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Section 816.101)a) Continued <br />• (2) Open pit mining with thin overburden. Rough backfilling and grading <br />shall occur in accordance with the time schedule approved by the regulatory <br />authority, on the basis of the materials submitted under 30 CFR 780.18(b)(3). <br />which shall specifically establish in stated increments the period between <br />removal of coal and completion of backfilling and grading. <br />(3) Area strip mining. Rough backfilling and grading shall be completed <br />within 180 days following coal removal and shall not be more than four spoil <br />ridges behind the pit being worked, the spoil from the active pit being <br />considered the first ridge. The regulatory authority may grant additional <br />time for rough backfilling and grading if the permittee can demonstrate, <br />through a detailed written analysis under 30CFR 780.18 (b)(3), that <br />additional time is necessary. <br />Overburden Volumetric Analysis <br />• Calculations regarding Thick or Thin Overburden as defined in 816.104- <br />105 cannot be applied to the proposed mining operation, because of the <br />unique geologic character of the coal and overburden and the associated <br />unique pit configurations. By observing Maps 7 - 13. Geologic Cross <br />Sections A•G and the associated Figure 32, Typical Pit Cross Section, it <br />is evident that because of the steep dips of the coal and overburden. <br />the geometry of the pit does not coincide with overburden and coal <br />thicknesses. Therefore. Kerr Coal has based calculations regarding <br />thick or thin overburden upon volumetrics, as illustrated in Table 74. <br />Pit Volume Calculations. In order to project anticipated overburden <br />backfill volumes, extensive tests on the overburden material were <br />performed by CTL Thompson Inc. (See Exhibit 23. Physical Properties of <br />Overburden.) resulting in calculation of a probable swell factor for <br />backfilled overburden of 24 percent. This swell factor reflects <br />backfilling with either scrapers or rear-dump haulage trucks and <br />compaction due to normal haulage traffic. <br />u <br />H:1857\ V OL.3\SECTION.816 <br />01/25/95 9:54em WP51/cmc 816.128 Revised 01/30/95 <br />