03-14-1994 Council Packet - Laserfiche WebLink

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Request for Council Action continued page 5 of 10 Mar*h 11, 1994 Zoning File #1901 Ellen Sones of the Minnehaha Creek Watershed has advised that the current mitigation plan presented in your preliminary plans. Exhibit Z. have been conceptually approved by the staff of the Watershed District. She has called for the publication of the permit in the Environmental Quality Board Bulletin. After the 30 day period, which she advises would end some lime at the end of April, the application can then be brought to the Minixhaha Creek Watershed Board for their regular monthly meeting in May to review both the final mitigation plan and stormwater treatment/control plan. The earliest possible permit approval from the Watershed District will probably be in the latter part ot May of this year. Staft has asked Ellen Sones to send a letter to the developer advising them of the current review schedule. Representatives of the DNR Trails asked the City not to act on the preliminary plans at the January meeting of the Planning Commission pending resolve of certain downstream drainage concerns, adequacy of culverts under Luce Line and the impact of increased runoff from development on ponding areas adjacent to Luce Line. The DNR met with the applicant and staff and have approved the drainage plans as amended and have agreed to allow culvert replacement and alteration of the trail to make the stormwater controls work (review Exhibit R). Review Exhibits Ql-3, topographic maps of the Luce Line area, southeast culvert (18" at the Coffin property) will be replaced. The DNR has agreed to allow the trail to be lowered approximately 1’ allowing for an emergency overflow to assure residence on north side of Luce Line will not be flooded. The DNR has asked that direct drainage to ditch along north side of Luce Line on Coffin property be minimized as much as possible because of the inability to widen and deepen ditches because of the steep elevations adjacent to trail. The DNR has been convinced that we are dealing with a very small watershed. Drainage currently exits the property at 18 CFS and will be reduced to 5 CFS. Throe retention ponds have been developed on the Coffin property. The culvert at the north side of the Luce Line will be reduced to 12" and exit on the south side at 18". This again is another attempt to reduce flow. The City Engineer and applicant’s engineer have worked closely on the downstream drainage concerns of neighbors and Planning Commission, specifically drainage as it leaves the Coffin property running along the west side of the road until it exits via culvert to the east to the White Oak Circle neighborhood (review Exhibits V and W). Shawn Gustafson reaffirms that the new drainage controls on the Coffin site will not magnify drainage problems on Dougan property. It may in fact slightly improve. Mr. Gustafson will be available for Council ’s questions at your March 14th meeting. The DNR seems to be less concerned with the detention pond in the southwest comer of the Dickey property. Runoff currently exits property at about 117 CFS and after development will exit at W CFS. Drainage will flow along via an existing drainage path to the southwest and eventually to the 36" 75’ long culvert beneath Luce Line, No changes are proposed in this drainage.