08-17-1987 Planning Packet - Laserfiche WebLink

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Zoning File #1177 August 11, 1987 Page 3 reports (exhibits M & 0). That same report also includes a plan of original site conditions (exhibit L). The original elevations show the front line of the house to be 16 feet higher than the lake elevation. The walkout area is shown 6 feet higher than lakeshore elevation in proposed contour plans with the drainage swale at 8 feet above the lakeshore elevation. *:ike Lynch has submitted the engineering revie\. of the grading and drainage plans submitted by Mr. Kopischke. He approves the drainage swale method and concurs that the flattened slopes within the lakeshore yard will reduce the velocity of runoff resulting in less potential for erosion and greater treatment potential. Lynch cautions that if soil materials removed with original excavation are to be used in backfilling that slope grades must be minimized. Once soils are disturbed they lose their cohesiveness with soils that remain undisturbed. Slope grades must be no greater than 3.1 but preferring 4.1 whenever possible. He also calls attention to the 6 feet height difference of flattened yard area in relation to shoreline and seeks information on the wave height and run-off factor for this section of shoreline. Kopischke has been advised of this request and will prepare the necessary information. Staff has also discussed revising the proposed plan (exhibit M) providing gentler slopes as follows: a) Along the north side extend elevations into flatter area reducing need for extensive retaining wall - attempt to provide 4.1 slopes - may only need small retaining wall adjacent to house where area is restricted. b) Allow retaining walls at 114 elevation in front of house to protect more stable undisturbed soils - this really involves replacement of existing stone wall. c) Fill in excavated area to the west (lakeside) of stone retaining walls - remove timbered walls and provide 4.1 slopes when feasible but nothing less than 3.1. The extension of the higher elevations at the north and south sides of the property will lessen the "tunnel effect" created by the original excavation. The reduction in use of retaining walls will also lessen this effect but most important erosion potential will be greatly reduced with gentler slopes and less use of retaining walls. Mr. Kopischke has also been advised of staf's recommendation regarding the original grading and drainage plan. Kopischke will submit revised plans including staff's suggestions. If the