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- 18 - There is the potential for some seepage from the embankment reaching the alluvial valley floor just downstream from the embankment by short-circuiting around the sediment pond. Table 1 gives a comparison of mean water quality of ground water at the mine site. OW-9 is located within the drainage proposed for location of the refuse embankment. The existing water quality is very poor, with a mean conductivity of 5105 umhos/cm and a sulfate level of 3084 mg/1. This is characteristic of water draining from the Mancos Shale. Due to the existing poor water quality, it is not expected that seepage from the refuse embankment will decrease water quality in the downstream colluvial material beyond that present. OW-11 is an existing water well present in the alluvial material downstream of the proposed refuse site. This welt has an extremely high sodium absorption ratio (SAR) of 23.1. The water quality of this well varies greatly from the expected quality of alluvial water for the area and suggests that contamination is occuring possibly due to casing or completion technique. The applicant has committed to drilling another well for alluvial monitoring at the mine site. This well will be drilled in adequate time to collect a year of baseline before construction begins at the refuse disposal site. This well will be placed to detect impact, if any, to"the alluvium from seepage at the disposal site. The alluvium present in the vicinity of the Coal Ridge No. 1 Mine and adjacent to the Colorado River is recharged by the Colorado River surface water and by surface runoff from the upland area. The subcrop of the Wheeler seam is located approximately 55 feet above the alluvium and dips, steeply away from the alluvial body. Undermining of the alluvial body will not occur during the life-of-mine. Therefore, dewatering of the Wheeler seam due to mining is not expected to impact the alluvium or surface water system of the Colorado River, Hydraulic mining requires large quantities of water for operations such as cutting of the coal and in the slurry line transporting fine refuse to the waste site. The operation has facilities designed to process and recirculate the majority of water required for the operation. The water circulation is designed as a closed-system, with the major water loss occurring through evaporation, adhesion to the coal and refuse, and by seepage underground during mining, The application projects that water loss through these processes will require a makeup of approximately 600 acre feet of water annually to the system. The Coal Ridge No. 1 Mine has acquired water rights more than sufficient to augment their annual projected water loss.