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<br />MIDWEST SURV IENG <br />. <br /> <br />TEL No.612-7S6-920S <br /> <br />Jun 24.94 11:31 No.OOl P,02 <br /> <br /> <br />MIDWEST <br />Land Surveyors & Civil En ineers, Inc. <br />1" c.oD Rapl4J Jfl\ld. <br />Oooa .,w., UN 15W <br />Ph. '11-'18808909 J'u:f1J.78WJ08 <br /> <br />Mr. Lon Aune <br />City Of R08evl11e <br />2660 Civio Center Drive <br />ao.eville, Mn. 55113 <br /> <br />Rei Cav. and A8.ou4..t4;l8, LTD. <br />Lot. on Minn..ot. 8t~eet <br /> <br />June 2., 1994 <br /> <br />Dear Mr. AWlC I <br />. <br /> <br />Aa raque.ted t have written a 8ummary of the .torm water runotf oalculatlon8 <br />f~ thia sit.e. <br /> <br />The runoff c;:alClulations for eM.. aite were prepare for.. 10 year etorm event. <br />per R08eville 8tandards. Throughout the Tw1n Ci y a~ea, re.ident1al storm <br />sewer .ystems are typically designed for Ii or JiO year storm event.s with <br />ponding areas .{zed to the 100 year event. por ra nf.1ls greater than the 10 <br />yoar storm evont ov.rlan~ flow i~ relied on. <br /> <br />The Rational Method wag used to cllICl\11ate the ra es of runoff. From this <br />method runoff is determined by factoring in drat age aroa, types of 80il, <br />amount of impervious surface, slope ot the land Il l:ainfall .tntonaity. 'the <br />dra.:lI'Uilg'e "rea includeliJ the proposed site plul!J he area direotly .a.gt to <br />We.tern Avsnue. Rainfall intensity i. determined rom tabl.. pr.pa~ed by the <br />.tate of Minne80ta .ndare ba.eCl on rainfall data or our region. 80il types <br />are p~ovided in manuals pr.par.d by th. Soil Cons rvation Servioe. <br /> <br />A SO year .to~ would increase the runoff rate to be propo.e~ sale from 1.5 <br />CFa ~o 1.9 CFS. The depth of flow in a ewale wi h a 3 foot bottom and 311 <br />aide slopes 'Waula b. appro~1m..tely 0.6 feet de p c1\)riD9 t.he . p41llk :L'unoff <br />period for a 10 year .vent .torm and 0.65 feet fo a 50 y.ar .vent. <br /> <br />Under exi.tillg condition. .. portion of the !lite !runOff drains thro'Ugl& the <br />aouthwe.t corner of the .ite. Under th8 propoBec1jPlan this corner will a180 <br />be the pOliJitivft overflow ,hould the storm sewer .Y~..It.m fail. Overflow would <br />occur at an elevation which would protect surroun~ng building.. <br /> <br />Hopefully this an.wer" the Clo~.rn. which you hadl. <br />I <br /> <br />I <br /> <br />Sincerely, <br /> <br />~e.t Land surv.~()r. & ~ivil Engineers, xnc. <br />1A~ ~'PE <br />