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pillar has been computed to provide a minimum safety Factor of five <br />against rupture under the mar.imum possible loading by the refuse <br />materials. The access drifts to the refuse disposal area will be <br />sealed by the installation of concrete plugs in Lf~e coal pillar <br />area after mining. The plugs will be designed to withstand the <br />maximum possible pressure, computed to be 260 psi. The bulkhead <br />and pillar design will be refined during the detailed mine design <br />process and with consultation and approval by MSHA. <br />The delivery system includes the following components: <br />1. Refuse will be collected in the plant, and will be temporarily <br />stored in a refuse bin. <br />2. The coarse refuse from the refuse bin will be crushed to a <br />size of 1/4 to 1/2 inch and will be fed into a miring tank <br />with make-up water and thickener underfloor to form a slurry. <br />• 3. The slurry vrill be pumped from the pump station through a <br />slurry line along the portal and to the refuse disposal area. <br />9. The slurry delivery pipe will conduct the slurry to the <br />highest point in the refuse disposal chamber, and v.~ill be <br />allowed to fill the chamber from the base. The delivery pipe <br />will be installed in the development drives, prior to the <br />hydraulic mining of the rooms. <br />5. The water used to slurry the refuse will be collected in a <br />decant tower constructed in the mined-out rooms, placed during <br />retreat from the mined area as mine development work is <br />performed, as the rooms themselves will not be accessible <br />after mining. <br />6. The decant water will be recycled by gravity to the prepara- <br />tion plant, for reuse as a slurry water in tt~e system. <br />. NCIG - Coal Ridge #1 4-49 ABC/1145/910509 <br />TR-7 <br />