07/25/2007 Env Bd Packet - Laserfiche WebLink

Home Search

• • (e) For a site or part of a site characterized by HSG C or D soils, the stormWater management plan shall focus on incorporation of water quality BMPs. The order of preference for BMP's is biofiltration, filtration, wetland treatment system, extended detention basin, NURP ponding. (f) The runoff volume infiltration/detention standard of paragraph (b) is modified for public linear (roadway, sidewalk and trail) projects as follows. Type of Construction Standard Hydrologic Soil Group New _.4,0 acre No change. impervious New < 1.0 acre BMPs must be sized for the runoff if • - 11.11 Rural to Urban Section volume generated from impervious surface within the contributing area n Expansion/ by an 0.8-inch event. — Reconstruction 11- 1 Ile 1■U Ill ■:. - II Mill & Overlay , No permit required. (iii) Peak Stormwater Runoff Control Stormwater runoff rates for the proposed project must not exceed runoff rates for the critical two-year and 100-year frequency events. For those site areas not covered by hard surface in the pre-existing condition, runoff rates are to be determined for the pre-settlement condition. The following curve numbers shall be utilized for pre-settlement condition modeling: Curve Number for Use with Pre-Settlement Conditions Hydrologic Soil Group Runoff Curve Number* A 3__Q B 58 c n D 11- 1 Ile 1■U Ill ■:. - II - It's"- — (iv) Bounce and Inundation Period. The project must meet hydroperiod standards adapted from "Stormwater and Wetlands Planning and Evaluation Guidelines for Addressing Potential Impacts of Urban Stormwater and Snowmeit Runoff on Wetlands," (Minnesota Stormwater Advisory Group, June 1997), as follows: La keNVetla nd Susceptibility Class Highly susceptible inundation Period Permitted Bounce ft Two-Year event Pre-development Existing Inundation Period for 10-Year or Greater Event Existing DRAFT DOCUMENT 15