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and storage times to completely control a 10-year 24-hour precipitation event. This system will <br />collect all runoff from the mine site and should actually lower present total suspended solids <br />(TSS) contribution from this area over the life of the mine. Increased TDS levels in this water <br />from mining disturbances are expected, but are projected to be within acceptable discharge levels. <br />and will be mitigated by dilution. Regular monitoring of these flow rates and water quality will <br />give adequate control of this current water source to protect water quality in Calamity Draw. <br />The discharges from the mine enter Calamity Draw at a point about 2.5 miles above the <br />confluence of Calamity Draw and the San Miguel River. <br />The above-mentioned parks consist of recent undifferentiated aeolian silts and sands overlaying <br />the Dakota and Burro Canyon Formations. The perennial flow nature of both Tuttle and <br />Calamity Draws is largely due to the local irrigation practices. Over the years this more or less <br />constant source of water in these drainage systems has encouraged the growth of vegetation. <br />This has, resulted in. the cha.".n becVmlllg more eroslonally .Citable but more Llcl0ed. <br />Surface water monitoring practices and frequencies are described within the permit application. <br />Also see Findings Section B, Item 11 E, of this document for a summary of surface and ground <br />water monitoring practices to which WFC has committed. <br />D. 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 <br />through Quaternary aeolian and alluvial deposits. The lower Dakota and underlying Morrison <br />Formations are regional aquifers, although water from the Dakota Formation is not heavily <br />utilized due to its high salinity. The Morrison Formation water is widely used for stock and <br />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 <br />mid-1986. The well appears to have been completed in a clay lens. The alluvial water table <br />fluctuates seasonally within 5 to 10 feet of the surface with highest water levels in August and <br />lowest water levels in January. Recharge is primarily derived from irrigation return flow and <br />secondarily from flow in Calamity Draw. Transmissivity varies from 6.6 to 10.1 ft2/day. The <br />hydraulic conductivity varies from 0.4 to 0.6 ft/day. The water is characterized as a saline, hard, <br />neutral pH, calcium sulfate water with average TDS of 3291 mg/l. <br />The aquifer overlying the coals in the upper strata of the Dakota Sandstone is unconfined and <br />flows generally toward the southwest. Water levels fluctuate between 3 and 23 feet below the <br />ground surface. Highest levels (closest to the surface) of this water table occur between June and <br />August, as a result of irrigation, and lowest levels between December and March. Two wells <br />south of Calamity Draw (GW-N31 and GW-N32 on the monitoring stations map) have exhibited <br />limited water level fluctuations since their construction in mid-1986. <br />13