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<br />" <br /> <br />NPDFS Permit No. CO-0042161 <br />Salinity Control Study <br /> <br />TwentymiIe Coal Company <br /> <br />..... <br />...... <br />...... <br />""l <br /> <br />1.0 'Introduction <br /> <br />This Salinity Control Study was prepared to comply with the Regulations for Implementation <br />of the !Colorado River Salinity Standards through the NPDES Permit Program. These <br />regulati9ns require that treatment options be examined if a permit holder's discharge of salts <br />(total dl~solved salts or IDS) into a tributary of the Colorado River exceeds 1 ton/day or <br />350 to~ per year. This assessment is required under Twentymile Coal Company's (TCC) <br />current National Pollution Discharge Elimination System (NPDES) Permit C0.;()()42161. <br /> <br />Permit C0.;()()42161 covers discharge from outfall 001 into Fish Creek from the Fish Creek <br />Borehole at Twentymile Coal Company's (TCC) Foidel Creek Mine. The Foidel Creek Mine <br />is locatlld approximately 25 miles southwest of Steamboat Springs, Colorado as, shown on <br />Figure t. The locations of hydrologic monitoring and discharge points are shown on Map I, <br />and scheinatlcally in Figure 2. <br /> <br />Beginning in 1989 some mine water from underground operations was discharged into Fish <br />Creek through Outfall 001. The water is pumped from a mine dewatering system (the Fish <br />Creek BOrehole), and passes through a three-cell sedimentation pond prior to discharge at <br />Outfall ~l. Pumped water passes through a chemical mixing station for injection' of <br />coagulan(s, if needed, before entering the pond. <br /> <br />The impacts of this mine discharges on salt loading, salt concentrations, and streamflows <br />, <br />downstr~ of the discharge outfall are evaluated from flow rates and IDS concentrations of <br />the dischtrge and of Fish Creek in the vicinity of the discharge pOint. Records of flow rates <br />and IDS; concentrations at the discharge pOint were obtained from the discharge monitoring <br />reports ~uired by the NPDES discharge permit. Records of streamflow' and IDS <br />concentra~ions in Fish Creek have been maintained for hydrologic monitoring stations 16 and <br />1002 located above and below the discharge point. <br /> <br />Fish Cree~ is a perennial stream which exhibits typical seasonal variability, with rapid rise and <br />fall of flo~ rates during spring runoff, Plots of mean monthly flows from gauging stations <br />upstream j1nddownstream of the discharge point are provided in Figures 2 and 3, respectively. <br />The flow ~ecord for monitoring Station 16, located upstream of the discharge point, started in <br />March of a987. The flow record for downstream station 1002 started in May of 1979. Flows <br />are measured continuously at these stations. Mean monthly flows at the upstream and <br />downstreajn stations are similar; the influence of discharge from the Fish Creek Borehole, <br />(which be~an in 1989) is very small relative to all but the seasonal low flow. Plots of field <br />conductivity (specific conductance) are provided in Figures 5 and 6 for upstream and <br />downstrealn monitoring stations. Measured specific condllct!lnce is also quite similar at the two <br />stations, 4cept for one high value of specific conductance during low flow in the latter part of <br />1993. <br /> <br />AHA F'dename: J4SALCN1.DOC <br /> <br />Page 1 <br /> <br />11:59 AM 09n9/95 <br /> <br />