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• SEDIMENTATION POND NO. 1 <br />~~~~ ! - '~ to d, ~~ c~r5u"'"'" - <br />!~~'r~' e~N ~~ ~ o„~ ate-' <br />~' ~ ~ ~~~ <br />Sedimentation Pond No. 1 Is designed to contain surface runoff from the raw and <br />clean coal stockpile area generated by both the 10-year, 24-hour and 25-year, 24- <br />hour storm events. Additional volume is provided for sediment storage, and <br />provisions are made to clean the pond to maintain adequate sediment and storm <br />runoff storage capacity. Runoff from the north and east portions of the stockpile <br />y area is routed by a drop structure and 12-inch CMP culvert directly to the pond, <br />as shown on the Drainage and Sediment Control Map, (Map 20). The drop <br />structure was moved Approximately 15 feet towards the northwest corner of Pond <br />1 during backfilling of the North Cell. A berth along the north edge of Pond 1 <br />routes yard runoff the drop structure. Runoff from the south and west portions of <br />the stockpile area is routed to catchment basin which, in tum, routes the runoff <br />through an 18-inch CMP into the pond, also shown on Map 20. <br />Pond No. 1 incorporates a 12-inch gated decant as the principal spillway. The <br />• pond Is sized to contain the. runoff from the 25-year, . 24-hour storm, so no <br />emergency spilNvay is required. Refer to Table 1, Sedimentation Pond No. 1 <br />Design Summary, for design results. The watershed boundary for Sedimentation <br />Pond No. 1 is shown on The Drainage and Sediment Control Map, (Map 20). The <br />design drawings, storage capacity table and stage/storage curve are shown on the <br />Sedimentation Pond No. 1 Design Mep, (Map 21). The storage capacity table and <br />stage/storage curve illustrate the pond's available sediment and runoff storage <br />volume. Design calculations utilized In the pond's design are contained in the <br />following text of this exhibit. <br />• aej ~ vej <br />~ auoUd 4 euoVd <br />T7'~ .a~ ~7H~7-~6./Q~de~~o~ <br /> <br />/~°wa*°IyE7~6z1~-emal LLBL <br />alorJ Yej a1-3~A <br />12 <br />Revised 426196 <br />Minor Revision No. 30 <br />T00 90r8 Z£8 £0£ ~ Q-IBS-I»3 6T~80 96i6Zit'0 <br />