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Surface water monitoring practices and frequencies are described the permit application. Also see <br /> Section B, Item Q.C., of this document for a summary of surface and ground water monitoring <br /> practices to which Western Fuels-Colorado has committed. <br /> Ground Water <br /> The New Horizon Mines lie in a ground water basin defined by the Nucla Syncline. This broad <br /> northwest trending syncline is recharged along the Uncompahgre uplift to the northeast and <br /> discharges southwest toward the major rivers flowing through the area. <br /> Near surface ground water in the Nucla area is partially recharged by irrigation return flow through <br /> Quaternary aeolian and alluvial deposits. The lower Dakota and underlying Morrison Formations are <br /> regional aquifers, although water from the Dakota Formation is not heavily utilized due to its high <br /> salinity. The Morrison Formation water is widely used for stock and domestic wells. <br /> Very little hydrologic documentation is available regarding the alluvium found along the small <br /> tributaries draining the area. Peabody drilled one well in the alluvium of Calamity Draw in mid-1986. <br /> The well appears to have been completed in a clay lens. The alluvial water table fluctuates seasonally <br /> within 5 to 10 feet of the surface with highest water levels in August and lowest water levels in <br /> January. Recharge is primarily derived from irrigation return flow and secondarily from flow in <br /> Calamity Draw. Transmissivity varies from 6.6 to 10.1 Oday. The hydraulic conductivity varies <br /> from 0.4 to 0.6 ft/day. The water is characterized as a saline, hard, neutral pH, calcium sulfate water <br /> with average TDS of 3291 mg/l. <br /> The aquifer overlying the coals in the upper strata of the Dakota Sandstone is unconfined and flows <br /> generally toward the southwest. Water levels fluctuate between 3 and 23 feet below the ground <br /> surface. Highest levels (closest to the surface) of this water table occur between June and August, <br /> as a result of irrigation, and lowest levels between December and March. Two wells south of <br /> Calamity Draw(GW-N31 and GW-N32 on the monitoring stations map)have exhibited limited water <br /> level fluctuations since their construction in mid-1986. <br /> The Upper Dakota aquifer is predominantly recharged by return flow from the West Lateral Irrigation <br /> Ditch. Some recharge is probably derived from infiltration of precipitation and subsurface ground <br /> water flow. The transmissivity of the overburden (Upper Dakota aquifer) varies from 3 to 53 ft''/day, <br /> averaging 13.3 ft'-/day. The McWhorter analysis of pit inflow conservatively estimated that the <br /> hydraulic conductivity of the overburden was 0.61 ft/day. Hydraulic conductivity calculations from <br /> field tests of the overburden showed a range of 0.39 to 1.05 ft/day, indicating moderate permeability. <br /> The water found in the overburden is characterized as very hard, saline, calcium/magnesium sulfate <br /> water with neutral pH. TDS levels vary from 1 494-1 0074 mg/1 and average 4613 mg/I. Sulfate <br /> concentrations are very high, varying from 875 mg/I to 6872 mg/l and averaging 3176 mg/l. In some <br /> of the overburden wells, sulfate, TDS, manganese and fluoride exceed recommended standards for <br /> livestock drinking water. In addition, concentrations of manganese and fluoride exceed the <br /> agricultural use standards in some wells. <br /> 6 <br />