01/25/2011 Env Bd Packet - Laserfiche WebLink

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Where should we add requirements for pre treat ment /forebays. (JI\l TO ASK AT l`KDA) DRAFT 01 -19 -2011 (d) The proposed activity may not reduce hydraulic efficiency of the drainage -ways at any point upgradient of the applicant's parcel boundary. (e) The property owner must record a declaration, or a public owner execute a maintenance agreement, that prohibits plowed snow storage in a location from which runoff will be conveyed without adequate pretreatment (minimum of 25 feet of overland drainage on grassland or other rough vegetated surface to trap flow) or sheet flow directly into a wetland. This requirement does not apply to snow removed from public roadways. (f) Soil amendment, excavation or filling pursuant to development may not impede groundwater flow so as to create a substantial risk of loss of function to any wetland. (g) The runoff volume infiltration/detention standard of paragraph (b) is modified for public linear (roadway, sidewalk and trail) projects not part of an industrial, commercial, institutional or residential development. Public linear projects shall meet the requirements of the Rice Creek Watershed District (RCWD) or Vadnais Lakes Area Water Management Organization (VLAWMO) as applicable. (7) Peak Stormwater Runoff Control. Stormwater runoff rates for the proposed project at the site boundary, in aggregate, must not exceed existing runoff rates for the critical two -year and 100 -year frequency events. Any increase in a critical event rate at a specific point of discharge from the site must be limited and cause no adverse down gradient impact. The following curve numbers shall be utilized for existing condition modeling of those site areas not covered by impervious surface in the existing condition: Curve Numbers for Use with Existing Condition Pervious Areas 0.5" x surface area (ac) for fully vegetated Type 2 and 3 wetlands Upland Restoration/Conservation 0.85" x surface area (ac) Restoration of Degraded Wetlands 0.25" x surface area (ac) Impervious Disconnection Up to 0.5" x disconnected impervious area (ac) Soil Amendments /Tilling 0.3" x surface area amended (ac) (d) The proposed activity may not reduce hydraulic efficiency of the drainage -ways at any point upgradient of the applicant's parcel boundary. (e) The property owner must record a declaration, or a public owner execute a maintenance agreement, that prohibits plowed snow storage in a location from which runoff will be conveyed without adequate pretreatment (minimum of 25 feet of overland drainage on grassland or other rough vegetated surface to trap flow) or sheet flow directly into a wetland. This requirement does not apply to snow removed from public roadways. (f) Soil amendment, excavation or filling pursuant to development may not impede groundwater flow so as to create a substantial risk of loss of function to any wetland. (g) The runoff volume infiltration/detention standard of paragraph (b) is modified for public linear (roadway, sidewalk and trail) projects not part of an industrial, commercial, institutional or residential development. Public linear projects shall meet the requirements of the Rice Creek Watershed District (RCWD) or Vadnais Lakes Area Water Management Organization (VLAWMO) as applicable. (7) Peak Stormwater Runoff Control. Stormwater runoff rates for the proposed project at the site boundary, in aggregate, must not exceed existing runoff rates for the critical two -year and 100 -year frequency events. Any increase in a critical event rate at a specific point of discharge from the site must be limited and cause no adverse down gradient impact. The following curve numbers shall be utilized for existing condition modeling of those site areas not covered by impervious surface in the existing condition: Curve Numbers for Use with Existing Condition Pervious Areas Hydrologic Soil Group Runoff Curve Number* A 39 B 61 C 74 D 80 * Curve numbers from USDA -NRCS, Technical Release 55 (8) Design Criteria Alternative Format 16