1988-04-11_PERMIT FILE - C1981008A (9)

Home Browse Search

Structural Controls. The Nucla Mine lies in the Colorado Plateau Physiographic Province within the Canyon Lands Section (Price and Arnow, 1974). This section is an upwarped plateau containing several large folds, laccolithic mountains that rise above the plateau surface, deeply incised drainage and an intricate set of deep canyons (Lohman, 1965; lorns et al., 1965). Structural control on the shallow ground water in the area, i.e., upper Dakota sandstone and alluvium, appears to be insignificant. This is principally due to the large extent of sandstone outcrops. This allows recharge to occur along topographic highs rather than structural highs with water table conditions predominating. However, an artesian head may be developed if a lesser coal bed or sandstone aquifer is confined by impermeable strata. Piezometric surfaces in deeper formations such as the lower Dakota, Burro Canyon, Morrison and Entrada Formations whose ground water is under artesian pressure closely conforms to structural influence (Lohman, 1965). In these formations, recharge occurs along structural highs, i.e., an outcrop which corresponds to the limb of a syncline or the fractured crest of an anticline. Movement of water within these formations is down dip with faults acting as boundary conditions or conduits for flow. These artesian waters are the principal suppliers of water to areas near Grand Junction which is northwest of Peabody's Nucla mining operation. Regional Ground Water Recharge, Movement and Discharge. The principal areas of ground water recharge are in the plateaus and mountains, which receive the greater amounts of annual precipitation. Ground water movement is from areas of recharge to areas of natural discharge, which include springs, gaining reaches of springs and areas of phreatophyte growth. Ground water consumption by phreatophytes and hydrophytes in the Colorado and Utah parts of the upper Colorado Region has been estimated by Robinson (1958) to be more than 2 million acre-feet per year. Ground water occurs under both water table and artesian conditions. Water table conditions commonly exist in shallow alluvial aquifers along the larger streams, in principal recharge areas, and in the relatively flat-lying rocks that predominate certain sections of the region. Artesian conditions occur locally throughout the region but are prevalent in the bedrock aquifers of the major structural basin. Regional Ground Water Quality. In the upper Colorado Region, fresh water is generally available from shallow aquifers in most consolidated units in areas above 7,000 feet in 7-3 Revised 04/11/88