.050 0.82 0.93"July 31, 2000" 62290-2 18:45 Storm Event #4 <5.0 56 0.70 <0.010 <0.0050 <0.010 <0.020 0.0078 <0.040 0.037 25.0 58 23.0 23.0 200 0.220 0.35 0.160 0.95 0.18 0.79 1.13"August 3, 2000" 62336-1 13:45 Base Flow #3 <5.0 130 0.65 <0.010 <0.0050 <0.010 <0.020 <0.0050 <0.040 0.024 <2.0 26 13.0 19.0 240 0.260 0.46 0.067 0.94 0.36 0.87 1.30"August 23, 2000" 62526-2 12:05 Base Flow #4 <5.0 160 0.21 <0.010 <0.0050 <0.010 <0.020 <0.0050 <0.0040 0.200 98.0 38 21.0 7.2220 0.230 0.30 0.097 1.10 0.068 1.00 1.17"August 23, 2000" 62526-3 11:45 Storm Event #5 <5.0 120 0.28 <0.010 <0.0050 <0.010 <0.020 <0.0050 <0.0040 0.250 52.0 <20 15.0 21.0 170 0.190 0.36 0.084 1.40 0.32 1.32 1.72"September 13, 2000" 62731-2 15:00 Base Flow #5 <5.0 120 0.22 <0.010 <0.0050 <0.010 <0.020 <0.0050 <0.040 <0.020 12.0 54 18.0 9.2 220 0.17 0.27 0.046 1.20 <0.050 1.15 1.20"September 17, 2000" 62758-1 11:00 Storm Event #6 <5.0 92 0.41 <0.10 <0.0050 <0.010 <0.020 0.0063 <0.040 0.037 12 36 10.0 21 120 0.14 0.41 0.110 0.81 0.25 0.70 1.06"October 12, 2000" 62999-1 13:30 Base Flow #6 <5.0 220 0.39 <0.010 <0.0050 <0.010 <0.020 <0.0050 <0.040 <0.020 2.1 35 11.0 10 330 0.067 0.15 0.120 0.89 0.05 0.77 0.94"November 15, 2000" 63376-1 12:00 Storm Event #7 <5.0 140 0.52 <0.010 <0.0050 <0.010 <0.020 0.0087 <0.040 0.100 21 110 37.0 44370 0.60 1.00 0.078 2.80 <0.050 2.72 2.80Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\gis\figures_pdf\Sec2-3.doc using a database constructed by FDEP staff (Hand et al. 1990, 1996) using data from 2,000 Florida stream monitoring locations. These percentile values, which range from 0 (best quality) to 100 (poorest quality), are then averaged to generate the WQI. The final averaging process ignores water quality categories for which no data are available. The WQI calculated for a given stream-monitoring site can therefore represent the average of from 1 to 6 categories. Although the index can be calculated based on a single category, the use of additional categories provides greater reliability (Hand et al. 1990, 1996).

FDEP recommends the following interpretation of WQI values, based on an analysis of Florida stream data and the US EPA National Profiles Water-Quality Index (Hand et al. 1996):
0 < WQI < 45 = “good” water quality 45 < WQI < 60 = “fair” water quality WQI > 60 = “poor” water quality. Data for four of the six possible water quality index categories was collected at the two sampling stations. Overall water quality at both stations is rated “poor” based on

Table 2.3-5 Water Quality Indices Category Subcategory Drew Street Spring Branch Water Clarity TSS 50.9 70.9 Overall 57.1 64.9 BOD 89.3 90 COD 32.8 46.2 Oxygen Demand

TOC 49.2 58.6 Overall 66.1 62.9 Total Nitrogen 54 61.8 N itrate + Nitrite 70.2 47.7 Nutrients
Total Phosphorous 74.2 79.3
Bacteria Fecal Coliform 90 90
Overall 66.0 72.2Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\gis\figures_pdf\Sec2-3.doc the average of base flow samples taken during this monitoring program with quality at the Spring Branch station rated moderately poorer than at the Drew Street station Table (2.3-5).

2.3.3.1 Petroleum Hydrocarbons Petroleum hydrocarbons include oil and grease; the “BTEX” compounds: benzene, toluene, ethyl benzene, and xylene; as well as other polynuclear aromatic hydrocarbons (PAHs). The most common sources of petroleum hydrocarbons are associated with vehicle usage. These sources include parking lots and roads, leaking storage tanks, automobile emissions, and improper or careless handling or disposal of oil; therefore, petroleum hydrocarbons are typically concentrated along transportation routes. Petroleum hydrocarbons are acutely toxic at relatively low concentrations.

For this study, oil and grease was used as an “indicator” pollutant for petroleum hydrocarbons. The sampling plan specified that if oil and grease concentrations above 5.0 mg/l were detected, then tests would also be conducted for petroleum hydrocarbons. Oil and grease was not detected; therefore, tests for petroleum hydrocarbons were not conducted. While petroleum hydrocarbons are certainly present in any urban area, they do not appear to be a significant concern in the portion of the Stevenson Creek Watershed
that was monitored.

2.3.3.2 Oxygen Demand Oxygen-demanding substances were measured by testing for Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), and Total Organic Carbon (TOC). Maintaining appropriate levels of dissolved oxygen is one of the most important considerations for the protection of fish and aquatic life. The state standard for dissolved oxygen in Class III waters is 5.0 mg/l or greater.

The direct impact of storm water runoff on dissolved oxygen conditions in receiving waters is normally not as important as the secondary impacts. Secondary impacts of low dissolved oxygen conditions include nutrient enrichment, eutrophication, and increased sediment oxygen demand.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\gis\figures_pdf\Sec2-3.doc Table 2.3-6, Base Flow Oxygen Demand
Date BOD 5 (mg/l) COD (mg/l) TOC (mg/l) Stevenson Creek - Drew Street

June 20, 2000 5.9 30 15 July 12, 2000 <2.0 37 12 August 3, 2000 2 45 11 August 23, 2000 <2.0 <20 11 September 13, 2000 19 58 24 October 12, 2000 <2.0 22 10 Mean 5.0 34 14 WQI 89.3 32.8 49.2 Spring Branch - Kings Highway June 20, 2000 7.8 43 19 July 12, 2000 6.1 62 20 August 3, 2000 <2.0 26 13 August 23, 2000 98 38 21 September 13, 2000 12 54 18 October 12, 2000 2.1 35 11 Mean 5.8 43 17 WQI 90 46.2 58.6 Frequency of Exceedance in Florida Streams STORET-10% 0.8 16 5 Median 1.5 46 14 STORET-90% 5.1 146 37 Base flow sampling results values (Table 2.3-6) in comparison to Florida averages), and storm event sampling results (Table 2.3-7) in comparison with Nationwide Urban Runoff Program (NURP) data from the Tampa Bay Sampling sites are provided. Three laboratory measurements appear to be in error and, therefore, were not used. The laboratory is unable to specifically identify the source of the error; however, the error may have been caused by a
standard solution that was
more concentrated than specified by the test. These

erroneous measurements include the base flow sample taken on August 23, 2000 at the Kings Highway Station, the storm event sample that was composited on the same day and location, and the September 17, 2000 storm event sample taken at Drew Street. These readings are suspect due to the much lower COD measurements taken on the same sample. COD should normally be higher than
BOD 5 , and no case should BOD 5 be significantly greater than COD. This is because BOD measures the actual oxygen consumption of microorganisms, and COD measures the amount of oxidant required to oxidize the available organic matter; therefore, a BOD that is higher than a COD implies that more organic material was consumed than was available for consumption.

BOD was still high relative to typical Florida streams even without considering the erroneous measurements. Moderately higher BOD concentrations were present at theStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\gis\figures_pdf\Sec2-3.doc Table 2.3-7 Storm Event Oxygen Demand

Date BOD 5 (mg/l) COD (mg/l) TOC (mg/l) Drew Street June 30, 2000 2.1 30 9.3 July 20, 2000 24 54 15 July 24, 2000 7.2 26 8.2 July 31, 2000 8.9 29 7.4 September 13, 2000 <2.0 58 11 September 17, 2000 60 i 38 30 November 15, 2000 14 93 27 EMC 12.19 47.3 15.7 Kings Highway June 30, 2000 3.3 <20 10 July 17, 2000 2.2 <20 4.6 July 20, 2000 14 43 12 July 31, 2000 25 58 23 August 23, 2000 52 1 <20 15 September 17, 2000 12 36 10 November 15, 2000 21 110 37 EMC 15.35 43.5 16.5 Tampa Bay NURP Minimum 0.7 5 0 Mean 5.4 58 14 maximum 28 210 88

i Erroneous measurement – not usedStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\gis\figures_pdf\Sec2-3.doc Spring Branch station than were observed at the Stevenson Creek station. COD and BOD were near the state average.

2.3.2.3 Solids Solids are one of the most common contaminants found in urban storm water. Solids originate from many sources including the erosion of pervious surfaces and dust, litter and other particles deposited on land surfaces from human activities and the atmosphere. Stream bank and streambed erosion also appears to be a major source of solids in the
Stevenson Creek Watershed.

Solids contribute to water quality, habitat and maintenance problems in Stevenson Creek Watershed. Elevated levels of solids increase turbidity, reduce the depth of light penetration within the water column, and limit the growth of desirable aquatic plants. Solids that settle out as bottom deposits and can alter habitat for fish and bottom-dwelling organisms. Solids also provide a medium for the accumulation, transport and storage of other pollutants including nutrients and metals. Sediment- bound pollutants interact with the water column through cycles of deposition, re-suspension, and re-deposition.

Suspended solids (TSS) concentrations in base flow were high at the Spring Branch station and near the Florida average at the Drew Street station. As expected, suspended solids concentrations increased substantially during storm events with the Spring Branch station experiencing higher concentrations than the Drew Street station. Results are provided on Tables 2.3-8 and 2.3-9.

2.3.2.4 Metals Metals detected in the Stevenson Creek Watershed include aluminum, lead, and zinc. This finding is typical. Aluminum is the second most abundant naturally occurring metal and lead and zinc are the most commonly detected metals in stormwater runoff 1

. Likely sources of the lead and zinc present in the Stevenson Creek Watershed include vehicle usage, atmospheric deposition, and erosion. A major finding of the NURP study
is as follows:

1 Lead and zinc were detected in 94% of NURP samples.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\gis\figures_pdf\Sec2-3.doc Table 2.3-8 Base Flow Solids

Date Total Suspended Solids (TSS, mg/l) Total Dissolved Solids (TDS, mg/l) Stevenson Creek June 20, 2000 6.8 200 July 12, 2000 <5.0 350 August 3, 2000 8.4 210 August 23, 2000 <5.0 300 September 13, 2000 <5.0 240 October 12, 2000 18 300 Mean 6.78 267 WQI 50.9 - Spring Branch June 20, 2000 16 270 July 12, 2000 15 240 August 3, 2000 19 240 August 23, 2000 7.2 220 September 13, 2000 9.2 220 October 12, 2000 10 330 Mean 12.73 253 WQI 70.9 - Frequency of Exceedance in Florida Streams STORET-10% 2 - Median 6.5 - STORET-90% 26.5 -Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\gis\figures_pdf\Sec2-3.doc Table 2.3-9 Storm Event Solids

Date Total Suspended Solids (TSS, mg/l) Total Dissolved Solids (TDS, mg/l) Stevenson Creek June 30, 2000 <5.0 130 July 20, 2000 15 110 July 24, 2000 6 94 July 31, 2000 30 86 September 13, 2000 6 220 September 17, 2000 26 140 November 15, 2000 26 240 EMC 18.3 147 Spring Branch June 30, 2000 8.8 100 July 17, 2000 39 41 July 20, 2000 14 120 July 31, 2000 23 200 August 23, 2000 21 170 September 17, 2000 21 120 November 15, 2000 44 370 EMC 25.13 168 NURP Mixed Urban - Mean 67 -Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\gis\figures_pdf\Sec2-3.doc Heavy metals (especially copper, lead and zinc) are by far the most prevalent priority pollutant constituents found in urban runoff. End-of-pipe concentrations exceed EPA ambient water quality criteria and drinking water standards in many instances. Some of the metals are present often enough and in high enough concentrations to be potential threats to beneficial uses.

Metals can be toxic to aquatic life, and lead and zinc concentrations exceeding state standards were often measured during the monitoring program- more often in storm flow and more often at Spring Branch. Metals concentration for both of the monitoring stations are shown on Table 2.3-10 along with comparison to state water quality criteria and NURP data. The standards for lead and zinc are hardness-dependant, and the
standard for lead was often less than the detection limit.

2.3.3.5 Nutrients Nitrogen and phosphorus are the principal nutrients of concern in urban storm water. The major sources of nitrogen and phosphorus in the Stevenson Creek Watershed are likely associated with landscape runoff (fertilizers and organic debris) and atmospheric deposition. Improperly functioning septic tank systems and animal waste may also be an important source.

There are a number of parameters used to measure the various forms of nitrogen. Ammonia (NH 3 ) nitrogen is the nitrogen form that is usually the most readily toxic to aquatic life. Nitrate (NO 3 ) and nitrite (NO 2 ) are the inorganic fractions of nitrogen. Very little nitrite is usually found in storm water. Total Kjeldahl nitrogen (TKN) measures the organic and ammonia nitrogen forms. The organic fraction is determined by subtracting
the NH 3 from the TKN.

Total phosphorus measures the total amount of phosphorus in both the organic and inorganic forms. Ortho-phosphate measures phosphorus that is most immediately biologically available. Most of the soluble phosphorus in storm water is usually present in the ortho-phosphate form.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\gis\figures_pdf\Sec2-3.doc Table 2.3-10 Metals

Aluminum 1 Lead Zinc Date Type of Flow Measurement (1) Measurement Class III-Fresh Standard Measurement Class III-Fresh Standard Stevenson Creek June 20, 2000 Base Flow #1 <0.20 <0.0050 0.00488 <0.020 0.14096 July 12, 2000 Base Flow #2 <0.20 <0.0050 0.00818 <0.020 0.19874 August 3, 2000 Base Flow #3 <0.20 <0.0050 0.00488 <0.020 0.14096 August 23, 2000 Base Flow #4 <0.20 <0.0050 0.00818 0.200 0.19874 September 13, 2000 Base Flow #5 <0.20 <0.0050 0.00672 <0.020 0.17441

October 12, 2000 Base Flow #6 0.33 <0.0050 0.00720 0.022 0.18258

June 30, 2000 Storm Event #1 <0.20 <0.0050 0.00224 <0.020 0.08400 July 20, 2000 Storm Event #2 <.20 <0.0050 0.00195 0.029 0.07645 July 24, 2000 Storm Event #3 <0.20 <0.0050 0.00206 <0.020 0.07929 July 31, 2000 Storm Event #4 0.69 0.0071 0.00163 0.038 0.06778 September 13, 2000 Storm Event #5 <0.20 <0.0050 0.00488 <0.020 0.14096 September 17, 2000 Storm Event #6 0.62 <0.0050 0.00274 0.036 0.09603 November 15, 2000 Storm Event #7 0.27 0.0054 0.00488 0.066 0.14096 Spring Branch June 20, 2000 Base Flow #1 0.25 <0.0050 0.00533 <0.020 0.14944 July 12, 2000 Base Flow #2 <0.20 <0.0050 0.00444 <0.020 0.13238 August 3, 2000 Base Flow #3 0.65 <0.0050 0.00444 0.024 0.13238 August 23, 2000 Base Flow #4 0.21 <0.0050 0.00579 0.200 0.15784 September 13, 2000 Base Flow #5 0.22 <0.0050 0.00401 <0.020 0.12370

October 12, 2000 Base Flow #6 0.39 <0.0050 0.00868 <0.020 0.20673

June 30, 2000 Storm Event #1 <0.20 <0.0050 0.00180 <0.020 0.07262 July 17, 2000 Storm Event #2 0.44 0.0130 0.00081 0.049 0.04249 July 20, 2000 Storm Event #3 0.32 <0.005 0.00159 <0.020 0.06681 July 31, 2000 Storm Event #4 0.70 0.0078 0.00152 0.037 0.06485 August 23, 2000 Storm Event #5 0.28 <0.0050 0.00401 0.250 0.12370 September 17, 2000 Storm Event #6 0.41 0.0063 0.00286 0.037 0.09876 November 15, 2000 Storm Event #7 0.52 0.0087 0.00488 0.100 0.14096

NURP -Nationwide Mean Residential Mixed Urban Commercial 0.144 0.114 0.104 0.135 0.154 0.226 Tampa Bay NURP Minimum Mean Maximum 0.012 0.058 0.320 0.020 0.097 0.300

1 There is no aluminum standard for freshwater. The aluminum standard for Class III marine waters is 1.5 mg/l.Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\gis\figures_pdf\Sec2-3.doc The degree to which nitrogen and phosphorus are present can determine the trophic status and amount of algal biomass produced. Excess nutrients increase biological productivity. The major impact associated with nutrient over-enrichment is excessive growth of algae that leads to nuisance algal blooms and eutrophic conditions. A secondary impact is the residual negative effect of decomposing algae in the form of sediment oxygen demand that depletes dissolved oxygen concentrations, particularly in
bottom waters.

Nutrient concentrations measured during the monitoring period are presented on Tables 2.3-11 and 2.3-12 in comparison with STORET and NURP data. Nutrient concentrations do not appear to increase with storm event flow; however, since storms produce high flows the resulting increases in masses are significant.

With respect to nutrients, the Spring Branch station had slightly worse water quality than did the Drew Street station with the primary difference being nitrogen forms at each of the station. Higher-than-average levels of inorganic nitrogen levels were recorded at the Drew Street station and higher-than-average organic nitrogen levels were recorded at the Spring Branch station. Ammonia nitrogen often exceeded the state standard during the monitoring period at both stations.

2.3.3.6 Bacteria Fecal contamination is one of the most severe water quality issues in Stevenson Creek. The magnitude and frequency of fecal counts reported in past monitoring (City of Clearwater 1992-1995)) as well as this current program are very high. The state threshold for ranking a stream in the top ten percent of Florida’s worst water quality with respect to fecal coliforms is 960 colony-forming units (CFU) per 100ml. The highest count during this study was 20,000 and previous studies have recorded similarly high counts. The state standard for fecal coliforms in Class III waters is 800 counts per 100 ml.

The University of South Florida Department of Biology accomplished sampling for fecal contamination under a separate monitoring program. A bacterial source trackingStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\gis\figures_pdf\Sec2-3.doc Table 2.3-11 Base Flow Nutrients

Date Ortho Phosphate (mg/l) Total Phosphorus (mg/l) Total Kjeldahl Nitrogen

(mg/l) Nitrate + Nitrite

(mg/l) Organic-N (mg/l) Ammonia (mg/l) Total Nitrogen

(mg/l) Stevenson Creek - Drew Street Station June 20, 2000 0.45 0.56 1.1 <0.050 1.012 0.088 1.1 July 12, 2000 0.37 0.36 1.8 <0.050 1.66 0.14 1.8 August 3, 2000 0.2 0.27 0.81 0.18 0.719 0.091 0.99 August 23, 2000 0.17 0.21 0.82 0.27 0.732 0.088 1.09 September 13, 2000 0.12 0.21 0.89 0.44 0.74 0.15 1.33 October 12, 2000 0.18 0.38 1.1 0.27 1.062 0.038 1.37 Mean 0.25 0.33 1.09 0.20 0.988 0.10 1.28 WQI - 74.2 - 70.2 - - 54.0 Spring Branch - Kings Highway Station June 20, 2000 0.56 0.76 1.9 <0.050 1.79 0.11 1.9 July 12, 2000 0.64 0.73 2.1 <0.050 2.1 <0.030 2.1 August 3, 2000 0.26 0.46 0.94 0.36 0.873 0.067 1.3 August 23, 2000 0.23 0.3 1.1 0.068 1.003 0.097 1.168 September 13, 2000 0.17 0.27 1.2 <0.050 1.154 0.046 1.2 October 12, 2000 0.067 0.15 0.89 0.052 0.77 0.12 0.942 Mean 0.32 0.45 1.36 0.093 1.28 0.088 1.44 WQI - 79.3 - 47.7 - - 61.8 Frequency of Exceedence in Florida Streams
STORET-10% 0.02 - - 0.01 - - 0.5 Median 0.09 -- - 0.1 - - 1.2 STORET-90% 0.89 - - 0.64 - - 2.7 State Class III Standard - - - - < 0.02Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\gis\figures_pdf\Sec2-3.doc Table 2.3-12 Storm Event Nutrients

Date Ortho Phosphate (mg/l) Total Phosphorus (mg/l) Total Kjeldahl Nitrogen

(mg/l) Nitrate + Nitrite (mg/l) Organic-N (mg/l) Ammonia (mg/l) Total Nitrogen

(mg/l)
Stevenson Creek - Drew Street Station June 30, 2000 0.17 0.22 0.66 <0.050 0.601 0.059 0.66 July 20, 2000 0.1 0.17 0.78 <0.050 0.66 0.12 0.78 July 24, 2000 0.11 0.16 0.88 <0.050 0.59 0.29 0.88 July 31, 2000 0.14 0.3 0.65 0.51 0.592 0.058 1.16 September 13, 2000 0.2 0.26 0.87 0.55 0.833 0.037 1.42 September 17, 2000 0.24 0.49 1.2 0.23 1.146 0.054 1.43 November 15, 2000 0.34 0.57 1.6 0.34 1.569 0.031 1.94 EMC 0.19 0.31 0.95 0.36 0.86 0.09 1.31 Spring Branch - Kings Highway Station June 30, 2000 0.29 0.33 0.8 0.055 0.721 0.079 0.855 July 17, 2000 0.21 0.45 1.4 <0.050 1.25 0.15 1.4 July 20, 2000 0.2 0.27 0.93 <0.050 0.82 0.11 0.93 July 31, 2000 0.22 0.35 0.95 0.18 0.79 0.16 1.13 August 23, 2000 0.19 0.36 1.4 0.32 1.316 0.084 1.72 September 17, 2000 0.14 0.41 0.81 0.25 0.7 0.11 1.06 November 15, 2000 0.6 1 2.8 <0.050 2.722 0.078 2.8 EMC 0.26 0.45 1.30 0.14 1.19 0.11 1.41 State Class III Standard - - - - < 0.02 - NURP -Nationwide Mean Residential 0.143 0.383 1.9 0.736 2.636 Mixed Urban 0.056 0.263 1.288 0.558 1.846 Commercial 0.08 0.201 1.179 0.572 1.751 Tampa Bay NURP Minimum 0.02 0.02 0.01 0.18 0.04 0.52 Mean 0.09 0.23 0.34 1.1 0.4 2.0 Maximum 0.22 1.1 0.81 2.7 1.5 3.2Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\gis\figures_pdf\Sec2-3.doc (BST) method was applied to classify the source of fecal matter into three categories – human, dog, and wild animal. The report, which documents the results and findings, is provided in Appendix J

.
The source of most of the fecal contamination was identified as wild animal; however, significant human-sourced contamination was also discovered. The presence of fecal coliform bacteria from human sources was particularly evident at sample site STC1 (near the confluence of Spring Branch with the main branch), a site that is surrounded by onsite wastewater treatment and disposal systems (OSTDS). STC2, on Hammond Branch, was also impacted frequently by indicator bacteria from human sources, and is downstream from another cluster of residences serviced by OSTDS.

Some percent of isolates from other sources will misclassify as human isolatesthis is true of all BST methodologies. The rate of misclassification of isolates into the human category can be used to develop a cut-off point for significant levels of human isolates. In this database, about 20% of wild animal isolates are misclassified as human, and wild animal isolates have the highest rate of misclassification as human of all sources. The conservative rate of 25% is used as the cut-off point for identification of a significant percentage of isolates from human sources in any sample.

Valerie J. Harwood, a professor at the University of South Florida who conducted the BST study for this project, provided the following description of the significance of
fecal coliform in surface waters.

The goal of bacteriological water quality testing is, in large part, to identify water that contains human pathogens in order to protect public health. Ideally, water quality testing would reliably identify public health threats, while allowing full use of waters that do not constitute a health threat. This goal has been elusive, in part because of the limitations of the methods we use. It is difficult, time-consuming and expensive to directly quantify disease-causing bacteria and viruses, and virtually impossible to test for all possible pathogensin a water sample. Thus, we quantify indicator bacteria, whose presence moreor-less reflects the probability that there are pathogens in the water. A major problem with the fecal coliform indicator is that it is a poor predictor of some human pathogens, particularly enteric viruses, but can also be present in waters where there are few or no viral, bacterial or protozoan pathogens. The same problem exists when E. coli , a member of the fecal coliform group, or Enterococcus , a different bacterial group, are used as indicator organisms for water quality.Stevenson Creek Watershed Management Plan Final Report

2.3-35
J:\DATA\737626\gis\figures_pdf\Sec2-3.doc One of the major reasons that fecal coliforms are inadequate indicators is that they are present in the gastrointestinal tract of all warm-blooded animals and some cold-blooded animals. Some animal feces, i.e. those of humans, cattle, and swine, have a higher probability of containing human pathogens than the feces of most other species, therefore many water quality experts would place contamination from these animals in a “high risk” group. Human feces are considered particularly dangerous because of the human-specific viruses transmitted exclusively by human sources. Very low levels of fecal indicator bacteria from a high-risk animal group indicate a greater potential health hazard than higher levels of indicator bacteria from a low risk animal group. There is, however, no testing method approved by regulatory agencies such as the EPA that can be used to determine the source (i.e. cow, human, dog) of fecal indicator bacteria. Such a method would allow much more accurate risk assessment than we can achieve with standard testing methods. It would also allow regulatory agencies to more effectively identify and eliminate the source of bacterial contamination to natural waters, and would contribute greatly to the accuracy of total maximum daily load (TMDL) models.

Due to the history of high fecal coliform numbers in the urban Stevenson Creek watershed in Clearwater, Florida, the City of Clearwater funded a cutting-edge study of the sources of bacteria in this area. Based on land use patterns in the waters studied, one could predict significant fecal inputs from wild animals, particularly birds and raccoons, and from dogs. Other major candidates for fecal coliform contamination in this watershed include onsite wastewater treatment and disposal systems (OSTDS) whose drainfields are not functioning properly, or which have been bypassed. While limited steps can be taken to reduce the amount of dog wastes that enter surface waters, runoff from yards and other surfaces inevitably transports such waste to waters. Contributions from wild animal feces to the watershed are, if anything, more difficult to control than contributions from dogs. It is, however, possible to control the impact of human waste on water quality. Improvements in central sewer systems and OSTDS installations have greatly improved water quality overall in the U.S. since the implementation of the Clean Water Act in 1970. However, continued degradation of water quality in many surface waters, combined with heightened awareness of the dangers of waterborne pathogens, has led to renewed efforts to understand and mitigate the sources of microbial pollution in natural waters.
2.3.4 Nonpoint Source Loading Model A nonpoint source loading model was prepared to estimate pollutant loads from Stevenson Creek Watershed. This model uses the EPA Simple Method, which is an event mean concentration (EMC) approach. In this approach, mass loads are calculated as the product of the EMC and the stormwater runoff volume. The stormwater runoff volume is estimated as the fraction of rainfall appearing as runoff multiplied by the basin area. The EMC is constant; thus, this method is also refereed to as the “constant
concentration” method.Stevenson Creek Watershed Management Plan Final Report

2.3-36
J:\DATA\737626\gis\figures_pdf\Sec2-3.doc This loading model is intended to serve as an estimate. The water quality estimating procedures used for this project are very simple, yet water quality estimations by any means are not precise. Dr. Wayne Huber in the EPA SWMM User’s Manual expressed this fact very well.
Simulation of urban runoff quality is a very inexact science if it can even be called such. Very large uncertainties arise both in the representation of the physical, chemical and biological processes and in the acquisition of data and parameters for model algorithms

Nevertheless, the loading estimates for the Stevenson Creek Watershed presented herein represent a reasonable estimate that can be used to guide management actions.

The flow and water quality data collected for this project (Section 2.3.2) were used along with soils and land use coverage information to develop the runoff coefficients (Section 2.3.4.1) and EMCs (2.3.4.2); subsequently, this information was used in combination with an existing stormwater treatment evaluation to determine mass loads and loading rates. Additional details concerning the individual elements of the analysis are contained in the following subsections.

2.3.4.1 Runoff Coefficients Runoff coefficients are based on soils and landuse and represent the fraction of rainfall appearing as runoff. The relationship between rainfall and runoff is, however, not truly linear; thus, each unique rainfall event will have a different runoff coefficient for a given basin. During the dry season less runoff occurs because more water is required to wet the ground surface, and infiltration occurs at a faster rate. This is because there is less soil moisture. Runoff will occur on a pervious surface only if the rainfall rate exceeds the soil infiltration rate. Infiltration rates are lower when the ground is wet and become equal to zero when the ground is saturated.

The runoff coefficients developed for the Stevenson Creek Watershed are intended to represent the fraction of rainfall appearing as runoff for an average year. The vast majority of published runoff coefficients are intended for use in the Rational Formula for peak discharge rate estimation as opposed to runoff volume estimation.Stevenson Creek Watershed Management Plan Final Report

2.3-37
J:\DATA\737626\gis\figures_pdf\Sec2-3.doc While, by definition, there is no difference between these two types of runoff coefficients (peak rate or flow volume), runoff coefficients used in the Rational formula generally have factors of safety built in. For this reason the runoff coefficients developed for the Stevenson Creek Watershed are generally lower than published runoff coefficients.

The overall runoff coefficients for the monitored basin are 0.29 for the Stevenson Creek Station and 0.27 for the Spring Branch Station. These overall coefficients were calculated using the overall storm event runoff coefficients (Table 2.3-3) for the monitoring period and the overall runoff coefficient for a September 17, 2000 event. Assuming that, in an average year, 60% of the total rainfall depth occurs during the four wet months (June, July, August, and September), the overall coefficients were weighted 60-40 between the “typical wet season event” (September 17, 2000) and the overall monitoring period coefficients. Runoff coefficients developed for this project are shown
in Table 2.3-13.

Runoff coefficients for each unique soil-landuse combination were then developed. The weighted average of these coefficients match the calculated overall runoff coefficients which, in turn, are based on the monitoring data; thus, the runoff coefficients are, in a sense, calibrated. Obviously, runoff coefficients for soils/landuse combinations that are well represented in the monitored basins will be more accurate than combinations that are not well represented.

2.3.4.2 Event Mean Concentrations An EMC is the concentration that has a 50% probability of being exceeded during a storm event; thus, over the course of time, half of the storms will produce concentrations higher than the EMC and half of the storms will produce concentrations
lower than the EMC.

Landuse-based EMCs were developed based on a two-step process. In the first step, in-stream EMCs and runoff coefficients were developed using the monitoring data;Stevenson Creek Watershed Management Plan Final Report

2.3-38
J:\DATA\737626\gis\figures_pdf\Sec2-3.doc Table 2.3-13 Stevenson Creek Watershed Runoff Coefficients

Landuse Soil RC A 0.075 B/D 0.104 C 0.133 D 0.154 UND 0.098 A 0.421 B/D 0.439 C 0.457 D 0.469 W 1.000 A 0.421 B 0.439 B/D 0.448 C 0.457 D 0.469 W 1.000 A 0.347 B/D 0.367 C 0.387 D 0.402 UND 0.363 W 1.000 A 0.347 B/D 0.367 C 0.387 D 0.402 A 0.298 B/D 0.319 C 0.341 D 0.357 W 1.000 A 0.100 B/D 0.128 C 0.156 D 0.177 W 1.000 A 0.149 B 0.176 B/D 0.189 C 0.202 D 0.222 UND 0.170 W 1.000 Medium Density Residential Low Density Residential Commercial Agricultural

Institutional Industrial Highway/Utility High Density Residential Landuse Soil RC A 0.075 B 0.104 B/D 0.119 C 0.133 D 0.154 W 1.000 A 0.124 B/D 0.152 C 0.179 D 0.199 UND 0.146 W 1.000 A 0.050 B/D 0.080 C 0.110 D 0.132 W 1.000 A 1.000 B 1.000 B/D 1.000 C 1.000 D 1.000 W 1.000 B/D 0.046 C 0.110 D 0.132 W 1.000 B/D 0.046 C 0.110 D 0.132 W 1.000 Wetland Non-Forested Wetland Forest Water Upland Forest Recreational Open LandStevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\gis\figures_pdf\Sec2-3.doc Table 2.3-14 In-Stream EMCs

Paramete r Spring Branch EMC (mg/l) Stevenson Creek EMC (mg/l) Pb 0.006 0.004 Zn 0.079 0.030 BOD5 15.350 12.190 TSS 25.129 18.260 TP 0.452 0.310 TN 1.412 1.310 subsequently, the in-stream EMCs were used to develop landuse-based EMCs. The process used to develop EMCs for this project is described in the following three
subsections.

2.3.4.2.1 In-stream EMCs Statistical analyses were conducted using the storm event monitoring data to develop the in-stream EMCs. EMCs are commonly assumed to follow a lognormal
distribution. A normal distribution is the familiar bell-shaped curve. The lognormal distribution is similarly shaped; however, it is the natural log of the data that is distributed symmetrically about the mean
rather than the data itself. Studies 1 have shown that a lognormal distribution best represents EMCs. Lognormal distributions are used for many applications when the sample size is relatively small and variations between individual measurements are extreme. As the sample size increases the mean calculated using a lognormal distribution will approach the arithmetic mean.

In-stream EMCs for the Stevenson Creek and Spring Branch Stations are shown
in Table 2.3-14.

2.3.4.2.2 Existing Stormwater Runoff Treatment Exiting stormwater treatment areas are present in the Stevenson Creek Watershed. These treatment areas consist of permitted dry retention and wet detention pond as well as natural lakes and man-made depressional storage areas. The general locations of these
treatment areas are shown on Figure 2.3-11 inside the subbasin in which they are contained. Assumptions used in this evaluation of existing treatment are as follows:Stevenson Creek Watershed Management Plan Final Report

2.3-40
J:\DATA\737626\gis\figures_pdf\Sec2-3.doc Figure 2.3-11 Existing Stormwater Treatment AreasStevenson Creek Watershed Management Plan Final Report

2.3-41
J:\DATA\737626\gis\figures_pdf\Sec2-3.doc • Treatment depth . Permitted stormwater treatment areas are assumed to provide one inch of treatment for wet detention areas and one-half inch of treatment for dry retention areas. This is consistent with SWFWMD and City of Clearwater design criteria for stormwater treatment areas. Lakes and other “natural” BMPs are assumed to provide a maximum treatment depth of one inch adjusted downward based on the ratio of the BMP area to the tributary basin. This results in a treatment depth range of 0.01 to 1 inch. BMP efficiencies equal to one-half those for wet detention were applied and adjusted by the estimated treatment depth.

• Treatment Coverage . Water is treated only once. In other words water from a BMP (BMP A) which drains to a downstream basin that also contains a BMP (BMP B) is not treated again in BMP B. This assumption simplified the analysis and is rational for a number of reasons. First, most permitted BMPs do not receive runoff from offsite basins and, instead, drain directly to the primary storm sewer system. Second, BMPs in-line to the main storm sewer system will fill with water from the nearest areas first. Subsequent flows will either bypass treatment or reduce the treatment efficiency; therefore, it is reasonable to assume that these flows will not be treated. Treatment coverage is illustrated on Figure 2.3-12

. BMP efficiencies (Table 2.3-15) are based on literature values and adjusted for agreement with measurements taken during the monitoring program.

Table 2.3-15 BMP Maximum Efficiencies

Parameter Wet Detention Dry Retention Natural Treatment Pb 75% 80% 0.38 Zn 60% 80% 0.3 BOD5 50% 80% 0.25 TSS 75% 80% 0.38 TP 60% 80% 0.3 TN 30% 80% 0.15Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\gis\figures_pdf\Sec2-3.doc Figure 2.3-12 Treatment CoverageStevenson Creek Watershed Management Plan Final Report

2.3-43
J:\DATA\737626\gis\figures_pdf\Sec2-3.doc 2.3.4.2.3 Landuse-Based EMCs Landuse-based EMCs were developed based on the measured in-stream EMCs. The process used to develop EMCs was to vary estimates of landuse-based EMCs until agreement with recorded data as well as agreement between the two monitoring stations was achieved. This process was performed mindful of literature values of EMCs so that individual EMC values were not assigned outside of a reasonable range.

The results agree well with the recorded data at the Stevenson Creek Station; however, lead, zinc, BOD and TSS estimates agree less well with measured values at the Spring Branch Station. Obviously, land use variation alone cannot precisely account for variations in water quality from one location to the next; nevertheless, landuse-based EMCs can provide good wash-off quality estimates- both the strengths and the shortcomings of landuse-based EMCs are apparent in the Stevenson Creek Watershed water quality monitoring data.

EMC combinations that “made the numbers work” were found for lead, zinc, BOD, and TSS; however, these EMC combinations produced EMC values that were not reasonable for the land uses. The “true EMC” may not have been measured because of the limited number of samples that were collected. Another possible explanation for the difference is sediment re-suspension in Byrum Sump. The Spring Branch Station is located just downstream of Byrum Sump and it is likely that re-suspended sediments made up significant portions of the samples at this location. This would explain the elevated TSS levels as well as lead and zinc levels. There is normally a correlation between TSS and metals concentrations in stormwater runoff; furthermore, since lead and zinc tend to accumulate in sediments, higher levels could be expected in storm flow as
well as base flow.

The landuse-based EMCs are presented in Table 2.3-16 along with the percent variation from measured values at each station. Table 2.3-17 provides a listing of some of the literature values used for reference in this study.Stevenson Creek Watershed Management Plan Final Report

2.3-44
J:\DATA\737626\gis\figures_pdf\Sec2-3.doc Table 2.3-16 Landuse-Based EMCs for Stevenson Creek Watershed 1

1 All concentrations in mg/l 2 Percent difference between measured loads and calculated loads using landuse-based EMCs. LAND USE Pb Zn BOD 5 TSS TP TN Agricultural 0.004 0.029 15.36 27.64 0.96 1.27 Commercial 0.006 0.044 14.68 38.36 0.40 1.37 High Density Residential 0.013 0.147 20.49 51.41 1.14 2.35 Highway/Utility 0.029 0.138 20.49 40.80 0.32 1.35 Institutional 0.006 0.044 6.83 35.91 0.43 0.97 Industrial 0.004 0.081 12.29 51.14 0.43 1.16 Low Density Residential 0.001 0.009 11.52 7.75 0.25 1.14 Medium Density Residential 0.001 0.011 14.72 11.02 0.28 1.48 Open Land 0.001 0.010 10.67 5.98 0.10 0.81 Recreational 0.001 0.007 1.71 5.98 0.10 0.81 Natural Areas 0.001 0.002 7.68 2.72 0.18 1.03 Water 0.001 0.002 2.73 0.82 0.10 0.81
Agreement with Monitoring Data 2 Monitoring Station Pb Zn BOD 5 TSS TP TN Stevenson Creek 0% 0% 0% 0% 0% 0% Spring Branch 32% 43% 21% 24% 11% 1%Stevenson Creek Watershed Management Plan Final Report

2.3-45
J:\DATA\737626\gis\figures_pdf\Sec2-3.doc Table 2.3-17 Landuse-Based EMCs – Selected Literature Values 1

1 All concentrations in mg/l NURP Median LAND USE Pb Zn BOD 5 TSS TP TN Residential 0.1440 0.1350 10 101 0.383 2.636 Mixed Urban 0.1140 0.1540 7.8 67 0.263 1.846 Commercial 0.1040 0.2260 9.3 70 0.201 1.751
Stormwater Loading Rate Parameters for Central and South Florida LAND-USE Pb Zn BOD5 TSS TP TN General Agricultural - - 3.80 55.30 0.344 2.32 Commercial-High Intensity 0.2140 0.1700 17.20 94.00 0.430 2.83
Multi-Family 0.0870 0.0550 11.00 71.70 0.490 2.42 Highway 0.1890 0.1340 5.60 50.30 0.340 2.08 Industrial 0.2020 0.1220 9.60 93.90 0.310 1.79 Low Density Residential 0.0370 0.0320 4.40 19.10 0.177 1.77 Single Family 0.0480 0.0570 7.40 27.00 0.300 2.29 Open Land/Recreational 0.0250 0.0060 1.45 11.10 0.053 1.25 Water 0.0250 0.0280 1.60 3.10 0.110 1.25 Wetland 0.0250 0.0060 4.63 10.20 0.190 1.6
Hillsborough County LAND-USE PB ZN BOD5 TSS TP TN Agricultural 0.003 0.017 18.30 12.70 2.349 2.97 Commercial 0.004 0.026 2.67 22.92 0.279 2.032 High Density Residential 0.006 0.058 2.60 29.00 1.337 2.047 Highway/Utility 0.960 0.410 24.00 261.00 0.120 4.13 Institutional 0.004 0.026 2.67 22.92 0.279 2.032 Light Industrial 0.006 0.096 2.87 18.20 0.332 2.275 Low/Medium Density Residential 0.008 0.022 1.00 19.00 0.401 1.363
Open Land 0.001 0.006 3.80 11.10 0.050 2.598 Recreational 0.006 0.004 3.80 11.10 0.050 2.598 Upland Forest 0.000 0.000 0.00 0.00 0.000 0 Water 0.000 0.000 0.00 0.00 0.000 0 Wetland Forest 0.000 0.000 0.00 0.00 0.000 0 Wetland Non-Forested 0.000 0.000 0.00 0.00 0.000 0Stevenson Creek Watershed Management Plan Final Report

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J:\DATA\737626\gis\figures_pdf\Sec2-3.doc 2.3.4.3 Results Mass loads are divided into three parts: Gross load, removed load, and net load. These three types of loads are described as follows:

• Gross Load - The mass washed off, or mass generated.

• Removed Load - The mass removed by BMPS.

• Net Load - Gross load minus removed load.

Load totals are provided on Table 2.3-18 and presented visually in terms of loading rate (lb./ac) on Figures 2.3-13 through 2.3-16 . Additional details concerning the results of the nonpoint source loading analysis are provided in Appendix K

. These loading estimates are intended to represent an average year. The annual rainfall used for these calculations was 55.6 inches – this is based on the average annual rainfall depth reported by the SCS in the Pinellas County Soil Survey. According to the “constant concentration” method which was used (refer to Table 2.3.4.2), load estimates for other years (or time periods) could be made by multiplying the loads presented here by the ratio of rainfall, for the period of interest, to 55.6.

The highest load totals were calculated for the Upper Spring basin. Upper Spring basin is also the largest in terms of area; therefore, this result can be misleading. A better indicator of “hot spots” is loading rate, or pound per acre (refer to Figures 2.3-13 to 2.3- 16). Reviewing the results from a loading rate perspective shows the Middle Stevenson basin to have the worst stormwater runoff quality. For example, the net load of TSS originating from Upper Spring Branch is 108,743 pounds per year, and the net TSS loading rate is 65 pounds per acre per year. For Middle Stevenson Creek the net annual load of TSS is estimated at 59,604 pounds and the net TSS loading rate is 111 pounds per acre per year – a smaller load than Upper Spring Branch but a higher loading rate. The Middle Stevenson basin has an abundance of the three factors that cause high loads – soils with low infiltration rates, intense developed land use, and lack of treatment.Stevenson Creek Watershed Management Plan Final Report

2.3-47
J:\DATA\737626\gis\figures_pdf\Sec2-3.doc Table 2.3-18 Major Basin Loads

Watershed Pb Zn BOD 5 COD TSS TP TN Gross Load (pounds per year) Hammond Branch 10 80 36,441 46,777 903 3,861 10 Jeffords Street 5 38 26,273 29,436 574 2,790 5 Lake Belleview 15 118 37,515 73,482 1,080 3,903 15 Lower Spring 4 36 17,527 22,031 451 1,831 4 Lower Stevenson 11 75 33,941 49,546 817 3,715 11 Middle Stevenson 13 104 31,534 61,338 903 3,172 13 Upper Spring 36 325 84,074 147,929 2,907 9,021 36 Upper Stevenson 6 49 26,642 33,141 633 2,704 6 Total 100 826 293,948 463,680 8,269 30,997 100 Load Removed (pounds per year) Hammond Branch 1 9 3,049 6,362 104 236 1 Jeffords Street 1 5 2,889 4,090 74 208 1 Lake Belleview 5 27 8,861 24,454 274 554 5 Lower Spring 1 8 2,250 4,379 78 188 1 Lower Stevenson - - - - - - - Middle Stevenson 0 2 678 1,734 19 68 0 Upper Spring 10 71 15,068 39,186 607 1,048 10 Upper Stevenson 1 6 1,781 4,936 48 101 1 Total 20 128 34,576 85,142 1,205 2,403 20 Net Load (pounds per year) Hammond Branch 9 71 33,393 40,415 799 3,625 9 Jeffords Street 4 34 23,384 25,345 500 2,582 4 Lake Belleview 10 90 28,654 49,028 807 3,349 10 Lower Spring 3 29 15,277 17,651 373 1,644 3 Lower Stevenson 11 75 33,941 49,546 817 3,715 11 Middle Stevenson 13 102 30,856 59,604 884 3,104 13 Upper Spring 25 254 69,006 108,743 2,300 7,974 25 Upper Stevenson 4 43 24,861 28,205 585 2,603 4 Total 80 697 259,372 378,538 7,064 28,594 80Stevenson Creek Watershed Management Plan Final Report

1 3.2 HUMAN-SOURCED FECAL CONTAMINATION STUDY
The sampling and subsequent analysis of fecal coliforms (refer to Section 2.3.3.6 ) that was conducted last year (July 2000 – December 2000) confirmed that fecal coliforms from human sources are present in the watershed. While human input does not appear to be the dominant source of fecal coliform in the watershed, the levels of human-sourced fecal contamination measured during this study (refer to Appenxix J ) are cause forconcern. Human feces are considered particularly dangerous because of the humanspecific viruses transmitted exclusively by human sources. This significant finding underscores the need for accurate information concerning the sources of fecal
contamination within the watershed.
Further study is needed to better define the origins, magnitude, and spatial extent
of fecal contamination from human sources in the Stevenson Creek Watershed. This study will provide information needed to plan and prioritize improvements directed at reducing fecal contamination within the watershed.

3.2.1 Purpose of Further Study
While circumstantial evidence implicates improperly functioning onsite wastewater treatment and disposal systems (OSTDS) in contamination of the Stevenson Creek Watershed, direct evidence is not available. The possible contribution of illicit sewage connections, sewage overflows, and the sub-drain system underlying the streets may also be contributing to the bacterial loading, and while there is a high likelihood that the source is OSTDS, information is not available concerning which OSTDS areas are contributing to the problem.Stevenson Creek Watershed Management Plan Final Report

2 3.2.2 Plan of Study
Some of these issues can be addressed through further study, and a four-step approach is recommended. First, better information regarding the locations and other basic attributes of existing OSTDS and the sanitary sewer system is needed (Step 1). Secondly, additional sampling and field investigations are needed to direct attention to areas that are problematic with respect to fecal contamination (Step 2). Next, focused microbiological sampling can provide direct proof that OSTDS are contributing to water quality impairments (Step 3). Finally, the results of Steps 1 – 3 can be used to reach conclusions concerning the origins, magnitude, and extent of human-sourced fecal contamination within the Stevenson Creek Watershed as well as to provide information needed to plan improvements.
These four steps (Existing Data Compilation and Review, Data Collection and Conventional Sampling, Focused Microbiological Sampling, and Data Evaluation) are more specifically described below.

Existing Data Compilation and Review (Step 1) Existing information concerning the OSTDS and sanitary sewer system should be compiled. In regards to OSTDS, this information should include locations, approximate age, general topography, soil type, and material type, as appropriate. In regards to the sanitary sewer system, this information should include interviews with city staff, results from smoke tests, video logs, rainfall, and flow monitoring as well as population and overall plant flow and capacity data. These sewer system data can be used to provide evaluations concerning the overall soundness of the sanitary sewer system as well as the feasibility of connecting OSTDS areas to the central sewer system.
One of the main purposes of the sanitary sewer evaluation is to assess the likelihood of sewage releases to the environment through overflows, cross-connections, or pipe structural problems. Loose pipe joints and cracks would not be expected to causeStevenson Creek Watershed Management Plan Final Report

3 measurable exfiltration due to high groundwater; however, the possibility of capacity problems due to wet weather inflows should be investigated, as should the possibility of significant cracks or cross-connections with the storm sewer system.
The locations of septic tanks is generally not available (refer to Section 2.3.1.2) but can likely be inferred by cross-referencing sewer service bills and property tax data or other city and county databases. Approximate age can be estimated based on the age of the dwelling or structure, and recent repair permits. The septic tank points can be intersected with available soil data to assign soil type and seasonal high water elevation.
These OSTDS and sewer system characteristics will be used to plan the sampling program and to seek relationships between these characteristics and fecal contamination. The Healthy Beaches Tampa Bay study, an extensive, multi-agency study of Pinellas and Hillsborough County waters, can also be used to identify other areas of interest for the study if desired.

Data Collection and Conventional Sampling (Step 2). The data from Step 1 can be used to develop a field investigation and sampling program designed to “zero-in” on problem areas. Field investigations can be used to collect evidence of illicit sewage connections to the storm sewer system and other problems (i.e. soggy drainfields, etc.). Water quality samples would be collected in channels and storm sewer pipes. The recommended sampling program would consist of a large number of samples from a minimum of two events. The large number of samples is for purposes of better and more refined delineation of problem areas. The sampling frequency will be selected based on costs with a minimum of one sample representative of dry conditions and one sample representative of wet conditions. Stormwater runoff samples are desirable, but introduce cost and logistic problems that should be carefully considered before they are included in this study. All samples will be analyzed for fecal coliforms; in addition, limited bacterial source tracking using antibiotic resistance analysis may be employed.Stevenson Creek Watershed Management Plan Final Report

4 The sampling program will draw attention to problem areas, and together with the information collected in Step 1, will be used to design a microbiological sampling program that is focused on identifying areas where OSTDS usage is problematic.

Focused Microbiological Sampling (Step 3) A detailed microbiological study should be undertaken that explores the prevalence of human pathogens (enteric viruses) and E. coli from human sources at various Stevenson Creek sites. Antibiotic resistance analysis for the source of fecal bacteria will indicate whether the contamination is dominated by human or animal sources. “Tracer” studies, in which a specific bacteriophage (bacterial virus) that cannot infect humans is flushed down the toilets of volunteer homes, can provide evidence of the rate of viral transport from OSTDS to surface water. Bacteriophage studies are superior to dye tracer studies because the bacteriophage particles are similar in size and soil adsorption properties to human viruses, therefore their transport rate is a better approximation for that of viral pathogens than dye particles, which often predict an overly rapid transport rate. Piezometer wells can be used to trace the direction and magnitude of a contamination plume.
If sufficient funds are available, a countywide study could be conducted in which the experiments mentioned above are conducted in OSTDS drainfields situated in various types of soil with different separation distances from the water table, and of various ages. Because they are time-consuming and require a great deal of expertise, such studies are rarely conducted and would contribute a great deal to our understanding of the processes governing transport of human pathogens from OSTDS drainfields.
Data Evaluation (Step 4) The data collected in Steps 1 – 3 will be used to develop and prioritize improvement plans. In addition, correlations and other relationships will be sought so that the results of this study may provide useful information to other areas of Pinellas County that experience fecal contamination problems.Stevenson Creek Watershed Management Plan Final Report

5 3.2.3 Dissemination of Results to End Users
A multi-county task force should be formed with representatives from entities such as city public works, the Pinellas County Department of Health, the University of South Florida, the Southwest Florida Water Management District, Tampa Bay Water, and the Florida Department of Environmental Protection. The purpose of the task force would be to foster communication and facilitate problem solving on water quality issues and studies. The synergistic potential of such a group could serve as a model for similar groups across the state and the nation.Stevenson Creek Watershed Management Plan Final Report

3.3-1 J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC3-3.DOC 3.3 RECOMMENDED WATERSHED MAINTENANCE PLAN
Comprehensive, regular maintenance of stormwater management systems is essential to ensure the systems, once constructed, continue to function within their original design parameters for many years. Maintenance is also often required for aesthetics and safety reasons. This section outlines recommended maintenance practices
and schedules for the Stevenson Creek Watershed.

Open Channels. Excessive vegetation and sediment accumulation can create new flooding problems, and worsen those problems which already exist. In some instances, excessive exotic invasive vegetation and sedimentation can inhibit the growth of beneficial flora and fauna. Excessive vegetation in open channels, particularly exotic or invasive species and plants with stiff, woody stems, can greatly increase the resistance to flow, thereby reducing the capacity of the channel to convey floodwaters and ultimately resulting in higher flood levels. Excessive sediment accumulation reduces the cross sectional area and hydraulic radius of the channel, creating a similar effect. In addition, sedimentation within concrete-lined channels can allow the growth of nuisance vegetation where none was assumed to exist in the roughness coefficients used original design calculations; as has occurred within the channel segment between Court Street and
Pierce Street.
Proposed Watershed Management Plan Projects 1A, 1E, 1F, 2A, 4B, and 4C are improvements to the main channels that incorporate features that will allow improved access for maintenance, including approximately 4,000 linear feet of new maintenance access roads adjacent to Stevenson Creek and Spring Branch. These maintenance access ways typically consist of earthen roads that will facilitate equipment access for slope mowers, small dump trucks, and excavators. The width of the proposed access ways varies from 12’ to 25’ depending on the nature of the anticipated maintenance activities, whether access will be from one side or both sides of the drainage course, and the availability of land.Stevenson Creek Watershed Management Plan Final Report

3.3-2 J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC3-3.DOC The recommended maintenance practice for open channels is mowing, and if necessary, hand removal of invasive vegetation. Spraying of herbicide should be used only in rare cases where lack of access and/or manpower prohibits the alternative methods. Any herbicide spraying should be conducted in compliance with the City of Clearwater National Pollutant Discharge Elimination System (NPDES) permit, which requires the implementation of a spray reduction program. The recommended maintenance type and frequency for each major open channel segment within the Stevenson Creek Watershed is presented Table 3.3-1.

Table 3.3-1 Recommended Channel Maintenance Plan
Channel Segment Applicable Improvement Project Recommended Maintenance Type(s) Recommended Frequency

Stevenson Creek Stevenson Creek - US Alt. 19 to Douglas Avenue Stevenson Creek Estuary Restoration Plan (U.S.A.C.O.E.) Periodic removal of exotic and invasive plant species Once every 2-5 years, or as needed Douglas Avenue to Betty Lane N/A Periodic removal of exotic and invasive plant species Once every 2-5 years, or as needed Betty Lane to Proposed Sediment Sump Control Weir Stevenson Creek Phase 1 (W.K. Daugherty Plans) Initial dredging of accumulated sediment, periodic removal of exotic and invasive plant species Once every 2-5 years, or as needed

Palmetto Street Sediment Sump WMP Project 2A Dredging Annually

Palmetto Street to Drew Street N/A Periodic removal of exotic and invasive plant species Once Every 2 years, or as needed Drew Street to Pierce Street Stevenson Creek Phase 1 (W.K. Daugherty Plans) Periodic removal of accumulated sediment Once every 5 years, or as needed Pierce Street to Court Street Stevenson Creek Phase 2 (CDM Plans) Mowing Semi-annuallyStevenson Creek Watershed Management Plan Final Report

3.3-3 J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC3-3.DOC Table 3.3-1 (Continued) Recommended Channel Maintenance Plan
Channel Segment Applicable Improvement Project Recommended Maintenance Type(s) Recommended Frequency
Mowing of embankment slopes and grassed areas Monthly during the growing
season Court Street to Druid Road WMP Project 3A (Glen Oaks)
Initial monitoring and maintenance of created wetland
areas Quarterly for the first year, Semi-annually thereafter, until beneficial vegetation is well established Repair vandalism damage to gabion walls As needed Druid Road to Jeffords Street Stevenson Creek Phase 2 (CDM Plans) Dredge sediment from Jeffords Street sediment sump Semi-annually, or as needed

Jeffords Street to Lakeview Road WMP Project 4A Mowing Semi-annually
Mowing Semi-annually Lakeview Road to Bellevue Boulevard WMP Project 4B Removal of sediment from behind rock weirs Annually, or as needed
Mowing of embankment slopes and grassed areas Monthly during the growing season until tree canopy is established, semi-annually thereafter Bellevue Boulevard to St. Thomas Drive WMP Project 4C

Removal of sediment from upstream of proposed Bellevue Blvd control weir Annually, or as needed

St. Thomas Drive to Belleair Boulevard N/A None N/A

Belleair Boulevard to South Ridge N/A Mowing Semi-annuallyStevenson Creek Watershed Management Plan Final Report

3.3-4 J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC3-3.DOC Table 3.3-1 (Continued) Recommended Channel Maintenance Plan
Channel Segment Applicable Improvement Project Recommended Maintenance Type(s) Recommended Frequency
Spring Branch Stevenson Creek to Douglas Avenue N/A Periodic removal of exotic and invasive plant species Once every 2-5 years, or as needed Douglas Avenue to Sunset Point Church N/A Jurisdiction of Pinellas County N/A

Sunset Point Church to King’s Highway WMP Project 1A.1 Mowing Semi-annually
Byram Pond WMP Project 1E Dredging Annually Byram Pond to Union Street WMP Project 1F Mowing Semi-annually

Hammond Branch Stevenson Creek to King’s Highway N/A Periodic removal of exotic and invasive plant species Once every 2-5 years, or as needed Flagler Drive Ditch, Highland Avenue to Keene Road N/A Mowing Semi-annually

CSX Railroad north swale, Highland Ave. to Sharondale Drive WMP Project 5A Mowing Semi-annually

Jeffords Street Branch 600’ west of Lake Ave to Lake Avenue. WMP Project 7C Mowing Semi-annually
Mowing of embankment slopes and grassed areas Semi-annually Proposed Pond at Barry Road and Tuscola WMP Project 7C

Initial monitoring and maintenance of created wetland
areas Quarterly for the first year, Semi-annually thereafter, until beneficial vegetation is well established
In addition to the main channel segments listed in the above table, maintenance of the CSX railroad ditch that runs parallel to Maple Street, from Betty Lane to NorthStevenson Creek Watershed Management Plan Final Report

3.3-5 J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC3-3.DOC Greenwood Avenue is recommended. The City currently owns a narrow tract of land adjacent to the south side of the ditch that could be used for maintenance access. Regular maintenance of this ditch would alleviate a structure FPLOS deficiency at 512 Washington Avenue.

Created Wetlands and Littoral Shelves. Proposed Projects 1C, 2D, 3A, 6A, 7A, 7B, and 7C are improvements that incorporate created wetland and/or littoral shelf areas. Monitoring and maintenance of created wetland areas is recommended to ensure the success of the wetland plantings. Maintenance should be conducted quarterly for the first year, and semi-annually thereafter, until beneficial vegetation is well established.

Inlets and Control Structures. Curb and ditch-bottom inlets should be inspected at least annually for blockages due to vegetation, sediment, trash, etc, and for structural integrity and safety. Cleaning of existing and proposed catch basins, or water quality inlets, and CDS units should be conducted based on an established schedule. The City of Clearwater currently has two (2) vacuum trucks for this purpose, and is in the process of purchasing a third one. Periodic inspection of all existing and new water level control structures for structural integrity, safety, accumulated sediment, vegetation, and blockages should be conducted by qualified engineering staff. Vegetation and
accumulated sediment should be removed as needed from around water level control structures to ensure their proper functioning.

Culverts and Storm Sewers. The Stevenson Creek Watershed contains many existing culverts and storm sewers that are several decades old. Most of these culverts are still in serviceable condition and do not require regular maintenance. Those that were identified to be in an obvious state of deterioration are recommended for replacement in one of the 28 recommended projects described in Section 3.1. However, all infrastructure is continually deteriorating, and culverts, storm sewers, and inlets should be inspected periodically (approximately every 3 to 5 years) to identify those in need of replacement. When culverts and storm sewers are identified for replacement, the design should beStevenson Creek Watershed Management Plan Final Report

3.3-6 J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC3-3.DOC evaluated to determine the appropriate size for the culvert to meet current design criteria for flood protection level of service.

Golf Course Best Management Practices . There are currently three golf courses within the Stevenson Creek Watershed. The two largest courses include the Clearwater Country Club Course and the Clearwater Executive Course. The third course is the Glen Oaks Golf Club, a small course that under this plan is proposed to be converted into a stormwater detention facility. Golf courses are some of the most highly maintained developed areas in the state. The expanses of turf grass, manicured landscaping, and sparkling blue water traps lead some people to think that because these areas are not paved, that they are beneficial to the environment. What most people don’t realize is that a considerable amount of physical and chemical manipulation of the natural environment must be undertaken to create this illusion of perfection. The physical alterations include site grading and changing historic drainage patterns, removing native vegetation, and planting exotic, typically high-maintenance vegetation. The chemical manipulations include applications of:

• Fertilizers to help the exotic vegetation survive in the foreign environment,

• Insecticides to protect the exotic vegetation against predators for which they have no natural defense,

• Herbicides to reduce competition from other exotic species, and

• Fungicides to counteract the effects of the excessive amounts of water the exotic turf grasses require. When these chemicals are used, the excess typically is found in surface and ground water, where they can be extremely detrimental to the environment. The effects of pesticides and fertilizers on surface and groundwater quality should motivate golf course operators to opt for application methodologies and the selection of substances with the least potential to cause water quality problems.
A comprehensive program of best management practices specifically for golf courses was developed by the University of Florida Institute of Food and Agriculture Sciences (IFAS). This program discusses ways to reduce or eliminate the need forStevenson Creek Watershed Management Plan Final Report

3.3-7 J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC3-3.DOC fertilizers and pesticides, and recommends more environmentally friendly substances to
use when needed. Some of the recommendations include:

• Use native plants in the landscape. Native plants have adapted to the environment and require less water to survive. They also have natural defenses against many predators, which will reduce the need for pesticides. Native plants will also provide habitat for wildlife.

• There are turf grasses that have been developed for use on golf courses that are hardier and require less water and fertilizer. The Pinellas County Agricultural Extension Office has information on these newly developed grasses.

• Before using a pesticide, identify the target pest. This is essential for the selection of the proper pesticide to be used. Once the pest is identified, check with the IFAS to determine the recommended pesticides for that species. These recommendations will consider soil properties such as runoff potential, leaching potential, and the relative toxicity of the pesticide.

• The application methodology is an important factor to consider when using pesticides and fertilizers. Applications directly on the soil or incorporated into the soil will likely make more product available for leaching or runoff loss. Applications to foliage may lose some product to evaporation, absorption into the foliage, or decomposition in sunlight and thereby would reduce the amount available for wash-off and transport to water bodies.

• Create littoral shelves within the water traps and plant them with emergent aquatic vegetation. The vegetation will improve water quality and reduce the occurrence of algal blooms. Fewer chemicals will be needed to keep the water
features clear.

• Use organic pesticides and fertilizers when possible. Many products have been developed especially for use on golf courses and have been tested successfully by the IFAS. Information on these products is available from the county extension
service.Stevenson Creek Watershed Management Plan Final Report

3.4-1 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Sec3-4.doc 3.4 PUBLIC AWARENESS AND INVOLVEMENT PROGRAMS
An essential component of any restoration plan is a focused and integrated public education and involvement program. Many agencies, both public and private, have information for the homeowner regarding practices that can be implemented at the individual home level for the benefit of the local environment. Most residents, when educated regarding their immediate environment and their potential impact upon it, become more interested in acting more responsibly.

3.4.1 Adopt-a-Creek Program for Stevenson Creek
One of the most successful methods of encouraging public involvement/awareness in the Tampa Bay area is to establish a citizen’s group that “adopts” a piece of property or natural feature. Adopt-a-Pond, Adopt-a-Highway, and Adopt-a-Shoreline are examples of such programs in which a group of citizens accepts the responsibility of maintaining a section of the property on a regular basis. The Adopt-a-Pond program in Hillsborough County has been very successful in the past years, and a similar program for Stevenson Creek could be implemented. The program would encourage residents along the creek to take interest in keeping the creek clean and to help prevent water quality problems.

No regularly scheduled program of adoption and maintenance is currently offered for Stevenson Creek, despite the obvious interest and concern of the local residents. It is recommended that a program of this nature be implemented within the watershed, to accomplish the maintenance and enhancement as needed. The greatest benefit to the watershed would be the regular removal of trash and exotic vegetation within and adjacent to the creek. The creek can be segmented and the responsibilities distributed among the various civic groups and homeowner associations. A group leader will be trained in plant identification and the proper methods of eradication. Pam Leasure with the Pinellas County Department of Environmental Resources (telephone: 727-464-4793) can be contacted if there is an interest in implementing an Adopt-a-Creek program for the
Stevenson Creek Watershed.Stevenson Creek Watershed Management Plan Final Report

3.4-2 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Sec3-4.doc 3.4.2 Proper Use of Pesticides and Fertilizers

3.4.2.1 Pesticide Use
Pesticides are applied to control a pest species, usually by reducing the population toan acceptable level. This objective can sometimes be achieved without damage to nontarget species. However, when pesticides are broadcast sprayed over lawns and fields, a variety of onsite non-target organisms is impacted. In addition, much of the sprayed pesticide invariably drifts away from the intended site and deposits in non-target organisms and ecosystems. Many pesticides are not thoroughly tested prior to distribution and long term effects are not determined until too late. The pesticide DDT is a well-known example. Although the use of DDT was banned in the United States over twenty-five years ago, there are several sites within Tampa Bay where sediment concentrations exceed the No Observable Effects Level (NOEL) (TBNEP 1996).

A preferable alternative to pesticide use is integrated pest management (IPM). Within the context of IPM, acceptable pest control is achieved by employing an array of complementary approaches. The can include:

• use of natural predators, parasites, and other biological controls

• Use of pest resistant varieties of turf grass and landscape plants. Native plant species are frequently more resistant to pests and pathogens than non-native species.

• Modification of environmental conditions so as to reduce the optimality of the pest habitat. This would entail not planting monocultures of specific plants.

• Careful monitoring of pest abundance, and using pest-specific, less toxic pesticides such as Bacillus thuringensis.

• Use of pesticides only when they are required as a specific component of the IPM. Information regarding insect pests, the proper use of pesticides and IPM is available at the Pinellas County Cooperative Extension Service or visit the web site at http://gnv.ifas.ufl.edu/~FAIRSWEB/IPM/IPMFL/IPMFL.HTM

.Stevenson Creek Watershed Management Plan Final Report

3.4-3 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Sec3-4.doc 3.4.2.2 Fertilizers
Most homeowners use too much fertilizer in their landscapes. Over-fertilizing actually encourages the growth and proliferation of certain insects and diseases and increases maintenance needs. When choosing fertilizers, homeowners should request products that contain nutrients in water-insoluble or controlled-release form. These fertilizers dissolve slowly into the soil, reducing amount of nutrients lost in stormwater runoff. The PCCES has free information regarding the most environmentally friendly fertilizers to purchase, and how they should be applied. This information can be obtained
at the extension office or at the web site listed above.

3.4.3 “Green” Thumb Landscaping Practices
The University of Florida Cooperative Extension Service, in partnership with the Tampa Bay National Estuary Program, the Florida Sea Grant College Program and numerous other environmental agencies, has prepared a Landscaping Guide for the Florida Yards and Neighborhoods Program. This informative guide describes the benefits of using native plants in the landscape and how to recreate the habitat that was lost when development occurred. The guide explains such practices as composting, mulching, fertilizing, and watering, and how these common practices can be undertaken without comprising the environment. The program also touches on such issues as maintaining waterfront property in a non-invasive manner, how to maintain a septic system, and how to attract wildlife to your backyard. This information is free from the
PCCES or visit the web site at http://coop.co.pinellas.fl.us /

. A valuable source of information for creating an environmental landscape is the National Wildlife Federation (NWF). This organization has prepared a program that educates homeowners in the benefits of landscaping to attract wildlife and provides the basic information needed to develop wildlife habitat in a residential setting. This program is called the Backyard Habitat program, and participating residents can have their houses certified as habitat by the NWF. This and other useful topics are discussed
on their web site at http://www.nwf.org/

.Stevenson Creek Watershed Management Plan Final Report

3.4-4 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Sec3-4.doc Another successful program is the Naturescape Urban Wildlife Enhancement Program, developed by the Pinellas County Department of Environmental Management (PCDEM). The booklet was produced for the residents within the Allen’s Creek watershed, but the principles are applicable to all watersheds in central Florida. The booklet provides ideas on how to reduce water loss when irrigating the landscape, how to use less pesticides and fertilizers, how to create wildlife habitat, and what plants to put in the landscape, as well as what plants to avoid. This booklet is free and can be obtained
from the PCDEM.

The Southwest Florida Water Management District has produced a significant amount of information on Xeriscaping. This method of landscaping reduces the amount of water that is needed by planting native and non-native plants that require little water, reducing the square-footage of water-dependent turf-grass, and by planting species that do require water in zones that can be irrigated more efficiently. Other aspects of Xeriscaping include the use of mulch to reduce moisture loss from the soil, and the use of mulch made from exotic species such as melaleuca and eucalyptus or from recycled wood products.
Information can be obtained from SWFWMD free or for a nominal fee. The SWFWMD Tampa Field Office can be contacted at (813)-985-7481 or on the world wide web at http://www.swfwmd.state.fl.us/watercon/xeris/swfxeris.html . Information about native plants can be obtained at the Florida Native Plant Society web site at http://www.fnps.org/index.html . Additional information regarding xeriscaping can be
obtained from the PCCES on their web site at http://coop.co.pinellas.fl.us/Toughcom.htm

.
3.4.4 Florida Yards and Neighborhoods Program
The Pinellas County branch of the Florida Yards and Neighborhoods Program was developed by the National Estuary Program and is managed by the Pinellas County Cooperative Extension Service. This program utilizes the educational elements by helping neighborhoods work together to treat area-specific problems such as nutrient- andStevenson Creek Watershed Management Plan Final Report

3.4-5 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Sec3-4.doc chemical-rich stormwater runoff, yard waste disposal, misuse of chemical biocides, and improper shoreline maintenance.

The first step in participation with this program is a preliminary meeting with FYNP staff and homeowners associations requesting participation in the program. Each of the homeowners is given a detailed questionnaire to determine their specific yard maintenance activities. If a neighborhood meets the requirements for investigation by the FYNP, a team of environmental specialists performs inspections, targeting problems associated with landscape practices and stormwater runoff. Results of these inspections are analyzed and presented to the homeowners association along with suggestions on ways to remedy current environmental problems through sustainable yard maintenance practices.

3.4.5 Storm Drain Marking Program An important component of public education for watershed management is the storm drain-marking program. This program enlightens citizens about the potential adverse effects of stormwater runoff entering surface water bodies. Many people allow paint, petroleum products and yard wastes to wash into gutters and into storm drains without consideration of the potential effects on surface waters. The storm drain marking program involves simply painting legible messages on the drains to remind the public where the drains lead. Within the Stevenson Creek Watershed, the messages may read “NO DUMPING - DRAINS TO CLEARWATER HARBOR," or “DUMPING HERE
POLLUTES STEVENSON CREEK AND CLEARWATER HARBOR”. Some of the messages may include illustrations of fish, manatees, wading birds, or dolphins.

The storm drain marking program has been successfully implemented within other areas of the City of Clearwater, and could be implemented within the Stevenson Creek Watershed without significant expense. Volunteers from local schools and civic groups could be organized to conduct the marking under the supervision of officials from various Tampa Bay agencies such as Tampa Baywatch, Tampa Bay National Estuarine Program, and city and county government. Items needed for the drain marking include trafficStevenson Creek Watershed Management Plan Final Report

3.4-6 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Sec3-4.doc cones, a broom, paint, safety vests, instruction sheets, and stencils. These items can be purchased or fabricated from materials costing less than $220.00.Stevenson Creek Watershed Management Plan Final Report

3.5-1 \\TAMFS01\PRJDATA$\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC3-5.DOC 3.5 EXOTIC PLANT ERADICATION PROGRAM
Native plant communities evolve with a complex relationship of natural controls that keep them in balance. These natural controls may include environmental requirements, competing plant species, herbivores including insects, and pathogens. When exotic plants are introduced to areas, they often have a competitive advantage over native plants because natural controls of the exotic plants are not present. Removal of exotic plant species and restoration of native communities includes supplemental control methods to replace natural controls. These supplemental controls may include manual and/or mechanical removal, physical control such as fire or water level manipulation, chemical control including application of herbicides, and biological controls such as natural insect or pathogenic controls. The ultimate exotic plant control objective is to remove exotic species and re-establish natural conditions that will restore normal competitive processes, reducing the potential for re-invasion and the requirement for continual maintenance.
Exotic plant species commonly found in the Stevenson Creek Watershed are listed in
Table 3.5-1:

Table 3.5-1 Exotic Plant Species Found in the Stevenson Creek Watershed

Scientific Name Common Name Scientific Name Common Name Casuarina equisetifolia Australian pine Melaleuca quinquenervia Melaleuca

Colocasia esculenta Wild taro Melia azedarach Chinaberry Dioscorea bulbifera Air-potato Panicum repens Torpedo grass Eichhornia crassipes Water-hyacinth Ricinus communis Castor bean
Enterolobium contortisiliquum Ear-pod tree Sapium sebiferum Chinese tallow tree

Hibiscus tiliaceus Mahoe Schinus terebinthifolius Brazilian pepper Hydrilla verticillata Hydrilla Typha sp. Cattail Leucaena leucocephala Lead tree Urena lobata Caesar's weed Ludwigia peruviana Primrose willow Wedelia trilobata Wedelia
Citation: Florida Exotic Pest Plant Council. FLEPPC 1999 List of Florida's Most Invasive Species. Internet: http://www.fleppc.org/99list.htmStevenson Creek Watershed Management Plan Final Report

3.5-2 \\TAMFS01\PRJDATA$\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC3-5.DOC Current exotic plant control techniques used by City of Clearwater employees for non-aquatic vegetation include manual removal, herbicide application, and burning. Mechanical removal is not effective for control of Australian pine, Brazilian pepper, or
melaleuca when used alone because the disturbance of soil creates conditions for regrowth from seeds and root fragments, and allows further invasion by pioneering exotic plants. Intense follow up with other control methods, preferably herbicide, is also required. Burning and water level manipulation are not applicable within this watershed due to the high density of the residential and commercial areas.
Aquatic nuisance vegetation is removed from lakes and ponds via herbicide application, manual removal, and the installation of native species. Private contractors do the majority of the exotic plant maintenance. The maintenance activity in the watershed is concentrated on the removal and treatment of emergent nuisance species such as Ludwigia peruviana , Typha sp., and Eichhornia crassipes. These plants can choke waterways and cause flooding.
3.5.1 Brazilian Pepper Brazilian pepper is the most aggressive exotic in the watershed, and has been found in every terrestrial plant community. This exotic forms dense monocultures in previously disturbed areas and along roadside ditches. Brazilian pepper seeds are commonly dispersed by birds and small mammals.
Removal techniques for Brazilian pepper currently used in the City of Clearwater include manual removal and herbicide application. Herbicide application involves basal bark application of a Garlon 4/diesel solution in a minimum 4-inch band approximately 6 to 12 inches above ground. The Garlon 4/diesel solution consists of two ounces of Garlon 4, Ortho X-77 spreader, and one quart diesel mixed into three quarts of water. Diesel is added to the herbicide to increase adherence to the stem, and decrease the potential for wash-off during rainfall. Retreatment may be required for larger stems. Dead stems are left standing to decay, or are removed to a landfill or mulch site. Mist application of a Garlon 4/diesel solution using one part Garlon 4 in 50 parts water is also required for treatment of seedlings under mature trees. Garlon 4 should also be applied toStevenson Creek Watershed Management Plan Final Report

3.5-3 \\TAMFS01\PRJDATA$\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC3-5.DOC roots to eliminate regrowth. Safety equipment required during application includes a respirator, safety face shield, rubber gloves, and protective clothing. Eyewash should be carried to flush eyes in case of accidental splash or spray.
3.5.2 Australian pine Australian pine also spreads through dispersion of seeds deposited along shorelines. Australian pine grows rapidly, forms dense monocultures, and tolerates saline conditions and a wide range of soil moisture. The dense shade and thick litter layer produced by stands of Australian pine prevent germination and growth of native species that provide food for birds and small mammals. Australian pine boles do not decay readily after being killed by girdling and tend to dry without decaying (“petrify”).
Australian pine removal techniques currently used in the City of Clearwater include cutting of the stem with a chainsaw, and spraying the stump with the Garlon 4/diesel solution described for Brazilian pepper. The cut stem is left to dry (“petrify”) for later disposal or use as fuel source. The effects of herbicide application will be noticeable within 3 to 7 days of application. Although trees can be treated throughout the year, herbicide application in April and May is most effective, followed by applications in June or July. Retreatment is performed after one month if required for larger trees. Small stems can be hand-pulled, bagged, and burned. The Garlon 4/diesel solution is also applied to roots to eliminate regrowth. Safety equipment required during application is the same as described for Brazilian pepper.

3.5.3 Melaleuca Development activities, water level alterations, and climatic conditions make all areas in south and central Florida vulnerable to invasion by this exotic. Melaleuca grows very rapidly with trees as young as two years producing seeds. Melaleuca bark is thick and fire resistant; consequently, this exotic cannot be controlled by fire. Viable seeds formed on trees cannot be killed with herbicide or by cutting of the stem because any interference with water flow through the xylem to the seed capsules triggers immediate
seed release.Stevenson Creek Watershed Management Plan Final Report

3.5-4 \\TAMFS01\PRJDATA$\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC3-5.DOC Melaleuca removal techniques currently utilized in the City of Clearwater include removal as encountered including manual cutting of the trunk, followed by stump treatment with herbicide Garlon 4. Seed capsules are put in plastic garbage bags within 20 minutes of stem cutting for disposal at the Pinellas County landfill. Landfill disposal includes burial at a depth sufficient to allow decay of the seed capsules, eliminating the potential for future sprouting. Stems are cut up and left to decay. Small seedlings are hand pulled, bagged, and burned; saplings too large to be pulled are sprayed with Garlon 4. Garlon 4 is also applied to the ground within an approximately 10-foot radius of the trunk to prevent growth of seedlings. Retreatment is provided as necessary at approximately six-month intervals.

3.5.4 Other Exotics Other exotics currently present in areas within the watershed include ear-tree, chinaberry, Caesar weed, and air potato. These exotics are more easily controlled than those listed above. Removal techniques currently used for ear-tree include girdle and application of the Garlon 4/diesel solution described for Brazilian pepper. Chinaberry and air potato are controlled through manual removal and application of Garlon 4. These
exotics are removed as encountered.

3.5.5 Estuary Restoration Plan The U.S. Army Corps of Engineers is currently reviewing an application from the City of Clearwater to participate in a Brownfields demonstration project using the Stevenson Creek Estuary. The proposed Section 206 project will involve the removal of approximately 80,000 cubic yards of muck sediments from the creek between the Douglas Avenue Bridge and the North Fort Harrison Bridge. In addition to the muck removal, the project will involve the removal of nuisance species that currently grow on some of the sediment deltas and on the shoreline of the creek. Species to be removed include cattail, torpedo grass, Brazilian pepper, melaleuca, and mahoe. Once the nuisance vegetation accumulated sediments are removed, the shorelines of the creek will be planted with native vegetation, such as mangroves, cord grass and giant leather leaf
fern.Stevenson Creek Watershed Management Plan Final Report

3.5-5 \\TAMFS01\PRJDATA$\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC3-5.DOC 3.5.6 Summary and Recommendations The proposed watershed improvements are expected to effect exotic control activities in areas currently being maintained, and to facilitate removal and maintenance activities in additional exotic species affected areas by increasing accessibility. Some exotic species removal may be proposed as mitigation for impacts to wetlands during watershed improvements.
Precautions must be taken during all grading and filling activities associated with the watershed improvements, as well as removal of large-stem exotics, to minimize the enhancement of seedbed conditions. Enhancement may arise from scraping of existing seedbeds or deposition of materials that provide a seed source for exotics.
Damage to non-target vegetation and potential water contamination are potential concerns for exotics control. Herbicides effective for Australian pine and Brazilian pepper control are not selective and many native species are highly sensitive to these herbicides. Over spray and heavy rainfall following application can wash the herbicide off the trunk and damage non-target vegetation and/or enter surface water. For these reasons, the use of injection techniques instead of basal bark or girdle applications is preferred for exotics control in wetlands. In addition, while the current practice of leaving stems to decay or “petrify” provides some habitat value as bird perches and small mammal cover, stems and debris generated from larger scale exotics removal activities
must be removed from wetland areas.
Exotic plant species control methods and recommendations discussed above are primarily applicable to the undeveloped public lands within the watershed. Development of a detailed plan for exotics removal and maintenance is recommended.Stevenson Creek Watershed Management Plan Final Report

3.6-1 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Sec3-6.doc 3.6 LEGAL AND REGULATORY FRAMEWORK
This section summarizes the existing legal and regulatory framework governing stormwater and environmental management within the City of Clearwater and the Stevenson Creek Watershed. The first four subsections outline the regulatory authority of federal and state agencies over watershed management issues. Implementation of the Watershed Management Plan will require close coordination with these agencies. The fifth and final subsection concerns the City of Clearwater and its stormwater and environmental legal framework governing items such as funding of capital improvement projects, stormwater levels of service, and municipal codes and ordinances regulating stormwater discharges, erosion control, etc.

3.6.1 U.S. Army Corps of Engineers
The U.S. Army Corps of Engineers (USACE) regulates dredge and fill activities within existing wetlands and other surface waters of the United States, including both natural and man-made lakes and ponds. Federal permitting of the recommended projects of the Stevenson Creek Watershed Management Plan will require close coordination with the USACE. The Environmental Resource Permit (ERP) program, implemented jointly in 1995 with the state water management districts, was designed to streamline the permitting process. Although the ERP application is described as a joint state and federal permit vehicle, the USACE application process can be lengthy and complicated even for relatively simple projects. The USACE issues four types of permits depending upon the type of activity proposed. The categories of permits include the 1) Letter of Permission, 2) Individual Permit, 3) Nationwide Permit, and 4) Regional or General Permit.
The permitting process for improvements proposed in this management plan will be a complex process. Because significant drainage improvements are proposed, a conceptual permit approach is recommended to facilitate the process. Once conceptual approval is achieved, the projects within the management plan can be permitted individually and expeditiously. More information regarding federal permitting can be obtained by calling Stuart Santos at (904)-232-2018 or by visiting the USACE web site at http://www.saj.usace.army.mil/permit/types_of_permits.htm.Stevenson Creek Watershed Management Plan Final Report

3.6-2 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Sec3-6.doc 3.6.2 U.S. Environmental Protection Agency
The National Pollution Discharge Elimination System (NPDES) is a federal program implemented as a result of the Clean Water Act. This program, in conjunction with the stormwater pollution prevention plan (U.S. EPA 833-R-92-001, October 1992) requires permit approval and compliance with water quality standards for stormwater discharges from municipal and industrial stormwater treatment facilities and construction sites. In 1998, the EPA issued the Municipal Separate Stormwater Sewer System Permit (MS4 Permit) for Region IV, that includes several municipalities including the City of Clearwater. The 1997 Stormwater Management Plan for the City of Clearwater addressed many of the requirements for compliance with the MS4 Permit, and made recommendations for current and future needs. The implementation of the capital improvements recommended in the Stevenson Creek Watershed management plan, along with the maintenance of standard best management practices during and after construction, will help ensure compliance with the MS4 Permit.

3.6.3 Federal Emergency Management Agency
In 1968, the Federal Emergency Management Agency (FEMA) began the national flood insurance program (NFIP), a cooperative program between FEMA and local governments, of which the City of Clearwater is a participant. The purpose of the NFIP is to identify and map areas of special flood hazards (SFHA), to regulate building construction and related activities within SFHA’s, and to make affordable flood insurance
available to owners of homes and businesses.
The maps of SFHA’s are known as flood insurance rate (FIRM) maps. Once adopted, FIRM maps can be amended by the local community through a formal FEMA/NFIP application process known as a letter of map revision (LOMR). As part of this Watershed Management Plan, the FIRM maps for the City of Clearwater, last updated in 1983, will be amended based on the existing conditions hydrologic and hydraulic modeling of the Stevenson Creek Watershed, and the corresponding 100- and 500-year floodplain maps and flood profiles illustrated on Figures 2.1-15 through 2.1-23.Stevenson Creek Watershed Management Plan Final Report

3.6-3 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Sec3-6.doc The basis for the revision will be better technical information, and a more detailed analysis than was conducted for the original flood insurance study.
Since 1990, the City of Clearwater has participated in the NFIP’s community rating system, which gives flood insurance premium reductions to policyholders in communities that take additional measures to reduce flood damages, beyond the minimum standards necessary to participate in the NFIP. Under the system, communities earn “credit points” for floodplain management activities within the four categories of public information, mapping and regulation, flood damage reduction, and flood preparedness. Communities are assigned a rating between 1 and 10, with class 1 requiring the most credit points and giving the greatest premium reductions, and class 10 providing no reduction in premiums. Currently, the City of Clearwater enjoys a “class 7” status in the CRS, which puts Clearwater in the top 16% of participating communities, and translates directly into a 15% premium reduction for policyholders within an identified SFHA.
Implementation of the Stevenson Creek Watershed Management Plan will qualify the City for additional credit points in the CRS through flood damage reduction. As indicated in Section 3.1, implementation of the flood protection capital improvements of the Plan will eliminate 73% of the identified structure flood protection level of service (FPLOS) deficiencies within the watershed. Under the CRS, additional credit points are also provided to communities that institute programs to relocate or floodproof structures within the 100-year floodplain. It is recommended that concurrent to implementation of the flood protection capital improvement (CIP) projects, the City work with FEMA, the NFIP/CRS, and the owners of the remaining FPLOS deficiencies to relocate or floodproof those remaining FPLOS deficient structures that cannot be cost-effectively remedied by the recommended CIP projects. FEMA provides technical assistance and inmany cases, grant money to help fund the flood proofing or relocation of floodsusceptible structures. Additional information regarding the National Flood Insurance Program is available at http://www.fema.gov/nfip

.Stevenson Creek Watershed Management Plan Final Report

3.6-4 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Sec3-6.doc 3.6.4 Sout h w est F l orida Water Manag e ment Dist r i ct / F l orida Depar t ment of Environmental Protection The Environmental Resource Permit (ERP) Program that became effective on October 3, 1995 governs watershed management activities in Florida including design of new development and stormwater management facilities with respect to allowable rates of runoff, stormwater treatment, and impacts to floodplains and wetlands. The program represents the merging of the former wetland resource permit program from Chapter 403, Florida Statutes (F.S.), with the management and storage of surface water (MSSW) permit program in Part IV of Chapter 373, F.S. The ERP Program applies statewide, except within the Northwest Florida Water Management District, where the former wetland resource permitting program remains in effect.
To allow an applicant to deal with only one agency when seeking an ERP, the review and approval or denial of the ERP permit application will be performed by either the Department of Environmental Protection (DEP), or the Southwest Florida Water Management District (SWFWMD), depending upon the type of activity involved. Operating agreements have been signed by the agencies to specify the responsibilities between them. Information regarding the type of activity that would require coordination
with the DEP is available at their web site at http://www.dep.state.fl.us/

. Any projects within the watershed that are funded fully or partially by the SWIM program will also require permit review by the DEP, to avoid the potential for charges of a conflict of interest. The majority of the permit applications for capital improvements within the Stevenson Creek watershed will likely be made through SWFWMD. Additional information on State Environmental Resource Permitting is available at http://www.swfwmd.state.fl.us/osp/permits.htm

.

3.6.5 City of Clear w ater

C o m p rehensive P l an. The City of Clearwater Comprehensive Plan, as adopted in May of 2000, includes nine major elements. Among the goals stated within these nine elements are the conservation, protection, and restoration of the quality of surface waters within the City,Stevenson Creek Watershed Management Plan Final Report

3.6-5 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Sec3-6.doc the conservation and protection of wildlife habitat, and the management of the quantity and quality of stormwater runoff. The comprehensive plan identifies the need to “continue to prepare stormwater management plans which will identify and prioritize the implementation of programs to improve and enhance stormwater quality and quantity.” Other specific goals, needs, and policies related to watershed management stated within the comprehensive plan are highlighted below:

Future Land Use Element

• No new development or redevelopment will be permitted which causes the level of City services (traffic circulation, recreation and open space, water, sewage treatment, garbage collection, and drainage) to fall below minimum acceptable
levels.
Utilities Element – Sanitary Sewer

• New septic tanks should not be permitted. Residents located in nearby unincorporated areas using septic tanks should connect to the City sewage system, as sewer lines become available.
Utilities Element – Stormwater Management

• The City of Clearwater needs to continue to monitor the stormwater management utility fee rate structure and amend it as required to remain competitive and maintain an adequate funding source to provide revenue for flood control, maintenance, retrofitting, and treatment of stormwater.

• The City of Clearwater needs to take advantage of any alternative funding opportunities that may become available from any State Agency with regard to watershed management and/or general stormwater improvements.

• The City of Clearwater needs to continue to reduce flooding problems and strive for abatement of flood damage to houses and streets.

• The City of Clearwater needs to continue to maintain, correct deficiencies and improve, where necessary, current levels of service. Maintenance andStevenson Creek Watershed Management Plan Final Report

3.6-6 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Sec3-6.doc improvement of the City Stormwater management system must be recognized as a service provided by the City on a regular and continuous basis.

• Natural and man-made wetlands need to be utilized for stormwater storage and protected as natural resources. Wetlands provide a natural wildlife habitat and groundwater recharge functions which are pivotal characteristics of the natural
and urbanized environment.

• The City of Clearwater needs to research and develop new methods that are technically, environmentally, and economically viable of treating stormwater runoff before final discharge to improve and enhance local surface waters.

Conservation Element

• The City shall continue to protect floodplains, drainage ways, and all other natural areas having functional hydrological characteristics.

Recommendations. With regards to level of service goals for drainage and flood protection, it is recommended that Policy 16.1.1 in the Comprehensive Plan be amended to coincide with the flood protection level of service (FPLOS) criteria adopted for the Stevenson Creek Watershed Management Plan. The primary FPLOS criterion is that there is to be no structural flooding (i.e., homes and businesses) for events up to and including the 100- year flood. This criterion refers to the low floor slab elevation (lowest inhabited floor) as the point of structural flooding. This is consistent with FEMA/NFIP guidelines, and has been widely adopted by counties and municipalities across the state and the country.
The secondary set of FPLOS criteria specifies allowable thresholds for street flooding. The criteria is based upon residential, collector, and arterial roadways being passable for the 10, 25, and 100-year flood events, respectively. “Passable” is defined herein as 6” of flooding or less at the lowest edge of pavement in a travel lane. No flooding is allowable on hurricane evacuation routes for events up to and including the 100-year flood. The following table summarizes the FPLOS criteria adopted for the Stevenson Creek Watershed Management Plan and the City of Clearwater:Stevenson Creek Watershed Management Plan Final Report

3.6-7 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Sec3-6.doc Proposed Flood Protection Level of Service (FPLOS) Criteria

FPLOS Category Allowable Flooding Depths
1. Residential Streets, 2 lanes Up to 6” Allowed for 10-year flood
2. Collector Roads, 2-4 lanes Up to 6” Allowed for 25-year flood
3. Arterial Roads, 4 or more lanes Up to 6” Allowed for 100-year flood
4. Hurricane Evacuation Routes No flooding up to 100-year flood
5. Habitable Structures No flooding up to 100-year flood

The above criteria is recommended for retrofit of existing City facilities that currently fall below the minimum levels of service. Due to varying levels of maintenance and the inevitable deterioration of public infrastructure over time, it is recommended that a safety factor be applied to all new stormwater management facilities serving new development within the City. The “safety factor” would help ensure these systems continue to function in the future at the minimum level of service, and could take the form of an additional 6” to 12” of freeboard applied to the minimum criteria stated above.
With regards to reducing damages and losses due to flooding, it is recommended that Policy 16.3 be amended to include a provision that would allow the City, in cooperation with FEMA and/or SWFWMD, to consider the purchase, relocation, or floodproofing offlood-susceptible private properties in cases where it is not technically feasible or costeffective to reduce flood levels through infrastructure improvements. The purchases, relocations, and/or floodproofing should be done in cooperation with willing owners of flood-susceptible homes and businesses, and only after infrastructure improvement alternatives have been explored within an adopted watershed management plan.
Community Development Code. The community development code for the City of Clearwater governs the design and construction of new development and re-development. The applicable divisions of this code include Division 7 – Erosion and Siltation Control, and Division 9 – General Applicability Standards. Within Division 9, the City of Clearwater Subdivision DesignStevenson Creek Watershed Management Plan Final Report

3.6-8 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Sec3-6.doc Standards and Stormwater Drainage Criteria Manual is incorporated by reference. The Stormwater Drainage Criteria Manual specifies the methods to be used for calculating peak rates of runoff. This document includes a requirement for redevelopment of land upon which no stormwater treatment or attenuation facilities exist, whereby the redeveloper is required to provide “treatment of 1⁄2” of rainfall as applied to the entire area of a development project, and 1⁄2 inch as applied over the portion of the site plan undergoing alteration in the case of redevelopment.” The manual also specifies the use of a pre-redevelopment weighted runoff coefficient of 0.2 for a site that drains to an area of known flooding problems, and a coefficient of 1⁄2 of the actual calculated coefficient for a site that does not drain to an area of known flooding problems. This requirement results in a reduction in peak rates of runoff from sites undergoing redevelopment. These provisions exceed the requirements of the SWFWMD, which in many cases of redevelopment do not require any treatment or attenuation.

Recommendations
To ensure compliance with the recommended drainage and flood protection level of service goals stated at the beginning of this section, the City of Clearwater Subdivision Design Standards and Stormwater Drainage Criteria Manual should be amended to include the proposed FPLOS criteria, with an appropriate safety factor to be applied to new development. It is also recommended that possible changes to the Stormwater Drainage Criteria Manual be considered that would allow some flexibility in the methods used to calculate peak rates of runoff, such as allowing the SCS method in place of the rational method. This change would reduce any potential liability the City may be taking on be specifying the hydrologic methods to be used for private development, as these methods may not be the most applicable in all situations.
Municipal Code of Ordinances.
The applicable portions of the City’s Code of Ordinances related to watershed management include the following chapters:
Chapter 32. Utilities. Article VI. of this chapter governs Stormwater Management. This article establishes the legal framework for the City’s Stormwater Utility inStevenson Creek Watershed Management Plan Final Report

3.6-9 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Sec3-6.doc accordance with Florida Statute 403.0893, and establishes the stormwater utility fee structure. Additional articles in this chapter govern Sanitary Sewers, Water Supply, and
Solid Waste.
Chapter 33. Waterways and Vessels. Section 33.003 of Article I prohibits the placing, discharging, or depositing of sewage, trash, garbage, etc., into navigable waters. This includes the banks and shores of any tributaries where this material “is reasonably likely to be washed into such navigable waters, either by ordinary tidal actions or by the action of rain, floods or otherwise.”
Chapter 47. Buildings and Building Regulations. Article I of this chapter specifies the methods and sources used to set the minimum floor elevations for new buildings or additions to existing buildings.
Chapter 51. Flood Damage Prevention . This Chapter governs management of the floodplain within the City of Clearwater including adoption of floodplain mapping, and requirements for new development and building construction, including encroachments into designated floodplains and floodways. Adoption and enforcement of this ordinance is required for participation in FEMA’s National Flood Insurance Program (refer to Section 3.5-3).
Recommendations
Dumping of yard waste into creeks, ditches, swales and even storm sewers is a fairly common practice throughout the Stevenson Creek Watershed (see Figure 3.5-1). This practice increases the workload of City maintenance crews, and degrades the quality of the stormwater by introducing nutrient-rich organic material to the system. When water levels and velocities rise due to heavy rainfalls, the material is washed into the Creek, and downstream where it ultimately deposits in the Stevenson Creek Estuary. The estuary has, in recent decades, become choked with highly organic sediments. Illegal dumping of yard waste has undoubtedly contributed to the accumulation of these sediments.
Section 32.274 of the Code of Ordinances prohibit the placement of solid waste into any creeks, watercourses, storm sewers, and ditches, within the City and prohibits the placement of “waste materials of any kind...which impairs the proper operation of theStevenson Creek Watershed Management Plan Final Report

3.6-10 \\tamfs01\prjdata$\DATA\737626\Reports\MGTPLAN\Final\Sec3-6.doc city’s sewer or drainage system”. Although these ordinances are interpreted to include lawn clippings, leaves, and fallen limbs, etc., such yard waste is not specifically mentioned in this portion of the Code. In order to facilitate the understanding and enforcement of this facet of the Code, it is recommended that “yard waste” be specifically included as a prohibited item.

Figure 3.6-1 Yard waste (Oak leaves) dumped by a resident on the banks of Upper Stevenson Creek. The City Should actively seek to educate its residents on the negative effects of the dumping of yard waste into its creeks, ditches, and storm sewers. If necessary, these education efforts should be followed by active enforcement of the applicable ordinances.Stevenson Creek Watershed Management Plan Final Report

3.7-1 \\TAMFS01\PRJDATA$\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC3-7.DOC 3.7 CAPITAL IMPROVEMENT COST ESTIMATES
For purposes of budgetary planning, cost estimates were made, in 2001 dollars, of each recommended capital improvement project. The cost estimates are based on the conceptual design and are subject to change pending completion of a more detailed design process. Costs for most items were estimated based on past or current similar Parsons ES projects, and by consulting the FDOT 1- and 3-year cost history listings dated February 2001. Mobilization and demobilization costs were typically estimated to comprise approximately 9% of the total construction cost.

Table 3.7-1 summarizes the total cost estimates for the individual projects, detailed
estimates of which are included as Appendix H . The estimates include land acquisition, engineering and related services (surveying, environmental permitting, etc.), construction, and contingency.
Cost estimates for acquisition of private property were based on the most recent assessed value as reported by the Pinellas County Property Appraiser’s Office, multiplied by a factor of 1.5 to include fair market value of the property plus legal fees.
The magnitude and scope of the recommended improvements, coupled with budgetary constraints, will require phased implementation of the plan over a number of years. The capital costs listed in Table 3.7-1 will need to be adjusted annually for inflation, up to the year of actual construction, based on the construction price indices for the applicable year(s). In the next section, the recommended prioritization rankings are presented which will facilitate the development of an implementation schedule.Stevenson Creek Watershed Management Plan

Final Report

Table 3.7-1. Stevenson Creek Watershed Management Plan Capital Cost Estimates

Project Estimated Capital Cost No. Project Description (2001 dollars) Spring Branch 1A.1 Spring Branch Conveyance Enhancements (Lower Portion) $526,115 1A.2 Spring Branch Conveyance Enhancements (Upper Portion) $960,703 1B Springtime Avenue and Douglas Avenue Bridges $830,830 1C Spring Branch Flood Detention Basin $2,634,542 1D Woodland Terrace Storm Sewer Replacement $446,783 1E Byram Pond Dredging and Expansion $831,636 1F Spring Branch Stabilization, Union Street to Byram Pond $933,969 1G Clearview Lake $620,212 1H Betty Lane Forested Habitat Preservation Site $1,100,000 Subtotal (for alternative 2 - excluding project 1B) $8,053,960 Lower Stevenson 2A Palmetto Street Sediment Sump $544,546 2B N. Missouri Ave. and Palmetto St. Drainage Improvements $486,615 2C Installation of Additional CDS Units $526,500 2D Overbrook Avenue Detention Pond $1,755,860 Subtotal $3,313,520 Middle Stevenson 3A Glen Oaks Stormwater Detention Facility $2,203,240 Subtotal $2,203,240 Upper Stevenson 4A Hillcrest Avenue Overflow Bypass Culvert $2,299,109 4B Upper Stevenson Creek Stabilization $1,415,843 4C St Thomas Drive / Bellevue Boulevard Creek Restoration $1,801,913 Subtotal $5,516,865 Hammond Branch 5A Flagler Drive / CSX Railroad North Swale Improvements $737,241 5B Palmetto Street Drainage Improvements $735,643 5C Saturn Avenue Drainage Improvements $303,382 5D Smallwood Circle Drainage Improvements $161,283 5E Lake Hobart Outfall Control Structure $14,300 Subtotal $1,951,848 Lk Bellevue Branch 6A Expansion of Lake Bellevue $1,337,884 6B Turner Street Box Culverts $1,554,761 Subtotal $2,892,645 Jeffords St Branch 7A Crest Lake Expansion $881,466 7B Duncan Avenue/Turner Street Detention Pond $1,494,952 7C Jeffords Street/Barry Road Detention Pond $1,690,634 Subtotal $4,067,053 Grand Total $27,999,132

3.7-2 Table 3.7-1 Costs.xlsStevenson Creek Watershed Management Plan Final Report

4-1 J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC4.DOC 

### SECTION 4.0 WATERSHED MANAGEMENT PLAN PROJECT PRIORITIZATION

As stated in the introduction, the objectives of this Watershed Management Plan are to identify the causes of the problems of flooding, surface water quality degradation, excessive channel erosion, and loss of riparian habitat; and to identify, evaluate and recommend solutions to these problems. The problems and the causes of these problems were identified in Section 2.0. Recommendations for solutions to the problems were made in Section 3.0. This section serves to prioritize the improvements on the basis of benefits provided, cost effectiveness, and logical precedence.
The projects recommended in this document, whether considered singly or as a whole, are economically justifiable, and clearly in the interest of public safety, health, and welfare. The management plan is consistent with the laws of the federal, state and local government, and follows the policies outlined in State, regional, and local comprehensive plans.
In this section, projects that can be expected to provide the greatest overall benefit in the most cost effective manner are identified using a project ranking procedure. This management tool is a convenient and effective method of recommending priorities for the allocation of available funding. To help identify the priority projects in the Stevenson Creek Watershed Management Plan, a set of comparative evaluation criteria were identified, and a project ranking matrix was developed. The evaluation criteria selected as a means of grading the relative merits of the recommended master plan projects are discussed below. Within each category, individual projects were graded on a scale from 0 to 10, with the lowest score indicating no real benefit and the highest indicating a high
beneficial value.

Flood Control Benefits. The relative flood control benefit of an individual project is a function of the number and type of Flood Protection Level of Service (FPLOS) deficiencies remedied by that project. The projects that rank the highest in this categoryStevenson Creek Watershed Management Plan Final Report

4-2 J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC4.DOC will either alleviate flooding over a large geographic area, or reduce flooding within a geographically concentrated large group of flood-susceptible homes and businesses. A score of one-half point was earned for each structure FPLOS deficiency and each residential street FPLOS deficiency remedied by the project. Remediation of each collector, arterial, and evacuation route FPLOS deficiencies earned scores of 1.0, 1.5, and 2.0 points, respectively. The scores were summed for each individual project. Two projects, (3A) Glen Oaks, and (4A) Hillcrest Avenue Bypass, initially exceeded the maximum score of 10, and thus were assigned a score of 10.

Water Quality Benefits. The relative water quality benefits of an individual project reflect the ability of the project to capture and remove pollutant loads from the stormwater runoff prior to discharge into downstream waterbodies. Those projects with little or no real water quality benefits receive a score of 0, while a project specifically designed to provide a high level of treatment of currently untreated stormwater runoff from a large drainage basin would receive a high score. In assigning scores in this category, the total suspended solids (TSS) and total nitrogen (TN) loads expected to be removed (lb./year) by each project were determined from the proposed conditions pollutant loading model. These removal rates were used as comparative indicators of relative water quality benefits. The project with the largest rate of pollutant removal (Glen Oaks), was assigned a score of 10, and the scores for the other projects are based on their individual pollutant removal rates, expressed as a fraction of the removal rates of the Glen Oaks Project.

Ecological Benefits. The potential ecological benefits of individual projects are ranked based on evaluations of the anticipated improvements to wildlife habitat that will be realized after project construction. Factors such as the size of the affected area, current quality and ecological conditions, and proximity to other habitat areas are considered in the evaluation of benefits and the relative ranking. Areas that currently provide no habitat, but will provide significant habitat upon project completion, will rankStevenson Creek Watershed Management Plan Final Report

4-3 J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC4.DOC the highest in the matrix. Conversely, those projects which will have no habitat impacts, such as the replacement of culverts for flood control, will rank the lowest.

Channel Erosion and Sedimentation Control Benefits. Projects which will have little or no effect in the remediation of channel erosion problems and sedimentation in the watershed are assigned a score of 0. Secondary benefits of projects that attenuate downstream peak discharge rates tend to reduce the potential for channel erosion, and therefore would earn the project a score of up to 5, depending on the magnitude of the attenuation and the proximity and severity of downstream erosion problems. Projects designed to permanently remedy severe channel erosion problems along a substantial length of channel would receive the highest ranking of 10. Projects that involve creation or expansion of maintainable sediment sumps on Stevenson Creek and Spring Branch would also receive a high score.

Recreational and Educational Benefits. The recreational and educational benefits associated with a project are those that provide new opportunities for the general public by accommodating the placement of features such as picnic areas and shelters, trails and boardwalks, nature parks, fishing, boating, and/or interpretive exhibits. Projects that provide no new opportunities for recreational and educational benefits receive a score of 0, and those that can provide a high level of recreational and educational opportunity would be assigned a score of 10.

Implementability. Implementability as a ranking criterion is an assessment of the relative severity of obstacles that must be overcome in order to construct the project. It is a cumulative assessment of factors such as property and easement acquisition requirements, permitting requirements, temporary impacts to nearby residences and businesses during construction, long-term maintenance and operation requirements, and relative ease of construction. A low ranking would be assigned to projects which would have a high degree of difficulty related to any or all of these issues. A high ranking would be assigned to a project with no foreseeable implementation concerns.Stevenson Creek Watershed Management Plan Final Report

4-4 J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC4.DOC Relative Benefits to Cost. As stated previously, all of the recommended projects of the Stevenson Creek Watershed Management Plan can be justified economically. However, because funding for public infrastructure improvements is not unlimited, it is useful to identify those projects that provide the most benefit for the least cost. In order to assign a score for this criterion, a total weighted benefits score was assigned to each project based on the sum of the weighted scores of the project in the five categories of flood control, water quality, ecological benefits, erosion control benefits, and recreational/educational benefits. The total benefit score was then divided by the preliminary cost estimate of the project in thousands of dollars. A multiplier was applied to the result to force an average score of 5.0, on a scale of 1 to 10, with 0 being the least cost effective and 10 being the most cost effective. A few projects earned scores greater than 10; these were subsequently reduced to 10. It should be noted that the result is not an actual benefit to cost ratio, but rather a relative measure of each project’s cost effectiveness compared to the other projects the plan.
While each of the listed ranking criteria is an important factor when evaluating the individual watershed management projects, it is not essential that each should have an equal weighting in the evaluation matrix. For that reason, weighting factors were assigned to each, ranging from 1 to 5, to establish the relative importance of individual ranking criteria. The following is a list of the weighting factors used:

Ranking Criterion Weighting Factor

Flood Control Benefits 5 Water Quality Benefits 4 Ecological Benefits 4
Channel Erosion and Sedimentation Control Benefits 3
Recreational and Educational Benefits 2 Implementability 2
Relative Benefits versus Cost 5Stevenson Creek Watershed Management Plan

Final Report Table 4-1. Stevenson Creek Watershed Management Plan Project Ranking Matrix

Flood Water Erosion Recreational/ Ability Relative Control Quality Ecological Control Educational to Benefits Weighted Project Benefits Benefits Benefits Benefits Benefits Implement vs. Cost Score Rank No. Project Description 5 4 4 3 2 2 5 Spring Branch 1A.1 Spring Branch Conveyance Enhancements (Lower Portion) 10 1.5 0 10 0 6 10.0 5.7 3 1A.2 Spring Branch Conveyance Enhancements (Upper Portion) 6.5 0.5 0 0 0 8 4.2 2.8 14 1B Springtime Avenue and Douglas Avenue Bridges 1 0 0 0 0 7 0.7 0.9 28 1C Spring Branch Flood Detention Basin 1 5.7 10 5 2 4 3.9 4.4 6 1D Woodland Terrace Storm Sewer Replacement 2.5 0.1 0 0 0 9 3.4 1.8 22 1E Byram Pond Dredging and Expansion 1.5 0.8 0 5 0 4 3.6 2.0 21 1F Spring Branch Stabilization, Union Street to Byram Pond 0 0 0 10 0 10 3.8 2.6 16 1G Clearview Lake 0.5 0.9 0 1 0 8 1.7 1.3 27 1H Betty Lane Forested Habitat Preservation Site 0 0 10 0 6 3 5.5 3.3 12 Lower Stevenson 2A Palmetto Street Sediment Sump 0.5 0.2 2 9 0 4 10.0 3.7 9 2B N. Missouri Ave. and Palmetto St. Drainage Improvements 1 0.9 0 0 0 9 2.1 1.4 24 2C Installation of Additional CDS Units 0 4 1 0 0 10 4.4 2.4 18 2D Overbrook Avenue Detention Pond 2 1.8 6 0 4 6 3.3 3.0 13 Middle Stevenson 3A Glen Oaks Stormwater Detention Facility 10 10 10 5 10 6 8.8 8.5 1 Upper Stevenson 4A Hillcrest Avenue Overflow Bypass Culvert 10 0 0 3 0 6 3.0 3.3 10 4B Upper Stevenson Creek Stabilization 0 0 0 10 0 8 2.5 2.2 19 4C St Thomas Drive / Bellevue Boulevard Creek Restoration 9.5 0.4 6 2 2 3 5.4 4.5 5 Hammond Branch 5A Flagler Drive / CSX Railroad North Swale Improvements 5.5 0 0 2 0 4 5.3 2.6 17 5B Palmetto Street Drainage Improvements 2 0 0 2 0 8 2.5 1.7 23 5C Saturn Avenue Drainage Improvements 1 0.2 0 0 0 9 2.2 1.3 26 5D Smallwood Circle Drainage Improvements 1 0.1 0 0 0 6 3.9 1.4 25 5E Lake Hobart Outfall Control Structure 0 0.8 0 0 0 10 10.0 2.8 15 Lk Bellevue Branch 6A.1 Expansion of Lake Bellevue 4.5 8.7 7 1 3 8 9.7 6.1 2 6A.2 Upper Lake Bellevue Culverts 7.5 0 0 0 0 10 10.0 4.1 8 6B Turner Street Box Culverts 4.5 1.2 0 0 0 7 2.1 2.0 20 Jeffords St Branch 7A Crest Lake Expansion 2 1.6 6 1 4 10 6.8 4.1 7 7B Duncan Avenue/Turner Street Detention Pond 7 0.8 4 0 0 5 4.2 3.3 11 7C Jeffords Street/Barry Road Detention Pond 8 2.8 5 10 0 3 7.0 5.5 4
Table 4-1 Rankings.xlsStevenson Creek Watershed Management Plan Final Report

4-6 J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC4.DOC The project prioritization ranking matrix for the Stevenson Creek Watershed Management Plan is presented in Table 4-1. It is noted that this ranking matrix evolved over time, with input from all the participating entities and the general public.
It should be stressed that the ranking process is, to a certain degree, a subjective process that is oriented towards personal values. It is, however, a valuable tool for screening projects and grouping them into relative priority classes. It is apparent through examination of Table 4-1 that those projects which serve multiple purposes rank the highest when compared to those with singular objectives. Also apparent is the observation that the projects that rank the highest generally have the highest scores in the relative benefits to cost category.

Logical Precedence. Although not included as a ranking criterion per se, the successful implementation of the Stevenson Creek Watershed Management Plan will require consideration of the logical precedence, or order of construction of the individual projects. Many of the projects will rely on the prior completion of downstream improvements, in order to avoid creating unintended flooding impacts. Or, a project might not function at its intended full capacity unless constructed in conjunction with another nearby project. Within the Stevenson Creek Watershed Management Plan, four groups of projects were identified that require ordering by logical precedence. The four groups could be constructed in any order, however the projects within each group must follow the specified sequences. For comparison, the project rank is provided for each project in the sequence, within Table 4-2 below:Stevenson Creek Watershed Management Plan Final Report

4-7 J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC4.DOC T a b l e 4-2. P r o je c t P r e c e d e n ce Project Precedence Grouping Required Sequence of Construction Project Rank (Independent of Sequence)
1. 1B or 1C 28 (1B), 6 (1C)
2. 1A.1 3
3. 1A.2 14 Spring Branch Group

4. 1G 27
1. 3A 1 Glen Oaks Group 2. 4A, 6B 10 (4A), 20 (6B)
1. 5A 17 Hammond Branch Group
2. 5C 26
1. 6A.1 2 Lake Bellevue Group
2. 6A.2 8

By examination of the Spring Branch Group in Table 4-2, it is apparent that construction of third-ranked project (1A.1) Spring Branch Improvements, Lower Portion, will require the prior construction of a lower-ranked project, either (1B) or (1C), in order to avoid downstream flooding impacts associated with the channel improvements. The preferred alternative, Project (1C) Spring Branch Detention Basin, is close in rank to project (1A.1) at a rank of 6. However, if Project (1C) cannot be implemented, for any reason, 28 th -ranked Project (1B) Springtime Avenue and Douglas Avenue Bridges must be built instead. This raises the question of how to assign priorities to two projects with widely different ranks that must be built together. This could be resolved by re-assigning some of the flood control benefits from Project (1A.1) to (1B), until the scores of the two projects in Table 4-1 are equal. The resulting weighted score would be 3.8, which would result in an overall rank of 8 for the combined projects (1A.1 and 1B). The relative benefits to cost scores for projects (1A.1) and (1B) would change to 9.1 and 7.0, respectively.
In the remaining project precedence groups, the project precedence follows the order of the project rankings. Projects not specifically listed in the above table areStevenson Creek Watershed Management Plan Final Report

4-8 J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC4.DOC considered “stand alone” projects that could logically be constructed at any point during plan implementation.

Public Acceptance. Public acceptance is a qualitative measure of the support for a particular project among the City’s taxpaying residents. In the early planning stages of a future public works project, public acceptance of the project can be difficult, if not impossible to gauge with any certainty. For this reason, it was not included herein as a ranking criterion. However, public involvement is a very important component of this plan; watershed improvements cannot be realized without the willingness and cooperation of residents within the watershed boundaries. For this reason, three (3) public meetings, or workshops, are being held to provide information and to receive comments and suggestions from the public. These comments and suggestions have helped to determine improvement projects and priorities. The first meeting was held in November of 1999, prior to the commencement of the project, to receive input from the public on known problems. A total of 68 questionnaires were received, containing descriptions by the residents of problems of sedimentation/erosion, water quality, and flood control. These questionnaires, along with the City’s complaint logs, were used to create a GIS map of the known problem areas, which was compared with the results of the computer modeling analyses by overlaying it on the 100-year floodplain map and the pollutant loading map. This information was then used in identifying areas to be targeted for watershed improvements.
The second meeting was held in January of 2001, where the results of the existing conditions analysis were presented along with the preliminary identified solutions for flood control, water quality, erosion and sedimentation. The residents were asked to comment in writing on the potential improvement projects. Approximately 70 residents attended, and 28 questionnaires were filled out. Most of the project-related comments received were positive, and many additional suggestions were made regarding specific components of the projects. These comments and suggestions were thoroughly reviewed and considered during the final completion of the Stevenson Creek Watershed Management Plan. Public meeting questionnaires from the first two public meetings areStevenson Creek Watershed Management Plan Final Report

4-9 J:\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC4.DOC included as Appendix L of this report. A third public meeting is scheduled to be held later this year to present the completed Plan during a City Commission workshop, which will be televised city-wide.
Through the public meetings, workshops, and meetings among members of the project team, five projects were identified as potentially controversial projects. Project 3A (Glen Oaks), although on City-owned property, will eliminate the existing golf course at that location, currently operated through a lease agreement by the non-profit Chi-Chi Rodriguez Foundation. Projects 4C (St. Thomas Drive to Bellevue Boulevard), and 7C (Jeffords/Barry Road Pond) were identified as potentially controversial projects due to the proposed acquisition of several residential properties. Projects 6A (Expansion of Lake Bellevue) and 7A (Crest Lake Expansion) were identified by the City Parks and Recreation Department as potentially controversial due to the proposed conversion of existing upland park areas to wetland habitat.
Winning public support for these projects through the City’s public information initiatives will be crucial to successful implementation of these projects. The final design and implementation of these projects must be sensitive to resident’s potential concerns regarding alternative recreational opportunities, the environment, safety, aesthetics, and property values.Stevenson Creek Watershed Management Plan Final Report

5-1 \\TAMFS01\PRJDATA$\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC5.DOC 

### SECTION 5.0 REFERENCES AND BIBLIOGRAPHY

5.1 DRAINAGE, HYDROLOGY, AND FLOOD PROTECTION
Reports
City of Clearwater 1997 Watershed Management Plan, Volume II . Post, Buckley, Schuh & Jernigan
City of Clearwater Comprehensive Plan . May 18, 2000, City of Clearwater Planning Department.
City of Dunedin Comprehensive Plan , City of Dunedin Planning Department
Pinellas County Storm Drainage Basin Study Technical Appendix – Spring Branch of Stevenson Creek Basin and Coastal Zone 4 Basin . October 1981, Henningson, Durham & Richardson, Inc.
Reducing Losses in High Risk Flood Hazard Areas: A Guidebook for Local Officials . 1985, Association of State Floodplain Managers
Repetitive Loss Report – City of Clearwater, FL . October 1998, FEMA
Summary Report for Stevenson’s Creek. August, 1988, W.K. Daugherty Consulting Engineers, Inc.
Technical Information Prepared in Support of Request for Stevenson Creek FEMA Letter of Map Revision. May 1998, Camp, Dresser and McKee.
Hydrologic and Hydraulic Models Documentation
FEMA, 1995. Guidelines and Specifications for Study Contractors

. Shearman, J.O., Kirby, W.H., Schneider, V.R., and Flippo, H.N. U.S. Geological Survey, 1986. Bridge Waterways Analysis Model. USDOT/FHWA Research Report No. FHWA/RD-86/106
Singhofen, P.J., and Eaglin, L.M. 1995-2000. AdICPR User’s Manual, Version 2.20.
USDA SCS, 1986. Technical Release 55, Urban Hydrology for Small Watersheds.Stevenson Creek Watershed Management Plan Final Report

5-2 \\TAMFS01\PRJDATA$\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC5.DOC Studies in Local Hydrology
Broska, James C., Barnette, Holly L., 1999. Hydrogeology and analysis of aquifer characteristics in west-central Pinellas County, Florida . U.S. Geological Survey OF 99-0185.
Gillen, Denis F., 1996. Determination of roughness coefficients for streams in west-central Florida. U.S. Geological Survey OF 96-226.
Lopez, M.A., Michealis, D.M., 1979. Hydrologic data for urban watersheds in the Tampa Bay Area, Florida. U.S. Geological Survey WRI 78-125.
Lopez, M.A., Woodham, W.M., Magnitude and frequency of flooding on small urban watersheds in the Tampa Bay area, west-central Florida. 1983. U.S. Geological Survey WRI 82-42.
Trommer, J.T., Loper, J.E., Hammett, K.M., and Bowman, G., 1996. Comparisonof estimated and observed stormwater runoff for fifteen watersheds in westcentral florida, using five common design techniques. U.S. Geological Survey OF 96-129.
Topography, As – Built Plans and Surveys

3 rd Avenue Drainage Improvements Record Drawings. March 2000, City of Dunedin Department of Public Works and Utilities.
City of Clearwater Stormwater Atlas. 1996-1999, City of Clearwater Public Works Administration, Engineering.
City of Dunedin Stormwater Atlas. 1999, City of Dunedin Engineering Section
Highland Avenue Stormwater Improvements As-Built Plans. November 1998, HDR Engineering, Inc.
MSSW and ERP permit information on file with the Southwest Florida Water Management District (various files).
Pinellas-Anclote Basin Aerial Photography with Contours. March 1977, May 1979, and December 1985, Southwest Florida Water Management District.
Spring Branch of Stevenson’s Creek Drainage Basin Field Survey Notes. March 1979, Pinellas County Engineering Department.Stevenson Creek Watershed Management Plan Final Report

5-3 \\TAMFS01\PRJDATA$\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC5.DOC Stevenson Creek – Channel Improvements – Phase II Plans. March 1995, Camp, Dresser and McKee.
Stevenson Creek Sediment Evaluation with Cross Sections. August 1999, City of Clearwater Public Works Administration, Engineering.
Stevenson’s Creek Watershed Channel Improvements, Phase 1 As-Built Plans. February 1993, W.K. Daugherty Consulting Engineers, Inc.
The Mall From Union Street to the South Terminus Record Drawings. July 1994, Seminole Engineering.
Villas at Renaissance Square (Old Sunshine Mall) Construction Plans. January 1999. Florida Design Consultants, Inc.
5.2 WATER AND SEDIMENT QUALITY
Reports
City of Clearwater 1997 Watershed Management Plan, Volumes II and III . Post, Buckley, Schuh & Jernigan
City of Clearwater City-Wide Surface Water Quality Technical Report , August 1992-September 1995. Post, Buckley, Schuh & Jernigan, Inc.
Stevenson Creek Estuary Preliminary Restoration Plan . October 2000, U.S. Army Corps of Engineers, Jacksonville District
Stevenson Creek Sediment Characterization and Removal Feasibility Study, Final Report , August 1998. BCI Engineers and Scientists, Inc.
Studies in Local Water Quality
Fernandez, M. and Hutchinson, C.B., 1993 Hydrogeology and Chemical Quality of Water and Bottom Sediment at Three Stormwater Detention Ponds, Pinellas County, Florida U.S. Geological Survey Water Resources Investigations Report 92-4139
Harper, H.H., Environmental Research and Design, Inc., 1994. Stormwater Loading Rate Parameters for Central and South Florida.
Kantrowitz, I.H., Woodham, W.M., 1995. Efficiency of a stormwater detention pond in reducing loads of chemical and physical constituents in urban streamflow, Pinellas County, Florida . U.S. Geological Survey WRI 94-4217.Stevenson Creek Watershed Management Plan Final Report

5-4 \\TAMFS01\PRJDATA$\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC5.DOC Lopez, M.A., Giovannelli, R.F., 1984. Water-quality characteristics of urban runoff and estimates of annual loads in the Tampa Bay area, Florida. U.S. Geological Survey WRI 83-4181.
Raw Water Quality Data
City of Clearwater Ambient Surface Water Monitoring Program, 1992-1995
Environmental Data Report , Approximate 1⁄4 Mile Radius, Clearwater Brownfields Area Clearwater, Florida, 1999. Environmental Data Management, Inc.
Marshall Street WWTP Parameter Monitoring Reports 1991-1999
Pinellas County Ambient Surface Water Quality Monitoring Program, Pinellas County Department of Environmental Management
Septic Tank Permit Database, 2000. Pinellas County Health Department
Southwest Florida Water Management District, Lake Bellevue Monitoring Program, 1996-1997

5.3 NATURAL RESOURCES

Internet sites
Audubon - Florida Audubon Society http://www.audubon.usf.edu/audubon1.htm
Florida Cooperative Extension Service http://www.wec.ufl.edu/
Florida Cooperative Extension Service-Wildlife Extension http://www.wec.ufl.edu/extension/
Florida Fish and Wildlife Conservation Commission - Homepage http://www.state.fl.us/fwc/
Florida Fish and Wildlife Conservation Commission - Florida's Endangered Species, Threatened Species And Species Of Special Concern http://fcn.state.fl.us/gfc/pubs/endanger.html

Florida Fish and Wildlife Conservation Commission - Publications http://www.state.fl.us/fwc/pubs/pubs.html
Florida Museum of Natural History http://www.flmnh.ufl.edu/Stevenson Creek Watershed Management Plan Final Report

5-5 \\TAMFS01\PRJDATA$\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC5.DOC Florida Natural Areas Inventory - Species and Natural Community Summary for Hillsborough County http://www.fnai.org/HILL-SUM.HTM
The Nature Conservancy http://www.tnc.org/
The Nature Conservancy http://www.tnc.org/frames/index.html?/html/list.html
University of Florida EDIS http://edis.ifas.ufl.edu/

USEPA Surf Your Watershed http://www.epa.gov/surf/
USFWS Region 4 http://southeast.fws.gov/
USFWS Biological and Natural History Information http://refuges.fws.gov/NWRSFiles/WildlifeMgmt/SpeciesAccounts/SpeciesAccou ntsIndexBirds.html
USFWS Endangered Species Homepage http://endangered.fws.gov/endspp.html
U.S. Natural Heritage Programs: Florida Natural Areas Inventory http://www.fnai.org/

Printed Material
Ashton, Ray E. 1996. Rare and Endangered Biota of Florida. Volume V. Birds

. University Press of Florida, Gainesville.
Exotic Pest Plant Council, 1997. List of Florida’s Most Invasive Species . EPPC Committee on Invasive Species.
Florida Natural Areas Inventory, 1990. Guide to the Natural Communities of Flor ida. FNAI and the Florida Department of Natural Resources.

Gilbert C.R. - Editor. Rare and Endangered Biota of Florida Volume II Fishes, 1992.
Humphrey, Stephen R. 1992. Rare and Endangered Biota of Florida. Volume I. Mammals. University Press of Florida, Gainesville.
Kale, H.W. II, and D.S. Maehr. Florida's Birds - A Handbook and Reference, 1990.
Moler, Paul E. 1992. Rare and Endangered Biota of Florida. Volume III Amphibians and Reptiles. University Press of Florida, Gainesville.Stevenson Creek Watershed Management Plan Final Report

5-6 \\TAMFS01\PRJDATA$\DATA\737626\REPORTS\MGTPLAN\FINAL\SEC5.DOC Rodgers J.A. Jr., H.W. Kale II, and H.T. Smith - Editors. Rare and Endangered Biota of Florida Volume V Birds , 1996.
USFWS, 1999.. South Florida Multi-Species Recovery Plan . Vero Beach Office, Florida
USFWS, 1989. Florida Manatee Recovery Plan ., Atlanta, Georgia.
USFWS, 1997. Endangered and Threatened Wildlife and Plants, Federal Register 50 CFR 17.11 and 17.12.
Wunderlin, Richard P., Bruce F. Hansen, and Edwin Bridges, 1998. Atlas of Florida Vascular Plants . Institute for Systematic Botany, University of South Florida.

Personal Communications
Lane, Geof, director, Clearwater Marine Aquarium.
Williams, Jane, member, Clearwater Audubon Society.1 

## Final Report
Bacterial Source Tracking Using Antibiotic Resistance Analysis of Fecal Coliforms
Stevenson Creek, Clearwater, Florida
June – December, 2000

Valerie J. Harwood and John E. Whitlock University of South Florida Department of Biology

( vharwood@chuma1.cas.usf.edu 

### )
March 20, 20012 Introduction
Various bacteria are found in the digestive tracts and feces of wild and domestic animals and humans. Some of these bacteria including fecal coliforms and fecal streptococci are used as indicators of fecal contamination when present in natural waters. Unfortunately, the mere presence of these indicator bacteria is not informative as to the source of fecal pollution, an important factor for risk-assessment and remediation. Consequently, several methods collectively known as bacterial source tracking (BST) methods have been developed to “fingerprint” fecal indicator bacteria in order to determine their host or source (e.g. human, dog, wild animal) and may be based on either the genetic make-up of the bacteria, or on physiological characteristics such as resistance to various antibiotics. Using antibiotic resistance analysis (ARA), it is possible to assess the source of indicator organisms based on a much larger subset of the bacterial population than is currently possible using genetic methods. ARA was used to determine the source of fecal contamination in this study essentially as described in Harwood et. al 2000.
In any BST method, a database of fingerprints, or patterns, of bacteria isolated from the feces of known source animals (e.g. humans, dogs, wild animals) must first be constructed and tested for its predictive accuracy. This database is called the calibration data set. Discriminant analysis, a multivariate statistical test, is used to analyze the data. The ability of the database to accurately predict the source of indicator organisms is assessed using isolates from known sources as “unknown” or test isolates. The database can also be self-crossed, that is, the database isolates are used as both the calibration data set and the test data set. The database used in this study consists of 3309 fecal coliform isolates from six sources, humans (domestic wastewater), dogs, cattle, chickens, pigs and wild animals (mainly raccoons and birds). The average rate of correct classification (ARCC) is a measure of the predictive accuracy of the database, and is obtained by self-crossing the database, adding the number of correctly classified isolates in all source categories, and dividing by the total number of isolates. The ARCC of this data set is 57.2% when 6 source categories are used in the analysis. The chance of an isolate falling into one of 6 categories by chance if categorization were random is 16.7%, therefore the antibiotic resistance patterns of fecal coliforms have substantial predictive capacity with respect to bacterial sources (Harwood et al., 2000).
In any database, some percent of isolates from other sources will misclassify as human isolates. The rate of misclassification of isolates into the human category can be used to develop a cut-off point for significant levels of human isolates. In this database, about 20% of wild animal isolates are misclassified as human, and wild animal isolates have the highest rate of misclassification as human of all sources. The conservative rate of 25% is used as the cut-off point for identification of a significant percentage of isolates from human sources in any sample.

Stevenson Creek
This study was initiated in order to identify the dominant source(s) of fecal contamination to Stevenson Creek in Clearwater, Florida. Five sites were chosen to represent areas where routine monitoring has shown high levels of fecal coliforms. Two of the sites were located at the composite samplers previously installed for the project (Comp1 and Comp2). Comp1 is located at the golf course on the main branch of Stevenson Creek; Comp 2 is located on Spring Branch off King Highway. Sites previously designated for monitoring efforts were sampled: STC1 at Spring Branch, STC2 at Hammond’s Branch and STC5 at Evergreen.
Sampling dates were June 27, July 25, August 22, September 19, October 23, November 13, and December 27, 2000. Isolation of fecal coliforms was poor from November with samples yielding only an estimate of population density and no information as to source of contamination. Consequently, additional samples were collected in December.3 Results
The dominant sources of fecal coliform isolates obtained from the five sites over the course of this study were wild animal, dog and human. The overall trend was for wild animal isolates to comprise the majority of fecal coliforms obtained when colony forming units (CFU) counts exceeded the acceptable limit of 200CFU/100ml. STC1 and STC2 sampled on 6/27/00 were the only observations where exceedingly high CFU counts co-occurred with a majority of human isolates. On 8/22/00 at STC1, the majority of isolates were dog and the CFU count was 300/100ml. Samples from the month of September yielded a majority of human isolates from all sites while densities of coliforms were low, ranging from 7-26 CFU/100ml. The above results suggest that source most frequently contributing to excessive fecal coliform counts was wild animals followed by human and dog isolates.
Some statistically significant relationships were apparent between the CFU counts and classification of isolates. The percentages of isolates from specific sources were compared to CFU/100ml using a regression analysis. There was a significant, inverse relationship between the percentage human isolates and the CFU count for Comp2, i.e. as the CFU count went down over the study period, the percentage of human isolates went up , P=0.019, r 2 = 0.87 (Fig. 9). While this relationship was not observed for the other four sites examined individually, it was observed when data from all sites were pooled, P=0.001, r 2 =0.34 (Fig 11). This indicates enough of an overall trend among the sites to maintain a significant inverse relationship between CFU and percent human. Likewise, when the percentage of wild isolates was compared to CFU counts in a similar test, a significant direct relationship was observed at STC 1, P<0.001, r 2 = 0.96. The CFU count decreased along with the percent of wild isolates, Fig 10. Again, a significant relationship was not observed for any of the other four sites when examined individually. However, when the five sites were pooled the regression was significant, P<0.001, r 2 =0.60 (Fig. 12). These results support the notion that wild animals are the predominant contributors to fecal contamination marked by elevated fecal coliform levels.
The relative importance of specific wild animals as contributors to high fecal coliform numbers is difficult to assess with confidence but is likely related to factors such as population size and density and their utilization of the territory adjacent to the sample sites. During the course of the study, birds were the most frequently observed wild vertebrates. Great white egrets, snowy egrets, little blue herons, and anhingas were frequently present in low densities during sample collection i.e one or two individuals. Waterfowl such as gallinules, coots and ducks, were observed in slightly higher densities (three or four individuals), but not as frequently. The largest aggregates of wild animals observed during the study period were flocks of migratory birds such as European starlings and boat-tailed grackles. These birds, however, were observed during the late fall months when fecal coliform densities were low. Gulls common to the coastal areas such as the black-headed gull and herring gull were not observed frequently near the sampling sites.
While human input may not be the major cause of elevated fecal coliform levels for most of the samples analyzed for this study, the domination of small populations by human isolates suggests that human sources contribute to low-level background contamination. This occurs when FC populations are low, near the transition to dry season and perhaps few isolates are washed into surface waters from draining storm water. Lowering water tables may also draw wastewater from small, otherwise innocuous leaks. Overall, there was little evidence of acute human fecal contamination on a large scale across the five site examined. However, there may be considerable human source influencing STC1 and STC2, which is detectable despite the presence of fecal coliforms from other sources. These sites were impacted by human fecal sources with the highest frequency and magnitude of the five sites. They were more frequently over 25% human and exhibited a higher mean % human than the other sites. The most pronounced human contamination of STC1 and 2 occurred in June where 56.7% and 47.7% of isolates examined were human. The density of human isolates at STC1 and STC2 may be approximated from the fecal coliform density using the percent classified as humans. This yields 11400 ‘human’CFU/100ml for STC1 and 2400 ‘human’CFU/100ml for STC 2, both of which exceed the limit of 200CFU/ml. Consequently, unlike any other sampling event in this study, the human input for these two sites in June were high enough to cause violation considering only human isolates.4 References
V. J. Harwood, J. Whitlock and V. H. Withington

. 2000. Classification of the antibiotic resistance patterns of indicator bacteria by discriminant analysis: use in predicting the source of fecal contamination in subtropical Florida waters. Appl. Environ Microbiol. 66:3698-3704.5 Table 1. Density of fecal coliforms from the five sites as determined by membrane filtration Colony Forming Units/100ml Site June July August September October November December
STC 1 20000 13000 300 26 35 1 6 STC 2 5000 2200 68 7 1 1 70 STC 5 1600 6400 115 7 1 1 24 Comp 1 12000 18000 110 9 6 30 17 Comp 2 20000 12000 0 16 960 10 120
Mean 11720 10320 118.6 13 200.6 8.6 47.4

Table 2. Percent wild isolates at Stevenson Creek sites, June – December Site June July August Sept Oct Nov Dec Mean Comp1 100.0 62.7 76.2 0 34.1 NA 0 45.5 Comp2 100.0 62.1 30.5 0 63.4 NA 0 42.7 STC1 43.3 42.1 21.7 3.1 0 NA 0 18.9 STC2 40.9 43.2 10.5 16.7 NA NA 0 22.3 STC5 80.6 67.7 46.7 6.3 NA NA 0 40.3

Table 3. Percent human isolates at Stevenson Creek sites, June – December Site June July August Sept Oct Nov Dec Mean # > 25%

Comp1 0 3.7 4.8 62.5 20.5 NA 75 27.8 2 Comp2 0 6.9 25.4 93.3 15.9 NA 90.5 38.7 3 STC1 56.7 31.6 13.3 90.6 12.5 NA 71.4 46.0 4 STC2 47.7 16.2 10.5 83.3 NA NA 75 46.5 3 STC5 0 22.6 10 75 NA NA 82.5 38.0 2

Table 4. Percent dog isolates at Stevenson Creek sites, June – December Site June July August Sept Oct Nov Dec Mean Comp1 0 0 19.1 37.5 36.4 NA 25 19.6 Comp2 0 0 42.4 6.7 2.3 NA 9.5 10.15 STC1 0 18.4 65.0 3.1 87.5 NA 28.6 33.7 STC2 0 18.9 79.0 0 NA NA 25 24.6 STC5 0 6.5 43.3 18.8 NA NA 17.5 17.26 Density of Fecal Coliforms for Each of Five Sites Over Seven Months

0 5000 10000 15000 20000

June July August September October November December
MonthColony Forming Units per 100ml

STC 1 STC 2 STC 5 Comp 1 Comp 2

Figure 1. CFU/100ml from the five sites over seven months.

Density of Fecal Coliforms for Each of Five Sites Over Seven Months

1 100 10000

June July August September October November December
MonthColony Forming Units per 100m

STC 1 STC 2 STC 5 Comp 1 Comp 2

Figure 2. CFU/100ml from the five sites over seven months, graphed on a log scale.7 Figure 3

Figure 4. Categorization of Isolates from Each of Five Sites on 6/27/00

0 20 40 60 80 100 120

Comp1 Comp2 STC1 STC2 STC5 SitesPercentage of Isolates Classified into each Source

% human

%wild
% dog

Categorization of Isolates from Each of Five Sites on 7/25/00

0 10 20 30 40 50 60 70 80

Comp1 Comp2 STC1 STC2 STC5 SitesPercentage of Isolates Classified into each Source

% human

%wild
% dog8 Figure 5.

Figure 6. Categorization of Isolates from Each of Five Sites on 8/22/00

0 10 20 30 40 50 60 70 80 90

Comp1 Comp2 STC1 STC2 STC5 SitesPercentage of Isolates Classified into each Source

% human

%wild % dog

Categorization of Isolates from each of Five Sites on 9/19/00

0 10 20 30 40 50 60 70 80 90 100

Comp1 Comp2 STC1 STC2 STC5 SitePercentage of Isolates Classified into each Sourc

% human %wild % dog9 Figure 7. Categorization of Isolates from the Three Sites from Which Fecal Coliforms were Obtained on 10/23/00

0 10 20 30 40 50 60 70 80 90 100

Comp1 Comp2 STC1 STC2 STC5 SitesPercentage of Isolates Classified into each Source

% human %wild % dog

Categorization of Isolates from Each of Five Sites on 12/27/00

0 10 20 30 40 50 60 70 80 90 100

Comp1 Comp2 STC1 STC2 STC5 SitesPercentage of Isolates Classified into each Category

% human %wild % dog

Figure 8.10 Monthly Observations from Comp2 Plotted as % Human vs Log CFU/100ml

-20

0 20 40 60 80 100 120

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Log CFU/100ml% Human

Figure 9.

Monthly Observations from STC 2 Plotted as % Wild vs Log CFU/ 100ml

-20 -10

0 10 20 30 40 50 60

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Log CFU/100ml% Wild

Figure 10.