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I <br />Memo yjBoncslroo <br />vS AndMk& <br />|\]| Assodares <br />•niliiwi 4 ArcMitcii <br />Pnj%ctN§m9: 1745 Fox Street Ctiwit: CityofOrono <br />To: Tom Kellogg FHoNo: 139-05-000 <br />From: Lance Hoff Date; 5-19-05 <br />Ho: Drainage Review <br />Developer Sued Azhari & Omar Abukhadra <br />Engineer Gronberg & Associates. Inc., Long Lake <br />Submittal: Drainage Calculations, Rational Stonn 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) including the FES discharging to <br />the pond. <br />3. Outflow velocities from the FES discharging to the pond and at the por>d outlet should not <br />exceed 5 fps 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 pond 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 cte to 0.8 cfs 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 />BotfMtno, Roamf, AndaiOk and AssoctolM, Inc.www.bonttroo.com <br />OtlfMf <br />23»IMNM h|JI <br />•MainSiRMl <br />tatai <br />0 <br />n?i» <br />fiitai <br />rn.mmi’imm-mnm <br />msteSMSwmm m%m <br />fn MSB <br />OSiOtei <br />i7n»*i <br />SI CM <br />mrnrn. »IS14SSI <br />faa.flB»l4ai <br />1 <br />t <br />(MSteMi <br />Rote M7 S4I4774 <br />F« Ml MMill