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Water Quality Monitoring Plan Climax Molybdenum Company Version_ R4 Permit No M-1977-493 2.0 SITE DESCRIPTION 2.1 General Setting The Climax Mine is located primarily within the Tenmile Mining District, extending into Summit, Lake, Eagle and Park Counties of Colorado. The mine site includes an open pit mine, underground mine workings, mill/crusher facilities, associated tailings impoundments, and water control facilities. The terrain at the site is mountainous with elevations ranging from approximately 10,800 feet above mean sea level (msl) in the vicinity of the mine to more than 14,000 feet msl on nearby mountain peaks. Weather conditions can be severe at the mine, with temperatures ranging from -20°F to approximately 75°F and an annual average snowfall of 272 inches. Average annual precipitation is 23 inches, of which about 80 to 90 percent falls as snow. Within the site there are three primary watersheds: the Arkansas River Valley, Eagle River Valley, and Tenmile Creek Valley.The mine and mill are located on the Continental Divide between Tenmile Creek and the East Fork of the Arkansas River,with the tailing impoundments located in the Tenmile Creek Valley and the Eagle River Valley(Figure 1). 2.2 Site Hydrogeology Climax Mine is located in the Mosquito-Tenmile Range of the southern Rocky Mountain Cordillera. The ore body is hosted by two Precambrian rock formations, the Idaho Springs Formation, and the Silver Plume Granite. The Idaho Springs Formation is a meta-sedimentary rock, metamorphosed 1.7 billion years ago during a period of major geologic activity. Its major components are biotite schist and gneiss. Silver Plume Granite occurs in stocks, dikes and sills that intruded the Idaho Springs Formation approximately 1.4 billion years ago. These two formations also are intruded, to a lesser degree, by early Tertiary diorite porphyry and quartz monzonite approximately 60 million years old. The Climax ore body lies just east of the Mosquito Fault, an important local structure that trends roughly north-south, and that dips approximately 60 degrees to the west. The fault, as shown on Figure 1, runs north-northeastward across the Tenmile Creek valley over a distance of approximately 30 miles. The Mosquito Fault presents a discontinuity between the Precambrian bedrock on the east with the Paleozoic and Tertiary bedrock on the west. Groundwater in the vicinity of the Climax Mine site is generally present within a thin veneer of alluvium and glacial till overlaying the bedrock, and ranges from near ground surface to a few tens of feet below ground surface. Groundwater occurrence within the bedrock is limited to the upper fractured portion of the bedrock units.A hydrogeologic study of the underground workings(Titan, 1994) indicated that the bulk permeability of the bedrock is relatively low and that the bedrock is not capable of transporting significant quantities of groundwater. Additionally, it was shown that the presence of the Mosquito Fault provides a hydraulic barrier to lateral flow of groundwater in the bedrock. Due to the location of Climax facilities within three different watersheds, each drainage basin is described separately in Section 3 of this WQMP. The descriptions include hydrogeological setting and monitoring sites. Additional information on site hydrogeology is in the conceptual hydrogeological model provided to DRMS in May 2012 (Arcadis, 2012)to fulfill commitments made in TR-18. EPP—Appendix C March 2018 2