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The original Findings Document for the Coal Ridge No. 1 Mine detailed the potential cumulative impact of the two operations for the worst-case, life-of-mine situation. That document may be consulted for details of the regional and local hydrologic conditions for the Coal Ridge No. 1 and Eastside Mines. Since the permit for Coal Ridge No. 1 is being renewed allowing only reclamation, potential impacts will now be considerably less than previously predicted. Both the Eastside and Coal Ridge No. 1 underground mines are located along the Grand Hogback, and both are in proximity to the Colorado River. The permit areas of the mines are approximately 7 miles apart along the strike of the Grand Hogback, and are shown in Figure 1. The Eastside Mine is permitted to mine coal from the E seam of the Iles Formation, which is stratigraphically below the Wheeler Seam and is separated from it by about 200 feet of interbedded sediments. Inflows to the Eastside workings are from the E seam, and flow is less than 2 GPM. There is no inflow from the roof or floor rock. Only very minor, unmeasurable inflow has occurred into the tunnels at Coal Ridge No. 1, and no further tunnel development is to occur. Due to poor continuity and hydraulic conductivities of potential aquifers in the Mesaverde Group, to the steep dips of the rocks in the Grand Hogback at both sites, and to the considerable distance between the mines, cumulative effects of the two operations on ground water quantity or quality in bedrock aquifers are extremely unlikely. The Coal Ridge No. 1 mine surface facilities are located on alluvial and colluvial terraces adjacent to the Colorado River, while the Eastside Mine is located in Harvey Gap, on a tributary to the Colorado. There is abundant use of shallow ground water from the alluvium of the Colorado and its tributaries, raising the possibility of cumulative impacts from the two mines on alluvial water and also the surface water of the Colorado. At Eastside pumped mine water is routed into the sediment pond, and is all disturbed-area runoff. Since no discharge of water from the Eastside sediment pond into Harvey Gap drainage has occurred, there has been no impact by the operation on alluvial ground water quality. Similarly, the Coal Ridge No. 1 sediment control structures will be left inplace until revegetation standards have been met. Assuming proper maintenance of surface water control structures at both operations, no cumulative impacts on alluvial groundwater quality are expected. Worst-case predictions of surface water quality impacts from the Eastside Mine involved an increase in dissolved solids in Harvey Gap drainage from 755 mg/1 to 1054 mg/1. This could occur only during the low-flow, non-irrigation season, with maximum possible discharge from the sediment pond at Eastside occurring (see original Coal Ridge No. 1 CHIS document). Such conditions are unlike~y to occur, The Eastside sediment pond has in fact never discharged up to this time, even during periods of active mining, -9-