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April 2014 15 10381640A <br />generally lower than the other groups. The groundwater in this group exhibits higher concentrations of <br />calcium, magnesium and sulfate and lower alkalinity than the other groups. Barium concentrations in this <br />group are below 1 mg /L, which is lower than the other groups. <br />Group 2 (MW -2 and MW -3): The monitoring wells in this group are screened from 100 to 200 ft bgs across <br />the Niobrara /Codell contact. The wells in this group are located less than 100 feet downgradient of the <br />CKD disposal area A2. The groundwater in this group is sodium - chloride type water with TDS <br />concentrations between 5,000 and 10,000 mg /L. The groundwater in this group exhibits higher alkalinity <br />concentrations than the other groups and the barium concentrations in this group are between 1 and <br />2 mg /L. <br />Group 3 (MW -4, MW -6 and MW -7): The monitoring wells in this group are screened at depths greater <br />than 180 ft bgs, in the Niobrara Formation above the Niobrara /Codell contact'. The wells in this group are <br />located greater than 500 feet downgradient or side - gradient of CKD disposal area A2. The groundwater <br />samples collected from the wells in this group have exhibited trending constituent concentrations and <br />have taken longer to reach equilibrium with the surrounding formations than the groundwater samples <br />collected from the wells in the other groups. The groundwater in this group is sodium - chloride type water <br />with TDS concentrations that are greater than 10,000 mg /L. The groundwater in this group exhibits higher <br />sodium and chloride concentrations than the other groups. Barium concentrations in this group are above <br />2 mg /L, which are higher than the other groups. <br />4.2 Solid -Phase Geochemistry <br />Golder collected and analyzed native materials and CKD as part of the 2012 field program. These <br />materials included: <br />• One sample of silt from the screened interval of well MW -5; <br />• Four samples of limestone from the screened intervals of wells MW -6 and MW -7; <br />• Two samples of sandstone from below the screened intervals of wells MW -6 and MW -7; <br />and <br />• Two samples of CKD from a borehole drilled in area A2. <br />Additionally, analytical testing of the CKD material was conducted by Secor and Holnam ( Secor 1998). <br />The results of the solids analysis are discussed below. <br />' Screened lithology of MW -4 is unknown. MW -4 is assumed for this discussion to be part of Group 3 <br />based on the well depth, hydraulic characteristics and chemical signature. <br />Golder <br />i. \10 \81640a\ 0400 \gwcharwellinstallfieldrep_fnl 30apr14 \10381640a gwcharrpt_holcim boettcher_fnl 28apr14 with holcim edits docx <br />Associates <br />