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GCC Rio Grande, Inc. <br />Page 2 <br />5/27/2015 <br />6) The submittal for TR -05 contains data from two TCLP analysis for samples collected on January <br />13, 2015. Please clarify which results represent the different operating temperature of the kiln. <br />7) Please provide the paste pH for the kiln dust material in both analysis. <br />8) Has the Applicant/Operator run a TCLP or similar analysis on the raw material coming out of the <br />mine and going to the kiln? <br />9) Please explain why the total metals in both samples are orders of magnitude greater than the results <br />of the TCLPs. The Division's staff believes more metals would have expressed and leach through <br />the TCLP process. Please explain this apparent discrepancy in the samples total metals and what <br />was reported in the TCLP results. <br />10) The Division believes that only two samples collected on only one day (January 13, 2015) may <br />not be representative of kiln baghouse dust. Please collect additional samples to more completely <br />characterize the kiln dust. The Division would prefer to have analytical testing done on multiple <br />mixed grab samples collected over a span of at least weeks. The Division believes that TCLP is <br />an appropriate test to run to characterize waste; however, the Division believes the TCLP does not <br />adequately characterize mine rock waste. Please collect additional samples over a greater temporal <br />period. Please subject the additional samples of the kiln baghouse dust to Multiple Extraction <br />Procedure (MEP), EPA method 1320. <br />11) In order for the Division to approve the placement of the kiln baghouse dust into the quarry with <br />no hydrologic barrier, (such a HDPE liner and/or a compacted clay liner) the Division will require <br />an extensive groundwater monitoring plan with both upgradient and downgradient wells. Please <br />provide a groundwater monitoring plan which contains at a minimum the following information <br />such as; background data, well locations, well depths, well logs, geologic information, the screened <br />intervals on every well, well construction methods and well completion methods. <br />12) The approved post -mining land use for the affected lands is rangeland. The sampling results <br />submitted indicate that there are high concentrations of heavy metals in the dust. Will the <br />vegetative species in the approved seed mix absorb or uptake the heavy metals located in the <br />backfilled dust? If plant absorption or uptake of the heavy metals occurs, will bioaccumulation of <br />heavy metals pose a danger to grazing livestock? Could high levels of heavy metals in the soil <br />impair revegetation efforts? <br />13) The Division is currently reviewing the total metals and TCLP data with the Colorado Division of <br />Health and Environment's Hazardous Materials and Waste Management Division (HMWMD). <br />The Division will follow-up with any comments and concerns received from HMWMD. <br />