2011-08-09_REVISION - C1981019 (10)

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• • • RULE 2 PERMITS Groundwater accumulating in the pit backfill and flowing into the deeper bedrock units on the downdip side of the reclaimed pit would likely have the same characteristics as the water in the Streeter Fill well or the Streeter pond or in similar spoil springs (Williams• and Clark, 1994). Analytical data for these sampling points are summarized on Table 2.04.7 -49. The above information suggests that it is possible that a reclaimed pit aquifer (if one develops) will flow entirely into the undisturbed strata and that there will be no or limited discharge into the surficial valley fill from the reclaimed pit. Potential Surface Water Quantity Impacts As described above, Little Collom Gulch is ephemeral, and showed no evidence of surface flow during 18 months of baseline monitoring. Elimination of springs within Little Collom Gulch will therefore have no measurable effect on surface water quantity in Little Collom Gulch. There may be an effect on peak flows in the West Fork of Jubb Creek, due to the elimination of recharge to three springs adjacent to the Collom Lite pit, but this effect is not expected to be measurable or statistically significant. Once the mining has been completed and the pit has been saturated, the contributions to surface water from springs originating from infiltration into the Collom Lite pit would return to normal. Other than those directly eliminated by the pit, no springs are likely to be affected by the Little Collom X pit. Potential Surface Water Quality Impacts Potential impacts to the surface water quality from the proposed Collom Lite and Little Collom X mining operations are considered here. As described above, Little Collom Gulch is ephemeral, and showed no evidence of surface flow during 18 months of baseline monitoring. There is therefore no basis on which to determine relative changes in surface water quality for Little Collom Gulch. Potential mining impacts will be limited to the shallow valley fill groundwater regime, discussed elsewhere, rather than surface water. The West Fork of Jubb Creek is intermittent, and is only affected by a potential reduction in spring/seep source area by construction of the Collom Lite pit. Water infiltrating into reclaimed pit and spoil areas may later enter the West Fork of Jubb Creek via springs, if the elevation of the springs is below the final pit outflow elevation, and if the spring is connected to a stratigraphic interval that is exposed along the downgradient highwall of the reclaimed pit. The reclaimed pit outflow elevation is 7275 amsl, while the potentially affected springs are either located above this elevation, or have a source stratum which falls above this elevation where it intersects the highwall. Springs V10 and V32 are located above the pit outflow, at elevations 7295 and 7600, respectively (based on 25 foot contours). Spring/seep V1 is located at approximate elevation 7170, below the pit outflow, but is roughly 3200 feet from the pit disturbance boundary, not accounting for the highwall side slope. V1 is generally down -dip from the pit, and the bedrock dips at roughly 8 percent. The spring's source layer must therefore intersect the highwall approximately 256 feet (3200 x 0.08) above the spring elevation, or roughly 7426 ft amsl. This is well above the pit outflow elevation. Therefore, water in contact with the overburden fill will not impact water quality in the West Fork of Jubb Creek, and will instead discharge to groundwater, generally within Little Collom Gulch. Potential for Spoil Spring Water Discharge Impacting Downstream Areas For Collom Lite, there are two separate ground water conditions in the mining area — the saturated groundwater zone and the unconfined perched aquifers above the deeper zone. The saturated ground water conditions exist below a depth of 7150feet (based on the 2005 WMC report). Any pitwall seepage from the 7150 feet level and below is to be expected since the ground water at this depth will be coming Collom — Rule 2, Page 139 Revision Date: 8/5/11 Revision No.: PR -03