CCP 09-30-2002 - Laserfiche WebLink

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The City's storm water management plan lists the seven wetlands and Valentine Lake as Tier 3 water bodies, which indicates that the intended uses do not include direct human contact with the water. Tier 3 water bodies include all DNR protected lakes, wetlands, and watercourses not included in Tiers I and 2. Tier I consistently supports swimming and Tier 2 lakes are capable of supporting swimming or having significant public use. . Based on the site and utility plan and storm water analysis provided by Rehder and Associates, Inc., the AUAR study area can be divided into six unique drainage areas as shown in Figure 12. The areas are defmed by topographic boundaries, storm drain alignments and where water discharges from the site. The areas are addressed individually within this section. For most of the existing site, runoff from pavement (parking lots and roadway surfaces) is carried via storm sewer to the receiving wetlands and carries with it the sediment and pollutants associated with these types of areas untreated to the water body. A few areas drain into municipal storm sewer either via overland flow or via storm sewer connections. Area I, which will not undergo any site plan changes at this time, flows to the existing storm sewer system on Lexington Avenue to the east. Area n drains into Wetland A, which crosses the southem property line in the southeast quadrant. Area ill drains to Wetland D within the study area at the northwest corner of the intersection of CR F and Fernwood Avcnue. Drainage from Wetland A flows into Wetland C outside of the study area and subsequently flows into Wetland D. Wetland D then discharges to the south through a culvert under CR F. . Area IV drains to Wetlands E, F and G. These are linked wetlands, which eventually drain out of the AUAR study area north along Hamline Avenue. Area V flows into Wetland I and then out of the site to the northwest. The northeastern portion of Area V (the Building 0 site) is not expected to undergo any site plan changes at this time, Area VI, which will undergo only slight site plan changes at this time, drains onto the adjacent roadways and into existing storm sewer at the northeast corner of the study area. According to the Comprehensive Drainage Survey Maintenance Plan and Ponding Recommendations prepared for the City of Arden Hills (dated May 1999), there are no planned regional storm water ponds in or near the AUAR study area. Design criteria for on-site storm water treatment arc listed below. . The total phosphorous removal efficiency for each pond or pond network must be at least 65 percent. (LSMP) . The permanent pool for wet ponds should have a volume equal to or greater than the runoff resulting from a 2.5-inch rainstorm under complete watershed development. (RCWD Rules, adopted August 12, 1998, and LSMP) . Storm water runoff rates for the proposed project must not exceed existing runoff rates . for the critical one-year or two-year and IOO-year frequency events. (RCWD Rules) Guidant Campus Master Plan Draft AUAR - 21 - September 2002