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• The density of the slurry in the trench must be at least 15 pounds per cubic foot <br />less than the density of the S-B Backfill to displace the slurry in the trench during <br />backfilling. <br />Controlling the in-trench slurry properties is important in constructing and <br />conducting a slurry wall operation. At minimum, standard in-trench slurry test <br />will be run twice per day, at least once in the morning and once in the afternoon. <br />The experienced contractor will deal with Trench sedimentation conditions. The <br />contractor selected will have the knowledge and experience to deal with the site <br />conditions. <br />2. Soil-Bentonite Backfill: <br />• Mixing and Placing Soil-Bentonite Backfill: <br />Soil-Bentonite Backfill will be mixed until "homogeneous" and achieves a <br />"slump" of 7 to 16 cm (2.75 to 6.3I inch) as measured using a slump cone <br />(ASTM D143). Mixing and placing will be done adjacent to the trench using <br />earthmoving equipment such as dozers and excavators. <br />On-site soils will be used andlor amended to achieve a fines content of at <br />least 15 to 20%. <br />• Field Sampling of Soil-Bentonite Backfill: <br />• Grab samples of the soil-Bentonite Backfill will be obtained from the work <br />platform, placed in plastic bags, sealed and sent to the approved laboratory for <br />testing. Typically, one grab sample will be taken for testing for every 400 to 1000 <br />cubic meters of Backfill. It is not recommended to obtain grab samples in situ <br />from the backfilled trench; none will be obtained in situ. <br />• The Applicant/Operator agrees to have preformed those laboratory tests <br />considered customary and appropriate for asoil-Bentonite Backfill. <br />• Construction Considerations: <br />• In the design specifications, the key-way will be specified to a minimum <br />depth or to refusal of the trench excavating equipment, whichever is less. <br />According to drill logs the bedrock is claystone bedrock that is hard to very hard. <br />• Joining slurry wall corners and closure of the "loop" will be done using <br />survey control to ensure that lapping of wall segments does not occur. Where <br />slurry walls meet at an angle or straight on, excavation will proceed at a minimum <br />of 5 feet past the meet point as surveyed at the bottom of the trench. <br />