2012-01-09_HYDROLOGY - M1977300 (2)

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Mr. Randy Whicker January 9, 2012 Well Location 6 Near alluvial monitoring well MW3A at a location likely to allow completion in the Illinois fault zone - Deep 7 Southeast end of the South Waste Rock Pile, near surface water monitoring site SW -001 Page 2 Total minimum Purpose depth, feet below ground surface 200 Detect mine pool flow to Ralston Creek and alluvium /bedrock head differences 200 Distinguish Waste Rock Pile - sourced pollutants from pollutants in Illinois Fault wells (wells 5 and 6) The locations and depths of these monitoring wells are based in part on the recommendations for monitoring wells provided on page 75 of U.S.G.S. Open -File Report 2011 -1092, which provides that: Direct measurement of groundwater migration from the mine pool would require new monitoring wells that are completed in bedrock. If some of these wells were collocated and nested with existing monitoring wells completed only in the alluvial aquifer, they could better document differences in hydraulic head between the bedrock and alluvial aquifers and provide data on the potential direction groundwater may be flowing from one aquifer to another and (or) into Ralston Creek. Additional strategically located bedrock monitoring wells at a variety of depths would provide better three - dimensional understanding of groundwater flow and quality. Time series water level, temperature and geochemical monitoring are suggested in all such wells. Possible locations of other new bedrock monitoring wells include the vicinity of the Minnesota Level and outboard of the mine workings, and in the subdrainage formed in what is referred to as the "Schwartz Trend." The two deepest wells (minimum depths 800 feet and 1,000 feet) are necessary for characterizing the mine pool's impact on the regional groundwater regime. These wells will provide data regarding groundwater flow and quality at a depth slightly below the elevation of Ralston Reservoir. The wellbores shall be a minimum 4 inches in diameter in order to increase the probability of intersecting fracture porosity (compared to a smaller diameter borehole) and to facilitate tremie pipe access upon plugging and abandonment. The Division will address the precise location and of each well through the TR adequacy review process. Please include the following specific information in your TR application: 1. Identification of the drilling fluid to be used (for example air, mud, water), 2. A description of the development methods to be used for restoring aquifer hydraulic properties that may be altered during drilling, 3. Identification of the proposed screened /completed depth intervals, and 4. A description of the method to be used for determining rock hydraulic properties. To ensure prompt compliance with Hard Rock Mining Rule 3.1.7(7)(a), all monitoring wells must be installed as soon as weather conditions permit, following the Division's approval of the TR, but in no event later than 90 days after approval. The additional bedrock groundwater monitoring wells installed pursuant to the TR shall have the same monitoring parameters and frequencies as the existing alluvial wells. The Division has discussed the requirements set forth in this letter with the Water Quality Control Division (WQCD). The WQCD has confirmed that none of the requirements set forth in this letter will