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B. The permeability of the backfill shall be less than 1 x 10-7cm/sec when tested in accordance with ASTM <br /> D 5084.The slump of the backfill shall be 3 to 6 inches,and the density of the backfill shall be at least 15 <br /> pcf greater than the density of the slurry. <br /> C. The fines in the backfill soil shall have sufficient plasticity so that the material can be rolled by hand into <br /> a 1/8"thread without crumbling. The water content of the backfill material shall not exceed 20%prior <br /> to blending with bentonite and/or slurry. <br /> D. Material excavated from the trench is not expected to meet the above requirements for backfill. Excess <br /> sand and gravel excavated from the slurry trench will need to be"wasted"and not included in the final <br /> backfill mix. The"wasted"sand and gravel shall be replaced with approved supplemental fines. <br /> Supplemental fines may have to be stockpiled along the slurry wall alignment.The Contractor is <br /> responsible for identifying an off-site supplemental fines source and delivering the material to the site. <br /> Supplemental fines are anticipated to be from the Davis Farm Fines ockpile. Davis Farm Fines used as <br /> supplemental fines shall have a minimum of 65%(dry unit weig ssing the No.200 sieve and shall <br /> have a PI greater than 15.The Contractor is responsible ford ' g the material to the site. <br /> E. Dry bentonite at a minimum rate of 1.0%of the dry weig back I terial will be added to the <br /> backfill prior to mixing. <br /> 2.6 SLURRY TRENCH CUTOFF <br /> A slurry trench cutoff wall shall be construe -• to the li rades,and cross sections indicated on the <br /> drawings.The trench shall have essentiall •ails,a 'mum width of 36 inches,and shall <br /> extend through the overburden and weath. •d be, •• ey a minimum depth of 4 ft into the <br /> designated stratum as shown on •- •rawin; <br /> 2.7 TOLERANCES <br /> A. The following tolerances sha o the s • trench dimensions and construction. <br /> 1. The slurry tr-' . -nt be constructed as shown on the project drawings and shall not <br /> deviate fr. enterline or- an 1 ft left or right. <br /> 2. The slurry ' h shall be mb within 3%of vertical. <br /> 3. The depth of th. rry ch shall be measured or surveyed to within 3 inches of the desired <br /> elevation. <br /> 4. The excavating tool shall be at least as wide as the design width of the slurry trench. <br /> 5. Overlaps and changes in direction of the slurry trench shall require a full depth over excavation at <br /> least 5 ft beyond the centerline of the trench. In cases where the trench must be re-excavated(for • <br /> example,due to an extended shutdown,cave-in, rework,etc.)the overlap into acceptable backfill <br /> shall be at least 10 ft. <br /> 2.8 EQUIPMENT <br /> A. Trench Excavation <br /> Loloff Slurry Wall 3156 00-5 <br />