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overburden holes to proof de a more uniform density of sample sites across the Wedge coal recovery area, sample thicknesses of overburden (40, 50, 60 and 110 feet) not included in the earlier Phase I sampling, test for constituents not included on the Phase I parameter list, and confirm the extents of unsuitable constituents identified by the Phase I drilling program. The Lennox coal seam will be sampled at the thickest overburden site. . The combined Phase I and Phase II sampling~iTntensity will be 1 hole/40 acres. W ~" a* ~ 5 P ~u ,U- C~at~, S gµ~~i v-q /x'fCh S ~ 7 . .. Sample Contamf nation Numerous overburden sample contamination problems have been documented over the last ten years in the western United States. Drilling fluids, foam additivesi and muds can appreciably affect the soluble constituents (especially EC, SAR, and NH4) in the sample. During rotary drilling for cores or cuttings, it is necessary to use a drilling medium such as air, water, or mud for lifting cuttings from the borehole. For overburden baseline studies, it is recononended that air be used whenever possible, water second, and ~~ mud or foam avoided unless absolutely necessary to overcome circulation problems or to ~. lift cuttings from deep holes (Barrett et al., 1980; Power and Sandoval, 1976•,' Dollhopf et al., 1981; and Peabody Coal Company, 1987). A chemical analysis should be obtained on the _, water, foam, and/or drilling mud whenever they are utilized. Random sample contamination often results in serious misinterpretations of the data. Many previously reported unsuitable copper, molybdenum, zinc, and especially lead concentrations were more apt to have been caused by drill stem grease contamination than natural mineralized strata. Dollhopf and Goering (1983), Dollhopf et al. (1981), Peabody Coal Company (1988), antl Rochelle Coal Company (1984) all demonstrated that significant contamination resulted from zinc, copper, molybdenum, and lead based dri li stem joint lubricants. A noncontaminating drill stem joint lubricant should be utilized when copper, lead, zinc, molybdenum, or other metals are included on the baseline parameter list. Peabody suspects the excessive iron and manganese values present in the Phase I Yoast samples can be attributed to the core samples having been contaminated by drill stem grease. Elevated values of iron and manganese appear systematically about every ten feet in each core section. This correlates closely with the frequency that each core barrel would have been emptied and regressed. Peabody will use a noncontaminating drill stem joint lubricant (aluminum or lithium based) on all of the Yoast Phase II sample sites. The four holes will be drilled exclusively 3