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• Most of the two point calibrations are performed by using the PH 7 and PH 10 buffer solutions since <br />the PH of most waters sampled at the NH1 and NH2 mining areas range between 7 and 9 PH units. <br />However, the lower buffer solution (PH 4) is used for two point calibrations prior to measuring water <br />historically know to exhibit PH values less than 7 PH units. One point calibrations involve using the <br />PH 7 Buffer solutions. <br />Appendix 15-1 presents the current parameter list for surface water quality sample analyses at NH1 <br />and NH2 mining areas. As requested by CDMG in a letter from Mr, John Dcerfer submitted to <br />Peabody on May 4,1987, Peabody has revised the parameter list to show total recoverable analyses <br />of metals instead of total analyses. Total recoverable analyses for the parameters listed Appendix <br />15-1 have been perfommed since March 25 of 1987. <br />Chromium and silver levels were measured several times during the 1987 water year and the first <br />half of 1988 at both surface and ground water monitoring sites, at the NH1 and NH2 mining ares. <br />Analyses for total recoverable and dissolved chromium indicate that ground and surface water <br />concentrations do not exceed the 10 ugll laboratory detection limit used. Colorado Department of <br />• Health (CDOH) drinking water limits for chromium are 50 ug/I for both ground and surface water. <br />Analyses for dissolve silver and total recoverable silver do not exceed the 10 ug/I and 0.1 ug/I <br />laboratory detection limits used, respectively (see Appendix 153). The CDOH drinking water limit <br />is 50 ug/I for ground water and 0.1 ugA 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 Renner <br />of CMLRD, it was agreed that future analyses for either of these parameters could be dropped if <br />there were no water quality standard exceedances for two consecutive sample periods. <br />Grand Water Moni6airg <br />The ground water monitoring program, will define hydrogeologic conditions and mining-related <br />changes in ground water levels, quality, and quantity within and adjacent to the permit area through <br />bond release. The monitor wells are completed in spoils, alluvium, overburden, Dakota coal, <br />underburden, the overburden and coal, and overburdeNcoaUunderburden. The monitorwell network <br />consist of 36 monitor wells drilled and installed by Peabody and 5 more by WFC. Seventeen of the <br />wells are located at NH1 Mine and 24 are at the NH2 mining area. Table 15-3 summarizes pertinent <br />information for each of the monitoring wells. Exhibit 2.04.7-1-A shows the location of each monitor <br />• (Revised 12-31-96) 15-6 <br />