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• 2.05.3(61 Overburden <br />The narrative description of overburden removal with reference to appropriate maps <br />and cross-sections has been presented in Section 2.05.3(2). The material volumes of <br />coal, coal processing waste and overburden including interburden and partings are <br />shown in Table 5-4. The maximum fill volume is presented in Table 5-5. <br />OEI has recently drilled additional water monitoring locations which has concurrently <br />yielded more extensive geologic information. As a result, the overburden and coal <br />quantities have been recalculated to reflect the latest information. These values are <br />appropriately reflected in Table 5-4. <br />Oakridge Energy, Inc. plans to conduct apre-mining survey to establish horizontal and <br />vertical control for the pit area. In conjunction with this survey, OEI will conduct <br />several profile surveys of the pit/fill landscape slated for disturbance. These profiles <br />will be no more than 500 feet apart and oriented more or less parallel to the geologic <br />cross-section. Points along each profile will be located every 100 feet and elevations <br />determined. As mining begins, only the crest and tce of each mine/fill bench need be <br />located along these profiles. The amount of coal and overburden material removed <br />(mined) from each profile will show up as a decrease in elevation. Conversely, the <br />amount of overburden placed in the fill will show up as an increase in elevations. <br />. Upon reaching the steady-state pit, a balance will be performed to fully quantify the <br />swell factor. <br />From the early mining activities the swell factor has been estimated at 30%. This swell <br />is based upon a calculation made from the existing pit and fill area. It should be noted <br />that there is a slight variance between the original topographic maps and those t7own in <br />1990 by Air Photo Surveys. Thus, the most recent determination of swell continues to <br />be subject to revision in the future based upon more accurate data. Should the actual <br />swell factor be significantly greater or less than the current estimated, then the mine <br />and reclamation plans will be amended and submitted to the Division. The profile <br />survey will be conducted on an annual basis, when mining resumes. <br />Prior to placement of material in the permanently reclaimed spoils area (box cut spoil), <br />and after the removal of soil materials, the applicant placed a sandstone underdrain in <br />the bottom of the spoil. The size of the underdrain was as designed with no less than <br />15 feet of sandstone, more than 2 feet in diameter, and had the following approximate <br />size distributions which were confirmed during placement: <br />2' - 1': 40% <br />4" - 0 : 15% <br />u <br />Technical Revision 08 (v 1.3) 5-14 Revised 9/1997 <br />