2011-12-15_REVISION - M1977493 (2)

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Potential Area of Impacts Potential Contaminant Sources Direct (Governing) EPF /Control Internal Controls Densification Plant (SDP), 3 Dam Pump Station , East Interceptor, West Interceptor Tailing stored in TSFs TDL, 2 Dam, 3 Dam, 5 Dam Acid - generating overburden materials Diversion structures to prevent runon and to direct impacted runoff to treatment facilities, collection drains beneath and adjacent to OSFs Material segregation, concurrent reclamation Technical Revision (TR -18) Environmental Protection Plan T - 5.1 Arkansas River Watershed Climax Molybdenum Company Permit No. M- 1977 -493 T - 5.1.1 Potential Sources of Contamination The upper Arkansas River Watershed contains portions of the Climax site that supported the historic underground mining operations. Prior to closure of the underground mine, the entrance to the underground operation at Climax was through 5 -Shaft and the Storke Portal at the Storke Yard just east of the hairpin turn on Highway 91, in the upper Arkansas River Watershed. When the underground operation was terminated in December 1994, equipment was salvaged and pumping was curtailed allowing the deeper workings to be inundated. Water in contact with sulfide mineralization underground meets the definition of "Acid Mine Drainage" in Rule 1.1 (2), and thus, is a potential source of contamination to the upper Arkansas River Watershed should water levels rise uncontrolled. Storm water becomes impacted as it passes through the open pit area and collects in the underground mine workings. Former underground workings and the open pit are connected to the 5- Shaft located in the Storke Yard area and, as described below, a pumping station installed in 5 -Shaft maintains the water level by pumping water through the Storke Pipeline to the process water circuit in the Tenmile Creek Watershed. The Storke Yard historically incorporated some mine waste rock material for construction fill. The areas of the mine in the upper Arkansas River Watershed have been the focus of major reclamation activities since the late 1980s. Equipment was removed and buildings were demolished in preparation for final reclamation of the Storke Yard in 1995 and beyond. Impacted water from the Storke Yard area is directed to the Storke Wastewater Pump Station, described below. In addition to historic Climax operations, there are other non - Climax, abandoned mined land (AML) features present in the upper Arkansas River Watershed. As part of previous reclamation activities in this area, some impacted water from these AML features is directed to the Storke Wastewater Pump Station. A project to restore a buried segment of the East Fork Arkansas River running along the south side of the Storke Yard was completed in 2008. The area of the Arkansas River to the south - southwest of the Storke Yard was reclaimed in the late 1980s into the early 1990s. This area terminates in the gravel pit at the Climax property line. The East Fork Arkansas River runs through this reclaimed gravel pit before leaving the property and groundwater under the direct influence of surface water in this area is the source of domestic water for the mill as described in Permit Amendment AM -06 Exhibit G — Water Information. EPP: Version R2 T -17 December 2011