1995-09-29_REVISION - M1977493 - Laserfiche WebLink

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Y y , 4 1 for these wells are presented in Appendix A. The purpose of these wells was to determine the • depth to bedrock and ground water elevations in the drainage, as well as provide ground water quality monitoring. The ground water quality data from these wells is discussed later in this report. Arkansas River Valley The Arkansas River Valley is located south of the mine and on the East side of the Continental Divide (Figure 1). Within the drainage, ground water occurs very close to the ground surface within layers of alluvial sands and gravels, and glacially derived silts and clays. These soils overlay the Paleozoic Minturn Formation (west of the Mosquito Fault) and the Precambrian Silver Plume Granite (east of the Mosquito Fault). The thickness of the alluvial and glacial soils ranges between 10 to 20 feet in the Arkansas drainage. Hydraulic properties of the bedrock and soils in the drainage have not been measured, however, the results of a hydrogeologic evaluation on the flooding of the underground workings (Titan, 1994) determined that the bedrock on the east-side of the Mosquito Fault is of low permeability and not capable of transmitting significant quantities of ground water. This evaluation also determined that the Mosquito Fault creates a hydraulic barrier to east-west ground water flow within the bedrock. Demonstration of the Mosquito Fault as a hydraulic barrier to potential process water impacts to the Arkansas was discussed with Allen Sorenson of DMG during inspection and in verbal and written correspondence in the fall of 1994. Mine water associated with the 600 level of the underground workings at Climax is currently handled and monitored at the 5-Shaft pump station • where it is pumped over the Continental Divide and into the Climax Water Treatment System. The 5-Shaft pump station is an environmental protection facility identified in the Climax Environmental Protection Plan (S.M. Stoller, 1995). Climax conducts seep monitoring below 5- shaft between Highway 91 and the Storke facilities. Climax also monitors a well located 60 feet from the shaft for changes in water level on a monthly basis. Ground water flow direction in the Arkansas River Valley is generally westward, paralleling the flow of the Arkansas River. As in the Tenmile drainage, the ground water flow is controlled by the bedrock topography and outcroppings. There are no current active mining facilities located within the Arkansas River Valley. Inactive mining facilities are currently being reclaimed. Eagle River Valley The ground water in the Eagle River Valley also primarily occurs in the shallow alluvium above the bedrock. Data from test pits (Kumar and Assoc., 1993) located north-west of Robinson Lake indicated that ground water is present close to the ground surface and that alluvium in the valley primarily of silts, sands, and gravels. The alluvium overlays bedrock consisting of the Minturn Formation and Tertiary-aged quartz monzonite intrusives. The hydraulic properties of the Minturn Formation were determined from field packer tests conducted in open borings. A total of fifteen tests were conducted in four borings. The results of • the packer tests indicate that the hydraulic conductivity of the Minturn Formation ranges from 0 to 2900 ft/yr, with an average conductivity of 480 ft/yr. (Kumar &Assoc., 1994). Hydraulic properties of the overlaying alluvium were not measured, but the hydraulic conductivity of sands