GENERAL33488 - Laserfiche WebLink

Home Browse Search

_P4_ The applicant proposes to construct a 6 acre coal refuse pile, West I refuse disposal site, at the mouth of Ciruela Canyon. Observations of the disposal site have found a spring which could come into contact with the pile resulting in a leachate that may degrade water quality. The alluvial ground water quality in Ciruela Canyon may be impacted by the proposed placement of the disposal pile. The applicant has not provided an analysis of the impacts upon the hydrology that would occur by disposing of the refuse at this site. Also, the significance of alluvial ground water flows from Ciruela Canyon to agricultural areas in Picketwire Valley has not been defined. Therefore, an assessment cannot be made and disposal of refuse at the proposed site cannot be approved. The Division has stipulated, in the original Golden Eagle Mine permit document, that baseline quality and quantity data for alluvial ground water in Ciruela Canyon be gathered as a condition of permit approval. After the cessation of mining operations, the Golden Eagle Mine water would no longer be discharged. The applicant calculates that 79 years would be required to flood the workings. The recovery of the piezometric surface of the coal aquifer would occur in two stages. The first stage would be a relatively slow increase that would occur as the mine workings are filled by ground water inflows. Once the underground workings have been filled, the piezometric surface would rapidly rise toward its eventual steady state position. A permanent depression in the piezometric surface would exist in the vicinity of the flooded mine workings. The magnitude of the depression would not be large, but it may extend to a distance of 2 to 3 miles from the edge of the mine workings. Because the underground workings lie 400 to 500 feet below the portal areas, the piezometric surface of the mine water would not be expected to rise to a level where it would intersect the ground surface, thus discharging through the mine portals or shafts. There would be approximately twice as much ground water flow through the flooded mine workings than existed through the undisturbed coal prior to mining. The ground water flow would, however, be restricted by the undisturbed coal. The ground water would stagnate and react with fragmented roof, floor, coal, rock dust, and other materials within the one cavity. Oue to stagnation in the mine workings, water quality would be of lower quality than that currently pumped from the underground workings and would be similar to the quality of water measured at the New Elk Mine coal processing waste pile (Exhibit 6, Table 13). The total dissolved solids levels may equal or exceed 2600 mg/l. This mine water would spread as a plume of degraded water down the dip of the rock strata which is, in this case, downgradient. Based on the structural contours of the coal seam, water passing through the flooded workings would move in a northeasterly direction. It is anticipated that soluble materials would be readily flushed, but the low permeabilities of the effected rock strata downdip would slow the flow of water from the mine, causing the flushing action to persist over a long time period. Since the coal seam aquifer currently contains poor quality water, 806 to 1100 mg/1 total dissolved solids, and is not used as a water supply in the general area, the effects of mining on this aquifer will not materially damage the quality of ground water used off-site. Post-mining effects on the water quality in the stream/alluvial aquifer system would be expected to be less than those occurring during operations because m;,,P water would no longer be discharged from the underground workings.