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March 2010 Requirements for New Development and Redevelopment Projects Stormwater C.3 Update Contra Costa Clean Water Program Changes coming For some land uses, the threshold for treatment requirements drops to 5,000 (from 10,000) square feet of impervious area created or replaced. Applicants must evaluate feasibil- ity of infiltration or on-site use. Applicants may propose to provide treatment of runoff from an equivalent amount of impervious area, subject to conditions. Use of below-ground vaults and filters is still restricted; exceptions will be updated. Low Impact Development (LID) design procedures and criteria for treatment and flow-control facili- ties will stay the same. Applicants for approval of projects smaller than the threshold are encouraged to include site design measures to reduce runoff and source control measures to reduce pollutants in runoff. Projects larger than 2,500 square feet of impervious area must include at least one site design feature to reduce runoff. The San Francisco Bay Re- gional Water Quality Control Board adopted a Municipal Regional Permit (MRP) on October 14, 2009. The MRP consolidates and updates stormwater pollution preven- tion requirements for Bay Area municipalities. New requirements are phased in through 2012. Since 2005, in compliance with previous permits, Con- tra Costa municipalities have required applicants for devel- opment approvals to submit a Stormwater Control Plan. Those plans include controls for on-site sources of pollut- ants and features and facili- ties that treat and control the flow of runoff. Requirements for Stormwa- ter Control Plans are in the Clean Water Program’s Stormwater C.3 Guidebook, 4th Edition, available at www.cccleanwater.org. A 5th Edition including new MRP requirements is ex- pected in summer 2010. Applications deemed com- plete on or before December 1, 2009 and being diligently pursued and applications receiving final discretionary approval prior to December 1, 2011 are subject to the requirements in the current 4th Edition, at a minimum. Requirements for specific development projects are determined by the local juris- diction. Contact your local stormwater coordinator for further information. Regional permit has new rules Smaller projects must treat runoff Facilities to treat runoff will be required for auto service facilities, retail gasoline out- lets (gas stations), restaurants, and uncovered parking lots that create or replace as little as 5,000 square feet of imper- vious area. The threshold for other projects remains at 10,000 square feet. Smaller projects creating 2,500 square feet or more of impervious surface must include at least one feature that directs a portion of run- off from roofs or pavement into cisterns or rain barrels for reuse, directs runoff on to vegetated areas, or in- cludes permeable pavements. A list of these features, and examples, will be included in the 5th Edition of the Stormwater C.3 Guidebook. Bioretention facility treats runoff. Photo by Scott Wikstrom, City of Walnut Creek ---PAGE BREAK--- Summary of project thresholds, dates, and compliance requirements Threshold Effective Date Requirement All projects requiring municipal approvals or permits May 1, 2010 As encouraged or directed by local staff, preserve or restore open space, riparian areas, and wetlands as project amenities, minimize land disturbance and impervious surfaces, cluster structures, and direct runoff to vegetated areas. Use Bay-friendly landscap- ing features and techniques. Include Source Controls specified in Stormwater C.3 Guidebook Appendix D. Projects between 2,500 and 10,000 square feet requiring approvals or permits December 1, 2012 Install one or more of the following: Direct roof runoff into cisterns or rain barrels for reuse; direct roof runoff onto vegetated areas; direct runoff from sidewalks, walkways and/or patios onto vegetated areas; direct runoff from driveways and/or uncovered parking lots onto vegetated areas; construct sidewalks, walkways, and/or patios with permeable surfaces; construct bike lanes, driveways, and uncovered parking lots with permeable surfaces. Auto service, gas stations, restaurants and parking lots over 5,000 square feet December 1, 2011 Prepare and submit a Stormwater Control Plan as described in Chapter 3 of the Stormwater C.3 Guidebook, including features and facilities to ensure runoff is treated before leaving the site. Use the LID Design Guide in Chapter 4, including sizing factors and criteria for „treatment only.‰ All projects between 10,000 square feet and one acre August 15, 2006 Prepare and submit a Stormwater Control Plan as described in Chapter 3 of the Stormwater C.3 Guidebook, including features and facilities to ensure runoff is treated before leaving the site. Use the LID Design Guide in Chapter 4, including sizing factors and criteria for „treatment only.‰ Projects an acre and larger October 14, 2006 Select one of four flow-control compliance options from the Guidebook. Where required, design project features and facilities for hydrograph modification management (flow-control) as well as stormwater treatment. Prepare and submit a Stormwater Control Plan as described in Chapter 3 of the Stormwater C.3 Guidebook, and use the LID Design Guide in Chapter 4, including the sizing factors and criteria for „treatment and flow control.‰ Low Impact Development requirements to continue This fact sheet is a summary only. See the Regional Water Board Order and the Contra Costa Clean Water Program’s Stormwater C.3 Guidebook for actual requirements. March 2010 Chapter 4 of the Stormwater C.3 Guidebook includes a design procedure and criteria for Low Impact Development (LID) drainage design. Applicants for develop- ment approvals preserve natural drainage features; design buildings and circulation to minimize the amount of roofs and paving; substitute pervious surfaces such as turf, gravel, or pervious pavement for impervious pavement; disperse runoff from impervious surfaces to adjacent landscaping, and drain remaining imper- vious surfaces to bioretention or infiltra- tion facilities or flow-through planters. Contra Costa municipalities will continue to require these procedures and criteria be used for regulated development pro- jects, including capital improvement projects implemented by public agencies. Municipalities in Alameda County and some other Bay Area counties have, until now, allowed non-LID designs, includ- ing detention basins and proprietary devices, to treat runoff. Under the MRP, these municipalities must require LID be used to reduce runoff and to treat re- maining runoff before discharge off site. Contra Costa municipalities have strongly encouraged LID design for stormwater treatment since 2005. In 2006, the San Francisco Bay Regional Water Quality Control Board approved use of Contra Costa’s LID approach to meet new hydrograph modification man- agement (flow-control) requirements as well as treatment requirements. A forthcoming 5th Edition of the Storm- water C.3 Guidebook will include the fol- lowing changes mandated by the MRP: Applicants will be required to infil- trate or evapotranspirate runoff, or use runoff on-site, where feasible. The Guidebook will include criteria— such as highly permeable soils or available space for storage—for determining the extent to which infiltration, evapotranspiration, and on-site use are feasible on a particu- lar site. The Guidebook will continue to emphasize bioretention as a cost- effective and environmentally bene- ficial way to manage runoff. Applicants may propose to build and maintain LID facilities to treat runoff from an equivalent impervi- ous area at another site in the same watershed. In some cases, it may be possible to pay a fee in lieu of pro- viding LID facilities on-site. Currently, non-LID designs may be considered only when existing drainage systems must be retrofit and for some projects smaller than an acre built as part of a pedestrian- friendly urban landscape (see page 16 of the Stormwater C.3 Guidebook). These requirements may change based on a study and proposals the municipal permittees must submit to the Regional Water Quality Con- trol Board in December 2010. All thresholds are for impervious area, including roofs or pavement, that is created or replaced in connection with the project.