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<br />-z~- <br />Since the coal seam aquifer subcrops beneath Pete Canyon and the Middle Fork <br />of the Purgatoire River, the New Elk Mine workings could be depleting water <br />from these stream/alluvial aquifer systems. The amount of water depleted <br />should be minimal, given the small subcrop areas under these stream/alluvial <br />aquifer systems. The present depletion of surface flow and alluvial ground <br />water flow is minimal, since mine inflows are discharged back to the surface <br />water system. After mining ceases, water will be depleted from the <br />stream/alluvial aquifer systems which will not be returned. This depletion <br />will persist as the mine workings fill with water. Once the mine workings <br />have filled, surface flows and alluvial ground water flows should closely <br />approximate the flows which existed before mining occurred. <br />The applicant has provided a discussion of water quality effects of mine <br />discharges upon the Purgatoire River stream/alluvial aquifer system as a <br />result of the proposed mining activities at the New Elk Mine. The water <br />discharged from the New Elk Mine is a sodium-bicarbonate type water with art <br />average pH of 8.3, and an average total dissolved solids of 806 mg/1 (Exhibit <br />6, Table 5 of the Allen application). Under low flow conditions, this <br />discharge would increase the total dissolved solids in the river by 32 mg/1 <br />(Exhibit 6, Table 8). <br />At the New Elk Mine site, several historic and existing coal refuse piles are <br />located on the alluvial floodplain of the Middle Fork of the Purgatoire <br />River. Seepage from the refuse piles enters the stream-alluvial aquifer <br />system where it can affect water quality. An analysis of leachate from the <br />New Elk Mine waste pile (Exhibit 6, Table 13) shows this water to be a <br />sodium-sulfate, bicarbonate type water with a total dissolved solids <br />concentration of 2599 mg/l, and a pH of 8.0. Trace metal concentrations were <br />low. Under low flow conditions, seepage from 16.6 acres of waste pile would <br />increase total dissolved solids in the river by approximately 16 mg/1. In <br />combination with discharge from the Allen underground workings, this results <br />in a total increase of 48 mg/1 at low flow. Under average or high flow <br />conditions, the increase would be less. <br />The proposed operation in the New Elk permit revision application is to <br />relocate the Middle Fork of the Purgatoire River northward to allow for siting <br />of a preparation plant facility. This plan calls for the redisturbance of old <br />waste piles for construction of these facilities. With the acceptance of <br />Stipulation No. 4, the operator will be constructing the new channel and <br />refilling the old channel in a manner which will minimize disturbance to the <br />hydrologic balance. With the placement of an underdrain beneath the old <br />channel fill, levels of total dissolved solids being leached from the waste <br />should not increase above those levels already predicted. An increase in <br />total suspended solids is likely to occur during relocation of the channel. <br />The temporary diversion of the Middle Fork of the Purgatoire River will occur <br />during the historic low flow season and will be designed with sediment control <br />measures. Even so, some elevation in levels of suspended solids is expected <br />to occur. This increase would be short term extending through the <br />construction period only. <br />The relocated stream channel will be lined with riprap designed to withstand <br />erosive velocities of the 100 year 24 hour storm event. This channel lining <br />will mitigate the undesirable impacts to the hydrologic balance cause by <br />meandering of the stream through coal refuse. <br />