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characteristics over the entire study area and to obtain representative core <br /> hole locations from which cross sections could be developed. Following the <br /> initial data analysis and interpretation, general areas and percentages of <br /> suitable and unsuitable material were identified. The site specific horizontal <br /> and vertical variability and discontinuities of strata were evaluated. <br /> Phase II : Three additional sampling locations were approved for the Nucla East study area <br /> on August 7, 1987 by CMLRD (Peter O'Connor's letter to J. Lunan). Phase II <br /> drilling converged on the OIU problem areas to better define and confirm the <br /> extent of suitable, marginally suitable, and unsuitable material . Constituents <br /> which approached or exceeded guideline levels during the Phase I sampling were <br /> included on the Phase II analyses list. Modifying the second phase parameter <br /> list was desirable to reduce unwarrantable analyses costs and to focus on site <br /> specific conditions. <br /> Sampling Methodology - Phase I <br /> Intensity. Most OIU sampling and analysis studies indicate that drilling designs should <br /> be governed by geological factors, such as the lithologic variability and the depositional <br /> environment of the OIU strata (Barth et al ., 1981). Barrett et al . (1980) states that <br /> drilling designs and hole spacings must be determined on the basis of the unique set of <br /> geologic and geochemical conditions (i.e., lateral variability of strata) existing at each <br /> mine site. <br /> Recommended drilling intensities range from 1 hole per 40 acres to 1 hole per 640 acres. <br /> CMLRD (1982) suggests sampling 1 drill hole/640 acres with a minimum of 3 holes/site. <br /> USDI-OSMRE (1985a) recommends drilling 1 hole/160 acres with a minimum of 3 holes/site. <br /> WDEQ (1985) stipulates sampling 2 core holes and 6 cuttings holes per 640 acres during <br /> Phase I drilling. Phase II sampling is reserved for special handling situations and a <br /> density of 1 hole/40 acres is recommended. Dollhopf et al ., (1981) recommends a 600 meter <br /> grid (1 hole/90 acres) for initial characterization followed by additional drilling and <br /> analyses if any parameters of concern are indicated in the initial drilling. The circular <br /> zone of data extrapolation or the effective drill hole radius should be 750 feet. Lastly, <br /> Sutton et al . (1981) recommends sampling one site to adequately assess overburden <br /> variability on small permit areas of less than 40 acres. <br /> 6-1-12 Revised 04/11/88 <br />