11-09-06 Planning Comm. Agenda - Laserfiche WebLink

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3. The seed type for the ponding area should be revised to Type 350 applied at a rate of 350 pounds per acre. • Note revised 4. A note should be added that the seeding and operations should be in accordance with a technical letter issued by MnDOT dated November 14, 2005 and titled "Metro District Turf Establishment Recommendations". • Note added Stormwater Management Calculations 1. This submittal includes exfiltration for the infltration area. If the Exfltration is proposed as a means for this site, then a percolation test shall be completed and final data submitted for review. Testing was done on the existing soils and it was determined that a standard infiltration feature would not work in this location. Therefore after conversations with the watershed and based on the existing soil types encountered with soil borings, the proposed infltration basin has been revised to a biofltration feature. The soils beneath the surface of the biofltration basin will consist of 40% semi course washed sand or native soil, 30% MnDOT grade 2 compost and 30% native topsoil by volume to improve infltration potential. A 4" underdrain system will also be installed to collect water that can't permeate through the existing sails below the basin. 2. The pond area in the drainage calculations shall be accounted for separately from other drainage areas. A curve number of 100 should be used for the ponding area. • The ponding area has been separated and the CN of 100 is used. 3. A storm sewer pipe capacities spreadsheet should be submitted for review. • Spreadsheet enclosed. 4. Documentation should be provided as to the outlet path, location, and elevation of the adjacent wetland to a creek, river, or lake to ensure that it is not part of a larger isolated wetland without an outlet. • After investigation of 2' contour data for Ramsey County an emergency overFlow path was defined. This path and contour data was given to the surveyors. A GPS crew located the elevations along the overflow path and these shots are shown on a 11x17 drawing in the drainage calculation package. These findings indicate that the adjacent basin is not isolated and the overflow lies at an elevation of 869.76 and continues south to Kohlman Lake as shown with the shots. This elevation is over 14' below our lowest floor. Please call if you have any additional questions or comments. Sincerely, ~ Craig G. Schlichting, P.E. PLOWS ENGINEERING, INC. 6776 Lake Drive NE, Suite 110 Lino Lakes, MN 55014 ph (651) 361-5210 fax (651) 361-5701 email: crai<> a,plowe.com