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• Inflow Study. Statistical summaries of the historical data base are provided after presentation of the 2002 data. Statistical summaries of water levels or flows are presented as well. Figure 135 provides the location of Foidel Creek, in relation to panels 12 right (12 Rt), and 9 Rt through 6 Rt. Figure 136 provides the Middle Creek profile over panels 2 Rt through 6 Rt. Figure 137 provides the Fish Creek Profile over panels 13 Rt and 14 Rt. 3.1 Bedrock Groundwater Monitoring Hydroeeoloev: TCC's underground mining operations aze located on the southwest flank of the Twentymile Park Basin. This is an enclosed synclinal ground water basin, rimmed by outcrops of major lithologic units. Ground water in the Twentymile Park Basin exists primarily under confined conditions within the bedrock units. All ground water aquifers in the general area, except the alluvial aquifers, are recharged by infiltration in outcrop areas, located primarily in the southern and western margins of the Twentymile Park Basin. Recharge is limited, due to low average annual precipitation and the loss of moisture through evapotranspiration and sublimation in this semi-arid climatic zone. Ground water occurrence and movement within the bedrock aquifer system is controlled by geologic structure and lithology. Ground water movement tends to follow the structural dip of the lithologic units toward [he basin axis. The general trend of movement in the permit area is to the north and northwest. This results in confined aquifer conditions down gradient from the outcrop area. A detailed discussion of the geology/hydrology for the site is available in the 7tverrtymile Coal Conapaey, Foidel CreekMhre Permit C-82-056, Volume I, Rules 2.04.6 and 2,04.7. • The Twentymile Park Basin is underlain by a lazge, high quality coal reserve. This reserve, mined by underground operations, is known as the Wadge Seam. The Wadge Seam lies within a sequence of sedimentary rocks characterized by shales, claystones, muds[ones, siltstones, sandstones, and minor coal stringers referred to as the Wadge Overburden, The Wadge Overburden is hydrologically isolated from the two major bedrock aquifer units in the Twentymile Park Basin, the Twentymile Sandstone aquifer and the Trout Creek Sandstone aquifer, which lie above and below the Wadge Overburden, respectively. Lying above the Twentymile Sandstone is a minor aquifer unit, known as the Fish Creek Sandstone. All these geologic units are monitored within the Foidel Creek Mine pernvt area. The Wadge Overburden is directly affected by the mining operation. Dewatering of this zone in the area of mine opemtions is currently being conducted. The Wadge Overburden lies approximately 1100 feet below the ground surface. The Wadge Overburden sequence varies in thickness from 50 to 100 feet, averaging approximately 75 feet, and is characterized by low permeability (0.01 to 0.1 ft/day), limited continuity, low yield and relatively poor water quality. Above the Wadge Overburden is the first major regional aquifer, known as the Twentymile Sandstone. The Twentymile Sandstone aquifer is confined above and below by low permeability shale and interbedded siltstone/shale units. The unit varies in thickness from 100 to 200 feet and is hydrologically isolated from the underlying Wadge Overburden sequence by a low permeability marine shale, which has a thickness of up to 700 • feet. Approximately 125 feet above the Twentymile Sandstone is the 35-foot thick Fish Creek Sandstone. The Fish Creek Sandstone is a discontinuous minor unit in the area that was the contact for a small coal seam that had been surface mined. 3