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1.0 INTRODOCTION <br />This re ort <br />p presents the ground-water and surface-water <br />monitoring results for Trapper Mine for 1993. Significant mine <br />activities during 1993 include the closure of the B and C pit areas, <br />the opening of Hawken (H) pit (G coal seam) in late August, the <br />expansion of A pit in the East Pyeatt area, the start-up of a second <br />operational ash disposal site in A pit (Middle Pyeatt drainage area), <br />and a decrease in dewatering well pumpage in D pit. An additional <br />NPDES site was installed in October, 1993 (015, Grouse Gulch). <br />Ground-water monitoring of the aquifers associated with Trapper <br />Mine started in 1974. The ground-water flow regime has been divided <br />into the major sandstones and coal/adjacent sandstone aquifers. This <br />division of the aquifer systems was selected at clay and shale units <br />which have the potential to retard vertical movement. A blue pull- <br />, out index presents the schematic of the aquifer units at Trapper on <br />one side and the basic well data table on the other. It is suggested <br />moving this index sheet to the section of the report being reviewed. <br />Aquifer properties are presented in Table 2-1 of the 1990 Annual <br />Hydrologic Report. <br />The Twenty Mile Sandstone is the lower-most aquifer monitored at <br />Trapper Mine. The 0 coal seam and adjacent sandstones are the second <br />aquifer monitored. The Q and R coal seams and sandstone between <br />these two coal seams have been labeled the QR aquifer. This is one <br />of the major aquifers of interest because D, E, and C pits mine the <br />Q and R coal seams. The K, L, and M coal seams and the sandstones <br />which are stratigraphically in this interval are called the KLM <br />aquifer. The KLM aquifer is above the QR aquifer, but below the HI <br />aquifer. The H and I coal seams and sandstone between these two <br />1-1 <br />