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• <br />DIVISION OF MINERALS AND GEOLOGY <br />Department o(Natural Resources <br />1 I I ]Sherman 51., Room 215 <br />Denver, CO 80203 <br />Phone: 1303) 866-3567 <br />FAX: (3031 832-8106 <br />October 07, 1993 <br />Gary W. Wendt <br />Peabody Western Coal Company <br />1300 South Yale Street <br />Flagstaff, Arizona 86001 <br />RE: Seneca II Mine (C-80-005) <br />Technical Revision 26 <br />Dear Mr. Wendt: <br />~ III IIIIIIIIIIIIIIII <br />STATE OF COLORADO <br />O_F'~~[~ <br />NtiL ~~ <br />IB)6 ~ <br />Roy Romer <br />Governor <br />Michael B. loop, <br />Drvision Director <br />We have received your response to our adequacy questions regarding the above mentioned <br />technical revision. The response thoroughly addressed our concerns, with a few exceptions. <br />Following aze additional questions and comments concerning the submittal. <br />1. PWCC submitted a new exhibit, Exhibit 7-2B, as we requested. The copies we received, <br />however, were not certified by a registered professional engineer or professional <br />geologist, as required by Rule 2.10.3(2). Please submit two certified copies of Exhibit <br />7-2B. ' <br />2. PWCCs response to Item 12 of our letter included a statement that PWCC believes it <br />is inappropriate to compaze water use standards to water quality data collected prior to <br />the establishment of the standazds. Although it is not appropriate to enforce standards <br />with regard to data collected prior to the establishment of the standards, it is useful to <br />evaluate trends in water quality over time, especially at those sampling stations where <br />those limits have been exceeded. An evaluation of trends can be useful in interpreting <br />whether high levels exist as a result of background conditions, or as a result of mining <br />activities. There appears to be a deficiency in the permit application package in this <br />regard, in that surface water quality trends do not appeaz to be discussed. As such, the <br />Division requests that PWCC provide a discussion and a graphical or tabular <br />presentation of: 1) TDS trends at all surface water monitoring stations, and 2) trends <br />for other parameters at each station where those parameters have exceeded established <br />standards. For example, station SW-S2-10 has exceeded standards for dissolved solids <br />and sulfate concentrations, so a discussion of trends for those parameters since October, <br />1986 would be appropriate. <br />