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rained Area—Underivina$01 Tyne <br /> The sotl types In the watershed were determined by using the USDA's online Web Soil <br /> Survey W. This tool produced a map which showed that most low-lying areas were <br /> dominated by Type-D soils (that Is, poorly-inMrating soils)and that upland-ares were <br /> mainly Type A (weli-ir MvUng) with some Type B (moderately well WMrabng) and a <br /> minimai.-amount of Type C(moderately-toiY irntiltrating). Soli type areas are presented in <br /> the foftowing table. The attached Exhibit 4 document shows the map,soil descriptions,and <br /> HSG assignment}. <br /> • atws nJM363 <br /> e A 44.4 e 7.9%C 0.3 VM D 18.1%a W 31 <br /> Runoff Curve Number(RCN)Computation <br /> As noted above,the TR-SS method was used to determine runoff volumes resulting from � <br /> rainfall events. To determine these volumes, this:method.requires.the computation of a <br /> Runoff Curve.Number(RCN which is a function of land use and sotl type. To combine the , <br /> soil type data with-the land use data, the following assumptions were made: f <br /> • Areas appearing as Nvatse on the soli map are the aggregate of the lake area and I <br /> severed smaller pockets of water within wetlands. a . <br /> • Areas of wetland are all Type D soils, minus the area of water within the wetlands. <br /> • Soil Was A. S. and-C and the remaining Type D (non-wetland) are reasonably <br /> evenly distributed throughout the remainder of the watershed, and these soil type <br /> areas have been pro-rated proportionally among the other land uses. <br /> RCNa were then assigned to each Land use according to TR-55 tables. The aggregation of <br /> this data Is summarized In the Mbwing table. <br /> t <br /> a <br /> Atflces inMinors,Iowa,Minnesota,and Wisconsin <br /> 2001 International Lane. Sulle 300, Madison,WI 53704-3133 <br /> (MB)242-T"9 (coo)446-vara <br /> FAX: (6W)242-5684 WEB ApDRESS: www.n=-M.com <br /> . . . . . eapei.eakrtmo.»�roat»�ac� <br /> 1 <br />