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• rocky base material. As these streams cross the Wet Mountain Fault and <br />the more permeable adjacent upturned sedimentary units, significant <br />surface and base flow is lost to the groundwater system. This reduction <br />in surface flows typically extends downstream where stream channels are <br />incised into more permeable sedimentary units. Poorly sorted <br />colluvial/alluvial base materials provide an effective mechanism for <br />transfer to the groundwater system. <br />Mine Area. For the Southfield mine and adjacent areas, surface water flow <br />quantities for Newlin and Magpie Creeks have been determined both through <br />modeling and direct physical measurement. Because of the ephemeral nature <br />of lower Newlin and Magpie Creeks, flow measurements have been limited to <br />those few instances when active flows occurred. <br />In modeling surface flows for Newlin and Magpie Creeks and other area <br />drainages, several different methods have been utilized in an attempt to <br />• develop the most accurate representation of actual flow conditions. The <br />following modeling methods have been utilized: <br />o TM-1 Method: "Manual for Estimating Flood Characteristics of <br />Natural Flow Streams in Colorado" (Colorado Water Conservation <br />Board - Colorado Department of Natural Resources, 1916) <br />o Regression Equation Method: "Rainfall - Runoff Modeling and <br />Preliminary Regional Flood Characteristics of Small Rural <br />Watersheds in the Arkansas River Basin in Colorado" (USGS, 1981) <br />o MULTSED Method: "Proprietary Computer Software Program" (Simons <br />Li, Associates - Preliminary Data Base Report for GEC Coal <br />Company, 1981) <br />During the time the Southfield Mine (and previous Dorchester No. 1 Mine) <br />has been in operation, there has been only one instance of recorded flow <br />for Magpie Creek. On July 6, 1981, a high intensity thunderstorm resulted <br />in measured flow in Magpie Creek of 23 cfs. Given the limited available <br />information on Magpie Creek flows, GEC and the Colorado Mined Land <br />Reclamation Division, under the provisions of the Small Operator <br />2.04.1-27 <br />