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Cotter Corporation Water Quality Assessment CO0036251 <br />representative regional data shall be used to perform the regression analysis. Where a <br />regression analysis is not appropriate, a site - specific method should be used. <br />Hardness data for the Dolores River near the point of discharge of the JD -7 and JD -9 Mines' WWTF <br />were insufficient to conduct a regression analysis based on the low flow. Therefore, the Division's <br />alternative approach to calculating hardness was used, which involves computing a mean hardness. <br />The mean hardness was computed to be 203 mg/1 based on sampling data from WQCD sampling <br />location 85 (Dolores River above confluence with San Miguel) located approximately 3.5 miles <br />downstream from the confluence of East Paradox Creek with the Dolores River. Hardness data as <br />ca +mg from this location were available for a period of record from October 2004 through May 2005. <br />This hardness value and the formulas contained in the TVS were used to calculate the in- stream water <br />quality standards for metals for stream segment COGULD02, with the results shown in Table A -4. <br />The standards for stream segment COGULDO3a are specified as numeric values and not TVS equations, <br />and therefore determination of the hardness values for this segment is unnecessary. <br />Appendix A (WQA V 7.0) <br />Page 10 of 23 Last Revised 06/10/10 /AO <br />