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- The Entrada Sandstone (possible aquifer but no known springs) makes a narrow outcrop band, 110 -120 <br />ft thick, southwest and subparallel to the Salt Wash and Summerville outcrops. It is locally underlain by <br />the very thin (10 ft) siltstones and mudstones of the Carmel Formation. <br />- Sandstones of the Navaio Sandstone (possible aquifer within the region) forms a 3,000 foot wide bench <br />below (south of) the mine site at a distance of 2,000 to 5,000 feet away. This bench slopes to the <br />northeast (toward) the mine and is about 7,000 feet long. It then narrows to an outcrop band of about <br />600 -800 feet wide as it continues to the northwest and southeast along the limb of the Gypsum Valley <br />anticline. There are no known springs along the outcrop near the mine. The Navajo and the formations <br />beneath it are broken locally within two miles of the mine by faults that parallel the axis of the Gypsum <br />Valley anticline. These faults generally displace slices of rock downward toward the valley and are the <br />result of removal of salt from the core of the anticline. The Navajo is about 400 feet thick here. <br />- Sandstones of the Kaventa Formation underlie the Navajo and form a narrow outcrop band. It is a <br />possible aquifer, but no known springs occur in the area. It is 200 feet thick in this area. <br />- Wingate Sandstone forms broken cliffs beneath the Kayenta, all more than 5,000 feet south of the <br />mine site. It is also a possible aquifer in the region, but no known springs occur near the mine. The <br />Wingate is more than 200 feet thick most places. <br />- The Chinle Formation is predominately mudstone, but contains some sandstone beds. No water is <br />known to occur in the Chinle in the area of the mine where the unit is 500 -600 feet thick. <br />-The Moenkopi Formation is not exposed along the walls of Big Gypsum Valley. However, it likely exists <br />beneath Monogram Mesa where it would be over 1,700 feet deep at the mine site. It is predominately <br />siltstone and mudstone, but does contain some sandstone beds. <br />- The Cutler Formation underlies the Chinle in the outcrops on the north side of Big Gypsum Valley. Only <br />small exposures occur more than a mile south of the mine. It contains sandstone and conglomerate <br />beds and some mudstone inter -beds. The sandstones could be aquifers, but no water is known to occur <br />near the area of the mine. The thickness is unknown near the mine due to only the upper part being <br />exposed, but it could be as much as 3,000 feet thick beneath Monogram Mesa. <br />- The Cutler overlies the Paradox Member of the Hermosa Formation which is exposed along the lower <br />slope and floor of Big Gypsum Valley. It consists of an upper limestone unit with interbedded shales and <br />minor sandstone beds that overlie thousands of feet of shale and evaporates. <br />- The floor of Big Gypsum Valley is contains alluvium with islands of Hermosa protruding through. <br />9. Groundwater Quality Data <br />Due to the absence of groundwater in the sandstone horizon of the mine, there is no water quality <br />information to report for the Salt Wash Member of the Morrison Formation. The only groundwater <br />expected to be encountered within two miles down - gradient of the mine is in the Burro Canyon <br />Formation, which is stratigraphically 350 -400 feet above the dry mine, separated by the Brushy Basin <br />6 <br />