2018-07-09_REVISION - C1982056 (3)

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Response: - As noted in the previous response, soil recovery and replacement depths can vary significantly depending on topography, aspect, exposure, host materials, drainage patterns, and other factors. The Topsoil Stockpile Summary (Table 49A) has been reviewed and updated to include all current stockpiles, and a supplemental table (Table 49A-1) has been developed to correlate disturbance areas, soil stockpiles, and soil replacement depths. These updates and additional materials, along with revised TOC and reference information accompany these responses for insert ion/replacement in the PAP. 2.05.6(6) Subsidence Survey, Subsidence Monitoring, and Subsidence Control 57. Page 2.05-191.7 indicates hydrologic monitoring of surface and alluvial wells sites will be conducted along Fish Creek to assess the subsidence impacts resulting from mining in the WMD. This page indicates that results of relevant ongoing hydrologic monitoring will be incorporated into the semi-annual subsidence reports. Please review the results of the relevant hydrologic monitoring data and provide an assessment of the mining impacts on the Fish Creek AVF and include it in the subsidence report discussed in the item above. Response: - The referenced hydrologic monitoring is part of TC's ongoing hydrologic monitoring program, as approved under our hydrologic monitoring plan. The noted monitoring activities have been, and continue to be conducted, consistent with the approved monitoring schedule, to document current conditions and allow identification and assessment of any significant changes that may be related to the ongoing mining activities. While not included in a subsidence report, as noted in the previous response, the results of this ongoing hydrologic monitoring and the related assessment is documented and reported in the Annual Hydrology Report submitted to the CDRMS. In order to avoid future confusion, the reporting reference noted has been modified to reflect these considerations, and copies of the revised text are included with these responses for replacement in the PAP. TA2 — The approved subsidence monitoring included with recent AHR reports for the impacts related to Fish Creek is insufficient. The proposed page 2.05-191.7 of the renewal states that, "The results of ongoing hydrologic monitoring are included and evaluated in the Annual Hydrology Report. " This was the monitoring plan approved by the Division in PR -08. The AHRs have not been adequately following this plan. The 2016 and 2017 reports have a subsidence section included in section 4.0; however, the section refers the reader to the reports by Michael Berdine dated May of 2017 (2017 AHR). This is contradictory to the approved monitoring program. Section 4.0 in the AHRs does not include an analysis of the data from these reports. Section 5.0 only includes general statements of there being no new subsidence impacts to Fish Creek and a few sentences regarding historical impacts. Future AHRs should include an analysis of the Fish Creek subsidence data and water quality data in Section 4.0 to satisfy Rule 2.05.6(6)(c). Response: - The referenced language on page 2.05-191.7 addresses subsidence monitoring for the Northern Mining District, as noted on page 2.05-191.5. With approval of PRI 5-11, an additional section was added to the subsidence monitoring discussion in the permit addressing subsidence monitoring requirements for the ongoing and future mining in the Wolf Creek Reserve (refer to pages 2.05-191.8 through 2.05-191.10). As noted on page 2.05-191.10; Active monitoring wells within the projected subsidence area(s) will be monitored on the regular hydrologic monitoring schedule. If monitoring results, specifically water levels, indicate any significant changes due to undermining or subsidence, TC will conduct fiurther testing and/or inspection to determine whether or not the integrity of the well has been compromised. If the resulting information indicates that the well has been damaged beyond repair, and if the well is needed for ongoing and fittitre monitoring, TC will prepare and submit a revision to the permit for a replacement well, and then will construct and initiate monitoring of the replacement well. As indicated by the approved permit language, the hydrologic monitoring focuses on maintenance of the integrity of the hydrologic monitoring system, and does not specifically include analysis and reporting requirements, other than assessment of well integrity, if indicated. Similarly, Rule 2.05.6(6)(c) does not specify hydrologic analysis or reporting requirements. As part of the normal process for preparation of the Annual Hydrology Report, TC will continue to review the monitoring data, and for any identified monitoring anomalies, provide an assessment and explanation of potential causative factors including, if relevant, subsidence effects.