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CO-0000906 <br />New Elk Mine Water Quality Assessment <br />• Figure A-2: Relative Rate of Water Infiltration as Affected by ECW and SAR with <br />Modification to Show Upper Limit for SAR = 9 <br />20 <br />IV <br />16 <br />o! <br />Q <br />1c <br />0 c? <br />c <br />0 <br />n. <br />L <br />0 <br />E <br />0 <br />l0 <br />v J <br />Electrical Conductivity (ECW) of Irrigation Water <br />• <br />Because SAR is a ratio, the Division acknowledges that additions to the effluent in the form of <br />calcium can allow for significant and toxic amounts of sodium to be discharged while the SAR ratio <br />is still met. To prevent this from occurring, Division procedures are to determine sodium limits <br />using the SAR standard and the existing quality for calcium and magnesium. <br />First, the Division must determine the maximum sodium in-stream that may be discharged. Because <br />of the inverse relationship between Na+ and the combination of Ca ++ and Mg++ in the SAR equation, <br />the existing quality for calcium and magnesium has been determined to equal the 15th percentile. <br />Using the ambient water quality data in Table A-5, the calcium and magnesium existing quality were <br />determined as follows: <br />Ca++ = 33 mg/l - 20.0 mg/meq = 1.7 meq/1 <br />Mg++ = 8.2 mg/l - 12.15 mg/meq = 0.67 meq/1 <br />Appendix A (WA version s-a(FABL)) Page 21 of 29 Last Revised August 26, 2008 <br />0 2 3 4 J