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Summary of State Stormwater Standards

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Summary of State Stormwater Standards Summary of State Stormwater Standards Office of Water Office of Wastewater Management Water Permits Division June 30, 2011 DRAFT (This document is draft as EPA is accepting any necessary corrections) This document summarizes the post‐construction stormwater standards for all 50 states and the District of Columbia. The following table briefly presents the information on selected aspects of each program (such as size threshold and the type of volume control requirement). The program names are linked to the full summary later in the document. Each summary follows a consistent format for comparison purposes. These summaries were based on regulations, design manuals, or other information published by each program. The sources used to develop the summary are identified. State water quality agencies were given the opportunity to review and comment on their standard summary. Where individual states have commented on their standard, those comments have been incorporated into this draft. For comments or corrections contact: Jeremy Bauer US Environmental Protection Agency [email protected] Volume Control Requirement ? ? Retention Treatment Exception EPA Region EPA Program Date required Where Size Threshold Redevelopment Standard Capture and treat 1” Connecticut 1 acre disturbed (non-regulatory – only Same as new 1 2009 MS4s area described in the development manual) Treat 1” times No increase in 1 acre disturbed impervious area plus current 1 Maine 2008 MS4s area 0.4 times pervious stormwater runoff area Post to pre, Recharge (post minimize recharge Treat 0.5” (1” in Wetland 1 acre disturbed development volume loss, follow 1 Massachusetts 2009 critical and other areas area to predevelopment Stormwater areas) volume) Management Standards 1 acre disturbed Infiltrate, Same as new 1 New Hampshire 2003 MS4s area / 100,000 sf evapotranspire, or development outside MS4s capture first 1” WQv Same as new requirement may development if < be waived or 40% IC; >40% IC Capture and treat State- 1 acre disturbed reduced by then reduce IC by 1 Rhode Island 2011 WQv equivalent to wide area applying 50% or water 1.2” rainfall runoff disconnection- quality and based LID recharge for 50% practices of area 1 acre WQv may be 2003 development, reduced where Reduce IC by State- Capture 90% annual 1 Vermont (Draft redevelopment non-structural 20% or treat 20% wide storms 2010) and/or increase practices are of WQv IC employed. Maintain groundwater 50% TSS 1 acre disturbed recharge volume or reduction or State- area or increase infiltrate runoff for 2- equivalent to 2 New Jersey 2009 wide IC by ≥ 0.25 year storm (post existing BMP; acres development volume 80% TSS removal to predevelopment to new IC volume) RR for post- Same as new development volume Single family development but if Remaining WQv not State- 1 acre disturbed (0.8” – 1.2”) to homes less than not possible IC 2 New York 2010 retained must be wide area replicate pre- 5 acre reduced by 25%, treated development disturbance and/or 25% WQv hydrology treated RR for 1-year event (post-development RR practices RR to reduce 2010 State- 5,000 sf runoff volume to should be runoff by 20% 3 Delaware (Draft) wide disturbed area predevelopment employed to the from existing volume) or 0% MEP. conditions2 effective IC Same as new development if <40% IC, For >40% IC, volume control required 2009 State- 5,000 sf Manage 0.9” / 1” of 3 Maryland for 50% of existing (2000) wide disturbed area rainfall imperviousness, no channel protection for existing imperviousness Volume Control Requirement ? ? Retention Treatment Exception EPA Region EPA Program Date required Where Size Threshold Redevelopment Standard For sites < 1 acre; Remove 1” of runoff Same as new from IC. Sites <1 acre: development; 1 acre disturbed 3 Pennsylvania 2006 MS4s All sites: No post Capture 2” of runoff modeling area development runoff from contributing IC. guidance for pre- volume increase for development IC the 2-year storm District of State- 5,000 sq ft of 3 2004 Narrative standard Columbia wide land disturbance 20% (sites > 1ac) 1 acre disturbed 10% (sites ≤1ac)P 3 Virginia 2008 MS4s Narrative standard area reduction from existing condition Keep and manage 0.2” reduction of on site 1” rainfall 1” on site 1 acre disturbed 3 West Virginia 2009 MS4s from 24-hour storm retention standard area preceded by 48 and additional 0.2” hours of no rain reductions exist 1 acre disturbed 4 Alabama 2009 MS4s Narrative standard area Varies by WMD – From first ½ inch runoff to 1.25 times Must meet percent 1995 - State- 4,000 sq ft predevelopment imperviousness plus Same as new 4 Florida presen wide imperv area volume in closed an additional one half development t basins only inch of runoff for online retention systems. Treat runoff from 85% 1 acre disturbed Same as new 4 Georgia 2007 MS4s of storms (1.2” area development rainfall) Manage 80th 1 acre disturbed percentile Same as new 4 Kentucky 2010 MS4s area precipitation event development runoff (0.75”)2 1 acre disturbed 4 Mississippi 2009 MS4s Narrative standard area In 20 coastal 1 acre disturbed counties area; ; Water Coastal-Non supply residential: Non-coastal: 1” watersh Same as new 4 North Carolina 2006 10,000 sf IC; rainfall; eds, development Residential w/in Coastal: 1.5” rainfall nutrient ½ mile shellfish sensitiv waters: 10,000 sf e IC waters, ONRWs 1,000 ft from 1 acre disturbed Volume control varies Same as new 4 South Carolina 2006 MS4s shellfish waters, area by practice development retain 1.5” of rainfall If retention standard cannot Infiltrate, be met, 80% 1 acre disturbed evapotranspire, Same as new 4 Tennessee 2010 MS4s TSS removal area harvest, or use first development standard applied 1” of rainfall to remaining volume Volume Control Requirement ? ? Retention Treatment Exception EPA Region EPA Program Date required Where Size Threshold Redevelopment Standard 1 acre disturbed Same as new 5 Illinois 2009 MS4s Narrative standard area development Phase I only: 1 acre disturbed Same as new 5 Indiana 2003 MS4s Treat runoff from first area development 1” of precipitation 5 Michigan MS4 permit withdrawn in November 2010 Reduce IC and/or Treat ½ inch runoff implement State- 1 acre disturbed 5 Minnesota 2006 from new imp. stormwater wide area surfaces > 1 acre management practices Treat WQv equivalent 20% WQv State- 1 acre disturbed 5 Ohio 2009 to 0.75” rainfall runoff treatment and/or wide area volume 20% IC reduction Infiltrate runoff to Size of infiltration 40% TSS achieve 60% -90% State- 1 acre disturbed area is limited to reduction from 5 Wisconsin 2010 of predevelopment wide area 1%-2% of site parking areas and volume based on IC area. roads or MEP level 1 acre disturbed 6 Arkansas 2009 MS4s Narrative standard area 1 acre disturbed 6 Louisiana 2007 MS4s Narrative standard area 1 acre disturbed 6 New Mexico 2007 MS4s Narrative standard area 1 acre disturbed 6 Oklahoma 2005 MS4s Narrative standard area 1 acre disturbed 6 Texas 2007 MS4s Narrative standard area WQv depth can 1 acre disturbed be adjusted Same as new 7 Iowa 2009 MS4s Treat 1.25 inch WQv area locally based on development historical data 1 acre disturbed 7 Kansas 2004 MS4s Narrative standard area 1 acre disturbed 7 Missouri 2008 MS4s Narrative standard area 1 acre disturbed 7 Nebraska 2005 MS4s Narrative standard area 1 acre disturbed 8 Colorado 2001 MS4s Narrative standard area Infiltrate, 1 acre disturbed evapotranspire, or Same as new 8 Montana 2010 MS4s area capture for reuse development runoff from first 0.5” 1 acre disturbed Treat 0.5” runoff from Same as new 8 North Dakota 2009 MS4s area IC development 1 acre disturbed 8 South Dakota 2003 MS4s Narrative standard area Volume Control Requirement ? ? Retention Treatment Exception EPA Region EPA Program Date required Where Size Threshold Redevelopment Standard 1 acre disturbed 8 Utah 2010 MS4s Narrative standard area 1 acre disturbed 8 Wyoming 2010 MS4s Narrative standard area 1 acre disturbed 9 Arizona 2002 MS4s Narrative standard area Biofiltration may Retain volume from 1 acre of th be used if Local program 9 California 2003 MS4s 85 percentile storm disturbed area retention is defined event infeasible 1 acre disturbed 9 Hawaii 2007 MS4s Narrative standard area Treatment volume may be 1 acre disturbed 80% annual runoff locally Same as new 9 Nevada 2010 MS4s area volume treatment determined development based on historical records Retain first 0.52 inches of rainfall 1 acre disturbed Same as new 10 Alaska 2009 MS4s from 24 hr event area development preceded by 48 hrs of no precip. 1 acre disturbed 10 Idaho 2000 MS4s Narrative standard area 80% average annual Capture and treat 1 acre disturbed runoff volume 10 Oregon 2007 MS4s 80% annual area reduction average runoff (for Phase I) Volume predicted from 6 month 24 hr storm OR 91st percentile 24 hr runoff 2000 sf of new Same as new Infiltrate, disperse, volume indicated by and/or replaced development 10 Washington 2007 MS4s and retain onsite to continuous runoff IC or 7000 sf when size MEP model. Max flow rate disturbed area threshold is met. where 91% of runoff volume (determined by model) will be treated Stormwater Program Summary – Connecticut Program Name: Connecticut DEP Stormwater Management Program Program Status: State NPDES Regulations, Phase II MS4 General Permit (2009), Connecticut Stormwater Quality Manual (2004) Regulatory Authority: Stormwater Quality Manual, which contains the stormwater standard described below, is non-regulatory. Phase II MS4 general permit does not contain a specific stormwater standard. Standard
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