07/25/2007 Env Bd Packet - Laserfiche WebLink

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wetland Moderately susceptible Pre - development + 0.5 feet Existing plus 1 day Existing plus 2 days Slightly susceptible Pre - development + wetland 1.0 feet Existing plus 2 days Existing plus 14 days Least - susceptible wetland /Lake No limit Existing plus 7 days Existing plus 21 days (c) Design Criteria. (i) Infiltration BMPs must be designed to provide: (a) Adequate pretreatment measures before discharge of runoff to the primary infiltration area (b) Drawdown within 48 -hours from the end of a storm event Soil infiltration rates shall be based on the appropriate HSG classification and associated infiltration rates (see Table 1 in Appendix C). Infiltration area will be limited to the horizontal areas subject to prolonged wetting; and (c) A minimum of three feet of separation from the seasonal high water table. (fj) Permanent sedimentation and water quality ponds are- required andmust be designed to provide: (4-a) Water quality features consistent with NURP criteria and District wet pond criteria (see appendix) .t (2b) A permanent wet pool with dead storage of at least equal to the runoff from a 2.5 -inch rainfall over the area tributary to the pond:; an (4) An outlet structure capable of preventing migration of floating debris and oils for at least the one -year storm. during or after construction. (h) Stermwate Management s under this -rule must confer -with - - - - " - • - - - - - .. - Plans. Detention basins must be designed to provide: (a) An outlet structure to control the two -year & 100 -year frequency events to pre - settlement peak runoff sites; and bbl An identified overflow spillway sufficiently stabilized to convey flows greater than the 100 -year Qritical storm event. DRAFT DOCUMENT 16 • • •