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• • iZ r via. !i`;aH'c- J 1 & M d tr- n ^ n c tr Planning 0 Engineering • Surveying 't*;4.1 d/ t. _.. 0 . January 17, 2006 •er Iv ;t t,)(-1`m e , Mr. Allen Munson 3165 North Shore Drive Wayzata, MN 55391 Subject: Drainage Study Dear Mr. Munson: Please find enclosed our Drainage Study Analysis for the Munson residence at 3165 North Shore Drive, Wayzata, MN. Runoff calculations were made for both existing and proposed conditions to identify the change in drainage due to new construction. Our analysis indicates the existing drainage pattern is through the northeast neighbor's lot and around the south side of the Munson residence down to Lake Minnetonka. (Refer to attached drainage area maps) The proposed grading and landscape changes direct a majority of the drainage runoff to the southern side of the residence down to the lake and reduces the drainage on the northeast neighbor's lot. Our calculations are tabulated below: Area A represents drainage that remains on the Munson's site. Area B represents drainage to the northeast neighbor's property. The analysis indicates the proposed site improvements reduce the off-site runoff across the neighbor's property and the total runoff rate is increased slightly. Below is a chart, from our calculations, representing the difference in discharge from areas A and B. Runoff Conditions to selected Discharge Location Existing Proposed Total Runoff Design Conditions Conditions Inc./Decrease Area A, Area B, Area A, Area B, Area A, Area B, Storms cfs cfs cfs cfs cfs cfs 2 yr 0.457 0.647 0.652 0.473 0.195 -0.174 10yr 0.948 1.340 1.350 0.980 0.402 -0.360 100yr 1.371 1.940 1.950 1.418 0.579 -0.522 U:\MISC\3165Nshoredrive.doc 10580 Wayzata Boulevard, Suite 1 • Minneapolis, MN 55305-1525 Office (952) 546-7601 • Fax(952) 546-9065 www crhnalImarlcnn rnm