2012-03-07_PERMIT FILE - C2010088 (22)

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ALLUVIAL VALLEY FLOOR DETERMINATION CAM - COLORADO PROPOSED COAL LOADOUT NEAR FRUITA MESA COUNTY, COLORADO slightly above the shale. The nearby well log data indicate that Reed Wash may be incised into the Mancos Shale, but exposures of Mancos have not been confirmed along the channel. The soil maps provided by the NRCS and permit Map 06 are "analogs" of the extent of any streamlaid deposits. The bottom of the wash is narrow, generally 20 to 25 feet wide, with a few wider sections up to 50 feet. The number designations for the various monitoring wells have changed somewhat since they were originally installed. Well logs RW -Ia, RW -3, and RW -4 are the active monitoring wells RW -1, RW -3, and RW -4, respectively. Two wells were originally installed with the RW -2 designation. The well log for RW -2 in Appendix B is not the same well as is currently being monitored, the location of which is provided in Figure 2. The location of the RW -2 referred to in the Appendix B well log is provided in Appendix B. Ground Water Ground water was encountered in the four monitoring wells within the saturated alluvial material overlying the low permeability Mancos Shale. The depth to water in the four wells is currently either in the lowest portion of the silty clay layer or within the alluvium (ranging from about 11 to 20 feet bgs). The depth to water, measured in 1981 in these wells (Appendix B), was somewhat shallower, ranging from approximately 7 to 18 feet bgs. Ground water elevations, as measured in the four monitoring wells in June 2010, indicate the ground water flow direction is from the northeast to southwest toward the Colorado River and locally toward Reed Wash (Figure 2). The approximate elevation of the Colorado River is 4,440 to 4,441 feet above mean sea level (amsl), compared to ground water elevations of 4,461 feet amsl at the north end of the property to 4,446 feet amsl at the south end of the property. The ground water flow direction is toward the Colorado River from the upland areas to the north and the river elevation is several feet lower than the June 2010 ground water elevations; therefore, it is unlikely that the ground water beneath the proposed loadout facility is influenced by the Colorado River. It is probable that ground water beneath the property is, in part, the result of irrigation in upland areas. The water quality of the alluvial ground water beneath the property indicates the alluvial ground water originated in the Mancos Shale, or at least traveled through the Mancos Shale or shale- derived soils. 4