1988-04-29_PERMIT FILE - C1981008A (54)

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Lastly, ameliorating reclamation practices will primarily be utilized in those areas where . unsuitable spoil reaction or acid-base potential values are identified by the regraded spoil quality control program. Reclamation practices will include either a selectively handled suitable spoil topdressing or incorporating adequate quantities of agricultural grade limestone. Acid- and Toxic-Forming Materials at Nucla East. Acid- and toxic-forming materials were identified within the Nucla East study area; however, only the acid-forming material occurs within the projected mining disturbance area (see Tab 6, Appendix 6-5 and Exhibit 6-7, Geologic Cross Section and Sample Locations for Nucla East Study Area). Therefore, some ameliorating activity such as mixing, normal burial, or special handling will be required to replace a suitable four-foot root growth medium and to prevent leachates and runoff from entering the ground water system or discharging into the surface water system. No roads will be surfaced with the acid-forming materials. Mitigation of all unsuitable zones within the underburden material (five percent of all unsuitable zones which were identified) will be by avoidance, i.e., these zones will not be disturbed by mining activities. Certain areas of overburden and interburden will also be avoided due to the projected disturbance area boundary described within this application (Exhibit 12-3, Operations Plan - Nucla East) or excessive Dakota coal seam depths. These additional avoided areas comprise about 60 to 65 percent of all unsuitable zones which were identified. The identified unsuitable sodic strata which occurs in the southwestern portion of the study area (Sites 872E and •882E) will be avoided entirely. Complete mixing of the thicker, calcareous overburden Unit 1 (30.5 feet) and interburden Unit 3 (6.7 feet) with the thinner, acidic overburden/interburden Units 2 (4.5 feet) and 4 (2.9 feet) would produce a suitable alkaline spoil (see Tab 6, Attachment 6-1 , Table 6-1-10). Partial mixing of alkaline and acidic materials is anticipated during cast blasting, dozer pushing, and scraper handling due to the thinness of Units 2 and 4 and the stratification of alkaline and acidic strata. Normal overburden/interburden handling operations may also effectively bury the acid-forming strata. Typical overburden/interburden handling operations are described in Tab 12, Coal Resource Recovery Plan and Tab 20, Backfilling and Grading. The overburden/interburden material excavated by dozer and scraper from the cropline pit will be placed in box cut spoil stockpiles as shown on Exhibit 12-3, Operations Plan - Nucla East. Based upon the 21-4 Revised 04/11/88