1989-10-10_REVISION - M1988112 (12)

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in Waste Rock Disposal Area A in the approved permit will be • disposed in Waste Rock Disposal Area D. Waste rock from the East Pit will be hauled to Area B, Area C or the South Area for disposal. Some waste rock from the West Pit will be used to backfill the East Pit in accordance with the approved permit (See Section D.3.4.2 of the approved permit). The remaining waste rock will be hauled to the southern or northern disposal areas. Once mining commences in the West Pit, waste rock disposal could occur concurrently in several disposal areas. D.3.5 Stability The stability of the amended waste rock disposal areas has been evaluated using criteria previously approved for the original permit. The stability of the waste rock disposal areas which have not been amended for this permit. is described in Section D.3.5 of the approved permit. The criteria include judgement based on past experience with similar facilities in • conjunction with computerized slope stability analytical methods. The computer program used, PCSTABL4, 'was developed at Purdue University and is described in detail by Carpenter (1985). The circular (CIRCLE2) subroutine was used to evaluate the stability of the amended waste rock disposal facilities. In addition, each amended facility was evaluated for long-term static and pseudostatic loading conditions for both the construction configuration and the reclaimed configuration. A maximum pseudostatic coefficient of 15 percent gravity (0.15 g) was used for horizontal acceleration. The analyses assumed that due to the nature of the waste rock ,and the pile configuration, a phreatic surface would not develop within the pile. The results of the stability analyses for each of the amended waste rock disposal areas are summarized on Figures D.3-1 through D.3-3. For the South Waste Rock Disposal Area the analyses indicate that the minimum long-term static factor D-7