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Evaluating Stormwater BMPs

Evaluating Stormwater BMPs. Frank Henning Region IV Land Grant Universities Liaison. What Low Impact Development Is and Is Not. Stormpond Design Volumes. Georgia Stormwater Management Manual, Vol. 2 ARC 2001. Water Quality. Volume. Knoxville, TN Development Manual.

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Evaluating Stormwater BMPs

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  1. Evaluating Stormwater BMPs Frank Henning Region IV Land Grant Universities Liaison Insert Unit # and Title

  2. What Low Impact DevelopmentIs and Is Not

  3. Stormpond Design Volumes Georgia Stormwater Management Manual, Vol. 2 ARC 2001

  4. Water Quality

  5. Volume Knoxville, TN Development Manual

  6. Reducing Runoff Volume

  7. Flow Volume

  8. Green Infrastructure/LID • Preserves natural environments • Retains stormwater volume for infiltration, evapotranspiration, or use • Removes the volume from the stream • Mimics natural hydrology, often enhances groundwater recharge and base flow • Removes pollutant load associated with the volume retained • Does not transfer pollution to ground water • May need additional storage to address stream protection and flood prevention requirements

  9. Natural Area Preservation • Soils and vegetation – already present = free • Inlet/Outlet control – direct inflow/overland flow = free • Storage volume = predevelopment conditions • Natural areas generally are counted as net zero • Can they store, infiltrate, evapotranspirate more than the design volume? Wetlands Franklin, TN Maryville TN Buffers Maryville TN Springhead

  10. Soil Enhancement Program • Cost – usually minimal or low • Storage – enhance void space and infiltration rate of soil • Soil – amended soil and native soil infiltration rate • Vegetation – selection based on site • Inlet/Outlet – direct inflow, overland or directed

  11. Vegetative Cover

  12. Reduce Pollutant Loads • Proper fertilizer and pesticide use • Maintain vegetative cover • BMP is a nutrient sink, not a nutrient source • (how green is green?) • Stormwater contains nutrients

  13. Disconnection Programs • Storage – based voids, and infiltration rate of soil, impervious area disconnected (capture area) • Soils – amended or uncompacted native soil • Vegetation – selection based on the site • Inlet/Outlet – downspouts, sheet flow over vegetated areas to swales, sewers, waterbodies

  14. Tree Canopy Programs • Storage volume - based on pool volume, void space of amended soil, native soil infiltration rate, evapotranspiration rate, capture area • Soil – structural or amended for storage/pollutant uptake • Vegetation - trees for largest amount of evapotranspiration, other benefits • Inlet /Outlet Controls – must provide!

  15. Rainwater Harvesting & Use • Storage volume – • Water Use – irrigation or other use • Soils - infiltration • Vegetation – evapotranspiration • Inlet/Outlet - must be provided • Outlet protection – reduce erosion

  16. Green Parking – Permeable Pavement

  17. Green Roofs • Storage – soil depth/voids • Soils – amended, structured • Vegetation – intensive (shallow soil- sedums or drought tolerant species) or extensive (deep soil-small tree, shrubs) • Inlet /Outlet – direct capture/roof drains • Structural – must perform analysis

  18. Raingardens/Bioretention • Storage Volume – based on pool design, amended soil void space, capture area • Soils - native soils are removed and replaced with amended soil • Vegetation - herbaceous (low evapotranspiration) • Inlet/ Outlet controls - direct inflow and provide for bypassing larger events

  19. Volume Comparison Burnsville, MN Neighborhood Rain Garden Study Barr Engineering

  20. Other GI/LID Benefits • Air quality improvement • Community beautification • Energy savings • Health benefits • Heat island reduction • Property value improvement • Recreation and wildlife

  21. Acknowledgements Module contributors: Material for this module was adapted from presentations and publications by Region IV EPA Watershed Protection Division Module editors: [Insert names and affiliations here for at least 2 peer-reviewers] Southern Region Landscape Team: Amy Shober (UF/IFAS); Lucy Bradley (NCSU); Eve Brantley (Auburn); Wendi Hartup (NCSU); Barbara Fair (NCSU); Frank Henning (USEPA/UGA); EsenMomol (UF/IFAS); Kerry Smith (Auburn); Dotty Woodson (Texas Agrilife); Sheryl Wells (UGA) Funding for this module provided by: USDA-NIFA National Water Program, Southern Regional Water Program special project funds Graphic design: Emily Eubanks - UF/IFAS Center for Landscape Conservation and Ecology; Amy L. Shober – UF/IFAS Gulf Coast Research and Education Center

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