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fi <br />fon to an existing <br />submitted as part of <br />ke, rip rap <br />1938. <br />ken by the Board of <br />mlt. <br />shed District. <br />ering Co. dated <br />19, 1988. <br />7-153. <br />them that permit <br />ding pre and post- <br />cel ved August 8, 1988; <br />red by McCombs Frank <br />ke, rip rap <br />988. <br />s not complete within <br />tact the District at <br />ector may view the <br />Orono <br />Vm <br />.4 <br />Engineers <br />Planners <br />Surveyors <br />August A, 1988 <br />Joe Pallansch <br />Washington Scientific Industries, Inc. <br />2605 West Wayzata Boulevard <br />P.O. Box 340 <br />Long Lake, MN 55356 -0340 <br />SUBXCT: Washington Scientific Indistries, Inc. <br />Storage Pond <br />100 Year Storm Run-off <br />MFRA #8749 <br />Dear Hr. Pallansch: <br />Enclosed are seven copies which show the contours of a storage <br />store run-off from a 100 year frequerxiy storm. Three copies also stow the <br />drainaoe area in blue, from which this run-off will occur and include <br />aoDroximately 90X of the proposed new addition to your building. Basically <br />tWs is ths only portion of your property ttot will have <br />to the proposed addition and therefore, we have computed the required storage <br />volune from the changes in run-off in this area only. <br />The total area that we are concerned with is 8.3 acres. It <br />that the coefficient of run-off changes from 0.53 to 0.^ due to <br />of the roof area as a result of the new const^tion. This <br />^-off from this drainage area from 20.7 cubic f^ per f <br />CSF. The rate of flow allowed from this area is the <br />construction and that was 20.7 CFS. In order to maintain ^his rate of run-off <br />from the area, it is required to construct a storage pond which will TO <br />constructed along an existing swale approximately 200 east of the west property <br />line. <br />The storage pond can be constructed by cleaning out and lowering the bottom <br />of the drainage ditch and putting in a small dam in the ®*^®® ppp <br />fo nofthroS^^it tlt%a“atr/Lrth^st"a^ as If. runoff f^ <br />The ponding area that we show will hold a volume of approximately 20,500 cubic <br />feet^at the 1,013 contour elevation. The invert of the pipe sTOuld TO at <br />1,010.5. We are also including with this letter mass curve calculat^ns <br />computed by the rational method. Copies of this information sTOuld be <br />delivered to Mr. Kevin Larson, of Eugene A. Hickock and Associates, by the end <br />of the day on August 8, 1988. <br />RG:aju <br />Enclosu]