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Water Quality Monitoring Plan Climax Molybdenum Company <br /> Version R4 Permit No M-1977-493 <br /> 5.0 NPLS, DATA ANALYSIS AND REPORTING <br /> This section describes the methodology used to establish numeric protection levels (NPLs) at POC wells: <br /> ARwell and ARK-MW-001 D in the Arkansas River Watershed; EVMW-3S, EVMW-3D, and EV-MW-004 in <br /> the Eagle River Watershed; and GW#2 and TM-MW-002D in the Tenmile Creek Watershed. Also <br /> presented are the data analysis and reporting procedures for the POC wells and internal monitoring <br /> locations, other than those established above either Eagle Park or Clinton Reservoirs. Section 6 addresses <br /> data evaluation requirements for monitoring sites above Eagle Park and Clinton Reservoirs. <br /> 5.1 Numeric Protection Levels (NPLs) for POC Wells <br /> Colorado Revised Statute (C.R.S.) 25-8-202(7) and the December 14, 2010 Memorandum of Agreement <br /> (MOA)between CDPHE,WQCC,and DRMS clarify that the WQCC is the entity solely responsible to adopt <br /> water quality standards and classifications for state waters. The MOA provides that DRMS will establish <br /> points of compliance for discharges to groundwater and must provide reasonable assurance to the WQCD <br /> and WQCC that compliance with the Colorado Revised Statute(C.R.S.)25-8-202(7) has been obtained by <br /> using the groundwater standards and classifications established by WQCC as the basis for setting <br /> enforceable performance limits, adopting rules and regulations to establish points of compliance for <br /> discharges to state waters other than point source discharges to surface water, and other requirements as <br /> included in the MOA. The WQCC has not established classified uses for groundwater at or near Climax for <br /> which standards specific to the area have been adopted, therefore the Interim Narrative Standard under <br /> the CBSG is applicable for POC wells at Climax. The Interim Narrative Statewide Standard(CBSG Section <br /> 41.5(C)(6)(b)(i)) provides that"ground-water quality shall be maintained for each parameter at whichever <br /> of the following levels is least restrictive: (A) existing ambient quality as of January 31, 1994, or (B) that <br /> quality that meets the most stringent criteria set forth in Tables 1 through 4 of [CBSG]". As described in <br /> both TR-18 and TR-24, the DRMS-approved EPP adopted NPLs for two wells (ARwell and GW#2) using <br /> both the CBSG tables and existing ambient quality. <br /> In November 2016 DRMS requested that Climax provide a demonstration that the groundwater monitoring <br /> plan and groundwater conditions comply with Regulation 41, the Colorado Basic Standards for <br /> Groundwater; 5-CCR-1002-41 (CBSG). Climax submitted a Regulation 41 Compliance Demonstration <br /> report to DRMS on December 8, 2016 (Tetra Tech, 2016b)to demonstrate that groundwater at the Climax <br /> mine achieved the most stringent criteria in the CBSG Tables with the exception of manganese (Mn), and <br /> possibly pH, at certain POC wells. This WQMP revision is submitted pursuant to consultation with the <br /> DRMS and in response to DRMS letters of October 20,2017 and November 15,2017; DRMS has requested <br /> that Climax submit to DRMS an updated WQMP that adopts CBSG table values as NPLs as provided for <br /> in the Interim Narrative Standard for all POC wells currently identified in the WQMP, with the exception of <br /> manganese in the Arkansas River and Eagle River basins, and pursue discussions with the Colorado <br /> Water Quality Control Division (WQCD) and Colorado Water Quality Control Commission (WQCC) to <br /> develop site-specific groundwater classifications and standards for manganese for the Arkansas River and <br /> Eagle River basins. DRMS also requested that Climax submit a plan for modifying its permit to set NPLs <br /> and for pursuing discussions with WQCD and WQCC; Climax's plan was submitted January 18, 2018. This <br /> revision of the WQMP is in accordance with that plan; it specifies NPLs for all indicator parameters in <br /> groundwater with the exception of manganese in the Arkansas and Eagle River Basins. NPLs for <br /> manganese in these two basins will be addressed following the above referenced process involving the <br /> WQCD and WQCC. <br /> Each watershed at Climax has a minimum of two POC wells. One to monitor shallow, alluvial groundwater <br /> conditions and one to monitor deeper, bedrock groundwater conditions. <br /> EPP—Appendix C March 2018 21 <br />