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2"d Geochemistry Review 3 3 May 2011 <br />May Day Conversion CN-1 File No. M-1981-185 <br />B. Adequate. <br />14) Adequate. <br />15) A. The Applicant has not satisfactorily responded to this concern. The information <br />provided is not adequate to describe or address potential impacts to groundwater <br />resources as required by Rule 6.4.21(8)(b). The depth to ground water is unknown <br />except where ground water is observed in the underground mine workings or where <br />ground water emerges at the ground surface. Therefore, the Division should require <br />additional hydrologic testing and analyses to adequately characterize the ground water <br />regime. <br />B. The maps and figures provided with the application indicate at least 11 proposed drill <br />pads. Some of these are in locations that might be suitable sites for conversion to <br />monitoring wells or piezometers. <br />16) Adequate. <br />17) A. The Division does not agree that "dry stack underground tailings mitigates all <br />potential surface and ground water quality mining impacts." The mine site is located in <br />an area of relatively high precipitation and even if the proposed tailings deposition area is <br />above the water table in the unsaturated zone and currently dry, that is no guarantee that <br />it will always be so and there may be a risk of periodic wetting due to ground water <br />infiltration. Fine-grained tailings located where they may undergo repeated wetting and <br />drying is an ideal scenario for weathering that can leach contaminants and generate acid- <br />rock drainage. The Applicant proposes "appropriate ground water and surface water <br />monitoring." The Applicant will need to develop a rigorous testing and monitoring <br />program, and depending on conditions in the mine, measures may be needed to isolate the <br />tailings from current and future infiltrating ground water. <br />B. It is not entirely clear what information is intended to be conveyed in Figure D-1B <br />Dry Stack Tailings Disposal Sites. The Applicant should clarify whether both the red <br />dots and the thick red line intended to depict tailings disposal areas. <br />C. Exhibit D, Mining Plan, page 4. The mining plan states that "wet-submerged tailing <br />disposal will be researched and implemented upon demonstration the underground <br />disposal sites are suitable and that the tails will not induce environmental impacts." The <br />Applicant should describe the research and testing that will be done to evaluate the <br />suitability of wet-submerged tailings disposal and to demonstrate that the tails will not <br />induce adverse environmental impacts. <br />D. The Applicant's statement that "surface and ground water quality have not been <br />affected by past mining activities" may not be accurate. Based on recent water quality <br />data from sample sites SW-1 and SW-2, the La Plata River displays noteworthy increases <br />in the concentrations of several constituents (Al, As, Cd, Fe, Mn, Ni, Pb) as it flows past <br />the mine site. These increases may be caused by ground water discharge that has been