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• approached orexceeded guideline levels during the Phase I sampling were included <br />on the Phase II analyses list. Modifying the second phase parameter list was <br />desirable to reduce unwarrantable analyses costs and to focus on site specific <br />conditions. <br />Sampling Methodology -Phase I <br />Intensity. Most OIU sampling and analysis studies indicate that drilling designs should be <br />governed by geological factors, such as the lithologic variability and the depositional environment <br />of the OIU strata (Barth et al., 1981). Barrett et al. (1980) states that drilling designs and hole <br />spacings must be determined on the basis ofthe unique set of geologic and geochemical conditions <br />(i.e., lateral variability of strata) existing at each mine site. <br />Recommended drilling intensities range from 1 hole per 40 acres to 1 hole per 640 acres. DMG <br />(1982) suggests sampling 1 drill hole/640 acres with a minimum of 3 holes/site. USDI-OSMRE <br />(1985a) recommends drilling 1 hole/160 acres with a minimum of 3 holes/site. WDEQ (1985) <br />stipulates sampling 2 core holes and 6 cuttings holes per 640 acres during Phase I drilling. Phase <br />• II sampling is reserved for special handling situations and a density of 1 hole/40 acres is <br />recommended. Dollhopf et al., (1981) recommends a 600 meter grid (1 hole/90 acres) for initial <br />characterization followed by additional drilling and analyses if any parameters of concern are <br />indicated in the initial drilling. Thecircularzoneofdataextrapolationortheeffectivedrillholeradius <br />should be 750 feet. Lastly, Sutton et al. (1981) recommends sampling one site to adequately <br />assess overburden variability on small permit areas of less than 40 acres. <br />A Phase I drilling program was implemented at New Horizon 2 in 1984 to describe overburden, <br />interburden, and underburden characteristics over the entire study area, to obtain representative <br />core hole locations from which cross sections could be developed, and to define the extent of <br />suitable, marginally suitable, and unsuitable material. Three strategic and systematic drilling <br />locations, spaced at 2,000 and 3,000 feet apart, were selected after evaluating the geologic cross <br />section requirements and existing coal cropline/recovery information. Overburden (defined as all <br />stratigraphy above the upper Dakota coal seam) thickness at Sites 871 E, 870E, and 872 was <br />approximately 30, 60, and 100 feet, respectively. The locations of these holes are shown on Map <br />Revised 27 Aug 2002 10 <br />