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-19- A worst case projected impact to surface water quality was made based upon the following scenarios. The low flow surface water condition was used to predict worst case. These low flow condition occur during periods of non-irrigation from October 15 to April 15, when the Grass Valley Reservoir outlets are closed to store water for the irrigation season. Base flow occurs due to seepage through the reservoir embankment. Base flow is 0.5 cfs at an average TDS of 755 mg/1. This base flow was merged with the maximum orifice flow of the pond located at the refuse disposal site with a predicted worst case TDS value of 1910 mg/1 at a flow of 0.1 cfs. This resulted in a predicted increase in TDS to 948 mg/1. This data was merged with orifice flow from the pond at the surface facilities projected to have a worst-case chemistry of 1690 mgfl of TDS at a flow of 0.1 cfs. This resulted in an increase of TDS to 1054 mg/1 for the worst case chemistry. This condition could exist only during the non-irrigation season, so the increase is not considered significant to irrigation use of the stream water. In summary, the level of TDS rose from 755 mg/1 to 1054 mg/1., with a flow of 0.7 cfs. The alluvium along the Colorado River directly adjacent to the Harvey Gap Drainage could be negatively impacted by this increased level of TDS. During the snowmelt period, the alluvium is recharged by the surface water system. Therefore, the alluvium immediately adjacent to Harvey Gap could experience a rise in the level of TDS from early spring to April 15 (start of outflow from the Grass Valley Reservoir). A well completed in the Colorado alluvium had a TDS level of 760 mg/1. The worst-case quality projection for Harvey Gap water was 1054 mg/1. As this was an extreme projection of worst case, and would not exist for long periods of time, any degradation of water quality within the alluvium should not be significant. The worst case condition of TDS increase was also projected for the irrigation season. The lowest outflow from the Grass Valley Reservoir during this period was projected as 7 cfs (from a hydrograph submitted in the Eastside permit application). A water quality of 330 mg/1 TDS for this discharge was used. Merging this flow and concentration with outflow from the ponds of the refuse and surface facilities areas gave a rise in TDS to 352 mg/1 downstream of the mine. This rise is insignificant and would have no effect on the usability of the water. In summary, the level of salinity in the Harvey Gap surface water system was not projected to rise significantly during the critical irrigation season. The level of TDS could rise in a worst-case scenario during the non-irrigation season. The alluvium directly recharged by the Harvey Gap surface water system could experience a rise in TDS levels. However, due to the already high level of TDS in the alluvium, this rise is not projected to diminish the agricultural use of the alluvial water. The potential for diminution or degradation of bedrock groundwater in the area for mining activities at Eastside was found to be negligible. This is due to the small size of the mine, the lack of communication of the coal seam with overlying and underlying beds due to interbedded shale layers, and the lack of potential of any rock strata within the affected section to supply a quality ground water resource.