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� � <br /> �;. <br /> CITY of �RONO <br /> � <br /> �� �' :j"� Post Office Box 66•Crystal Bay,Minnesota 55323•Municipal Offices <br /> , k �� ; �Y�, <br /> � �d� ,���_� On the North Shore of Lake Minnetonka <br /> � ��^��-�,,, <br /> R��Y,�,,�.. <br /> December 23 , 1987 <br /> James H. Parker, P.E. and L.S. <br /> Advance Surveying & Engineering Company <br /> 5811 Cedar Lake Road <br /> Minneapolis, MN 55416 <br /> Re: On-site System Design for Robert Posthumus <br /> Dear Mr. Parker: <br /> We are in receipt of a site evaluation report and on-site system <br /> design for the Robert Posthumus property located on Lots 58 and 59, Morse <br /> Island Park, Hennepin County, Minnesota, on Big Island. <br /> We find that based on the site evaluation information submitted, your <br /> system design is not acceptable for a number of reasons. Your report is <br /> beautifully presented but contains specific errors and mistakes indicating <br /> a lack of thoroughness and a lack of understanding of proper mound sewage <br /> treatment system design. The following specific inadequacies are brought <br /> to your attention: <br /> 1. The system has been designed to fit the shape of the property <br /> boundaries and does not take into account the topography of the site. <br /> In a properly designed mound system, the longitudinal axis of the rock <br /> beds should be parallel with the contour lines. Your design indicates <br /> rock beds skewed at a 45 degree angle with contour lines. <br /> 2. Your report and design criteria indicate a 3� land slope across <br /> the mound. In fact, based on the contours presented on the site plan, <br /> the actual land slope across the mound site is 11.5� with incremental <br /> slopes between the provided contour lines ranging from 10$ to 20�. <br /> Based on the actual 11.5$ slope, your ca�culations and assumptions for <br /> basal width, for downslope and upslope dike widths, depths of sand <br /> layer, etc., are all invalid. <br /> 3. Although with a mound design the actual average perc rate is of <br /> relatively minor consequence, in this case I note that percolation <br /> hole no. 2 is not labeled on the site p1an, and you failed to indicate <br /> which percolation holes were used in obtaining the 13 MPI average. It <br /> appears that no borings and no perc holes are located within the <br /> boundaries of the mound area proposed. <br /> BUILDLNG&ZONING-473-7357 • ADMIIVISTRATION&FINANCE-473-7358 • PUBLIC WORKS-473-7359 <br /> ASSESSING <br />