2011-03-01_REVISION - M1977493 (6)

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Mr. Eric Scott Climax Mine - Response to DRMS Adequacy Review Comments Permit M-1977-493; Amendment AM-06 March 1, 2011 Page 4 of 16 Response: Clean water diversions are not shown above the OSF's on the figures in Exhibit F and G since there is minimal up-gradient drainage area that would justify construction of such diversions based on the currently-planned configuration of these facilities. CIVIC is committed to voluntarily implementing best management practices (BMPs) on its mine site to prevent impacts to runoff from mine materials in order to reduce the volume and flow-rate of water to be treated. Therefore, CIVIC will evaluate the feasibility of clean water diversion systems above the OSFs on a case by case basis as the sequencing for overburden placement becomes more defined. This evaluation will consider the use of interim run-on diversions, primarily in the area of the McNulty OSF. As indicated on Figure AM-06-C-03, there is an existing run-on interceptor upgradient of the current McNulty OSF. Depending on the placement sequencing for overburden in this area, maintaining and/or relocating this diversion will be considered throughout the course of mining operations. Exhibit G - Water Information Exhibit G Comment: Regarding PMP flood control/capacity as presented in section G-7 of AM-06, how and how often will it be determined that sufficient flood storage capacity is being maintained • during mine operations? How often is the site PMP event evaluated/modeled to determine that the projected PMP flood capacity is sufficient? Otherwise Exhibit G is adequate as submitted. Response: During mining, the storage capacity and dam crest heights of the operating TSFs continuously change as additional tailing is deposited in the facilities. Therefore, CIVIC will regularly monitor the facilities to verify that the specified PMP flood storage allowance is being maintained. The monitoring program will consist of an annual survey of the TSF configuration and monthly determinations of available PMP flood storage capacity. The annual survey, along with actual tailing deposition and water level data, will be used as the basis for a flood storage accounting process to document PMP management status on a monthly basis while mining occurs at the site. For years in which mining has occurred, an annual report will be prepared that documents the flood storage and release status for the year. The required PMP flood storage capacity for the TSFs has been determined as described in Section G-7.7. The flood storage capacity requirements will be re-evaluated when significant changes have been made to the flood routing systems at the site that have the potential to impact the capacity requirements. A re-evaluation will also be made if it is determined that changes to the methods used to model the PMP flood or changes to the design PMP event are warranted. If such re-evaluation becomes necessary, the revised flood storage capacity requirements will be documented and reported to DRMS. The revised requirements will then be used in the ongoing monitoring described above. 0