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SURFACE DRAINAGE OF THE ROAD SYSTEMS AREA <br /> General Description. The Road Systems Area is located in and <br /> includes portions of the Coal Creek tributaries of Upper Coal Creek, <br /> Oil Well Creek, North Fork Dutch Creek, South Fork Dutch Creek, <br /> Dutch Creek and Bear Creek. The Road Systems Area is divided into <br /> 30 contributary drainage sub-basins as shown on Plate I. Twenty- <br /> eight of these sub-basins each terminate at, and are designated by• <br /> the number of, a culvert. Drainage sub-basins Numbers 1 and 2 are <br /> the total drainage basins for Bear Creek and Dutch Creek, respec- <br /> tively, and are included for informational purposes. Each culvert <br /> has a capacity in excess of the maximum runoff from a 24-hour rain- <br /> fall of a storm having a recurrence interval of 10 years as required <br /> by the "Surface Mining Reclamation and Enforcement Provisions" (3) . <br /> Flood and Runoff Analysis. The Soil Conservation Service (SCS) <br /> method (4) of computing runoff was used for the Road Systems Area. <br /> The roads have modified the natural runoff patterns by ditch inter- <br /> ception and culvert concentration. The areas contributing runoff to <br /> each culvert were determined from the Company's 1" - 400' scale <br /> topographic maps and from the USGS 1:24,000 scale topographic map <br /> "Placita, Colorado." The area, drainage channel characteristics and <br /> concentration time for each of the contributary drainage sub-basins <br /> are shown in Table 1. <br />