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Background and Purpose

The Stevenson Creek basin encompasses approximately 6,000 acres in central Pinellas County, approximately 4765 acres of which lie within the limits of the City of Clearwater. The remainder of the basin, which consists of the upper reaches of the Spring Branch Subbasin, falls primarily within the limits of the City of Dunedin.

The primary objective of the project is to develop a watershed management plan for the Stevenson Creek basin, in accordance with a cooperative agreement between the Southwest Florida Water Management District and the City of Clearwater. It will be used as a tool in the planning, regulation, and management of Stevenson Creek for future development, and as a basis for determining and prioritizing capital improvements. This objective will be met in part, by conducting an analysis of the watershed in order to characterize the existing watershed conditions and recommend improvements for flood protection, natural systems, habitat, water quality, erosion control, public awareness and involvement, regulatory control, and capital improvements.

The second objective is to coordinate the development of the management plan for the freshwater portion of the basin with limited evaluation of the estuarine saltwater portion of the basin, to be performed in conjunction with the U.S. Army Corps of Engineers as the lead agency, as may be required.

Springtime Avenue between Brook Avenue and Stevenson Avenue
INFORMATION COLLECTION AND MANAGEMENT

Literature Search

The project will perform a literature search to review and assimilate available information pertinent to the study area under four major categories; flood protection, water and sediment quality, natural resources and drainage problems

Evaluate and Define Deficiencies of Existing Data

Existing available data shall be evaluated by the consultant to identify any missing data that are necessary to the study. Additionally, conflicting data will be identified. Missing or conflicting data will be evaluated to determine the appropriate method of obtaining the needed data or resolving conflicts.

City Official Sampling Water for its Quality

 

WQ station

Gage Installation in Spring Branch at King’s Highway

FIELD WORK AND DATA ANALYSIS

Field Work

Field investigations will be conducted to identify the drainage ways and tributaries and of existing drainage and stormwater management systems

Biological Resources

Parsons ES biologists are conducting an evaluation of the Stevenson Creek watershed in order to determine the existing conditions of the natural resources. Any undeveloped property and property already in public ownership will be assessed for potential use as wildlife habitat, stormwater retention and treatment or preferably, a combination of these uses. The assessment will determine the presence of essential habitat that needs preservation for endangered or threatened species, wetlands that are in need of hydrological or vegetative restoration, or highly disturbed areas that may be optimal for wetland creation. This provides the City of Clearwater with a "big picture" approach to watershed management, allowing the City’s resources to be put to use in the best manner possible. Cooperative funding mechanisms will be evaluated for potential capital improvement projects such as regional stormwater facilities, mitigation banks, bridge improvements and similar projects.

Two (2) automatic streamflow and water quality sampling stations will be installed within the study area near the mouths of Stevenson Creek and Spring Branch. Each installation consist of an ISCO automatic sampler, water level recorder, and a recording precipitation gage. The stage, rainfall, and flow monitoring data will serve as the basis for calibration and verification of the hydrologic and hydraulic models of the watershed. A streamflow rating curve will be developed for each of the sites by obtaining a minimum of ten (10) separate flow measurements using a flow velocity meter. Additional rainfall data will be provided by the CITY from its other stations located near or within the study area.

The two sampling stations are installed at the freshwater flow monitoring locations near the mouths of Stevenson Creek and Spring Branch. Flow-weighted composite samples will be collected for up to ten (10) separate storm events and six (6) ambient (baseflow) events during the period of study at each of the sampling stations and analyzed for the following water quality constituents

Total Suspended Solids

Total Dissolved Solids

Biochemical Oxygen Demand

Chemical Oxygen Demand

Total Organic Carbon

Nitrogen (NH3, TKN, NO2/NO3)

Phosphorus (Total P, Ortho-P)

Oil and Grease

Total Petroleum Hydrocarbons

Total Hardness

Metals (Aluminum, Arsenic, Cadmium, 

Chromium, Zinc, Nickel, Copper, and Lead)
Fecal coliforms/ABA

WATER QUALITY & NATURAL SYSTEMS CONDITIONS

  • Compilation of the Watershed Map

  • Land Use Data by Catchment

Parsons ES will inventory existing land uses for use in developing data for the storm water model. Parsons ES will summarize existing land use plans and policies developed by Clearwater, Dunedin, Pinellas County, and regional planning agencies to gauge future development potential.

  • Assessment of Current Storm water Treatment Capabilities

SWFWMD 1995 Land Use/Cover

POLLUTANT LOADING ANALYSIS

Pollutant Loading Model

  • Identify chemicals of concern
  • Develop pollutant loading model
  • Calculate gross pollutant loads generated at each sub-basin.
  • Estimate existing water quality treatment capabilities
  • Calculate net pollutant loads discharged from each sub-basin.
  • Determine Water Quality Levels of Service
  • Assess system deficiencies

Existing Conditions Water Quality Level of Service

WATERSHED MODELING (COMPUTER MODELING)

The model will be used to analyze the processes associated with flood control. The system will include the development of the runoff hydrographs and the routing of the hydrographs through the creek and the stormwater conveyance structures. The applicable Levels of Service for flood control will be established by the TEAM.

IDENTIFICATION OF PROBLEMS AND POTENTIAL SOLUTIONS

Evaluate Existing Conditions

The methods to be used for this task will include field studies, data analysis, and computer model simulations. The data analysis will include the approved Level of Service criteria to identify those areas where the existing system does not provide an acceptable Level of Service.

Develop and Evaluate Potential Solutions

After compiling and evaluating the existing conditions the development of potential solutions to address the identified flooding, sediment, and water quality problem conditions in the watershed. The identification of these potential solutions will take into account existing watershed development conditions.

 

Salvage yard - Potential Pollution Source

Potential solutions

    1. Floodplain, water quality and water quantity regulations and programs
    2. Maintenance practices and programs
    3. Non-point source pollutant load source reduction measures
    4. Base flow management and restoration
    5. Wetland restoration, enhancement, and creation
    6. Conservation and restoration of natural waterways
    7. Vegetated buffers along stream corridors and riparian areas
    8. Lined and unlined channels
    9. Selected or limited structure improvements
    10. Regional detention and retention facilities
    11. Non-structural improvements and methods, including source reduction programs
    12. Multi-use facilities
    13. Proposed revisions to designated land use or zoning
    14. Minimization of mitigation to that absolutely necessary to construction
EVALUATION AND PRIORITIZATION OF POTENTIAL SOLUTIONS

The potential solutions and projects will be evaluated and prioritized based on the City’s Level of Service evaluation criteria. The potential solutions shall include assessment of:

Lake on tributary 18-02-05, east of King’s Highway, looking at control weir inside skimmer structure.

 

    1. Drainage problems (erosion, sedimentation)
    2. Flooding (frequency: 10-, 25-, 100-yr, and severity: streets, yards, homes)
    3. Water quality (measurable and cost-effective improvements)
    4. Public safety and welfare
    5. Construction costs
    6. Relative benefits
    7. Requirements for right-of-way
    8. Operation and maintenance
    9. Permitability
    10. Public acceptance
    11. Economic support
    12. Land use
    13. Regulatory Enhancement


Site Survey 

Parsons Engineering Science, Inc. -- This page updated: 08/04/05