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Colorado Division of Mining Reclamation and Safety February 17, 2015 <br />Eric Scott 3 1400159 <br />in 1999 and 2000 for constituents such as chloride and TDS. This stabilization process may indicate an <br />initial influence of drilling water on water quality. <br />The highest concentrations of barium are found in samples collected from the Group 3 wells (MW -4, <br />MW -6 and MW -7). These wells are located greater than 500 feet from CKD disposal area A2. Group 2 <br />wells (MW -2 and MW -3) are located less than 100 feet from the CKD disposal area A2 and have lower <br />observed concentrations of barium. Likewise, observed TDS concentrations are higher in samples <br />collected from the Group 3 wells than the Group 2 wells. This suggests barium and TDS concentrations <br />reflect influence by native host materials rather than influence from CKD leachate. If the CKD deposited in <br />area A2 was an ongoing source for barium and TDS loading to the groundwater, higher concentrations <br />would be expected closer to CKD disposal area A2 in the Group 2 wells. This is particularly the case <br />given that MW -2 and MW -3 are screened across the Niobrara /Codell contact; groundwater would be <br />expected to flow along this contact in the Niobrara based on the understanding of Site hydrogeology <br />(Secor 1998, Golder 2014). Although TDS and barium concentrations in MW -4 increased during the 1998 <br />and 1999 sampling, the concentrations have been stable since 2010. <br />2.0 CKD LEACHATE CHARTERISTICS <br />Synthetic preparation leaching procedure (SPLP) testing was conducted by both Golder and SECOR on <br />CKD from the Site. Although SPLP analysis is not designed to definitively predict long term water quality, <br />it does provide an indication of the CKD leachate characteristics. The results of the testing are presented <br />in their entirety in Golder (2014), and can be summarized as follows. The SPLP leachate pH values are <br />greater than 12 for the CKD material and between 7 and 10 for the native materials. Groundwater pH <br />values in Site wells are between 7 and 9. These values are similar to values observed in the wells prior to <br />CKD placement in area A2, and do not show an increase over time that would be expected if the waters <br />were being influenced by CKD. In addition, the SPLP leachate concentrations were at least an order of <br />magnitude higher for the CKD material than for the native materials for: arsenic, barium, chromium, lead, <br />lithium, selenium, and thallium, and the majority of major ions. Dissolved metals concentrations elevated <br />above benchmark levels are only observed for barium in the Group 3 wells. Elevated or upward trending <br />concentrations of other constituents would be expected if CKD was influencing groundwater <br />concentrations in the Site wells. For example, potassium concentrations measured in the CKD leachate of <br />approximately 500 mg /L are two orders of magnitude greater than that of the native materials. However, <br />concentrations of potassium, which would be relatively conservative under these conditions, in <br />groundwater from all wells are typically less than 20 mg /L and show no consistent increasing trends in <br />concentrations. <br />For reference and comparison, CKD- influenced groundwater samples were collected and analyzed at <br />another, out of state Holcim site. Compared to the Boettcher Quarry, the groundwater water from the <br />comparison site exhibits a high pH of 12.6, high alkalinity of 2,120 mg /L as CaCO3, present as hydroxide <br />Golder <br />is \14\ 1400159 \0100 \0122 \tm- boettcho0imestone uar fnl- 17feb15 \1400159 tm- boettcherlimestone ua fnl- 17feb15.docx Associates <br />9 rY_ 9 QTY_ <br />