2018-12-12_REVISION - C2010088 (10)

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7 These general water quality relationships are not as pronounced for the baseline Colorado River surface water monitoring data, due to the many influences from the extremely large Colorado River drainage basin. Ground Water The occurrence of ground water in the permit area and adjacent area is controlled mostly by irrigation water and the Colorado River. Alluvial groundwater in the permit area occurs in river alluvium that lies over Mancos shale. The river alluvium is well-graded sandy gravel that was deposited in terraces. These terraces are areas of relatively flat land (located on either side of the flood plain) which are above the flood plain because of river erosion over the years down cutting below the level of the terraces. Along the banks of the Colorado River, the alluvium is directly impacted by flows in the river. The alluvial water within the permit boundary appears to be a result of flow from upland irrigation. The three proposed sediment ponds will be lined to prevent seepage of water, seepage of dissolved constituents, and mobilization of contaminants in pond substrates. The pond linings are required by USFWS conservation measures. Underlying the alluvium is the Mancos Shale, a shallow marine deposit comprised predominantly of marine shale, mudstone and claystone, with interbedded sandstone, siltstone, and limestone. Overall, the Mancos Shale restricts the movement of groundwater and generally acts as an aquitard and confining unit in the regional groundwater flow system. Rule 2.04.7(1)(a) requires investigation and description of each aquifer above, within and, if potentially impacted, below the lowest coal seam to be mined. Since the permit application is solely for a unit train loadout, no mining will occur and therefore no potential exists to impact bedrock groundwater. No investigation of bedrock groundwater was performed for the loadout. Groundwater that may occur in isolated interbedded sandstones within the underlying Mancos will not be required to be monitored as a result of Loadout operations. The land east of Reed Wash is a remnant of the former petroleum refinery operations. The site and adjacent lands were part of refinery operations that were conducted by the American Gilsonite Company beginning in 1957. Monitoring wells were installed in 1981 by Gary Refining Company. The wells encountered 15 to 23 feet of material that was described as silty clay "slope wash.” Underlying the silty clay is between 19 and 25 feet of the river alluvium , which consists of poorly- to well-sorted sand and sandy gravel. The Mancos Shale was encountered in all boreholes, ranging in depth from 34 to 48 feet. Three of the Gary Refining Company monitoring wells were selected for use by CAM for its baseline ground water monitoring (RW-1, RW-3 and RW-4). A monitoring well installed for a nearby acid sludge landfill was selected as a fourth monitoring well. This monitoring well, RW- 2, is located northeast of the acid sludge landfill. See Map 8, Hydrologic Monitoring Location Map, in the PAP for the location of these monitoring wells. Alluvial monitoring wells RW-1 and RW-2 are located within the permit boundary. RW-2 is