2009-05-22_GENERAL DOCUMENTS - C1981044

Home Browse Search

uses included 5,478 acre-feet for industrial purposes, 2,555 acre-feet for municipal water supplies, and 8,283 acre-feet for other unspecified uses (Steele et al., 1979). Industrial consumption has since increased by a total of 18,720 acre-feet per year due to use by the Craig generating station. Irrigation Use of Surface Water. Water for agricultural irrigation is generally obtained by simple stream diversion structures and networks of ditches for flooding grasslands and meadows during summer months. The short growing season precludes growing of warm weather crops such as corn. In the Williams Fork River, an even higher proportion of the water used is for irrigation of grasslands and hay fields. Aquifer Stratigraphy. Within the general vicinity of the Eagle Mine Complex, ground water exists in both bedrock and alluvial aquifers. Significant bedrock aquifers are (listed in ascending stratigraphic order) the Trout Creek, Middle, Twentymile, and White sandstones. The Middle, Twentymile and White sandstones are in the Williams Fork Formation; the Trout Creek sandstone is the uppermost member of the underlying Iles Formation. The main alluvial aquifers in the area are associated with the Yampa and Williams Fork Rivers. The alluvial aquifers probably contribute to baseflow of the rivers during dry periods. Coal seams, discontinuous sandstones, and siltstones and smaller alluvial bodies in the area of the mine are also water- bearing, but contain insufficient quantities of water to be considered significant aquifers. Ground Water Use. The Trout Creek Sandstone, the Twentymile Sandstone, and the White Sandstone are bedrock aquifers currently being used for ground water supplies in the general vicinity of the Eagle Mine Complex. The Middle Sandstone is not currently used as a ground water supply in the vicinity. The alluvial bodies associated with the Yampa River and Williams Fork River contain limited ground water and are not considered major aquifers in the general area. Alluvial bodies along the Yampa River up- and downstream of the general area, however, are significant sources of ground water. High yield irrigation and municipal water supply wells are completed in the Yampa River alluvium in those areas. Also, the Yampa River alluvium outside the vicinity is widely used as a source of domestic and livestock watering. Within the vicinity, alluvial ground water is not a significant source of water put to beneficial use. Ground water from the coals and thin sandstones are not considered aquifers, but they flow into the underground workings and the mine uses them for cooling, dust suppression, fire protection, and other industrial uses. Ground Water Recharge, Discharge, and Flow. The sandstone aquifers in the Big Bottom Synclinal Basin are recharged at their subcrops beneath the stream/alluvial systems of the Yampa and Williams Fork Rivers, and at their outcrops in upland areas. From a recharge area, flow would be generally northward, downdip toward the axis of the Big Bottom syncline. Faults may provide conduits of flow for ground water wherever a fault is not sealed with fine-grained gouge material. Ground Water Hydraulics The sandstone aquifers are under atmospheric pressure (water table conditions) near their recharge areas and under hydrostatic pressure (artesian conditions) within the structural basins or at discharge points. Hydrostatic pressures in the sandstone aquifers increase with depth and are at a maximum in the axial areas of the Big and Round Bottom Synclines. Artesian conditions are developed in aquifers which are confined by overlying and underlying strata with low permeabilities. Several of the wells drilled into the bedrock aquifers Eagle Mine Complex 7 Permit Renewal 05 C-1981-044 May 22, 2009