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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 Wu1er <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 azea is partially recharged by irrigation retum flow through <br />Quaternary aeolia~t 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 ft'/day. The hydraulic conductivity varies <br />from 0.4 to 0.6 fUday. The water is characterized as a saline, hard, neutral pH, calcium sulfate water <br />with average TDS of 3291 mg/1. <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 ftlday. 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/1 and averaging 3176 mg/1. 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 f]uoride exceed the <br />agricultural use standards in some wells. <br />6 <br />