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Williams Fork Formation within the Bowie member. Coal seams in the Bowie member aze the most <br />continuous of any of the Mesaverde coals. Their cumulative thickness is 33 to 54 feet. <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 <br />ridge bluffs of the Grand Hogback. <br />Quatemary unconsolidated sediments in the mine area, as represented by surface features, fall into <br />three geomorphic categories: <br />1) Alluvium: These Quaternary deposits include all sediments associated directly with the active <br />portions of the vazious stream channels and alluvial fans. <br />2) Terraces: Sediments associated with the inactive portions of the stream channels, particularly <br />those at much higher levels, have been categorized as Quatemary Terraces. <br />3) Colluvium: Colluvial deposits aze considered to be loose, heterogeneous rock masses composed <br />of soils and rock fragments which have been deposited chiefly by mass-wasting, usually at the <br />base of steep slopes. <br />Surface Water <br />The Coal Ridge No. 1 Mine permit area is located in the Upper Colorado River Basin, in portions <br />of 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 />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 s[andazds for the upper and lower Colorado <br />River basin (including the Colorado River and Alkali Creek). Water has been monitored since 1981 <br />on Alkali Creek and 1983 on the Colorado River. The Colorado Department of Public Health and <br />Environment receiving stream standazds for some metals have occasionally been exceeded in both <br />the Colorado River and Alkali Creek, but the elevated metals were not determined to be mine <br />related. See PAP pages 3-40 through 3-49 for more information on surface hydrology. <br />Only small ephemeral drainages cross the site. Al] surface runoff from disturbed azeas is either <br />directed to a sedimentation pond or approved for exemption (small areas) from treatment through <br />a sedimentation pond. <br />Groundwater <br />Hydrogeologica] field studies, including the establishment of a groundwater monitoring system of <br />the NCIG Permit Area, began in ]ate 1981. These studies included spring and seep surveys, alluvial, <br />colluvial, and bedrock groundwater monitoring, water quality and quantity analyses, aquifer testing, <br />and geologic mapping. <br />Potential water-beazing zones were identified in the Rollins, Middle and Upper Sandstone and the <br />Wheeler Coal. The first three units have been recognized as regional aquifers where the <br />6 July 25, 2001 <br />