2012-08-21_REVISION - M1980244 (32)

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50. Page 114, LVSC system monitoring — Given the requirement to maintain less than two feet of head on the low volume solution collection (LVSC) liner and the pumping rates observed in the AGVLF LVSC sumps, the Division requests the Applicant commit to monitoring water levels in the SGVLF at least daily, as is current practice in the AGVLF. RESPONSE. Prior amendment applications reviewed and approved for the Cresson Project presented at least weekly monitoring of the AGVLF. CC &V is committed to conducting undocumented daily monitoring on the approved AGVLF and proposed SGVLF by process operations and at least weekly documented monitoring of the approved AGVLF and proposed SGVLF by professional Environmental Resources Staff, as is the current practice at CC& V. 51. Paize 12 -10, section 12.4.2 — The Applicant cites changing conditions and project economics for reasons to vary the amount of backfilling in the mine pits. The Division understands the difficulty in committing to such a large undertaking. However, safety, water quality and aesthetics are important considerations to be considered in the reclamation phase of the Cresson Project. Furthermore, economics should not be a major reason for reducing the planned backfill during reclamation. In order to prevent major disagreements between the Applicant and the Division during the reclamation phase, the Division requests the Applicant commit to a minimum level of pit backfilling, should conditions shift to the impractical. These criteria should indicate which areas have the highest priority for backfilling and which are the lowest. These criteria should stress safety, water quality and aesthetics (and others if appropriate) as reasons for ranking. RESPONSE: Based on the anticipated mine plan as presented in Section 5.7.3 of the Project Description within Volume 1 of the application, the highest priorities for backfill to occur would be the main portion of the WHEX and western portion of the Globe Hill, should development of those areas occur. CC &V is committed to backfill these areas to promote free drainage of storm water runoff from these areas. The establishment of free drainage of storm water runoff is consistent with prior amendment applications reviewed and approved for the Cresson Project. The next priority would be the northern part of the WHEX portion of the East Cresson Mine area and Schist Island portion of the North Cresson Mine area should development of those areas occur. CC &V is committed to backfill these areas to the approximate existing ground surface. The lowest priority for backfill would occur in the Main Cresson Mine area at the end of the expected mine life. As also presented in Section 12.4.1 of the Project Description within Volume I of the application, should development of the North Cresson occur, CC &V is committed to North Cresson Mine Area Viewshed Conservation Plan. 52. Page 12 -14, 3`d paragraph — the Applicant states the relocated Grassy Valley stormwater drainage will be lined with clay to prevent infiltration into the active mining area. Flow velocities (transporting colloidal silts) in excess of five feet per second can erode the clay lining. Please discuss how the clay lining will be protected from erosion. RESPONSE: These are several means that can be implemented to protected clay lining from erosion that have previously been implemented at the Cresson Project, if needed. As implemented in the previously presented and approved "Sediment Pond" west of the AGVLF in Section 30 on Drawing C-4 of the Amendment No. 9 application for the Mine Life Extension Project in 2008, CC &V is committed to implementing means of controlling erosion of clay lined ponds. For example, CC &V could use of rip rap channels into the pond and/or place, to a minimum depth, a layer of cover rock on clay that does not reduce the overall required storage capacity of the pond. If deemed necessary at the time of construction of the facility, protective means for the clay material will be implemented if flow velocities (transporting colloidal silts) are expected to be in excess offive feet per second across the clay lining. 53. Page 12 -16, 2nd paragraph — the Applicant states that portions of benches created during operations will be retained and the overall reclaimed slope of the VLF will be 2.5H:1 V. Please provide a minimum criterion for intrabench slopes for reclamation. RESPONSE: Prior amendment applications reviewed and approved for the Cresson Project stated that portions of benches created during operations will be retained and the overall reclaimed slope of the VLF will be 2.5H.•IV, more specifically, the languages states the following: "the slopes of the VLFs will be recontoured to an overall slope of approximately 2.5H. I V. Portions of the benches created during operations will be retained, as appropriate, for geotechnical and erosional stability. The topography shown on Drawing F -1 and the financial warranty calculations presented in Section 13.0 of this Project Description have been