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2. Runoff from surface disturbance. <br />1. As discussed in Section ILA. of this document, the operator previously submitted a report <br />to the Colorado Department of Health (CDOH) addressing the feasibility of treatment <br />approaches to reduce salt contribution to the Colorado River. Based on review of the <br />report, CDOH determined that no action was required of the operator to reduce salt <br />contributions to the river and the operator has been exempted from specific numeric <br />limitations or construction of new treatment facilities. Quarterly total dissolved solids <br />monitoring is still required. <br />Mine discharge from the Roadside Mines were estimated to increase soluble salts in the <br />river by 0.1 percent and dissolved iron by 0.2 percent (November 4, 1982 DMG Findings <br />Document). These predictions have proven to be accurate to date. <br />In its 1982 Findings, the Division also predicted that water quality effects would be <br />"minimal and will not significantly decrease water quality in the Colorado River." Surface <br />and groundwater monitoring to date have supported these projections. <br />Water monitoring conducted by the operator since 1982 has not identified any <br />unanticipated effects on river water quality. Mine water discharges from approved CDPS <br />points will continue to be analyzed annually for the list of parameters in Table 18 -2 of the <br />permit. <br />2. Surface water runoff from disturbed areas on the mine site passes through sediment ponds, <br />with the exception of the small areas discussed in Section C.II. A.of this document. <br />Discharges from these ponds have historically met effluent limits in the mines' CDPS <br />permit except for discharges related to severe storm events. Effects on water quality due to <br />disturbed -area runoff have been and should continue to be insignificant. <br />Groundwater <br />Groundwater Quality <br />Four hydrologic units have been identified as aquifers that may be effected by the mining <br />operation. These are: Colorado River alluvium, strata overlying the Cameo coal seams, Cameo <br />coal seams, and the Rollins sandstone unit. Each of these will be addressed below as to the <br />mines' probable hydrologic impact. <br />Colorado River Alluvium <br />The Colorado River alluvium consists of silty sand intermixed with gravel along the canyon and <br />mine facility site. The alluvium varies between 0 and 60 feet in thickness and has a hydraulic <br />conductivity of 0.01 cm The main concern with the alluvial aquifer is the total dissolved salt <br />(TDS) content that mining contributes to the stream flow. The diminished quality of water <br />discharged from the mine due to salt and sediment loading is improved somewhat by allowing <br />the water to settle out the solids. The discharged mine water is given sufficient time to allow <br />gravity to settle the solids before discharge occurs to the Colorado River. Three NPDES points <br />discharged the mine water during active operations (Nos. 001, 002 and 004) and were subject to <br />Permit Revision No. 5 31 July 10, 2012 <br />