2005-01-31_REVISION - M1977208 (2)

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Response to Adequacy Letters (dated November 22 and December 17, 2004), CEMEX, Inc., Lyons Quarry, Permit No. M-1977-208, TR-04 and TR-O5. Page 3 of 3 • If seepage transport for C-Pit to the Dakota were possible, the travel time to the Dakota would likely be several hundred years or more (if the seepage arrived at all, given the artesian conditions in the Dakota). Considering the hydrogeologic setting of C-Pit and the results of the conservative transport model, ponded water in C-Pit is not reasonably expected to impact groundwater quality in the Dakota aquifer. Therefore, water in C-Pit does not required accelerated removal or treatment ~ ~`` from a groundwater quality perspective. Furthermore, groundwater monitoring is not required to the Dakota aquifer since it is not reasonable to expect C-Pit seepage to migrate across the ~\\ intervening low permeability bedrock formations to the artesian Dakota aquifer. Cemex's Proposal for Monitoring and Control of C-Pit Water Cemex's proposal is based on the position that there is no threat to groundwater quality resulting from C-Pit water and no significant short-term threat to wildlife (based on Cemex's wildlife report by Mike Figgs and responses from the Colorado Division of Wildlife and the U.S. Fish and Wildlife Service). Cemex will install a new detection well to confirm the findings on hydrogeologic setting and the ~ ~~ computer model results. The well will be installed southeast of C-Pit and will be screened in the .~d Fort Hays limestone and overlying/underlying shale for approximately 10 feet in each direction ~{~` (located on Attachment 1). The well will sampled quarterly and analyzed for the following six ` analytes of concern: dissolved selenium, dissolved thallium, pH, total dissolved solids, sulfates, ~U ()~' and chlorides. C-Pit will be sampled quarterly as a surface water source and analyzed for the k ~~ same six analyzes. A-Pit monitoring will cease and no other surface water will be monitored. V~ Water Treatment and Mitigation If water remains in C-Pit after December 2005 that does not meet the water quality standards put forth in TR-04, Cemex will file a Technical Revision for either treatment of the water and/or mitigation for wildlife impacts. This time frame of approximately one year does not present any threat to groundwater or wildlife and allows Cemex to pump the water to minimum feasible levels as planned. Furthermore, this will allow Cemex and the Division to review the data collected over that time. In order to provide the Division with adequate review time, Cemex respectfully requests an extension of the decision date to Februazy 28, 2005. Should you have any questions regarding this submittal, please feel free to contact me at (303) 823-2109 or Mr. Eric Hodek of my staff at (303)823-2115. Sincerely, `~~ Lohr Manager