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Mining Plan <br /> All mining will occur north of the Arkansas River. The Arkansas River forms a hydraulic boundary. The <br /> mining and reclamation will not affect groundwater flows on the south side of the Arkansas River. <br /> Three (3) mine cells are currently planned at the site. Two (2)of the cells will initially be dewatered prior to <br /> lining with slurry walls, clay liners, or combinations thereof. The other cell will be an unlined fresh water and <br /> siltation pond which will be mined with typical mining equipment that may include dredges and/or excavators <br /> in a manner that will minimize dewatering. An approved SWSP will be obtained prior to mining below the <br /> water table. <br /> Potential Lining&Mining Impacts to Local Groundwater Levels <br /> Properly constructed slurry walls, clay liners, or a combination thereof will tend to isolate the surrounding <br /> alluvial aquifer allowing for dewatering from within the lined cells without major impacts to water levels <br /> exterior to the lined cells. The lined cells will likely cause"mounding"of groundwater(increase in <br /> groundwater elevation)on the upgradient side (north and northwest)of the proposed lined cells and a <br /> "shadow effect" (reduction in groundwater elevation)on the downgradient side (south and southeast)of the <br /> lined cells. <br /> Any mounding effect on the upgradient side is anticipated to be relatively minor(on the order of a few feet or <br /> less) and will dissipate with distance from the mine. The shadowing affect will likely be minor on the order of <br /> less than a foot to a few feet and will also dissipate with distance from the lined cells. <br /> Due to the presence of the lined cells, limited to no affects are anticipated outside of the lined cell due to <br /> dewatering during mining. The mounding effect on the upgradient side of the lined cell may result in some <br /> increased flow in the Excelsior Ditch. Area wells, discussed below, should not be affected due to their <br /> distance from the lined cells. <br /> Area Wells Within Approximately 600 Feet of the Mine <br /> A review of permitted wells on file at the State Engineer's Office (SEO), Division of Water Resources(DWR) <br /> indicates there are ten (10) permitted wells(not owned by Martin Marietta)within 600 feet of the permit <br /> boundary. All of these wells are screened in the alluvium. Six (6)of these wells are on the west, northwest, <br /> and north (upgradient)sides of the mine. Two (2)of the wells is north and cross-gradient of the mine. Two <br /> (2)of the wells are on the south side of the river. In addition, several wells are on the site itself and are <br /> owned by the Martin Marietta. A map showing the approximate well locations is included in Figure G-1. <br /> A discussion of the wells not owned by Martin Marietta and located within 600 feet of the permit boundary <br /> are discussed below(note a domestic well is usually for household use but sometimes may also indicate <br /> use in yards and/or livestock watering): <br /> • RBK Construction, Inc. (57014F, 80290F): This is a gravel well permit that is shown on the State <br /> well permit map as approximately 485 feet from the permit boundary, however the permit <br /> documents indicate the gravel pit extends to an area just west of Baxter Road. This is a distance <br /> of approximately 100 feet west of fresh water and siltation cells. Because this is a gravel mine <br /> permit, it is unlikely that RBK will complain about dewatering effects at the Thunderbird Mine. <br /> • Bregar(213102): This well is located at 312 Baxter Road, approximately 185 feet north of and <br /> upgradient of the permit boundary and approximately 800 feet from and on the opposite side of the <br /> Ditch from the nearest lined cell. The use of this well is industrial. Water was first used in 1967 at <br /> a rate of 15 gpm. This well appears to no longer exist. <br /> Martin Marietta Materials—Thunderbird Sand and Gravel—MLRB 112 Permit Application <br /> Exhibit G-4 <br />