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~~-'~`~'' IIIIIIIIIIIIIIIIIII <br />RESPONSES TO CDMG LETTER DATED MARCH 8, 1994 <br />1. a. The Probable Hydrologic Consequences prediction utilizes only the surface water data collected <br />at the mine. As such, all data collected between April and October since 1981, exc~:pt for 1984 <br />and 1985 have been included in Appendix 2.5-A. Water quality data from 1984-1985 was not <br />included because flow data was not available at TR-a for those years as a result of the flooding <br />that occurred during 1984 which destroyed the gaging site. <br />b. Conductivity values were not used in the analysis and therefore are not presented. However, <br />all conductivity values presented in the 1993 Annual Hydrology Report (submitted 1994) do <br />reflect temperature corrected values. A further discussion of ground water conductivity values <br />is provided on revised page 4.6-141, Section 4.6.8.2. <br />All TDS values obtained for surface water were analytically derived. Thus, TDS values used <br />in the PHC analysis in Appendix 2.5-A are analytically derived values. However, some <br />ground water TDS values were mathematically derived. A discussion of those values is <br />provided on revised pages 4.6-141 and 4.6-142, Section 4.6.8.2. <br />d. Discussion of problematic flow and quality data is provided on pages 3.6-139 through 4.6- <br />142. <br />e. A reference to and explanation of Appendix 2.5-A and Appendix 2.5-B is provided on revised <br />page 2.5-105(b). <br />2. All pages have been revised to indicate a May 31, 1994 revision date. <br />3. A commitment to generate channel cross-sec[ions three times per year has been added on page 4.6- <br />140. <br />4. P&M will install an out-of-stream gage with a stilling well and continuous recorder at TR-b. A <br />commitment to this effect has been added on page 4.6-140. <br />5. P&M will institute a program to ensure data trcovery is notjeopardized by beaver activity. A <br />commitment to this effect has been added on page 4.6-140. <br />6. a All pertinent NPDES points have been added to the revised PHC provided in Appendix 2.5-A. <br />b. A discussion of the method used in the flow balance equation is provided in Appendix 2.5-A. <br />This methodology coincides with the CDMG suggestion and expands upon it to also use <br />continuous flow records from 1982 and 1983. <br />c. Observations regarding irrigation ditch usage is provided on revised page 4.6-139. <br />h(-~ ~,t::;~~ <br />JUN <br />& 1994 <br />'';vr~;c„ ~.; <br />~..~. <br />