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2.4 Mine Air Shafts <br /> ' There is a reclaimed airshaft, previously used to provide ventilation for the underground mine(s) in the <br /> area, located approximately 200 feet immediately south of the fuel spill area. Several other reclaimed <br /> mine air shafts in the vicinity are shown on the aforementioned USGS topographical map (see Figure <br /> ' 2 2) <br /> 3.0 REGIONAL GEOLOGY/HYDROGEOLOGY <br /> The subject site is underlain by the Cretaceous Dakota Formation with alluvial cover ap to several feet <br /> thick. The Dakota Formation is comprised primarily of sandstones and pebble conglomerates, which <br /> were deposited as beaches and bars as shallow seas encroached upon the area from the east, burying the <br /> Jurassic sediments of the Morrison Formation. The Dakota Formation commonly cz)ntains lenses of <br /> coal, deposited in lagoonal settings, which have been mined commercially in some locations. <br /> ' The Morrison Formation is comprised of many discontinuous layers of sandstone, shale, and limestone <br /> deposited in an ancient deltaic environment. Abundant plant and animal fossils wittan the formation <br /> ' have provided a wealth of scientific information about the time of the dinosaurs, as well as an ore <br /> source for first radium, then vanadium and uranium mining. <br /> ' The Dakota Formation sometimes provides a good aquifer, with recharge in the Abgo Mountains to <br /> the west, underlain by the impermeable Morrison Formation. Ground water within the Dakota <br /> Formation emerges in numerous springs along the rims of Summit and Bishop Canyons to the north <br /> and east of the subject site. <br /> ' Depth to ground water varies throughout the region. As previously mentioned, the static water depth of <br /> ' the nearest water well (1,200 feet west of the fuel spill area) is 25 feet below the ground surface. <br />