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The basis for selection of the 75-foot pile height was the <br />I criteria of a 1.5 or greater factor of safety under long term <br />conditions. The analysis showed that the criteria was achieved <br />for the 75 foot pile height provided that (1) any low strength <br />material (fine refuse) within 80 feet of the final toe location <br />was removed, mixed with coarse refuse, and placed within the <br />interior of the pile, (2) the internal rock drain vas constructed <br />and operating property, (3) the refuse material is placed and <br />compacted to the limits as speciftied herin, and (4) water is <br />prevented from impounding on the surface of the pile. The <br />minimum factor of safety for this condition is 1.53. Typical <br />failure surfaces for the maximum pile section (Section A-A) are <br />presented on Figure 4. <br />RECOMMENDED CONSTRUCTION PROCEDURES <br />INTERIM METHODS <br />Dorchester Coal Company proposes to install a belt press <br />operation which would reduce the moisture content of the <br />saturated fine material and allow more uniform mixture with the <br />coarse material. Prior to that installation, interim construction <br />methods are required in order to place the coarse and fine refuse <br />in a satisfactory manner. The present method of construction <br />' discussed previously under the existing conditions is acceptable <br />for interim methods prior to installation of the belt press. <br />' This conclusion is predicated on the assumption that the extent <br />I of the area containing the low strength saturated material is not <br />increased either horizontally of vertically and the excess water <br />8 <br />