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<br />Lined Pit Guide 5 September 2000 <br />Example #2 <br />Screen (US Standard) Percent by Dry Weight <br />3 inch 100 <br /># 4 40-80 <br />#40 25-60 <br />#200 20-40 <br />Minimum Plasticity Index of 10 <br />The design documents should include an S-B backfill testing report. This report should include a <br />description of test results used to prepare the S-B backfill mix design and should include proposed mix <br />proportions, gradations, slumps, densities, permeabilities, and moisture contents. Typically, the only <br />permeability testing to be required would occur during the mix design and testing phase. If the mix is <br />prepared and placed in accordance with the specifications, it can be assumed that the target <br />permeability will be met. <br />Mixing S-B backfill must be done in such a manner that the material is consistent. This can be done on <br />a sepazate mixing pad or alongside the slurry trench. It is important that all soil particles are coated <br />with slurry and that clods aze broken down. There should be a description of the S-B backfill mixing <br />protocol in the design documents, and the specifications should address minimum mixing standazds. <br />Once S-B backfilling operations have begun, it is recommended that trench excavation precede the toe <br />of the S-B backfill slope by at least 30 feet but not more than 100 feet. <br />Quality control test results for permeability (if needed), slump, density, and moisture content should be <br />supplied by the Contractor as required by the specifications and quality control plan for the S-B <br />backfill. Third party quality assurance testing should also be specified. Placement of S-B backfill <br />should be done such that there aze no pockets of trapped slurry. The plans and specifications should <br />describe acceptable backfilling methods and prohibit free dropping of S-B backfill. An example <br />specification and quality assurance protocol for S-B backfill mix is provided below. <br />S-B backfill slump ASTM C 143 1 set per 100 cu. yds. Slump 2-6 inches <br />S-B backfill gradation (various standazds) t set per 300 cu. yds. -65 to 100 percent <br />passing 3/8" sieve <br />-40 to 85 percent <br />passing #20 sieve <br />-25 to 40 percent <br />passing #200 sieve <br />