Laserfiche WebLink
Eo.sler n 141ashington Phase 11 Municipal Storer wafer Permit <br />• The wetland meets the criteria for "Hydrologic Modification of a Wetland" in Core <br />Element #6 Flow Control; and either <br />• It is a Catc2ory 4 wetland according to the Eastern Washington Wetland Rating System; or <br />• It is a Category 3 wetland according to the Eastern Washington Wetland Rating System and <br />the wetland has been previously disturbed by human activity, as evidenced by agriculture, <br />fill areas, ditches or the wetland is dominated by introduced or invasive weedy plant <br />species as identified in the rating analysis. <br />Basic treatment is required prior to discharge to Category 3 wetlands; a Category 3 wetland that <br />meets the above requirements may be used to meet metals treatment requirements. Oil control is <br />required for a discharge to wetlands if the Technical Thresholds/Requirements are met. <br />Mitigation shall be required for the impact of using a wetland as a stormwater treatment facility. <br />Appropriate measures include enhancement, expansion and/or preservation of a buffer around <br />the wetland. <br />Core Element #6: Flow Control <br />Requirements <br />New development projects that meet the regulatory threshold and result in 10,000 square feet <br />or more of new impervious surfaces shall construct stormwater flow control facilities for any <br />discharge of stormwater directly, or through a conveyance system, into surface water. <br />Redevelopment projects are not required to construct stormwater flow control facilities unless <br />required under a basin plan or other federal, state or local requirement. <br />The stormwater flow control facility shall be designed to protect stream morphology and <br />associated instream habitat from adverse impacts due to increased peak flows and flow durations <br />following development. Flow control facilities shall be selected, designed, constructed, operated <br />and maintained according to criteria established by the local jurisdiction. <br />In order to prevent localized erosion, energy dissipation at the point of discharge is required for <br />all projects unless site-specific conditions warrant an exception. <br />When Core Element #6 Flow Control is required, Core Element #7 Operation and Maintenance <br />also is required. <br />Exemptions <br />Direct discharges to the following surface waters are exempt from flow control requirements to <br />protect stream morphology: <br />1. Any river or stream that is: <br />• Fifth order or greater as determined from a 1:24,000 scale map; or <br />e Fourth order or greater as determined from a 1:100,000 or larger scale map. <br />Appendix I- Minimum Technical Requirements <br />Eastern Washington Phase II Municipal Stormwater Permit —August 1, 2014 <br />Page 17 <br />