2010-12-17_REVISION - C1981019 (140)

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Model development DRAFT 12 6 Bedrock hydrogeo/ogic units Nine bedrock hydrogeologic units are included in the regional model with the base of the model set as the bottom of the Trout Creek Sandstone member. The bedrock hydrogeological units included in the model, and selected structural contour surfaces and isopach (thickness) maps are as follows: • Bedrock units above D12 coal and below land surface or valley fil•! deposits in stream valleys; • D12 and E2 coals (D12 and E2 isopach, Figure 3.2); • Bedrock units between top of Fa coal to bottom of E2 coal; • F/G sequence (bottom of Gc coal to top of Fa coal) (F/G isopach, Figure 3.3); • Bedrock units between top of I sequence and bottom of Gc coal; • Bedrock units between top of KM and top of I sequence; • KM (KM isopach, Figure 3.4); • Bedrock units between top of Trout Creek Sandstone and bottom of KM; and • Trout Creek Sandstone (bottom of Trout Creek Sandstone structure contours, Figure 3.5) (Trout Creek Sandstone isopach, Figure 3.6). The land surface elevation (Figure 3.7) forms the top of the active model. The nine bedrock hydrogeological units from land surface down to the Trout Creek Sandstone are represented by 14 model layers as shown in Figure 3.8 and described below: • Layer 3 - top of D12 coal to top of bed rock units; • Layer 4 - mid distance between bottom of E2 coal and top of D12 coal to top of D12 coal; • Layer 5 - bottom of E2 coal to mid distance between bottom of E2 coal and top of D12 coal; • Layer 6 - mid distance between top of Fab coal and bottom of E2 coal to bottom of E2 coal; • Layer 7 - top of Fab coal to mid distance between top of Fab coal and bottom of E2 coal; • Layer 8 - mid distance between bottom of Gc coal and top of Fab coal to top of Fab coal; 2572-R3 Colowyo Coal Company, L.P. Water Management Consultants