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RESPONSE: <br />Cotter Corporation (N.S.L.)'s Response to December 14, 2010 Adequacy Review, <br />Comments 6(A), 8(A), 8(B), 11(E), 11(F), 11(G)(1), and 11(G)(2) <br />May 2, 2011 <br />Page 4, Item 6(A) — Replace MW10 and MW11 to Determine Baseline Conditions <br />Under Rule 6.4.21 (9) (b), the operator is required to collect ground water quality data adequate <br />to characterize baseline conditions and sufficient to serve as a basis for the evaluation of <br />reclamation performance standards. Monitoring wells MW-10 and MW-11 are the only <br />monitoring wells available with which to determine baseline bedrock ground water quality and <br />thus serve as a basis for the evaluation of reclamation performance standards for the mine pool. <br />However, both wells appear to be compromised. Therefore, in order to come into compliance <br />with Rule 6.4.21 (9) (b), the operator must replace these two wells in locations that will provide <br />the needed data. <br />MW 10 and MW11 were originally installed for the purpose of determining water levels above <br />the mine and understanding the groundwater flow system in the bedrock. The wells are still <br />suitable for this purpose, although their use as monitoring wells is compromised due to bentonite <br />intrusion into the screened zones. Two new monitoring wells will be drilled in the summer of <br />2011 to determine bedrock water quality upgradient of the deposit in an area that has not been <br />mined. The proposed location is in the SE1/4 of the SW1/4 of Section 25. The locations and <br />proposed well completion intervals are further described in the revised EPP Section 15. The <br />wells will be monitored quarterly in accordance with the DRMS- approved analytical suite. See <br />the schedule for completion contained in the response to Item 11(G)(1), below. <br />Page 5, Item 8(A) — Molybdenum Standard <br />Section 11 (c) (ii), page II -II. The EPP states that no surface water standard has been <br />established for molybdenum. The Operator should be advised that Water Quality Control <br />Commission (WQCC) Regulation No. 31, The Basic Standards and Methodologies for Surface <br />Water, amended 9 August 2010 and effective I January 2011, includes a 30 -day surface water <br />domestic water supply standard for molybdenum of 210 g/L (total recoverable). <br />RESPONSE: <br />Although the WQCC, which is part of the Colorado Department of Public Health & Environment <br />(CDPHE), adopted a table value water supply numeric level for molybdenum, the WQCC has <br />not applied it to Ralston Creek. <br />Page 5, Item 8(B) — Uranium sorbed in alluvium and fill <br />Section 11 (c) (iii), page 11-55. The EPP states "Infiltrating water which contacts these reactive <br />surfaces solubilizes the stored uranium salts and transports uranium into the groundwater <br />system." Has the operator done any geochemical analyses to identib, the stored uranium salts <br />that are present and their chemical compositions? If not, what uranium salts are assumed to be <br />present and what is the basis for the assumption? <br />