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Nix Site Groundwater Contamination Potential <br /> March 31, 2023 <br /> y <br /> 1 Permit Boundary <br /> r:)Approximate Slurry Wall Configuration <br /> ` l Exposed Groundwater <br /> 0 1,000 2,000 ft <br /> Figure 1.Nix Site locations showing unlined areas,slurry walls,and cell configurations <br /> Across the site, there is approximately 5-15 feet of overburden, consisting of clayey to silty <br /> sand that overlies the sand and gravel deposits that will be extracted for construction <br /> materials. Keller and others (2019) shows that the sand and gravel deposits belong to <br /> Upper Pleistocene cut-in-fill terraces along St.Vrain Creek that may correlate with the <br /> Broadway and Louvers alluvium along the South Platte River. Exploratory drilling indicates <br /> that economic deposits generally consist of gravely, fine to coarse grained sand and sandy <br /> gravel with a fines content generally ranging from about 2-4 percent and some areas with <br /> lenticular clay beds.The sand and gravel deposits directly overlie the bedrock in the area, <br /> which generally consists of silty fine to medium grained sandstone with some local <br /> claystone seams,likely the upper transition member of the Upper Cretaceous Pierre Shale <br /> with potentially thinner areas of Upper Cretaceous Fox Hills Sandstone which conformably <br /> overlies the upper Pierre Shale member. Cross section B-B' from Keller and others runs <br /> through a mine site (Varra Companies Pit 115) approximately 2,000 feet south of the <br /> southern border of the Nix Site. This cross section is shown below as Figure 2. <br /> DINATALE WATER CONSULTANTS 2 <br />