2011-05-10_REVISION - M1977300 - Laserfiche WebLink

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Environmental Protection Plan, Schwartzwalder Mine 15 -9 (g) Mine Pool Stabilization and Detoxification The plan for stabilization and detoxification of the mine pool will be developed as part of ongoing mitigation activities and investigation. The mitigation program must follow a logical path forward, to prevent uranium migration into the creek, followed by further investigation and source removal in the alluvium and fill, identification and sealing of any potential conduits between the mine pool and Ralston Creek, and evaluation of strategies for mine pool treatment and stabilization. In -situ treatment of mine pool water will be conducted to accelerate the current trend of decreasing levels of uranium in the mine pool, reduce concentrations of other metals, and coat interior wall rocks and mine rubble with a layer of iron sulfide that will physically and chemically inhibit further geochemical leaching. Alexco Resource US Corp (Alexco) has provided Cotter with a technical basis and conceptual plan to implement in -situ treatment of mine pool water to reduce concentrations of uranium and other metals through in situ formation of sulfide minerals. The proposed treatment will also form non - pyritic iron sulfide (FeS) within and throughout the mine pool workings to encapsulate the precipitated mineral forms of uranium, inhibiting the potential for re- dissolution or release of the uranium back into the mine pool. In situ mine pool treatment would be performed under Technical Revision 17 (TR 17) to Mining Permit M -1977- 300. (h) Monitoring Well Installation Four bedrock monitoring wells are proposed for installation in 2011: an upgradient (west- southwest) pair of replacement monitoring wells for existing wells MW10 and MW11, and a downgradient (east) pair of new bedrock wells. (1) Replacement Upgradient Bedrock Monitoring Wells The upgradient pair are intended to fulfill the requirements of the December 14, 2010 EPP Adequacy Review (DRMS, 2010) which requires that bedrock monitoring wells MW10 and MW11 be replaced with new upgradient monitoring wells to determine baseline bedrock ground water quality and thus serve as a basis for the evaluation of reclamation performance standards. MW10 and MW11 were originally installed for the purpose of determining water levels above the mine and understanding the groundwater flow system in the bedrock. The wells are still suitable for this purpose, although their use as monitoring wells is compromised due to bentonite intrusion into the screened zones. Two new monitoring wells will be drilled in 2011 to determine bedrock water quality upgradient of the deposit in an area that has not been mined. The proposed location is in the SE1/4 of the SW1/4 of Section 25. The replacement bedrock wells will be located in the same quarter - quarter section and within 500 feet of the existing wells MW10 and MW11. The replacement wells will be accessed via a previously disturbed road, although additional permitting and earthwork will be required to construct the drill pad. The proposed locations will be field verified and staked, prior to a contractor orientation and pre -bid meeting for qualified drilling contractors. An application will be submitted to DRMS describing the acreage of proposed disturbance, proposed well completion depths and materials, reclamation plan for the disturbed area, monitoring methods, and provisions for future access to the monitoring wells. The paired wells will be located within 100 feet of each other, and will be completed at different depths (as were MW10 and MW11) to determine vertical hydraulic gradients. Sampling will be performed using approved passive sampling methods (see ITRC, 2007) to avoid the potential for bentonite intrusion that occurred at MW10 and MW11. Because the monitoring methods may depend on the depth to water encountered in the 4109C.110510 Whetstone Associates