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Lined Pit Guide 3 September 2000 bentonite, 20-40 percent fines, and has a moisture content of 25-40 percent. The density of the slurry in the trench must be at least 15 pounds per cubic foot less than the density of the S-B backfill to displace the slurry in the trench during backfilling. Working Platform and Gayout Drawing An S-B slurry wall generally cannot be constructed in areas with a slope greater than 2 percent along the alignment. Site prepazation may require the construction of a clear and stable working platform 40 to 60 feet wide and at least 5 feet above the ground water level. The layout of the slurry wall should be illustrated on a 1 "=100' or other appropriately scaled drawing showing property lines, coordinates, contours, existing facilities, and drill hole locations. The erosion control plan should also be illustrated and described. It is important to route runoff away from the trench to protect the purity of the slurry. Bentonite The design documents or other preconstruction submittals should include the bentonite manufacturer's certificate of compliance. If these are unavailable during permitting they may be provided with the final construction report and certification, but the standards to be met must be in the technical specifications. Bentonite standards aze described in American Petroleum Institute (API) Standard 13A. The following example specification is typical for bentonite. YP/PV ratio API Std. I3A less than 3 Viscometer greater than 30 Filtrate Loss less than 15 cm3 Moisture Content ASTM D 2216 less than 10 percent Test results for each lot of bentonite must be provided. The specification should describe how the bentonite will be stored at the site. Water Suitable water must be used in the preparation of the bentonite slurry. Water that does not meet specifications must be treated or conditioned or another source of water located. An example of a typical water specification follows: pH Hardness Tota] Dissolved Solids Oil, organics, acids, alkali Chloride 6-8 less than 200 ppm less than 500 ppm less than 50 ppm each report