05-15-1989 Planning Packet - Laserfiche WebLink

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mp%V •■;n iTTfr* ■■ :■■ ■' - • ••■:'■■■; ■:mw <i'O'- mm ^*;^V" ■4 l5f.V '- r- I'v.'V'.'VUmmx:!r ■ • ■fTi' ki w mmx-m IT" »T X- ■:. 'y ’:XX^'ltmX'' C' immx'x •■'BCHOEU. & MA080N, INC.'4ENGINEERS • SURVEYORS • PLANNERS SOIL TESTINGTOSBO WAYZATA BOULEVARD • MIsasJETONKA, MN (818) S4S-7B01 • FAX |B1S| SRe-SdeO May 3, 1989 Mr. Mike Gaffron City Planner - Orono P. 0. Box 66 Crystal Bay, MN 55323 Subject: Lauer Hones, Inc. Site Drainage Basin Deign and Site Grading Dear Mike: Enclosed for your review and comnents Is the proposed grading and drainage plan and hydrology calculations for the subject project. Included on the grading and drainage plan ts the detention basin reoulred by the City. Prior to designing this basin, we re-surveyed the proposed basin area and discovered a large stand of 8" plus diameter trees located In the most feasible spot to construct the basin. In order to keep storm water runoff from continually ponding In this stand of trees, we designed the basin In such a manner that ponding would occur only during the more Intense storms (10 year return frequency or greater). To minimize ponding In the stand of trees, the detention basin design volume Is somewhat less than the volume suggested by Glen Cook. We feel, however, that the proposed basin provides a viable solution to your concerns. A simmary of the hydrology analysis Is as follows: I.Method of Analysis: Soil Conservation Service TR-55 Tabular Hydrograph using a 24-hour storm event. A. Drainage Area: 11.81 acres. B. Curve No.: 61, Golf Course, woods and brush II. 10-Year Frequency Storm Design: Precipitation - 4.3 Inches Peak Inflow to Basin - 9.0 cfs Peak Outflow to South - 2.4 cfs Water Level In Basin - 975.8 Maximum Volume of Water Detained In Basin - 13,000 cubic feet affirmative acton • EQUAL OPPORTUNITY EMPLOYER y%Mxmmm: \2 r.v;.■'?•''.v;. ^SmX'SXXXF^XX: :xr kK, XMXX ••li:. >• i ?•• • /^.tx t/-- m .mi (rts'iisi-