2011-03-14_REVISION - M1977493 (57)

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Permit Amendment (AM-06) - Climax Mine CM0000497 • Groundwater flow direction in the Arkansas River Valley is generally westward, paralleling the flow in the Arkansas River. As in the Tenmile drainage, the groundwater flow is controlled by the bedrock topography and outcrops. The groundwater quality in the Arkansas River Valley is monitored by well ARWeII. This well was installed in September of 1993 near the southwest corner of the former gravel pit pond on the north (west) side of Highway 91 (Figure AM-06-G-01, Exhibit G). The ARWeII was completed in alluvium and is therefore representative of alluvial groundwater conditions in the valley. The groundwater in the Arkansas River Valley is forced to the surface and reports to the Arkansas River downgradient of ARWeII. T-6.1.3 Eagle River Valley The groundwater in the Eagle River Valley also primarily occurs in the shallow alluvium above the bedrock. The alluvium overlays bedrock consisting of the Minturn Formation and Tertiary-aged quartz monzonite intrusives. As in the other drainages at Climax, the bedrock topography controls the direction of groundwater flow. Groundwater flow in the valley is also influenced by the presence of three surface water bodies; Chalk Mountain Reservoir, Robinson Lake, and Eagle Park Reservoir. Each of these reservoirs was constructed by excavating and building an engineered dam to impound water. Construction records for each dam indicate that a low permeability cut-off wall was excavated into the underlying bedrock to control groundwater. Cut-off walls under each dam present a physical barrier to groundwater flow. Therefore, significant and continuous groundwater flow in the alluvium and bedrock throughout the valley is unlikely as groundwater flow is intercepted by the reservoirs. Eagle Park Reservoir is located above the East Fork of the Eagle River. Groundwater exiting the drainage and the Climax property is intercepted by the Eagle Park Dam (4 Dam). Site observations indicate that very little groundwater exits below 4 Dam. Groundwater which does seep below 4 Dam is collected in a collection sump keyed into bedrock and pumped back to Robinson Lake. The average, intermittent pumping rate for the sump is approximately 10 gpm which reflects the low rate of groundwater seepage. In practical terms, groundwater does not discharge from Climax property into the Eagle River Valley. Groundwater quality within the Eagle River Valley is monitored quarterly by the EVMW monitoring well, which was installed in September, 1993. EVMW is located upgradient of Eagle Park Reservoir, as indicated on Figure AM-06-G-01 (Exhibit G). A cut-off wall below the Robinson Dam outlet area has been installed and keyed to bedrock to contain seepage from the upstream Robinson Lake reservoir. Captured seepage is collected and pumped back to Robinson Lake. This cut-off component restricts seepage from entering Eagle Park Reservoir. T-6.2 Groundwater Quality Groundwater wells are presently sampled on a quarterly basis. Analytical data for each of the four wells are presented in Appendix T-C. The long term data, including the data in Appendix T-C, strongly support the position that no impact to groundwater has occurred in the Tenmile Creek, Arkansas or Eagle River drainages. Given the history of the Climax Mine, groundwater does not appear to have been impacted in any of the affected drainages. T-7 Surface Water In addition to the water information provided in Exhibit G, information relative to surface water containment and control facilities, surface water quality, the Climax treatment and discharge permit, and surface water monitoring and sampling programs have been discussed thoroughly in Section T-5.0 and in the appendices referenced in that section. The CDPS Permit also contains a discussion of the surface water program at Climax. Maps showing water related features are found in the Figures AM-06-T-01 and Exhibit T T-25 May 2010