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WATER REPLACEMENT PLAN SPECIFIC DESCRIPTION STEVEN'S GULCH DRAINAGE BASIN TOPOGRAPHY Steven's Gulch is an ephemeral stream which drains an area of approximately eight square miles. It is a tributary of the North Fork of the Gunnison River and enters the North Fork at approximately 5,640 feet above sea level. The drainage basin reaches elevation 8,600 feet above sea level in the northwest and northeast parts of [he drainage basin. The stream channel is approximately five miles long with an average gradient of 11%. The flow trends from the head waters in a southwesterly direction and about midway turns to the southeast and then enters the North Fork of the Gunnison. Of the eight square miles contained within the Steven's Gulch Drainage Rasin, approximately 1,946 acres ate outside any existing or proposed long-term lease. That represents approximately 38.37, of the total drainage basin area. ALLUVIAL/COLLUVIAL DEPOSITS The major part of Steven's Gulch drainage pattern has either very shallow allu- vium or else alluvial sediments are not present. Only in a few locations where the gradient is more gentle than average, was a greater thickness of alluvial sediments deposited. One of these areas is in Section 13, T.13S., R.92W., where the CWI wellfield is located. In this area, four wells were installed in 1977 to provide a water supply and information about the water bearing strata. The wells are between 65 and 97 feet deep and screened in the lower, more per- • meable parts of [he alluvium. It was estimated that the alluvium in this area could yield about 27.8 gallons of water per minute (Wright Water Engineers Report, I977). The actual pumping rate is much lower. The water table in the alluvium shows high seasonal fluctuations. During April and May, the water level can be as high as four feet below ground surface; how- ever, during late summer, fall, and winter, the water level drops to as deep as 40 feet below ground surface. This area has been designated Renewable Resource Lands, and further information may be found in Section 2.04.7 of the Orchard Valley Mine Mining and Reclamation Permit Application. SOIL TYPE The information for the soils type within the Steven's Gulch Drainage Basin has been identified in the Paonia Area Soil Survey, January 1981, United States Department of Agrigultute, Soil Conservation Service Report. Soil types iden- tified within the area are Delson Very Stony Loam, 20 to 60 percent slopes; Delson Stony Loam, 3 to 20 percent slopes; and Delson Loam, 3 to 12 percent slopes. For a complete description and mapping of the area, please see Maps 7 and 7A, Colorado Westmoreland Inc., Orchard Valley Mine Underground Mining and Reclamation Permit. The soils identified within the CWI wellfields are Delson Loam on 3-12% slopes. This is a deep normally well-drained soil. Permeability is slow and available water capacity is high. Effective rooting depth is 60" or more. Surface run-off is medium. Hazard of erosion from wind is slight and from water is moderate.