2024-05-17_REVISION - M1977493 (4)

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Arkansas River valley. Inactive mining facilities are currently part of the Climax Mine reclamation program. 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 outcroppings. 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 G-01).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. G-4.3 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 seepage collection system keyed into bedrock with secondary containment. This seepage is pumped back to Robinson Lake. The average, intermittent pumping rate forthe 4 Dam Seepage Collection and Pump System is approximately 10 gpm which reflects the low rate of groundwater seepage. Groundwater quality within the Eagle River valley is monitored quarterly at the EVMW monitoring well,which was installed in September, 1993. EVMW is located upgradient of Eagle Park Reservoir, as indicated on Figure G-01. 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 using the Robinson Lake Seepage Pump System. This cut-off component restricts seepage from entering Eagle Park Reservoir. G-4.4 Groundwater Quality The groundwater monitoring program at Climax involves the measurement of water levels and the collection of water quality samples from the four monitoring wells described in the preceding sections. The location of these wells is presented on Figure G-01. Climax has an approved Water Quality Monitoring Plan (WQMP) pursuant to Rule 3.1.7(5) of the Mineral Rules and Regulations of the Colorado Mined Land Reclamation Board for Hard Rock,Metal,and Designated Mining Operations. The WQMP outlines a formal monitoring program of groundwater and surface water to demonstrate that the Environmental Protection Plan (EPP) requirements are being met. This plan was submitted and approved in 2018 as a Technical Revision (TR-27)to Climax Reclamation Permit No. M-1977- 493. Exhibit G G-18 May 2024