GENERAL33578 - Laserfiche WebLink

Home Browse Search

potential that surface water itnpacted by mining operations at the Eastside could impact the quantity and/or quality of water within the Colorado River alluvium. This potential impact is further addressed later in this section. No springs or seeps were located within the life-of-mine permit boundary. A perennial seep exists along the base of the Grass Valley Reservoir. The seep has an average flow of 5 gpm. Seeps along the base of the reservoir create the perennial flow in the Harvey Gap Drainage during period when no water is released from the reservoir for irrigation. The applicant completed two wells into the coals seams overlying the E Seam within the permit boundary. This in-seam water is typified as high in total dissolved solids (TDS), conductivity, and sulfate. The sodium adsorption ratio (SAR) is relatively low. The yields from these wells range from .023 gpm to .6 gpm. The applicant has also sampled water seeping into the gortal azea of the established mine. The quality of this water is more typical of fresh water and has little resemblance to the quality of water found in the wells of the overlying coal seams. The applicant communicated that the seep appears to be emanating from the burn zone overlying the uppermost entry. The source of the water is most probably recharge from snowmelt and runoff. The seep has an average yield of 2 gpm. The Probable Hydrologic Consequences section of the original Eastside Mine Findings Document described in detail the hydrologic and geologic environment at the mine, and is hereby incorporated into this document. Due to the extensive periods of inactivity, very little mine development has taken place at Eastside. For the same reason, there has been little or no hydrologic impact during the first two permit terms. Since all disturbed-area runoff as well as mine flow from the Eastside site is routed into a sediment pond, and since there have been no discharges from this pond, there have cleazly been no impacts of the operation on surface water quality. The worst-case predictions of the original Eastside Probable Hydrologic Consequences section would involve maximum sediment pond discharge during the low flow of Harvey Gap drainage, and would result in an increase in total dissolved solids from 775 mg/l to 1054 mg/l (calculations in original fmdings document). This impact would not affect irrigation, since the flow in Harvey Gap drainage would be less than 1 cfs during the low-flow season (non-imgation season, October through early April). Containment of the runoff from the 12 acres of disturbed area at Eastside will have negligible quantitative effect on the flows in Harvey Gap drainage. The Probable Hydrologic Consequences section of the original findings document also predicted negligible ground water impacts, and this assessment is still valid. Seepage of water into the workings has remained at less than 2 gpm. There have clearly been no detectable hydrologic impacts, based on study of Annual Hydrologic Reports submitted by Eastside Coal Company from 1984 through 1994. 13