2012-05-01_REVISION - M1977300 - Laserfiche WebLink

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E -0 Preface The primary purpose of this permit amendment application (Amendment 4) is to update the previously approved Reclamation Plan under the 1983 and 2001 Mine Permit Amendments. Mine reclamation was included in Section 15 of the July 31, 2010 Environmental Protection Plan (EPP) submitted to the Division of Reclamation, Mining and Safety (DRMS or Division) under Permit Amendment Application 2 (AM -02). The Division issued partial approval of AM -02 on March 6, 2012, with the condition that Section 15 of the EPP be revised to address items contained in Attachment A to a letter from DRMS to Cotter dated January 30, 2012 (DRMS, 2012a). The following information is intended to replace Section 15 of the EPP and to simultaneously address items outlined in Attaclunent A to the DRMS letter of January 30, 2012. Included are detailed remedial plans to address solid source term materials located outside of the underground mine workings (alluvial fill and waste rock pile), and to address the mine pool (including plans for mine dewatering with ex -situ mine water treatment and /or long -term in -situ treatment of the mine pool). E -1 Conceptual Considerations Revision of technical details of Section 15 of the EPP requires careful evaluation of sources of impacts, remedial objectives (both short- and long- term), regulatory requirements from various agencies, potential consequences to human health and the environment, and scheduling realities in terms of meeting all remedial objectives and achieving a fully reclaimed site in the shortest time frame possible. For example, a given remedial measure may help to address a given remedial objective, but can also introduce unintended risks and consequences to human health and the environment, consequences that can outweigh intended remedial benefits. A given remedial measure can also delay other remedial action implementation schedules and undermine timely attainment of overall remedial objectives. Cotter Corporation (N.S.L.) (Cotter) has developed remedial process plan flow charts for each of three identified sources of impacts to groundwater and /or surface water in Ralston Creek. These source terms include the mine pool, mine spoils historically placed adjacent to the mine, and mine spoils underlying or contained within the South Waste Rock Pile (South WRP). Under each source term, these flow charts show remedial options, decision points and sequenced interim steps leading to an expected remedial end point or outcome. The remedial process plan for solid source term materials (Figure 1) is relatively straight forward. Remedial options at each decision point have a high probability of successfully addressing associated problems and are expected to result in acceptable remedial outcomes. The remedial process plan for the mine pool (Figure 2) is more complicated because of many factors, including the complex nature of potential migration pathways, potential consequences of available remedial measures, and potential conflicts or constraints associated with regulatory permitting from various agencies. The term "RO Pump /Treat" in Figure 2 refers to a plan for mine dewatering based on reverse osmosis (RO) treatment of mine water with treatment residuals to be returned to the mine pool. The return of water treatment residuals to a mine pool is being employed at the Platoro Mine in Conejos County, Colorado. A key advantage of RO treatment with return of residuals to the mine is that the mine pool can be dewatered to a specified depth without the need for a large evaporative sludge pond which would pose new risks to human health, water quality in Ralston Creek, and the environment in general (including critical habitat for the endangered Preble's Meadow Jumping Mouse), and would also significantly delay initiation of dewatering as the alluvial fill would require remediation prior to pond construction. May 1, 2012 7