09-04-2002 Planning Packet - Laserfiche WebLink

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l\r. Wyatt Pige3 Re: Camp TEKO Ofono. MN August 7. 2002 acres and the actual impervious in this drainage area is approximately 0.4 acres. Based on the Nurp Pond Sizing worksheet we would need 0.11 acre-feet of pond to treat this area. We are proposing to construct a vegetative filter strip west of the existing bituminous parking area to slow runoff and promote pollutants to infiltrate into the soil prior to entering the adjacent wetland. This filter strip will treat the new dining hall addition plus some of the existing building. This filter strip varies in width from 30 feet to over 50 feet in some areas and maintains an 8.3% slope with deep-rooted, wet and shade tolerant vegetative material instead of grass. We have pond volume storage of 0.15 acre-feet; see attached Pond Volume Storage Worksheet. This filter is designed to accommodate over a 2" rainfall event. We are unable to use PondNET to evaluate the % of remo -al of pollutants in this strip since it does not have an outlet, however based on the Minnesota Small Sites BMP Manual, studies have shown that filter strips in agricultural areas that are made of grass and are 15 ’ wide can remove 50% of the nitrogen, phosphorus and sediment. The filter strip we have designed is over double the width that has been proven effective in agricultural areas. We believe that this is a perfect water quality Best Management Practice for this portion of the site because it slows down the runoff and traps pollutants. We are also treating an additional 0.24 acres of existing impervious. Currently, this area is highly vegetated around the wetland with sheet flow off of the adjacent parking lot to the east and the hill to the south across type B soils. We believe that with minimum grading and minimum fill we can achieve a highly effective vegetative strip. 'Wetland Protection We recently had a wetland delineation completed for this property by Kjolhaug Environmental Company on August 5, 2002. Based on this delineation. Wetland #1 in the northwest comer of the site is approximately 7,826 square feet, requiring a 16.5-foot buffer zone as shown on the attached plans. Wetland #2 in the southeast comer of the site is approximately 8,770 square feet, also requiring a 16.5-foot buffer. We will install double silt fence along the wetland edge in the northwest comer of the site when the vegetative filter is being constructed to reduce any erosion of exposed soil into the wetland. 650 BUTLER NORTH BUiLDiNG 510 FIRST AVENUE NORTH MINNEAPOLIS. MN 55403 OFFICE: 612 252 9070 FAX 612.252.9077 wnww tandfbrm net