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.• If the water quality in the Northwest Intake Pool deteriorates to the point <br />treatment is required, a treatment facility could be constructed near the <br />location of the soon to be reclaimed wash plant. Proposed flow routing is <br />presented on Figure 14-7. This routing would require the siphon to <br />temporarily become the primary dewatering system until a treatment <br />system could be designed near the North Decline dewatering pipe. <br />Should the North Decline mine discharge pipe fail for any reason, the <br />siphon and South Portal dewatering pipe can handle all mine inflows. <br />Therefore, a complete failure of the mine dewatering system is highly <br />unlikely. If the mine dewatering system did fail completely, the water level <br />in the mine would raise to the level of the Northwest Intake Portal. Seeps <br />would appear along Interstate 70 below the level of the reclaimed portal. <br />The relcaimed portal slope would probably become saturated so shallow <br />slope failures could develop. A massive slide or catastrophic failure is not <br />considered probable for the following reasons: <br />1. The portal was sealed with unclassified dirt. Water should find a <br />flow path through this dirt backfill without any significant water <br />impoundment. <br />• 2. Water emerging from the portal would flow parallel to the interstate <br />highway in a borrow ditch. The water would not flow across the <br />surface of the interstate highway. <br />3. The steel supports in the Northwest Intake Portal were not all <br />removed. Only the outby supports were removed. Therefore, the <br />slope above the portal backfill is still supported by steel square sets <br />which should thwart a massive slope failure. <br />The North Decline dewatering pipe drill pad will be constructed as shown <br />on Figure 14-8. Design for alternative sediment control is presented in <br />Appendix 14-6 beginning on page 14-6-74. Available topsoil will be <br />salvaged. The drill pad development is virtually all cut. Therefore, a <br />temporary spoil pile with a capacity of approximately 2000 cubic yards is <br />required. Topsoil and spoil will be placed in stockpiles located at the <br />North Decline reclaimed area shown on Figure 14-8. Topsoil from the <br />footprint of the spoil pile will be placed in the topsoil stockpile. The drill <br />pad will be reclaimed as soon as the dewatering pipe is operational. The <br />reclaimed area along with the area disturbed in the North Decline will be <br />seeded and mulched according to the reclamation plan presented above <br />in this tab section. <br />• 14-30i (Rev. 01 /01) <br />