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Dollhopf et al., (1981) recommends a 600 meter grid (1 hole/90 acres) <br />for initial characterization followed by additional drillino and <br />analyses if any parameters of concern are indicated in the initial <br />drilling. The circular zone of data extrapolation or the effective <br />drill hole radius should be 750 feet. Lastly, Sutton et al. (1981) <br />recommends sampling one site to adequately assess overburden variability <br />on small permit areas of less than a0 acres. <br />Seven core holes have been sampled over about 185 acres at tJucla ~~1ine <br />from 1976 through 1980. One of these holes (2C) was located o-rithin 300 <br />feet of Mine Areas 2 and 3. The sampling density of 1 hole/25 acres <br />meets the hole intensity criteria discussed above to adequately describe <br />the GIU variability. Drill hole descriptions and textural analysis <br />(Tables 6-6 and 6-7) indicate that there is little lateral variability <br />in the local depositional environn;ent. <br />Based upon the low variability, Peabody drilled and sampled one OIU core <br />hole in the 105 acre (actual disturbance area is 35 acres) study area <br />which encompasses Mine Areas 2 and 3. In addition, three OI cutting <br />holes were drilled and sampled fur Hine Areas 2 and 3 to accurately <br />delineate areas of acidic and/or saline overburden and interburden. <br />Sample Contamination. ~`lumerous overburden sample contamination problems <br />have been documented over the last 1C years in the western United <br />States. Drilling fluids, foam additives and nwds can appreciably affect <br />the soluble constituents (especially EC, SAR and NH4) in the sample. <br />During rotary drilling for cores or cuttings, it is necessary to use a <br />drilling medium such as air, water or rnud for lifting cuttings from the <br />borehole. For overburden baseline studies, it is recommended that air <br />be used whenever possible, water second and mud (or foam) avoided unless <br />absolutely necessary to overcome circulation problems or to lift <br />cuttings from deep holes (Barrett et dl., 1980; Power and Sandoval, <br />1976; Dollhopf et al., 1981; and Peabody Coal Company, 1985). A <br />cYiemical analysis should be obtained on the water, foam and/or drilling <br />mud whenever they are utilized. <br />i <br />6-20 Revised 3/6/87 <br />