1. Tom Schueler Update on Proposed Virginia Stormwater Regulations and Adapting them for the Ridge and Valley Winchester VA October 28, 2008

2. New organization launched in September 2007 to improve on the ground implementation of effective stormwater practices in 1300 communities and 7 States in the Chesapeake Bay Watershed Creating alignment among the local, state, federal and private sectors to solve the Bay stormwater problem through an independent network of concerned stormwater professionals Chesapeake Stormwater Network www.chesapeakestormwater.net

3. Core Themes  Land Development and Impervious Cover  Overview of New Stormwater Regulations  Adapting Practices for Karst Terrain  Discussion

4. Development is creeping up on us, and will defeat our efforts, if we don’t get our act together soon 76,800 acres of impervious cover and 232,500 acres of turf cover created each year, or nearly 1% of Bay watershed per year

6. Urban Nutrient Loads Are Fast Becoming a Big Slice of the Bay Pie Year Total N Total P 1985 2% 5% 2000 9% 15% 2005 19% 30% 2030 ?? ?? Only Bay nutrient load sector where we are seeing reverse progress In load reductions- source OIG (2007)

7. The ICM and Urban Subwatershed Management

8. New National Research Council Report Released Flow is a pollutant Direct relationship land cover and biological degradation Current piecemeal permitting system does not work Convert to a watershed based permitting system Numeric stormwater permit limits Urban stream classification and management More Industrial stormwater monitoring Findings: Urban Stormwater Management in the United States http://www.nap.edu/catalog.php?record_id=12465

9. VA DCR Stormwater Regulations Revised Draft SWM Reg just approved for administrative review and public comment (est. Spring 2009) Currently updating State SWM Handbook, using a stakeholder Technical Advisory Committee Currently creating a Virginia SWM BMP Clearinghouse web site and BMP evaluation process (initial draft BMP spec’s posted now)

10. Revised Method Based on Stronger Science Leads to Better Practice Design Truly Integrates all Practices Together Rewards a Treatment Train Less Room for BMP Math Games

11. 1. Site Load Standard What we do now –Total phosphorus (TP) as keystone –Most sites meet average land cover condition (0.45 lbs/acre/year) –Doesn’t apply to much of state What is proposed –TP basis for compliance; Total Nitrogen also calculated –Load limit tied to Tributary Strategy goals = 0.28 lbs/acre/year (TP) –State-wide application

12. Runoff reduction is defined as the total volume reduced through canopy interception, soil infiltration, evaporation, rainfall harvesting, engineered infiltration, extended filtration or evapotranspiration at small sites 2.Runoff Reduction (RR)

13. Stormwater Practices Differ Sharply in Ability to Reduce Runoff Volume Bioretention, Infiltration, Dry Swales and Related Practices Reduce Runoff Volumes by 50 to 90% Wet Ponds, ED Ponds and Constructed Wetlands and Filters Reduce Runoff Volumes by zero to 10%

14. Runoff Reduction Practices * 1.Protected Open Space Receiving Runoff from Developed Areas 2.Rooftop Disconnection (4 options) 3.Pervious Parking 4.Green Roof 5.Grass Channels 6.Bioretention & Dry Swales 7.Wet Swales 8.Infiltration 9.Extended Detention * Forest conservation, soil conservation, soil restoration are “self crediting” Each Practice Must Meet Design Specs to Receive the RR “Credit”

15. BMPs: Level 1 & 2 BMP Designs Level 1: good, standard design Level 2: enhanced design to boost nutrient removal

16. BIORETENTION DESIGN LEVEL 1 DESIGNLEVEL 2 DESIGN TV= (Rv)(A)TV= 1.25 (Rv)(A) Filter media at least 24” deepFilter media at least 36” deep One form of accepted pretreatmentTwo or more forms of accepted pretreatment At least 75% plant coverAt least 90% plant cover, including trees. One cell designTwo cell design UnderdrainInfiltration design or underground stone sump

17. 3. Treating Impervious Cover & Managed Turf Areas What we do now –Nutrient loads based on impervious cover What is proposed –Nutrient loads & treatment volume based on impervious cover + managed turf –Incentives to preserve forest cover

18. Site Runoff Coefficient (Rv) Site Rv = RvI * %I + RvT * %T + RvF * %F Site Cover Runoff Coefficients Soil ConditionRunoff Coefficient Forest Cover0.02 to 0.05* Disturbed Soils0.15 to 0.25* Impervious Cover0.95 *Hydrologic Soil Group (HSG) Forest A: 0.02 B: 0.03 C: 0.04 D: 0.05 Disturbed A: 0.15 B: 0.20 C: 0.22 D: 0.25

19. 4. Spreadsheet – Beta Version TN comps included Accomodates BMPs in series Compliance by site – BMP design by drainage area Water quantity compliance Accounting for forest treatment volume More bells, whistles – not as simple

20. Water Quality Compliance Spreadsheet

21. Draft VA-DCR BMP Specifications Rooftop Disconnection Filter Strips Grass Channels Soil Amendments Green Roofs Rain Tanks/Rainwater Harvesting Permeable Pavement Infiltration Bioretention –Urban Bioretention Dry Swales Filtering Practices Constructed Wetlands –Wet Swales Wet Ponds Extended Detention Ponds

22. Unique Development Conditions in the Ridge and Valley Karst Terrain Extremely large lot development Individual development projects are small Surface/subsurface drainage poorly understood Limited public water and sewer service Runoff reduction practices are new Limited experience by contractors, designers and reviewers Rural Runoff Reduction Practices for Karst Available from CSN Website

23. Key Karst Challenges Major increase in surface runoff Variable subsurface vulnerability Increased ponding or infiltration form sinkholes Leads to groundwater contamination Can cause practice or infrastructure failure Confusing surface drainage patterns (losing streams)

24. Guiding Philosophy for Stormwater Design in Karst Detailed on-site geotechnical survey first LID practices work well in karst Limited use of infiltration in karst terrain Avoid big contributing areas and deep trenches/pools Define stormwater hotspots and ensure full treatment before discharge No discharge to sinkhole w/o full water quality treatment Underground injection permits for sinkholes and deep infiltration

25. Two Stage Site Assessment: General Karst Vulnerability and Specific Geotechnical Investigation

27. BMP Selection in Karst Preferred –Bioretention (closed) –Rain Tanks/Cisterns –Green roofs –Dry swale (closed) –Sand filters Accepted –Filter Strips –Grass Channel –Soil Restoration –Small-scale Infiltration –Permeable pavers (closed) –Constructed wetlands (lined ) Discouraged –Wet ponds –Dry ED ponds –Bioretention (open ) Prohibited –Wet swale –Large scale infiltration

28. Designating Stormwater Hotspots Future status of development determines how much treatment is required and whether runoff can be infiltrated or discharged to a sinkhole

29. Bioretention Design Considerations in Karst Terrain: Line bottom with impermeable filter fabric Use underdrain to daylight safely Add sump stone layer below underdrain to increase RR Keep contributing drainage areas small Increase setbacks to buildings and infrastructure Shallow excavation OK (2 to 4 feet)

30. Process for Developing Better Stormwater Guidance in Karst Terrain Peer Review of CSN Technical Bulletin No. 1 Nov 3 rd Workshop in Ransom, WV Incorporate into state and local guidance Other issues