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

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Presentation on theme: "Stormwater Retrofitting Demystified! A training for local governments to cost effectively implement retrofits to meet MS-4 permit and Chesapeake Bay TMDL."— Presentation transcript:

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 9:30 – 9:40Welcome and Learning Objectives for the Day 9:40 – 10:00State Perspectives on Stormwater Retrofitting 10:00 – 10:45Session 1. Basics of Stormwater Retrofitting 10:45 – 11:15BREAK 11:15 – 12:30Session 2. Strategies to Consider Prior to Retrofits 12:30 – 1:30LUNCH 1:30 – 2:30Session 3. The Retrofit Discovery Process 2:30 – 3:45Session 4. Retrofit Costs, Delivery and Maintenance 3:45 – 4:00Concluding Remarks 4:00Evaluations!

3 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 Visit: Chesapeake Bay Stormwater Training Partnership

4 Session 1 Basics of Stormwater Retrofitting

5 1.Where do Nutrients and Sediment Come From? 2.Retrofit Categories 3.Envisioning Retrofits Session 1 Agenda

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 Relationship of Atmospheric Deposition to Urban Runoff Quality Nutrient Atmospheric Deposition 1 Stormwater Runoff Load 2 Pounds per impervious acre per year Total Phosphorus Total Nitrogen13 to measured rates during Washington NURP Study (MWCOG, 1983) 2 Simple Method annual stormwater runoff loads for one acre of impervious cover (Schueler, 1987) 3 About 40% of nitrogen deposition occurs through wetfall, which would presumably be quickly converted into runoff. 60% of nitrogen deposition occurs via dryfall, which is available for washoff in future storms, or may be blown over to pervious areas 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 Urban Land CoverTotal N (mg/l) Lawns 9.70 Highway 2.95 Streets (Variable) 1.40 Parking Lots 1.94 Rooftops 1.50 Source; CWP, 2003 Runoff sampling shows that lawn runoff is very high in nitrogen. Also, rooftop runoff concentration shows effect of atmospheric deposition

12 Total Nitrogen Loads By Sector in the Maryland Portion of the Chesapeake Bay Watershed Sector 2009 Load Target Load% Reduction Needed to Meet Target Million pounds per year Forest Atm. Deposition Wastewater % Urban and Suburban Runoff5.88 (12%)4.4225% Agricultural % Septics % TOTAL % Source: US EPA Chesapeake Bay Program, 2010

13 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

14 Phosphorus EMCs for different urban land covers Urban Land CoverTotal P (mg/l) Lawns 1.90 Highway 0.60 Streets (Variable) 0.50 Parking Lots 0.16 Rooftops 0.12 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

15 Phosphorus EMCs for different urban land uses Urban Land UseTotal P (mg/l) Residential 0.30 Commercial 0.22 Industrial 0.26 Freeway 0.25 Source: Pitt et al 2004 Residential runoff is slightly higher in TP concentration, which reflects the effect of vegetation and fertilization

16 Total Phosphorus Loads By Sector in Maryland Portion of Bay Watershed Sector 2009 Load Target Load% Reduction Needed to Meet Target Million pounds per year Forest Atm. Deposition Wastewater Urban and Suburban0.68 (22%)0.3943% Agricultural % Septics-0- 0 TOTAL % Source: US EPA Chesapeake Bay Program, 2010

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

18 Edge of Stream Unit Loading Rates for MD Using CBWM v Pounds/acre/year Total NTotal PTSS IMPERVPERVIMPERVPERVIMPERVPERV Urban Forest Source: CBPO, 1/4/2012

19 Discussion

20 1964 My Early Retrofitting Years Wiggle-tail

21 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

22 Why Retrofits Are Different Urban Retrofit PracticesNew Stormwater Practices Construction costs are 1.5 to 4 times greater Designers seek least costly options Assessment and design costs are higher Focus on low cost design and construction Sized to meet watershed restoration objectives Sized to meet local stormwater design standards Typically installed on public land Installed at new development projects Urban soils often cannot support infiltration Soils may support infiltration Fingerprinted around existing development More flexibility on where to locate practices

23 Why Retrofits Are Different Urban Retrofit PracticesNew Stormwater Practices Must be acceptable to adjacent neighbors Aesthetics are not always a major design factor Most are publicly maintainedMost require private maintenance Not all candidate sites are feasible Nearly all sites are made to work Tied into existing conveyance system Usually creates new conveyance system Integrated with other restoration practices Stand-alone practice Public investment in watershed infrastructure Private investment in stormwater infrastructure

24 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 Stormwater Regs: Final ESD regulations issued in May 2009 with local implementation to start in May of MS4 Permits: Phase 1 and Phase 2 backlog

25 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 Stormwater Regs: Final ESD regulations issued in May 2009 with local implementation to start in May of MS4 Permits: Phase 1 and Phase 2 backlog

26 Best Opportunities for Retrofitting in the Urban Landscape

27 Retrofit Categories

28 NEW RETROFITS Near Existing Stormwater Outfalls Source: CWP

29 NEW RETROFITS Within the Existing Conveyance System Source: CWP

30 Wet Pond Bioretention NEW RETROFITS Adjacent to Large Parking Lots Source: CWP

31 NEW RETROFITS Green Street Retrofits

32 NEW RETROFITS On-Site LID Retrofits

33 Retrofit Categories

34 EXISTING RETROFITS BMP CONVERSION DRY POND CONSTRUCTED WETLAND

35 BMP CONVERSIONS Rehabilitating Failed Infiltration Practices

36 BMP CONVERSIONS Adding Bioretention/Filtering to Ponds

37 EXISTING RETROFITS BMP ENHANCEMENT INCREASE IN HYDRAULIC RETENTION TIME

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

39 Discussion

40 Retrofitting requires: Sleuthing skills to determine what can work at highly constrained sites Simultaneously envisioning restoration possibilities and anticipating potential problems

41 Activity: Envisioning Restoration

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56 Activity

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58 Activity – Part 1

59 Questions?


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