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Evironmental Board <br />September 28, 2016 <br />Page 2 <br />5. ACTION ITEMS <br />A. Lino Lakes Elementary Renovation <br />Lino Lakes Elementary School was originally built in 1957. This renovation project will <br />result in an additional 4 classrooms totaling 7800sf to the building. There will also be a <br />large gathering space at the front/south side of the building and an outdoor classroom to <br />the west side of the building. <br />Mr. Asleson introduced Nick Mantel with Louck's Engineering who is in charge of the <br />renovation. <br />Grading Plan and Stormwater Management <br />On the 19.99 acre site, a drainage area of about 6.01 acres was included in the site <br />hydrological analysis. 1.34 acres of disturbed area is pervious area that will be replace to <br />match existing conditions. <br />The proposed site BMP's will consist of an infiltration basin for treatment, volume <br />control and rate control prior to discharging to the wetland to the north. The <br />reconstructed parking lot and the building addition will convey stormwater to the <br />infiltration basin using a storm sewer pipe system. The proposed site contains 46.3% <br />impervious surface area. Which includes the reconstructed portion of the parking lot and <br />roof drains that are being captured by the storm sewer system. <br />Ms. Kaufenberg inquired about the drainage of the impervious surface area and the <br />presence of infiltration ponds. <br />Mr. Mantel explained how the infiltration ponds will capture the required 1.1 inches of <br />rainfall over the new/reconstructed impervious surfaces on the site and the downspouts <br />from the building with a maximum drawn down time of 48 hours. <br />The proposed site contains two drainage areas. One area is the area where the new <br />infiltration pond will be placed. There will be a storm manhole directly upstream of the <br />infiltration basin and will include a 3 foot sump and energy dissipater with skimmer for <br />pretreatment. The other drainage area will flow offsite to the north. <br />A stormwater maintenance agreement will be required. <br />Soils <br />The soil also meet the infiltration standards for infiltration ponds. That is, it is an <br />assumed infiltration rate of 0.45 inches per hour based on the soil borings. <br />APPROVED MINUTES <br />