04-21-1986 Planning Packet - Laserfiche WebLink

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Zoning File #991/#1018/#1004 April 14, 1986 Page 3 of 5 The plans approved with the building permit and current proposal show a decrease in drainage towards the lake and a shift in approximately 1.24 acres of drainage area to the ponding area to the south (see Exhibit L). Per Exhibit M, the applicant's engineer in his summary (page 3) notes the increase in runoff to the pond would raise the pond level 0.4 feet in a 100 year storm and finds no appreciable effects on retention pond. Cook should advise if a compensatory excavation to increase pond storage capacity is required. The M.C.W.D. does not require permit review for the proposed shift in drainage. The applicant's consultant claims little effect on the pond and local watershed. The plans approved with the building permit provide for grassed slopes ranging from 946' to 938' elevations within 51 feet along the southern yard area (15% grade). Drainage from both the former Blohorn and Ulrich properties would drain down to the 938 elevation and out directly to the lake. The banks along the north side of the Blohorn property will be much steeper than those proposed on the Ulrich side of what would have become a ravine area. I have asked Cook to comment on the current plans proposed by the applicant. He contends the uniform or flatter grades and gentle grassed slopes to lagoon provides a more suitable treatment area for surface drainage. We both agree the original bowl area was ideal - providing retention and flat grassed areas for surface water treatment but the house now resides in the bowl area. Planning Commission Recommendation - Alternative of Action a) restore slopes to original contours. Ulrich side as proposed on building plans - Blohorn side per elevations reconstructed by engineer. b) approve current proposal c) create a grassed bowl area between both properties - eleva tions to be determined by City Engineer. Brief review of excavations - changes in elevations Per Exhibit I, the applicant's representative claims they have no knowledge of existing elevations prior to 11/84. Cook and I have attempted to recon struct elevations as we remember them at the time of our two visits to the site in October and November of 1983. Exhibits N & O attempt to show the depth of excavations, changes in elevations and drainage shifts. The original bowl area (majority of area now occupied by principal structure) we determined to have been at approximately the 938 elevation. The finished grade around the house is at the 946 elevation. The original ground elevation of the previous residence is at the 946 elevation but the garage elevation was at approximately 944 elevation. The foundation required excavations of 5 feet at the southern end ranging to 15 feet cuts to the north side. The majority of the fill and mounds of earth found on the site remain from the removal of all native soil from the foundation excavation in order to make room for the sand base under the foundation block and footings. The basement floor elevation is at 933.3 - code would require a 932.5 elevation (1 foot above the flood plain eleva tion of Lake Minnetonka),