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• In accordance with Rule 4.05.6(3)(b), Peabody Coal Company has committed to maintain a <br />minimum amount of sediment storage in Sedimentation Ponds 002, 003, 004, 007, and 008. <br />Sedimentation Pond 008 was constructed in 1987 to replace structure 007. The required <br />minimum sediment storage capacity is discussed in Appendix 7-6 within each sedimentation <br />pond design/a s-built report. <br />As a result of NOV C-65-081 (Sedimentation Ponds), G1LRD's staff requested Peabody perform <br />an annual sediment survey (e.g., January 14, 1986, Anne Baldri ge, CMLRD Comment ap4). This <br />NOV was issued prior to the Seneca II Permit Renewal Application (8/27/86) which was <br />subsequently approved by CMLRD. In this Permit Renewal Application and subsequent permit <br />revisions, these sedimentation ponds were reviewed and/or designed and field modified to <br />maximize the sediment storage capacity as discussed in Appendix 7-6. In addition, as part <br />of the 1986 and 1987 Annual Hydrology Report submitted to CMLRD, Peabody performed annual <br />sediment surveys and compared the results to the prior years results. <br />1986 Annual Hydrology Report <br />Following are the results of the sediment survey in the 1986 Annual Hydrology Report: <br />Introduction. Annual sediment surveys have been performed at the following ponds in both <br />1965 and 1986. Design information and calculations presented in the August 27, 1986 <br />Seneca II Permit Renewal Application are based on the 1985 pond survey data. <br />Sedimentation Pond 002. Design information and calculations for this pond were submitted <br />in the Seneca II Permit Renewal Application (August 27, 1986) and subsequently approved by <br />CMLRD. Based on the updrainage watershed characteristics, one 10-year, 24-hour <br />precipitation event would generate 5.07 ac-ft of sediment using M.U.S. L. E. <br />With the principal spillway elevation at 6611.2, the pond can store approximately 267.36 <br />ac-f t, or the egvi va]ent of the sediment generated from approximate]y fifty-three 10-year, <br />24-hour precipitation events. This indicates that a considerable amount of sediment <br />storage exists for this sedimentation pond and no remedial sediment clean-out work is <br />scheduled for the five-year permit term at this time. <br />• <br />7-11A-1 <br />