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_... <br />8. Embankment Construction. Embankment construction will consist of the placement <br />of all materials to lines, grades, end cross section. Grading will be done to <br />conform with Exhibit 13-5. <br />A keyway will be cut below existing ground. Suitable material from from the <br />excavation area will be placed in the keyway. The placing and spreading of fill <br />material will proceed from the lowest point on the embankment (keyway) in <br />horizontal layers of such thickness as to allow for a minimum compaction of 95 <br />percent of standard proctor. Compaction tests will be run on approximately <br />every 2,500 cubic yards of material placed in the embankment. Results of these <br />tests will be kept on file at the mine engineering office and will be available <br />for inspection if requested. Both the upstream and downstream slopes of the <br />embankment will be 3h:1v or flatter. The embankment will be abutted into <br />competent material (bedrock, sandstone) on either end of the embankment. <br />A horizontal drainage blanket will be constructed under the embankment as shown <br />an Exhibit 13-5 and described in Ground Engineering~s report in Attachment <br />13 -3A. Two different designs were included in the report. Peabody has decided <br />to implement the design which incorporates the minimum of one-foot thick <br />granular material. This is based on ease of construction and accessibility of ~ <br />blanket materials. A toe drain will also be incorporated, as described in this <br />same report, to discharge the flow from the drainage blanket without <br />jeopardizing the stability of the embankment toe. <br />During the 100-year storm, with the emergency spillway functioning as designed, <br />there will be 4.4 feet of freeboard. Taking into account 5 percent settlement <br />(1.0 ft. ), there will still be 3.4 feet of freeboard. <br />The entire embankment, including adjacent disturbance areas, disturbed by <br />construction will be stabilized with respect to erosion by seeding the area <br />immediately after construction is complete in accordance with the Reclamation <br />Plan. Areas in which the vegetation is not successful or where rills end <br />gullies develop, shall be repaired and revegetated in accordance with [he rill <br />and gully plan. <br /> <br />13-3-15 Revised 03/13/92 <br />