1989-10-10_REVISION - M1988112 (12)

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Following cessation of deposition in any area, tailings • will settle and consolidate. Tailings on the beach will initially be in a saturated condition. Subsequent evaporation will result in desiccation and shrinkage of the most recently deposited tailings to produce a relatively high density (90 pcf), low permeability (1 X 10_s cm/sec) material. See Section D.6.4.3 for a discussion of the deposition and consolidation modeling. During Years 7 and 8, the final years of operation of the facility, the deposition of tailings will be modified to create a surface expression similar to that required to meet the reclamation configuration. The modification to the disposal is discussed in Exhibit E of this amendment. The disposal area height capacity and volumetric relationships are shown on Figure C-13. The upper right hand quadrant of the figure shows the relationship of the disposal area surface elevations to the quantity of tailings storage • volume. The units of the horizontal axis are tons assuming that the tailings have a dry unit weight of 90 pcf. The curves in the upper right hand quadrant show the capacities of the upper and lower disposal areas below the elevation of 76,590 ft, and the capacity of the single disposal area which will occur above an elevation of 8,590 ft when the splitter embankment is covered with tailings. Tailings production at the expected rate of 4,680 tpd is shown on the lower right quadrant. At this production rate, an elevation of disposed tailings of 8,590 ft will be achieved in 3.75 years. Tailings distribution to each disposal area is indicated by the curves for the upper and lower disposal areas up to year 3.75. After 3.75 years, tailings deposition occurs in a single disposal area at a rate indicated by the total production curve. D-54