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1. At the time of introduction of the slurry into the trench,the slurry shall be a mixture of not less <br /> than 5%bentonite in water.Additional bentonite or admixtures may be required depending on the <br /> hardness and temperature of the water and the quality of the bentonite. The slurry shall have a <br /> minimum apparent viscosity of 40 seconds reading through a Marsh Funnel Viscometer,a pH <br /> between 6 and 8 units and a minimum density of 64 pcf,(1.03 gm/cc). <br /> 2. The slurry mixture in the trench shall have a unit weight not less than 64 pcf(1.03 gm/cc),not <br /> greater than 85 pcf(1.36/gm/cc)or 15 pcf less than the backfill unit weight,or as approved by the <br /> Slurry Trench Specialist.The sand content shall not be greater than 20%.The sand content shall be <br /> lowered by replacing the in trench slurry with fresh slurry or a desander may be used to lower the <br /> sand content. <br /> 2.2 BENTONITE <br /> A. Bentonite used in preparing slurry shall be pulverized(powder or ular)premium grade sodium- <br /> cation montmorillonite and shall meet the most current API S rd 13A,Section 4.The yield of the <br /> bentonite shall be 90 barrels per ton. <br /> 2.3 WATER <br /> A. Fresh water,free of excessive amounts of deleteri ub ces that adversely affect the properties of <br /> the slurry shall be used to manufacture bentonite slu e contractor shall be responsible for <br /> providing the construction water for the • t.The wa physical properties shall be in accordance <br /> with Table 1.It is the responsibility of the at t urry resulting from the water shall <br /> always meet the standards of this Specifica <br /> 2.4 ADDITIVES <br /> A. Admixtures of the type us-• • field or concrete slurries such as softening agents, <br /> dispersants,retarder o •lugg bridging agents may be added to the water or the slurries to permit <br /> efficient use of m• sr.• workability.The Owner's Engineer shall be advised of all additives <br /> used. <br /> 2.5 SB BACKFILL <br /> A. The material for tre •. . g shall be composed of fresh slurry,trench slurry,supplemental fines <br /> and selected soils obta om trench spoils.Trench slurry may be disallowed if additives are not <br /> acceptable to the Owne Engineer.The backfill mix shall contain a minimum of 1.0%dry-added <br /> bentonite by dry unit weight of backfill.The soil shall be friable and free from roots,organic matter, <br /> refuse,or other deleterious materials.The backfill shall be thoroughly mixed and reasonably well graded <br /> between the following gradation limits: <br /> Screen Size Percent Passing <br /> (U.S.Standard) By Dry Weight <br /> 2" >_80 <br /> 3/8" >_65 <br /> #20 40-85 <br /> #200 >25% <br /> Loloff Slurry Wall 3156 00-4 <br />