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Stormwater Retrofitting Demystified!

Stormwater Retrofitting Demystified!. A training for local governments to cost effectively implement retrofits to meet MS-4 permit and Chesapeake Bay TMDL requirements. . Workshop Agenda. Chesapeake Bay Stormwater Training Partnership . Visit: www.chesapeakestormwater.net.

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Stormwater Retrofitting Demystified!

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  1. Stormwater Retrofitting Demystified! A training for local governments to cost effectively implement retrofits to meet MS-4 permit and Chesapeake Bay TMDL requirements.

  2. Workshop Agenda

  3. Chesapeake Bay Stormwater Training Partnership Visit: www.chesapeakestormwater.net To learn how you can have access to: Discounted Webcasts Free One-day design workshops Intensive master stormwater design seminars Direct On-site technical assistance Self guided web-based learning modules

  4. Session 1Basics of Stormwater Retrofitting

  5. Session 1 Agenda • Where do Nutrients and Sediment Come From? • Retrofit Categories • Envisioning Retrofits

  6. Where do Nutrients and Sediment Come From?

  7. There are many sources of N and P in the urban environment

  8. The main sources of nutrients to the Bay Watershed are: • Runoff from Forests • Wastewater • Atmospheric Deposition to Open Water • Urban and Suburban Runoff • Agricultural Runoff • Septic Systems (N only)

  9. Much of the nitrogen in urban runoff is derived from atmospheric deposition, either in the form of dryfall or wetfall

  10. Other sources of nitrogen in urban runoff include: • Washoff of fertilizers • Nitrogen attached to eroded soils and streambanks • Organic matter and pet wastes on IC

  11. Nitrogen EMCs for different urban land covers Source; CWP, 2003 Runoff sampling shows that lawn runoff is very high in nitrogen. Also, rooftop runoff concentration shows effect of atmospheric deposition

  12. Many sources of TP in urban runoff • Blow in of organic matter onto impervious surfaces (leaves, pollen, clippings, flowers, etc.) • Phosphorus attached to eroded soils and streambanks • Fertilizer washoff • Atmospheric deposition

  13. Phosphorus EMCs for different urban land covers Source; CWP, 2003 The sources of phosphorus are more complex. While lawn runoff is high in nitrogen, atmospheric deposition is less important as a source of TP

  14. Phosphorus EMCs for different urban land uses Residential runoff is slightly higher in TP concentration, which reflects the effect of vegetation and fertilization

  15. Sources of Urban Sediment • Urban stream channel erosion • Wash-off from impervious areas • Erosion from pervious areas • Construction sites

  16. Discussion

  17. My Early Retrofitting Years Wiggle-tail 1964

  18. Why Retrofit ? • Local Watershed restoration • Meet IC Treatment Targets in MD • Comply with Bay-wide TMDLs (and local ones too) • Improve local stream habitat and diversity • Fix old mistakes/drainage problems • Improve performance of existing stormwater infrastructure

  19. Why Retrofits Are Different

  20. Why Retrofits Are Different

  21. Caution: The “rules” are in flux • MDE 2011 Guidance • CSN Technical Bulletin 9 • Roll out of New MS4 Permits • 6 New Urban BMP Expert Panels • New BMP Verification Protocols • Updated editions of MAST • Bad news: the numbers will change • Good news: the numbers will improve • Advice: use them for general planning and evaluation of alternatives • StormwaterRegs: Final ESD regulations issued in May 2009 with local implementation to start in May of 2010. • MS4 Permits: Phase 1 and Phase 2 backlog

  22. Dual BMP Reporting in MD • For MS4 Permits: • Report BMPs implemented ** • Report “Treated Acres” of Existing Impervious Cover * • For Bay TMDL/Local WIPs: • Report BMPs implemented ** • Report TSS, TN, and TP reductions • ** both are done using Appendix A of MS4 BMP Reporting • * ESD to MEP for existing IC defined as minimum site WQv • StormwaterRegs: Final ESD regulations issued in May 2009 with local implementation to start in May of 2010. • MS4 Permits: Phase 1 and Phase 2 backlog

  23. Best Opportunities for Retrofitting in the Urban Landscape

  24. Retrofit Categories • New Retrofit Facilities • Near Existing Stormwater Outfalls • Within the Conveyance System • Adjacent to Large Parking Lots • Green street retrofits • On-site LID retrofits • Existing BMP Facilities • BMP Conversions • BMP Enhancements • BMP Restoration

  25. NEW RETROFITSNear Existing Stormwater Outfalls Source: CWP

  26. NEW RETROFITS Within the Existing Conveyance System Source: CWP

  27. NEW RETROFITSAdjacent to Large Parking Lots Source: CWP Wet Pond Bioretention

  28. NEW RETROFITS Green Street Retrofits

  29. NEW RETROFITS On-Site LID Retrofits

  30. Retrofit Categories • Existing BMP Facilities • BMP Conversions • BMP Enhancements • BMP Restoration

  31. EXISTING RETROFITS BMP CONVERSION CONSTRUCTED WETLAND DRY POND

  32. BMP CONVERSIONSRehabilitating Failed Infiltration Practices

  33. BMP CONVERSIONSAdding Bioretention/Filtering to Ponds

  34. EXISTING RETROFITS BMP ENHANCEMENT INCREASE IN HYDRAULIC RETENTION TIME

  35. EXISTING RETROFITS BMP RESTORATION DREDGING AN UNDERPERFORMING POND TO RESTORE FULL PERFORMANCE

  36. Discussion

  37. Retrofitting requires:Sleuthing skills to determine what can work at highly constrained sitesSimultaneously envisioning restoration possibilities and anticipating potential problems

  38. Activity: Envisioning Restoration

  39. Activity

  40. Activity

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