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are used for calibration: 1) pH 10, 2) pH 7, and 3) pH 4. The buffer solutions are <br /> replaced monthly to ensure accurate calibration of the meter. Most of the two point <br /> calibrations are performed by using the pH 7 and pH 10 buffer solutions since the pH of <br /> most waters sampled at the Nucla and Nucla East mining areas range between 7 and 9 pH <br /> units. However, the lower buffer solution (pH 4) is used for two point calibrations prior <br /> to measuring water historically known to exhibit pH values less than 7 pH units. One <br /> point calibrations involve using the pH 7 buffer solution. <br /> Appendix 15-1 presents the current parameter list for surface water quality sample <br /> analyses at the Nucla and Nucla East mining areas. As requested by CMLRD in a letter from <br /> Mr. John Doerfer submitted to Peabody on May 4, 1987, Peabody has revised the parameter <br /> list to show total recoverable analyses of metals instead of total analyses. Total <br /> recoverable analyses for the parameters listed Appendix 15-1 have been performed since <br /> March 25 of 1987. <br /> Chromium and silver levels were measured several times during the 1987 water year and the <br /> first half of 1988 at both surface and ground water monitoring sites at the Nucla and <br /> Nucla East mining areas. Analyses for total recoverable and dissolved chromium indicate <br /> that ground and surface water concentrations do not exceed the 10 ug/l laboratory <br /> detection limit used. Colorado Department of Health (CDOH) drinking water limits for <br /> chromium are 50 ug/l for both ground and surface water. Analyses for dissolved silver and <br /> total recoverable silver do not exceed the 10 ug/l and 0.1 ug/l laboratory detection <br /> limits used, respectively (see Appendix 15-3). The CDOH drinking water limit is 50 ug/l <br /> for ground water and 0.1 ug/l for Segment 5 of the San Miguel River Basin. In a phone <br /> conversation on October 28, 1987 between Ted Smith of Peabody Coal Company and Steve <br /> Renner of CMLRD, it was agreed that future analyses for either of these parameters could <br /> be dropped if there were no water quality standard exceedences for two consecutive sample <br /> periods. Therefore, Peabody is requesting a variance from further analysis of chromium <br /> and silver in ground and surface water samples at the Nucla and Nucla East mining areas. <br /> Ground Water Monitoring <br /> The ground water monitoring program will define hydrogeologic conditions and <br /> mining-related changes in ground water levels, quality, and quantity within and adjacent <br /> to the permit area through bond release. The monitor wells are completed in spoils, <br /> 15-9 Revised 08/19/88 <br />