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Memo >i'' <br />.i <br />Bonestroo <br />Bofcne <br />AnderfikA <br />Asfoctoces <br />Cwflwtfi A A«cMi*r|( <br />Pn^^etManm: 1745 Fox Street Client CityofOrono <br />To: Tom Kellogg File No: 139-05-000 <br />From; Lance Hoff Date: 5-19-05 <br />Ne: Drainage Review <br />Developer: Sued Azhari & Omar Abukhadra <br />Engineer Gronberg & Associates, Inc., Long Lake <br />Submittal: Drainage Calculations, Rational Storm Sewer Design Calculations, Plans <br />Plan Sheets: Grading and Drainage, Storm Sewer <br />Date of Plans: 2-22-05, Latest Revision on 5-4-05 <br />Date Received: 5-12-05 <br />Summary of Recommendatlona <br />Based on our review of the 1745 Fox Street development, we offer the following comments. <br />1. Rational method storm sewer calculations should be submitted for review and approval. <br />2. Riprap should be provided at each flared end section (FES) inclur*' '* the FES discharging to <br />the pond. <br />3. Outflow velocities from the FES discharging to the pond and at the pond outlet should not <br />exceed 5 ff>s to avoid erosion (and resuspension of sediment in the pond). <br />4. The developer ’s engineer did a good job including a 10* wide aquatic bench at 10:1 slopes, but <br />the remaining pond slopes vary from 2:1 to 5:1. Slopes above the pond NWL should be 4:1 or <br />flatter. Slopes below the porul aquatic bench should be 3:1 or flatter. <br />5. The City's standard skimming pond outlet should be used (detail attached). <br />6. Low flow control should be added to the pond outlet design. For example, the addition of a weir <br />to an elevation of 936 in combination with a 6” orifice located at the normal water level will <br />reduce 2-yr peak flows from 2.0 cfs to 0.0 cfe while raising the 100-yr HWL only 0.1’ to 937.6. <br />7. A pond outlet detail should be included on the plans and submitted for review and approval. <br />8. Wetland buffers are proposed as a best management practice (BMP). Wetland buffer signs <br />should be placed along the edge of the proposed buffer to ensure that the buffers aren ’t mowed <br />OonMtne, Rocwm, AmHwMk mtf AMoctolts, Inc.www.bon0atroo.com <br />om <br />Mans IWIM <br />0 <br />IWf» <br />mm wmim <br />far SBI IVJWD <br />OOTMfOMrt: <br />mMtSMStV <br />tMta.Mimi <br />fm <br />(iSLOoHiOiaR <br />SLCkMLMNSBIil <br />nm UBAi m) <br />r«c3»2SI<2V <br />l«0 tMM MMMi m S» HS <br />CrafAba.! iOUO <br />RW Ml MB47I4mwimmm <br />mn. <br />I