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G:\COMMON\Holcim\25510\05 Correspondence\response to DRMS TR 10 review of Na letter\sueker revision 20141118\2014 1119 Response to TR 10 review letter .docx Mr. Timothy A. Cazier November 19, 2014 Page: 4/6 compositional “types” is entering into the MW -7 monitoring well. Trilinear diagrams, also known as Piper diagrams, were developed for select samples that had sufficient data for plotting. As shown in Figure 5, most groundwater samples plotted within the calcium plus magnesium, sulfate [Ca+Mg–SO4] type water field shown in the upper portion of the diamond. However, the MW -7 2008 sample is shifted away from the primary group of samples towards the sodium plus potassium, bicarbonate [Na+K– HCO3] type water while the MW -7 2009 sample is clearly a Na+K–HCO3 type water. These shifts in water composition occurred when depth to groundwater increased. MW -7 is completed within the Codell Sandstone and the underlying Blue Hill Shale. The MW -7 borehole was completed to a total depth of 70 feet below ground surface (ft bgs) with the upper 30 feet in the sandstone and the lower 40 feet in the underlying shale (Figure 6). The borehole was backfilled with silica sand to a depth of 42 ft bgs. The borehole was cased and a slotted screen interval was completed from 17 to 42 feet bgs across both the sandstone and shale bedrock. When the depth to groundwater increases at MW -7, the proportion of groundwater that may be contributed from the shale increases and may result in the observed shifts in groundwater quality with increased depth to groundwater. No other site groundwater monitoring wells intersect the Blue Hill Shale and no other site groundwater monitoring wells exhibit the wide variability in constituent concentrations observed at MW -7. The borehole log is included as Attachment 1 to this letter. 2) Literature Data: The DRMS has requested that ARCADIS provide some discussion related to the referenced Report to Congress as to whether or not bio-solids are included in the characterization of CKD at similar cement plants. The basis for this statement is that they indicated sludge samples analyzed for TR-06 suggest the addition of the bio- solids alter the chemistry of that typical for CKD. Response: We are not aware of biosolids being used as an admixture for CKD at other cement plants, and we were not able to obtain any data in that regard. Biosolids were originally used as a dust control measure. However, biosolids have not been used at the Portland facility for at least 10 years and represent a small percentage of the total waste in the facility. As such, it is unlikely that they will have a significant impact on the overall chemistry of the highly leachable constituents, such as potassium, sodium, and chloride present in the CKD and be observed in measurements taken 10 years later.