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Tom Schueler

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

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Tom Schueler

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

  2. Chesapeake Stormwater Network 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 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

  5. 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)

  6. The ICM and Urban Subwatershed Management

  7. New National Research Council Report Released Findings: Urban Stormwater Management in the United States • 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 http://www.nap.edu/catalog.php?record_id=12465

  8. 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)

  9. 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 1. Site Load Standard

  10. 2 .Runoff Reduction (RR) 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

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

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

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

  14. 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 3. Treating Impervious Cover & Managed Turf Areas

  15. Site Runoff Coefficient (Rv) Site Rv = RvI * %I + RvT * %T + RvF * %F

  16. 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

  17. Water Quality Compliance Spreadsheet

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

  19. 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

  20. 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

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