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As shown on the final topography, the drainage will be located on the south edge of the <br />permanently reclaimed spoils area. As the basic geotechnical assumptions for the spoils <br />were calculated for a saturated condition, the 1.8 safety factor holds true for the portion <br />of the spoils adjacent to the drainage realignment. Further, the rock underdrain will <br />drain any waters which accumulate near the base of the spoils. <br />As described in the hydrologic section, the sandstone which underlies most of the spoil <br />has no identifiable permeability. Consequently, no water will flow into the sandstone <br />from the spoil or into the spoil from the sandstone. There is no groundwater in the <br />base of the spoil as discussed in previous material and demonstrated by drilling data. <br />Surficial waters and infiltrate that exist along the drainage will be discharged via the <br />underdrain. Since construction of the underdrain, mine personnel have observed that <br />the underdrain is functioning as designed. Small flows have been observed in wet and <br />spring runoff periods. <br />PenmsnentYy Recleaned SpnJ1 Area <br />The permanently reclaimed spoil area is approximately 17 acres. The location of this <br />area is shown on Map 5-10. As described earlier, this azea consists of box cut spoil, <br />blasted sandstone, and overburden material (primarily alluvial terrace sands and <br />gravels) excavated to access the North Pit and the South Pit prior to achieving the <br />steady-state pit. As the spoil filled a segment of the original Carbon Junction Canyon <br />drainage channel, CDMG required OEI to design and construct the spoil area. as if it <br />was an engineered fill, meeting all the requisite performance standards. The final <br />configuration of the permanently reclaimed spoil area blends into the adjacent slopes of <br />the permit azea and provides complimentary topography for the adjacent golf course. <br />Slopes are 3:1 (h: v) or less and drain toward Carbon Junction Canyon. Spoil <br />placement was in four foot lifts which were compacted to specified tolerances. <br />Attainment of adequate compaction and the grade and slopes involved will ensure that <br />saturation and slope failure will not occur (See Stability Study, Appendix S-6). A <br />designed underdrain was placed prior to spoil deposition. <br />The Carbon Junction Canyon drainage has been rerouted around the spoil area. Carbon <br />Junction Canyon will flow to the southeast of the permanently reclaimed spoil area <br />after final reclamation. <br />One ephemeral seep has been located southeast of the Permanently Reclaimed Spoils <br />Area and northwest of the South Pit, adjacent to the pit access road. Inspection of the <br />seep in October 1997 revealed that the seep issues from a sandstone layer below the <br />level of the South Pit and above the level of the Permanently Reclaimed Spoils Area. <br />Flow from this seep enters the road drainage ditch and renters the ground <br />approximately 250 feet below the seep. Native hydrophytic vegetation has grown <br />• <br />Technical Revision 08 (v 1.3) 5-15 Revised 9/1997 <br />