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March, and 1179 umhos in July, indicating accurate calibration of the Nucla conductivity <br />meter (4.5-5.4 percent error). <br />The pH meter used to measure field-determined pH values at the Nucla Mine and Nucla East <br />mining area is calibrated by performing two-point calibrations prior to each daily round <br />of monitoring activities and one-point calibrations prior to each measurement using buffer <br />solutions of known pH values obtained from outside laboratories. Three buffer solutions <br />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 Nuc la and Nucla East Mines range between 7 and 9 pH units. <br />However, the lower buffer solution (pH 4) is used for two point calibrations prior to <br />measuring water historically known to exhibit pH values less than 7 pH units. One-point <br />calibrations involve using the pH 7 buffer solution. <br />Table 3 presents the current parameter list for surface water sample analysis at the Nucla <br />Mine. This revised surface water parameter list also applies to analyses performed on <br />samples obtained at all Nucla East surface water monitoring sites. <br />Baseline Monitoring Program - Nucla East. Surface water monitoring activities conducted <br />since July of 1986 at monitoring sites established in and around Peabody's proposed Nucla <br />East mining area have been consistent with the approved baseline monitoring program (see <br />Appendix 15-1, revised Nucla PAP). This program was proposed and outlined in a letter <br />submitted to Mr. Steve Renner from Peabody personnel on April 21, 1986. Approval of the <br />baseline monitoring program for the Nucla East mining areas was issued, with minor <br />amendments, in a letter received by Peabody from Mr, Peter O'Connor of CMLRD on May 6, <br />1986. The locations of each surface water monitoring site in the Nucla East area can be <br />found on Exhibit 1 of the 1988 Nucla AHR. Table 4 lists each Nucla East surface water <br />monitoring site, location and type of flow measurement performed. <br />Data Summary. Surface water data (including NPDES monitoring data) collected at both the <br />Nucla Nine and Nucla East mining area during the 1989 water year are presented in <br />Appendices A through E. Discharge measurements, rating tables, NPDES discharge monitoring <br />reports (DMR's), and water quality reports comprise monitoring information collected <br />exclusively during the 1969 water year. <br />8 <br />