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Proposed development. The existing site consists of flat terrain covered <br />with natural grasses. Miere are no impervious surfaces within the existing <br />site. Me proposed site consists of approximately 8.1 acres of oonneated <br />imervious surface and a storm sewer system with concrete pipes. <br />Estimates of the ex -sting and proposed storm water runoff rates and amounts <br />were made utilizing the Soil Conservation Service's ZR 55 method. Estimates <br />were made for the 10-year 24hour storm and the 100-year 24 hour storm. <br />Rainfall trequency data was obtained from the US Weather Bureau's Technical <br />Paper No. 40. A type II rainfall distribution was assumed. the results of <br />these storm water runoff estimates are shown in Table 1. r1he rates and <br />amounts shown in this table are for nunoff routed to the southeast corner of <br />the site. Under the existing conditions approximately 10.8 acres drains to <br />the southeast corner of the site and under the proposed conditions <br />approximately 19 acres drains to the southeast corner of the site. The <br />rates and amounts shown for the proposed conditions do not account for <br />ponding that Will occur at storm water inlets, roof tops, and a storm water <br />detention pond. This ponding will be utilized to reduce the peals discharge <br />rate to the level that existed prior to the Proposed develClPmmt or to a <br />level that is acceptable to the City of Roseville and the Rice Creek <br />Watershed District. <br />2 <br />