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Demonstration of Compliance Climax Molybdenum Company <br /> With Regulation 41 Permit M-1977-493 <br /> include the Sludge Densification Plant (SDP) that was incorporated into the system in 2007 to <br /> improve both water treatment efficiency(stage 1 metals removal) and sludge management. Most <br /> recently, the new Property Discharge Water Treatment Plant (PDWTP) was commissioned and <br /> began discharging treated water(stage 2 metals removal) in 2014. <br /> 5.2 Data Evaluation <br /> Groundwater monitoring wells GW#1 and GW#2, both shallow alluvial wells downgradient of the <br /> Mayflower TSF, were constructed in June 1987. These wells have been monitoring nearly <br /> continuously on a quarterly basis since that time, and the data are presented in Tables A-3.1 and <br /> A-3.3 included in Appendix B. The data at these locations indicate generally stable or improving <br /> water quality since January 1994. Since the resumption of mining and milling operations in 2012, <br /> water quality in both downgradient shallow groundwater monitoring wells (GW#1 and GW#2) has <br /> improved, indicating that mining and milling operations have not introduced new sources of <br /> groundwater contamination. <br /> With respect to establishment of an ambient-based value for manganese at POC well TM-MW- <br /> 002D representative of existing quality as of January 31, 1994, the observed concentrations of <br /> manganese at this location are higher than those observed in the upgradient deep-monitoring <br /> well TM-MW-001 D, suggesting that regional geology and not mining-related sources are <br /> contributing to manganese variability in bedrock groundwater at this location. With the exception <br /> of manganese, concentrations of all other monitored parameters are relatively low and generally <br /> very stable over the three year period of monitoring, suggesting that baseline conditions are well <br /> represented. <br /> Mining and milling activities re-started in 2012 and that resulted in the placement of additional <br /> tailing on Tenmile TSF beginning in early 2012 and Mayflower TSF beginning in mid-2014. <br /> Groundwater quality data from the downgradient monitoring and POC wells remain consistent, or <br /> improved, over this recent period. Thus,these data do not indicate that a new or increased source <br /> or sources of groundwater contamination were initiated within the meaning of the Interim Narrative <br /> Standard. Therefore, data generated subsequent to January 31, 1994, are relevant in estimating <br /> existing quality as of January 31, 1994, in accordance with the CBSG Interim Narrative Standard <br /> (41.5(C)(6)(b)(iii)). <br /> Consistent with the methodology approved by DRMS in Section 5.1 of the WQMP, the use of the <br /> mean concentration plus two standard deviations of the baseline data set were used to compare <br /> against monitoring data as the basis to demonstrate compliance with Regulation 41. <br /> 5.2.1 Analysis of Available Information to Determine or Estimate Ambient Quality <br /> In accordance with the Interim Narrative Standard of the CBSG, data collected subsequent to <br /> January 31, 1994 can be used to determine or estimate ambient quality as of January 31, 1994. <br /> In all instances, DRMS is to exercise its best professional judgment as to what constitutes <br /> adequate information to determine or estimate existing ambient quality, taking into account the <br /> location, sampling date, and quality of all available data. In the situation where the available <br /> information indicates that there have been no new or increased sources of groundwater <br /> contamination initiated in the areas in question subsequent to that date, data generated <br /> December2016 22 <br />