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irrigation (EC of 250-750 µmhos is considered "good" and 750-2,000 µmhos is considered "permissible"). <br />Sulfate is a Secondary Drinking Water Standard (aesthetic — smell) at 250 mg/1 which is only applicable to one <br />downstream user on Trout Creek with an alluvial well, which is not currently in use. Review of the PHC <br />indicates that the current discussion identifies and describes the potential for elevated values of these constituents <br />adequately, so no modifications are necessary or appropriate at this time. It is also appropriate to note that TC has <br />maintained full compliance with applicable effluent limitations under all relevant CDPS permits. <br />2.05.6(6) Subsidence Survey, Subsidence Monitoring, and Subsidence Control <br />55. Please depict and label the powerlines that exist within the Permit Area on Map 23b. <br />Response: - Map 23b has been reviewed and updated to show the location of all powerlines within and crossing <br />the Permit Area. Copies of the revised map accompany these responses for replacement in the PAP. <br />56. Section 2.05.6(6)(c) of the Permit discusses the subsidence monitoring program for the Foidel Creek Mine. <br />Since the last Permit Renewal (RN -06), it appears mining and subsequent subsidence has occurred in the <br />Western Mining District. Pages 2.05-191.6 to 191.8 discuss the monitoring requirements that pertain to the <br />areas mined/subsided since the approval of RN -06. Page 2.05-191.8 indicates that subsidence reports will be <br />submitted to CDRMS semi-annually, 60 days after the end of the period. The format of the report is included <br />in Exhibit 34. The last subsidence monitoring report submitted to the Division was received on July 18, 2007. <br />Based on the review of the subsidence monitoring program and approved mining sequence, it appears <br />subsidence monitoring should have been conducted and semi-annual reports submitted since the approval of <br />the RN -06 application. Was monitoring conducted for the structures and renewable resources lands in <br />accordance with the plan discussed on in Section 2.05.6(6)(c) of the permit? If so, please submit a report in <br />accordance with the format approved in Exhibit 34 with the results of the monitoring. <br />Response: - For the Northern Mining District, Western Mining District, and Wolf Creek Reserve, the <br />introductory portion of the subsidence monitoring discussions (pages 2.05-191.5 and 2.05-191.8) notes that TC is <br />not planning on establishing further subsidence monuments, or conducting further monitoring, other than as <br />specifically described. The rationale, as accepted and approved by the CDRMS in the related revisions, is that <br />extensive prior monitoring has demonstrated that the subsidence projections are conservative and effectively <br />provide a reasonable and accurate basis for projecting anticipated subsidence and related subsidence effects. <br />Given these considerations, the limited monitoring that occurred/will occur focuses on specific structures owned <br />by outside parties (Routt County, powerline owners, UP Railroad), for which coordination occurs directly with <br />those parties. The referenced reporting commitment previously existed for the Southwest and Eastern Mining <br />Districts, and was apparently not deleted when the text for the Northern and Western Mining Districts was added. <br />For these reasons, inclusion of the referenced reporting commitment for the Northern and Western Mining <br />Districts was not appropriate, and has been deleted (note that there is no similar commitment for the Wolf Creek <br />Reserve area). Copies of the revised text are included with these responses for replacement in the PAP. <br />57. Page 2.05-191.7 indicates hydrologic monitoring of surface and alluvial wells sites will be conducted along <br />Fish Creek to assess the subsidence impacts resulting from mining in the WMD. This page indicates that <br />results of relevant ongoing hydrologic monitoring will be incorporated into the semi-annual subsidence <br />reports. Please review the results of the relevant hydrologic monitoring data and provide an assessment of <br />the mining impacts on the Fish Creek AVF and include it in the subsidence report discussed in the item above. <br />Response: - The referenced hydrologic monitoring is part of TC's ongoing hydrologic monitoring program, as <br />approved under our hydrologic monitoring plan. The noted monitoring activities have been, and continue to be <br />conducted, consistent with the approved monitoring schedule, to document current conditions and allow <br />identification and assessment of any significant changes that may be related to the ongoing mining activities. <br />While not included in a subsidence report, as noted in the previous response, the results of this ongoing <br />hydrologic monitoring and the related assessment is documented and reported in the Annual Hydrology Report <br />submitted to the CDRMS. In order to avoid future confusion, the reporting reference noted has been modified to <br />reflect these considerations, and copies of the revised text are included with these responses for replacement in the <br />PAP. <br />3.02.4(2)(e)0)(D) Performance Bond <br />