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8CHOELL & M AD80N, INC. <br />ENGINEEPS • SURVEYORS • PLANNERS <br />SOIL TESTING <br />10S00 WAYZATA BCULEVARO • MINJNETOMKA. N/«si BS3A3-OAaS <br />(B1S| S4S-7S01 • FAX IBISl S4S-9GSa <br />May 3. 1989 <br />Mr. Mike Gaffron <br />City Planner - Orono <br />P. 0. Box 66 <br />Crystal Bay, MN 55323 <br />r-i <br />Subject:Lauer Homes, Inc. Site <br />Drainage Basin Deign and <br />Site Grading <br />Dear Mike: <br />Enclosed for your review and comments Is the proposed grading and drainage <br />plan and hydrology calculations for the subject project. Included on the <br />grading and drainage plan fs the detention basin required by the City. Prior to <br />designing this basin, we re-surveyed the proposed basin area and discovered a <br />large stand of 8" plus diameter trees located In the most feasible spot to <br />construct the basin, i.i order to keep storm water runoff from continually <br />ponding In this stand of trees, we designed the basin In such a manner that <br />ponding would occur only during the more Intense storms (10 year return <br />frequency or greater). To minimize ponding In the stand of trees, the detention <br />basin design volume Is somewhat less than the volume suggested by Glen Cook. He <br />feel, however, that the proposed basin p vides a viable solution to your <br />concerns. <br />A summary of the hydrology analysis Is as follows: <br />I.Method of Analysis: Soil Conservation Service TR-55 Tabular <br />Hydrograph using a 24-hour storm event. <br />A. Drainage Area: 11.81 acres. <br />B. Curve No.: 61, Golf Course, woods and brush <br />II. 10-Year Frequency Storm Design: <br />Precipitation - 4.3 Inches <br />Peak Inflow to Basin - 9.0 cfs <br />Peak Outflow to South - 2.4 cfs <br />Water Level In Basin - 975.8 <br />Maximum Volume of Hater Detained In Basin - 13,000 cubic feet <br />APRRMATTVe ACTION • EQUAL aPPOPTlJNmr' EMPLOYER