Laserfiche WebLink
Order <br />2009-0009-DWQ amended by 2010-0014-DWQ & 2012-0006-DWQ <br /> 35 <br /> <br />XIII. POST-CONSTRUCTION STANDARDS <br /> <br />A. All dischargers shall comply with the following runoff reduction <br />requirements unless they are located within an area subject to post- <br />construction standards of an active Phase I or II municipal separate storm <br />sewer system (MS4) permit that has an approved Storm Water <br />Management Plan. <br /> <br />1. This provision shall take effect three years from the adoption date of <br />this permit, or later at the discretion of the Executive Officer of the <br />Regional Board. <br /> <br />2. The discharger shall demonstrate compliance with the requirements of <br />this section by submitting with their NOI a map and worksheets in <br />accordance with the instructions in Appendix 2. The discharger shall <br />use non-structural controls unless the discharger demonstrates that <br />non-structural controls are infeasible or that structural controls will <br />produce greater reduction in water quality impacts. <br /> <br />3. The discharger shall, through the use of non-structural and structural <br />measures as described in Appendix 2, replicate the pre-project water <br />balance (for this permit, defined as the volume of rainfall that ends up <br />as runoff) for the smallest storms up to the 85th percentile storm event <br />(or the smallest storm event that generates runoff, whichever is larger). <br />Dischargers shall inform Regional Water Board staff at least 30 days <br />prior to the use of any structural control measure used to comply with <br />this requirement. Volume that cannot be addressed using non- <br />structural practices shall be captured in structural practices and <br />approved by the Regional Water Board. When seeking Regional <br />Board approval for the use of structural practices, dischargers shall <br />document the infeasibility of using non-structural practices on the <br />project site, or document that there will be fewer water quality impacts <br />through the use of structural practices. <br /> <br />4. For sites whose disturbed area exceeds two acres, the discharger shall <br />preserve the pre-construction drainage density (miles of stream length <br />per square mile of drainage area) for all drainage areas within the area <br />serving a first order stream14 or larger stream and ensure that post- <br />project time of runoff concentration is equal or greater than pre-project <br />time of concentration. <br /> <br /> <br />14 A first order stream is defined as a stream with no tributaries.