STORMWATER MANAGEMENT AND IMPAIRED WATERS. Eric H. Livingston Watershed Management Services, LLC Crawfordville, FL

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1 STORMWATER MANAGEMENT AND IMPAIRED WATERS Eric H. Livingston Watershed Management Services, LLC Crawfordville, FL

2 Impaired Waters Not meet their WQS Loss of designated uses

3 TOTAL MAXIMUM DAILY LOADS Section 303 (d) FCWA States list impaired waters Develop TMDL = WLA + LA + MOS Implementation plan Section , F.S. Listing of impaired waters Development and adoption of TMDLs TMDL implementation via BMAPs or NPDES permits TMDL pollutant loading cap =max. amount of pollutant loading that can be discharged to a healthy water body.

4 IMPAIRED WATERS: PROBLEMS AND POLLUTION SOURCES MAJOR POLLUTANTS OF CONCERN Nutrients, nutrients, nutrients! Oxygen demanding substances Fecal coliform bacteria MAJOR SOURCES OF POLLUTANTS = NPS Stormwater existing development Stormwater new development/redevelop Stormwater agricultural Leaching agriculture, landscape, OSTDS

5 Resulting in: Decreased recharge Increased speed of runoff Increased volume of runoff Increased pollutant loads THE STORMWATER PROBLEM Humans cause: Changes in land use, clearing of land Compaction of soil, imperviousness Development in floodplains, wetlands Alteration of natural stormwater systems Addition of drainage systems Addition of pollutants

6 STORMWATER DISCHARGES TO IMPAIRED WATER BODIES Section (1)(b)3., F.S. Can t add more pollutants causing the impairment of a water body since it doesn t meet WQS Treatment level is equal to Net Improvement Post-development load < pre-development load

7 IMPAIRED WATERS AND TMDLS IN NAPLES Water Body WBID Impairments TMDL? WLA % Reduction Naples Bay 3278R4 Copper, DO nutrients, Iron Gordon River Extension Gordon River Marine Golden Gate Canal NO 3278K DO nutrients YES TN 29% 3278R5 Copper, Iron NO 3278S DO-nutrients, Iron NO TMDL Net Improvement = POST-DEVELOPMENT LOAD < PRE-DEVELOPMENT LOAD WLA % REDUCTION

8 TMDLs & NPDES MS4 PERMITS MS4 Municipal Separate Storm Sewer System Your master drainage system Naples permit renewal November 2013 Requires implementation of a Stormwater Management Program to reduce stormwater pollutant loads Requires TMDL implementation plan once a TMDL is adopted Options include building regional treatment facilities, nonstructural P2 BMPs, and ensuring new development and redevelopment meet Net Improvement Minimize costs to local taxpayers in meeting TMDL % reduction requirements

9 VERY HIGH LEVEL OF TREATMENT Typical wet ponds get 35% TN, 55% TP removal Net Improvement requires 96% removal to meet TMDL for Imperial River Need to use combination of structural and nonstructural pollution prevention BMPs including Low Impact Development BMPs BEST MANAGEMENT PRACTICES

10 BMP TREATMENT TRAIN Runoff & Load Generation Conveyance and Pretreatment Additional Treatment & Attenuation Final Treatment and Attenuation Source controls Public ed Erosion control Roof runoff Florida Yards LID BMPs Swales Storage tank Catch basins Sediment sump Filter inlets Alum/PAM Oil/water separators Retention Detention Wetlands

11 LOW IMPACT DEVELOPMENT APPROACHES - Preventive Nonstructural BMPs Watershed planning Local planning Site (lot) planning Minimize disturbance Protect vegetation, trees Minimize soil compaction Reduce imperviousness Minimize pollutant sources Minimize sw volume/load PRACTICES - Mitigation Infiltration BMPs Basins Trenches Swales Pervious pavement Greenroof/cisterns Natural areas Wet detention with stormwater harvesting

12 WHAT DETERMINES WHAT THE SITE LOOKS LIKE? Traditional

13 LID STRUCTURAL BMPS Infiltration BMPs Basins Trenches Swales Pervious pavement Green roof/cistern systems Rain gardens? Biofiltration BMPs Street tree filters Landscape filter boxes Enhanced wet detention Stormwater harvesting Floating wetlands, littoral zone

14 INFILTRATION PRACTICES DESCRIPTION: Family of practices where the stormwater is retained on-site by infiltration or evaporation. PURPOSE: Reduce total volume Reduce flooding and pollutant loadings POLLUTANT REMOVAL: Percolation, evaporation Filtering and adsorption in soil

15 INFILTRATION PRACTICES Evaporation Swales Retention basins Exfiltration trenches Pervious Pavement Rain gardens Infiltration through at least 2 feet of sandy soil Seasonal High Water Table elevation

16 INFILTRATION SYSTEM DESIGN CRITERIA 1. Treatment Volume Infiltrate 0.5 runoff, or 1.25 X Imp Area. 2. HSG A or B soils, less than 30% clay hour recovery time (24-36 hr if grassed) 4. Good percolation test data 5. Seasonal high ground water or bedrock at least 2 feet beneath bottom of system must assess groundwater mounding 7. Do not use for erosion/sediment control 8. Proper construction is essential to prevent soil compaction 9. Inspect to ensure it doesn t clog and to test infiltration rate > 2 /hr

17 NAPLES SQUARE PROJECT Proposes pervious paver system to retain stormwater on-site. Can meet net improvement standard of POST TN LOAD < PRE TN LOAD 25% BUT, pervious paver systems must be carefully located, designed, build, inspected, and maintained to function. DEP and WMD rules do not have LID BMPs Statewide Stormwater Treatment rule created design criteria for LID BMPs Based on research at UCF SW Academy Basis for BMPTrains Model used to verify loads and removal Accepted and used by other WMDs

18 NAPLES SQUARE PROJECT Requested conditions for pervious paver system: 1. Meet design criteria in Ch. 11 of draft Stormwater Treatment Applicant s Handbook and data requirements in Part V Methodologies. 2. This assures system is at least 2 feet above the SHWT, the system s infiltration rate exceeds 2 /hr minimum, that on-site data are used for design, and that the system s infiltration rate can be easily checked during inspections.

19 NAPLES SQUARE PROJECT Pollution prevention LID BMPs recommended for project per City s stormwater code: 1. All landscaping is designed per Florida-friendly landscaping program 2. Pet waste pick up/disposal required 3. Cars and boats are washed on grass not parking. 4. Landscape islands in parking lots are recessed and planted with trees to provide shade and intercept rainfall thereby lessening stormwater.