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Coal Ridge No. 1 Mine C-1984-065: MT-08 April 2, 2019 <br /> <br />Page 4 of 27 <br /> <br /> <br />The Wasatch and Ohio Creek formations unconformably overlie the Mesaverde Group. These <br />formations consist of red and buff shale, red sandstone, and red to gray conglomerate and form the ridge <br />bluffs of the Grand Hogback. <br /> <br />Quaternary unconsolidated sediments in the mine area, as represented by surface features, fall into three <br />geomorphic categories: <br /> <br />1) Alluvium: These Quaternary deposits include all sediments associated directly with the active <br />portions of the various stream channels and alluvial fans. <br /> <br />2) Terraces: Sediments associated with the inactive portions of the stream channels, particularly those <br />at much higher levels, have been categorized as Quaternary Terraces. <br /> <br />3) Colluvium: Colluvial deposits are considered to be loose, heterogeneous rock masses composed of <br />soils and rock fragments which have been deposited chiefly by mass -wasting, usually at the base <br />of steep slopes. <br /> <br />Hydrology <br /> <br />Surface Water <br /> <br />The Coal Ridge No. 1 Mine permit area is located in the Upper Colorado River Basin, in portions of <br />three watersheds: the Colorado River, Alkali Creek, and South Canyon Creek. Proposed mining <br />operations beneath portions of the Alkali and South Canyon Creek watersheds did not occur. <br /> <br />Water from the Colorado River is of good quality and is used for domestic and irrigation purposes. <br />Salinity concerns have resulted in the establishment of standards for the upper and lower Colorado River <br />basin (including the Colorado River and Alkali Creek). Water was monitored in the Colorado River <br />through 1988. The Colorado Department of Public Health and Environment receiving stream standards <br />for some metals were occasionally exceeded in both the Colorado River and Alkali Creek, but the <br />elevated metals were not determined to be mine related. See PAP pages 3-40 through 3-49 for more <br />information on surface hydrology. <br /> <br />Only small ephemeral drainages cross the site. The sediment pond located at Coal Ridge No. 1 Mine was <br />reclaimed once revegetation success standards were met on the contributing reclaimed areas and runoff <br />from the areas met applicable State and Federal water quality standards. <br />Groundwater <br /> <br />Hydrogeological field studies, including the establishment of a groundwater monitoring system of the <br />Coal Ridge No. 1 Permit Area, began in late 1981. These studies included spring and seep surveys, <br />alluvial, colluvial, and bedrock groundwater monitoring, water quality and quantity analyses, aquifer <br />testing, and geologic mapping. <br /> <br />Potential water-bearing zones were identified in the Rollins, Middle and Upper Sandstone and the