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<br />, <br /> <br />" <br /> <br />...... <br />I-~ <br />tv <br />OJ <br /> <br />NPDE$ Permit No. CO-0042161 <br />SalinitY Control Study <br /> <br />TwentymiIe Coal Company <br /> <br />Monthly Ave. Cone. (mg/I) = <br /> <br />Ot' x Ct, + OIlS..x.QIIS <br />{Q16 + QIlS (cfs) } * 0.0026915 <br /> <br />where Q is the flow at stations 16 and 115 (upstream and discharge) and C the concentration at <br />each lociltion. <br /> <br />Baseline, conditions in Table 2 are used in Section 4 to evaluate reductions of the various <br />options in monthly salt loading, IDS concentrations, and streamflows downstream of discharge' <br />point. 'J'!hese options are described in Section 3, <br /> <br />Monthly- averages for flow, salt load, and IDS concentrations for Station 302, during the <br />baseline period (April, 1990 through September, 1994) can be compared with estimated vaJ.ues <br />in Table ;2. Station 302 is several miles downstream of the discharge outfall. The molllhIy <br />average ros concentration at Station 302 is usually lower than the calculated concentratiOns, <br />but onlypbout half of the monthly streamflows and monthly salt loads at Station 302 are higher <br />than estitltated. This suggests that both inflows (of lower IDS groundwater) and seepage loss <br />may be dccurring between the discharge outfall and Station 302 to accOunt for the apparent <br />reduction; in IDS and the intermittent reduction in streamflows and salt loads downstream of <br />the dischljrge outfall. <br /> <br />~ <br /> <br />AHA F'aIeoame: 14SALCNl.DOC <br /> <br />Page 11 <br /> <br />IU9AM 09n9/9S <br /> <br />i} :,1 <br />;:liJ <br />