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• uncompacted zone can be incorporated in the back of the RDA without negatively <br />affecting stability. The zone is defined by a distance behind the face for each bench <br />as shown on Fig. 8. Although compaction of the refuse in this zone should not be <br />required, we recommend that the material still be spread in maximum 2 foot lifts, <br />typical compaction efforts applied, and surface drainage maintained. We recommend <br />that future compaction testing be concentrated outside this zone, near the face of <br />the RDA to provide information in the area that affects the stability. <br />The uncompacted zone would be a sukable location to place high moisture <br />refuse during periods when the processing equipment is down or not operating <br />properly. This zone could also be used for the disposal of fine refuse. The fines <br />should be placed in isolated "cells" rather than a continuous layer. The fines should <br />not be a saturated slurry but can be high moisture, processed fines. If slurry <br />• disposal is required additional evaluation will be required. The cells should be about <br />100 to 200 feet wide, set at least 100 feet behind the uncompacted zone boundary. <br />The cells should be separated from each other by a distance equal to the width to <br />provide a coarser zone wkh higher permeability between the cells. The cells should <br />not be continuous vertically. We recommend a maximum height of 25 feet, with 25 <br />feet of coal refuse above the cell before a new cell is begun. <br />Drain System <br />The existing drain system should be continued along the base of both <br />drainages as RDA construction proceeds. The drain should consist of durable rock <br />placed to minimum dimensions of 16 foot width and S foot height in the base of the <br />drainages. The rock should consist primarily of 1 to 3 foot boulders, occasional <br />• <br />24 <br />