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SENECA II-W <br />POND 006 SLIDE <br />ABATEMENT PLAN <br />History <br />Sedimentation Pond 006 was constructed in the fall of 1989.In the spring <br />of 1990 a portion of the pond side slope failed and slid down the slope. <br />Subsequent to the slide, CMLRD wrote NOV C-90-O18 on May 23, 1990 which <br />contained specific abatement steps and deadlines. Peabody requested an <br />extension for completion of Step i, to submit a plan to stabilize the <br />slide area, to July 9, 1990. The plan was submitted on July 6, 1990. Due <br />to additional signs of instability discovered above the haul road after <br />the plan was submitted, Peabody contracted a geotechnical firm to <br />investigate the slide area, and subsequently requested the time period for <br />completion of Step 2, implementation of the plan, be extended an <br />additional 90 days to November 19, 1990. This would allow the inclusion <br />of field and laboratory data into a final abatement plan and permit <br />sufficient construction time. Investigative report, "Geotechnical <br />Investigation Pond 006 Slope Failure" is attached and considered a part of <br />the abatement plan. <br />The report presents two alternatives to stabilize the slide area. The <br />preferred plan, to remove and regrade the slide area, was presented in a <br />meeting between representatives of CMLRD, Ground Engineering Consultants <br />and Peabody Coal Company, on September 28, 1990. Additional concerns were <br />discussed in the meeting and in a letter dated October 2, 1990 regarding <br />the meeting. These concerns are addressed below. <br />Remove/Regrade Plan <br />Several different options were considered prior to selecting this plan. <br />The other options were costly, timely or difficult to construct. Even <br />under the worst case conditions this plan still provides a safety factor <br />of 1.74. In general, the plan requires the existing road to be moved <br />further into the hillside by approximately 15 feet. In addition, the <br />weathered material above the more competent bedrock on the pond side slope <br />will be removed. Once this is accomplished, the road subbase will be <br />on competent bedrock. The potential for sliding will be eliminated after <br />the above steps have been taken. <br />