Laserfiche WebLink
<br /> <br />Seepage from the refuse piles located in the alluvial flood plain, <br />however, does enter the stream-alluvial aquifer system where it can <br />affect water quality. An analysis of leach ate from the estimated <br />16.6 acres of this refuse shows the water to be a sodium <br />sulfate-bicarbonate type with a total dissolved solids concentration of <br />2599 mg/1 and a pH of 8.0 (Exhibit 6, Table 13), Trace metal <br />concentrations are low. <br />A water balance study was conducted for the New Elk Mine development <br />waste pile site and is contained in Exhibit 6 of the New Elk permit <br />application. In this study, the applicant has calculated the average <br />annual precipitation at the New Elk Mine to be 16,92 inches. Sublimation <br />of snow during winter, and evaporative losses were calculated to be <br />3.77 inches. During a normal year, runoff from the refuse piles is <br />calculated to account for all of the remaining available precipitation. <br />Based on the calculations included in the application, deep percolation <br />in most years will be essentially zero; that is, all precipitation will <br />evaporate or runoff from the soil. During wet years, as much as <br />.72 inches of water may be attributed to subsurface runoff (See <br />Exhiibit 6, pages 44-50 of the permit application). <br />Int'iltration of this runoff, based on an estimated 16.6 acres of refuse <br />being present, suggests that a mean flow of 0.001 cfs could issue from <br />the pile. Amass balance calculation using a Q7-10 low flow value of <br />l.E. cfs for the Middle Purgatoire and a total TDS value of 204 indicates <br />TDS values in the river would only increase about 2,0 mg/1 as a result of <br />this seepage. Calculation of SAR values for the Middle Purgatoire once <br />thus seepage is included also show no appreciable increase. Use of the <br />wager for either drinking or irrigation purposes is therefore, not likely <br />to be affected. <br />Since the cessation of mining operations, mine water from the New Elk <br />Mine is no longer being discharged, and the abandoned workings should <br />fill with water, a process taking up to 80 years. The piezometric <br />surface would partially recover, Because the underground workings lie <br />400 to 800 feet below the surface, the piezometric surface of the coal <br />aquifer would not be expected to rise to a level where it would intersect <br />the ground surface and thus cause discharge. A permanent depression in <br />the piezometric surface would exist in the vicinity of the flooded mine <br />workings. Given the assumption that the Allen seam is hydrologically <br />similar to the Maxwell seam, the depression may extend to a distance of <br />2 to 3 miles from the edge of the mine workings. <br />When pumping of water from the workings is discontinued, the water that <br />accu milates is expected to be of lower quality than that currently pumped <br />due to increased residence time (Exhibit 6, Table 5), The quality of the <br />stagnant mine water should be similar to the quality measured below the <br />New Elk waste piles (Exhibit 6, Table 13). Total dissolved solids may be <br />equal to or exceed 2600 mg/1. This mine water would spread as a plume of <br />degraded quality ground water down gradient from the mine. Based on the <br />structural contours of the coal seam, water passing through the flooded <br />workings would move in a northeasterly direction. <br />_P1_ <br />