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0 <br /> <br />depth of topsoil removal is planned at 1.75 feet. For the remaining 5 pond locations <br />the depth of topsoil removal will be on the order of 4 feet. <br />1. Site Preparation. Prior to placing fill, the area should be stripped of <br />organic topsoil or other deleterious materials. Stripping should <br />remove carbonaceous materials if exposed in bedrock excavation <br />areas. Given the moderate slopes at the Pond 013 embankment (on <br />the order of 10 to 20 percent) we recommend the slope below the <br />embankment be benched prior to fill placement. A benching detail is <br />shown on Fig. 11. <br />2. Acceptable Fill Materials. Suitable fill materials can be obtained from <br />pond excavations or from off-site borrow sources. Suitable materials <br />include native clay soils, clayey sand soils, and bedrock materials <br />which are broken down to these soil types (SC, GC, CL and CH). <br />Bedrock materials should be processed to produce asoil-like material <br />with a maximum particle size of 3 inches. The materials used as <br />embankment fill should have at least 25 percent fines (material finer <br />than No. 200 sieve). <br />• 3. Unacceptable Fill Materials. Materials not considered suitable for use <br />as embankment fill include the sand and gravel native soils. These <br />soils were found at a depth of 6 feet in the area of Pond 010, and at a <br />depth of 3 feet in the southern, lower elevation portion of Pond 012. <br />Also unacceptable are carbonaceous materials obtained from bedrock <br />excavations orwell-cemented sandstones which do not break down to <br />soil-like material. Highly organic soils or materials containing <br />construction debris are also not acceptable. Frozen soil is not <br />acceptable. <br />4. Fill Placement and Compaction. The embankment fills should be <br />placed in thin lifts (on the order of 8 to 12 inches loose thickness). The <br />fill should be moisture conditioned to within 2 percent of optimum <br />moisture content and compacted to at least 95 percent of standard <br />Proctor maximum dry density (ASTM D 698). The placing and <br />spreading of fill materials should be started at the lowest point of the <br />embankment. Fill placement and compaction should be observed and <br />tested by a qualified geotechnical engineering firm. <br />5. Monitoring and Inspections. Monitoring and inspections should be <br />performed by qualified individuals as outlined in CDMG regulations <br />4.05.6 (13). <br /> <br />LORENCITO COAL COMPANY, LLC <br />SMALL SEDIMENTATION EMBANKMENTS <br />CTL/T 26,559 11 <br />