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Drawdown in [he Wadge overburden unit during mining could also result in induced recharge directly from Foidel Creek. Induced recharge would be expected to show up with the onset of mining beneath the Foidel Creek Valley. • Stream depletions would be more than offset by mine discharge. After completion of mining, induced recharge would decline back [o premining conditions as potentiometric conditions equilibrate. if induced recharge from Foidel Creek or its alluvium was to occur, a response should have been observed with the onset of mining under the Foidel Creek Valley in 1984. Alluvial wells S-5 and S-6, completed near the mining operations beneath the Foidel Creek Valley, have shown no response because of initiation of mining beneath the valley. Average inflow during the first year of mining beneath Foidel Creek was 83.2 gpm. Induced recharge from Foidel Creek is a relatively small fraction of this total. Underground mining could also affect streamflow conditions in Fish Creek by changing ground water discharge to the stream or by induced recharge directly from the stream. The baseline hydrologic analysis indicates that very little groundwater discharges to Fish Creek from the deeper unit units along the reach where the Wadge overburden unit would be affected by underground mining. Thus, it does not appear that groundwater discharge from these units to Fish Creek will be affected. Mining related subsidence may result in minor shifts in recharge/storage/discharge relationships between Fish Creek and the associated alluvium. Relative elevations between alluvial deposits and base or high Flow levels may change, and location and extent of streamside alluvial deposits may be altered as minor changes in stream alignment along with accompanying erosion and deposition occur. These changes will occur along a very short segment of Fish Creek. This is located in the area above and immediately downstream of the 1" left panel. Both magnitude and significance of change will be limited by the small areal extent of alluvial deposits and the natural response of the dynamic stream system over time. Induced recharge is not likely to occur because of the aquitards located between the Wadge Coal and Fish Creek. The placement of underground mine waste in the adjacent surface mine pit is an activity that has the potential to affect surface water Flows or water quality characteristics. The placement of wastes in the pit decreases the storage • capacity. While this may result in less attenuation of pit overflows, the overall water yield due to displacement of fluids by solids is a temporary phenomena and relatively small when compared to surface runoff contributions to the pit. About 5 ft' of water will be produced for every yard of waste placed in the pit, provided the pit is at the overflow level. The estimated volume of waste rock disposed in the pit for the 32-year mine life is 231.000 CY. This would equate to a displacement of discharge of about 0.001 cfs. It is possible that, as the pit is partially filled, pit water evaporation could decrease and, therefore, discharge may increase slightly. Total salt load would remain unchanged, and any increase in Flow would be associated with a proportional decrease in dissolved solids. The leaching characteristics of the waste rock indicate that it will produce lower concentrations of soluble salts and trace metals than the backfill in which it is being placed. Therefore, we do not anticipate any incremental adverse water quality deterioration due to this activity, other than perhaps a slight shift in ionic composition of water discharged. The ionic composition of leach water from waste rock differs slightly from the ionic composition of backfill spoil water. The ]each tests suggest higher levels of sodium and lower levels of calcium in waste rock leachates than in backfill spoils. Thus, we could expect a slight shift in the chemical composition of discharge from the Area 2 pit. SAR values could increase slightly as a consequence, but the magnitude of increase should be slight and would depend upon the degree of cation exchange within the waste rock placed in the Area 2 pit. The inflow to the 6 Right Gateroad area began in the November and December of 1997. A comparison of the inflow rates to streamflow data (Exhibit 51, Figure E51-I) does not indicate any impact to the stream flow from the increased mine inflows. The stream flows before and after the inflows began are very similar and both the mine inflows and the stream inflows appear to be responding to seasonal variations in recharge and runoff. A comparison of the surface water quality of the 6 Right inflow to that of Foidel Creek water (Site 8) and to spoil water (Well 26-SP-2) is inconclusive (Exhibit 51, Table E51-I). The 6 Right water and the spoil water have similar conductivity, dissolved solids and bicarbonate concentrations. While the 6 Right water is similar to the .spoil water, it has an elevated sodium concentration. This may be due to ion exchange (see Exhibit 38 and APPROVED dUN 2 R 2000 PR 99-OS 2.05-160 03/28/00