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Inspection Report Response July 30,2018 Page 2 movement in the kiln. The third waste material is the sludge material that is removed from the lime scrubber system. The lime scrubber system is designed to remove very fine particulates as well as certain chemicals in the gas stream. It is the third waste material that was assessed for its chemical contents and environmental acceptability for placement into the mine pit. The scrubber waste was analyzed for 32 metals using EPA Methods 1312 (Synthetic Precipitation Leaching Procedure or SPLP), 6010 (Metals Analysis), 7470 (Mercury), and 365.4(Phosphorus). A detailed summary of the analytical results are presented in Table 1. The analysis identified the following metals above the Report Limit: • Boron—227 ug/L; • Calcium—77,500 ug/L; • Magnesium— 13,900 ug/L; • Potassium—4,280 ug/L; • Silica—2,300 ug/L; • Silicon— 1,080 ug/L; • Sodium—26,700 ug/L;and • Strontium—864 ug/L. These results were utilized along with site specific data on the permeability, porosity, and area of solid waste disposal along with generally acceptable conservative variables to develop conservative groundwater transport models of these metals to determine the likelihood for the leachate to potentially migrate off-site. The EPA BioScreen Model was utilized to estimate the potential transport distance of the metals. Since the analysis was performed for inorganic compounds, the organic partition coefficient (Koc) was replaced by soil water partition coefficient (Kd), the fraction organic coefficient(foc)was assigned a value of 1, and the I"order decay coefficient was assigned a value of zero to indicate no decay.. Due to the extremely low toxicity of the identified metals, TRNLWB was only able to identify Kd values for boron and strontium. The Kd values were 1.135 and 95 L/kg,respectively. The modeling indicated that the all the identified metals would attenuate within 150 feet from the solid waste source. This is primarily due to the extremely low seepage velocity within the Pierre Shale and the low initial concentrations of boron and strontium in the leachate, 0.227 mg/L and 0.864 mg/L, respectively The detailed analysis and variables are presented in Appendix B. In conjunction with the modeling, a "Geocheck Report" was ordered from Environmental Data Resources (EDR) and is presented in Appendix C. The report includes soil information for the area surrounding the quarry compiled from the USDA Soil Conservation Service SSURGO database; a USGS topographic profile map for the area; and a map of all groundwater wells with select information for each well and web links to regulatory agency database files associated with each well. A summary table of groundwater well information within one(1)mile of the quarry is presented in Table 2. The water well information indicates that the surrounding wells are not screened within the Pierre Shale and there is no indication that there is a reasonable hydrologic connection between the mining pit containing the waste material or any of the wells within a one mile radius from the pit. In addition to the modeling, a comparison of the metal leachate concentration to protective concentration levels for human health and the environment was necessary. The metal concentrations were initially compared to the National Primary and Secondary Drinking Water Standards. However, none of the identified metals are listed in the Drinking Water Standards. Due to the very low toxicity of the metals that were identified in the waste material, TRNLWB performed a comparison of the leachate concentrations with the US Department of Health & Human Services National Institute of Health (NIH) Recommended Daily Allowance (RDA) or