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EXFi1 1T <br />GERALD M. SUND[, co.u;a E o e« <br />I• - <br />IOlN 21JN AYEHUE S UTH • MINNEAPOUS, MN 55'll • PMONE (612 B!1•9]N <br />Mc. S[eve Rose <br />City of Moundsviev <br />2401 flighway No. 10 <br />Moundsview, Minnesoca 55112 <br />Uear Mr. Rose: <br />February 22, 1980 <br />Re: Onk iake Park Addi[Son <br />Hound,view, MSnnesota <br />Enclosed are cumpueattons mnde as part of our hydrologic <br />analyeis of the pronosed Scottland Green Pond to be lecated in the <br />south part of [he a6ove projecc. The analysis was maJe for existing <br />conditlons and also for fi.nal developmen[ of the watershed. <br />The hydralogic analysis of the watershed is intended Co <br />determine what 100 year discharge would occur at [he point where <br />the Scot[land Creen Pond will outlr_t for the two casea. For [he <br />ex3eting conditions case, land use was based on present eonditions <br />and pond contoura vere taken from maps prepared hy Egan Field and <br />Novack. A field survey vas made to de[ermirte rnn[rol elevatione at <br />outlet s[ructures. The s[udy indica[ed tha[ a 100 year dischazge <br />from the Scot[land Creen Pond area ehould be approxlma[ely 64 cubLe <br />fcec per eecond. Due to road elevetions to the aouth, it is likely <br />that extensive floo3ing would occur in the area of Ridge Lme and Loog <br />Lake Poad. <br />For the finel deaign case, full develapment of the waterehed <br />ie aeaumed. coetlsnd Creen Pond contouro ere beaed on prelLninary <br />contoure prepared by Development Concept, Inc., which hava prsviou ly <br />been preserted to the city. The outlet etnicture for Lhe pond ie <br />aesumed ta be ak the cplvert beneath the exiecing east entrencc- r,n <br />adir Scoctle ru brecn .a,3a. .-...,;.e. The prexent cul erk fiias art invert <br />elevation of 891.5. The propoaed control elevation vill be 892.0. <br />A[ final developmen[, Scottland Green Pond will be tequired Co <br />etore about 65 acre feet of vater end the m cimum diecharge will bc <br />epproxlmetely 5 cubic feet per eecond. The 100 year pond level vill <br />be 895.7. The lnrge amount af s[ornge provided and tt e lov diaeharge <br />reeul.te in ehe 10 day enowmelt event being eritical for ehe rite. <br />The pond dca3gn as pzopoaed will'have value !n theC peak d1s— <br />ch rgea v111 be subatantially reduced for the major etorm eventr (from <br />about 64 cfs to 5 cfa for the 100 year event). Retention ot v tee fn