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2. Groundwater <br /> The site will mine a sand and gravel deposit which is an alluvial from the recent period of <br /> Quaternary age formed on a bend of the Gunnison River. The alluvium is relatively shallow <br /> (averaging 30 feet thick in this region) and is underlain by Mancos Shale. The Gunnison River itself <br /> is actually cutting in the Morrison Formation, which is also known for its purple and green shales. <br /> Figure 1 below shows an example cross section of the regional geology. <br /> Figure 1 —Cross Section of Regional Geology <br /> This geology causes the groundwater level to be very close to the surface. Water is expected to be <br /> w <br /> 0_ Cn <br /> cr 3 Java fto ws <br /> a c C: green river <br /> N N & wasatch <br /> �.' mesa verde <br /> rnancos shale <br /> prec6mbrian Q'SSrc <br /> dakota <br /> encountered 4 to 6'below the surface. While the pit is being pumped down the water table will <br /> drop, but after reclamation this level is expected to return. The quality of the water is similar to the <br /> Gunnison River at this point. A substitute water supply plan will be in place to cover out of priority <br /> depletions during mining,with a permanent plan for augmentation eventually put in place for the <br /> permanent lakes. A gravel well permit will be necessary for the dewatering operations and lakes. <br /> Ground water quality is protected by dewatering below the operational floor in all of the pits, in <br /> addition to gravel filter berms around the pumps. During the mining of the east pit(Areas 6-10), <br /> groundwater from said pit will be pumped to the west pit,which will act as a large-scale sediment <br /> pond. All dewatering water will discharge through an approved NPDES before flowing to local <br /> waterways. <br /> BRS&G Pit 1 X Grcg Lewick and.4ssociatc PI.L<' <br /> March 2019 G-2 <br />