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(' . t 2335 Highway 36 W St. Paul,MN 55113 Tel 651-636-4600 Fax 651-636-1311 www.bonestroo.com February 25, 2011 �'Bonestroo Melanie Curtis Planning and Zoning Coordinator City of Orono Post Office Box 66 Crystal Bay, MN 55323 Re: 3095 North Shore Drive File No. 000139-11000-1 File No. 2011-00005 Dear Melanie: We have reviewed the plans for the proposed new home construction at 3095 North Shore Drive. The plans are dated 2-16-11. We have the following comments with regards to engineering matters: • The sanitary sewer main and service line should be shown on the plans. • We typically recommend that swales maintain at least a 2% slope to facilitate minor variations in final grading. The proposed swale on the lake side of the home is closer to a 1% grade. If this must remain at this flatter grade, we recommended draintile be placed within this swale. • In our stormwater review, we created a HydroCAD model to determine the pre and post construction high water levels of the closed basin west of the proposed home. In a 100- year storm event, the current low point fills with runoff and flows over the neighboring driveway at elevation 933.5. This would appear to cause some water damage to the garage at elevation 933.7. The proposed house, detached garage, and driveway increase the runoff to the existing low point. However, the addition of the pipe draining this area improves the overall drainage situation. A summary of the modeling results is below. Pre construction Post construction Freeboard to Gara e Floor 3105 North Shore Dr 933.7 933.7 - Gara e 100 -year high 933.7 932.3 1.4' water level 100-year back to 933.7+ 933.0 0.7' back HWL The proposed drainage system is able to handle the 100 year back to back storm without impacts to the neighboring property and is acceptable.