10-27-2004 Council Agenda - Laserfiche WebLink

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cent? an, 4 C Zan i2� 515 Little Canada Road, Little Canada, MN 55117-1600 (651) 766 -4029 / FAX: (651) 766 -4048 www. ci. li tale- Canada. mn. us MEMORANDUM TO: Mayor Fahey & Members of the City Council FROM: Joel Hanson, City Administrator DATE: October 22, 2004 RE: Ponding Revisions for Gervais Hills Preliminary Plat MAYOR Michael I. Fahey COUNCIL Jim LaValle Matt Anderson Rick Montour Bill Blesener ADMINISTRATOR Joel R. t-tausou The Developer for Gervais Hills has submitted a revised layout that provides for a larger storm water pond in the vicinity of Lot I. As you will recall, they offered to move the cul -de -sac about 60 feet to the south to accommodate larger drainage ponds that would approximate the size of the one designed for Lot 1 by the City Engineer. Due to topographical, drainage, and lot layout constraints, they have moved the cul -de -sac only 40 feet to the south. This resulted in a larger pond on the west side of the new street, but not the east. Therefore, the size is the new pond is not as large as what our City Engineer had designed, The differences are as follows: Engineer's Proposed Pond Dead Storage = 25,708 cubic feet Live Storage = 37,800 cubic feet Developer's Revised Pond Dead Storage = 12,677 cf. (50% of Engineer's) Live Storage = 31,543 cf. (84% of Engineer's) The Developer's original design only provided for 1,700 cubic feet of dead storage and 23,700 of live storage. Therefore, their revised pond is substantially larger. Furthermore, they were willing to increase the depth of their revised pond and that should provide an additional 1,000 to 3,000 cubic feet of capacity. Note: Dead storage is the volume of water below the normal water level, which is set by the elevation of the outlet. The City Engineer has stated that the main issue with the revised pond is that the smaller area for dead storage restricts treatment capabilities. In explaining why greater ponding was not possible, they offered the following explanations: I. Could not move the cul -de -sac farther south due to conflicts from the drainage coming from Viking Drive. 2. Could not move the cul -de -sac farther south due to not meeting minimum lot widths at the building setback line. 3. "There were some design issues in expanding the pond on the east side of the new road due to conflicts with the other ponds and their purposes, i.e. there wasn't enough room. - 1 -