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Demonstration of Compliance Climax Molybdenum Company With Regulation 41 Permit M-1977-493 5.0 TENMILE CREEK WATERSHED Appendix A presents the data calculations for Climax POC wells in accordance with Section 5.1 of the WQMP. Data in Appendix B were reviewed in accordance with Section 5.2.1 of the WQMP. As indicated in the tables all indicator parameters, with the exception of manganese and pH at well TM-MW-002D and pH at well GW#2, are at or less than CBSG table values in the Tenmile Creek Watershed. Manganese has been observed at concentrations above the most stringent CBSG table value at POC well TM-MW-002D. Field pH measurements at both wells have, on occasion, been observed at values below 6.5, the lower end of the CBSG table value range. A significant amount of reclamation work and EPF construction has been performed in the Tenmile Creek Watershed (Sections T-1.2 and T-5.3.2 of the EPP)to protect water quality, resulting in an improvement in water quality over time. Therefore, ambient levels for manganese can be determined following a review of available information referenced herein which show levels deemed representative of groundwater quality as of January 31, 1994. The following sections provide supporting information for manganese and pH at POC well TM-MW-002D, and for pH at POC well GW#2 for application of the CBSG Interim Narrative Standard to determine or estimate existing quality as of January 31, 1994. 5.1 Potential Contaminant Sources and EPFs The open pit mine, mill facilities, overburden storage facilities(OSFs), and the Robinson, Tenmile and Mayflower TSFs are all located within the Tenmile Creek Watershed. Specific lists of sources and EPFs are discussed in Section T-5.3.1 of the EPP. As discussed in the EPP, the Tenmile Creek Watershed from Fremont Pass to well beyond the Climax property line was historically mined and included mine-related facilities prior to the discovery and development of the Climax Mine. Climax undertook reclamation and water treatment measures beginning in the 1970s that have stabilized and dramatically improved environmental conditions in the watershed. The positive effects of these improvements are documented by the recovery of the aquatic ecosystem in Tenmile Creek from a virtually sterile condition prior to 1970. For this evaluation, it is important to note that all of the potential contaminant sources within the Tenmile Creek Watershed were present before 1994, including the Tenmile and Mayflower TSFs. Long-term water quality data from Tenmile Creek demonstrate that the development of the current Climax water management and treatment system has resulted in significant water quality improvements over the past several decades. The Climax water management and treatment system, which terminates at the base of 5 Dam, contains the principal EPFs in the Tenmile Creek Watershed. This system discharges treated water meeting requirements of CDPS Permit CO0000248 at Outfall 001 located near the property line. Under the CDPS permit, discharge of water from the site, including process water and mine waters, are required to meet water quality limits. Contaminants that might be released from the potential sources discussed in Section T-5.3.1 are captured and treated prior to discharge. Individual EPFs, which are part of the water management and treatment system, along with other EPFs present in the watershed, are discussed in detail in Section T-5.3.2 of the EPP. Several improvements to the water management and treatment system implemented in the last decade December 2016 21