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<br />4.0 SLURRY WALL CONSTRUCTION <br />4.1 Slurry Wall Design <br />The slurry wall design will be constructed as shown on the attached cross section and <br />drawing. The slurry wall alignment will be 15 feet inside the permit perimeter of Area C <br />(see Exhibit C-3). The slurry trench wall will have vertical walls not less than 30 inches <br />in width and will continue through the foundation materials and into the bedrock. The <br />slurry wall will not be constructed in areas with a slope greater than 2 percent along the <br />alignment. <br />4.2 Slurry Material <br />The slurry mixture will be comprised of a stable colloidal suspension of bentonite in <br />water and will be prepared and controlled in accordance with current American <br />Petroleum Institute (API) Standard138 and the following specifications: <br />A. The slurry that is introduced into the trench will be a mixture of not less <br />than 64 pounds per cubic foot, consisting of a minimum 5.5 percent <br />bentonite per unit weight of water, to assure that the prepared slurry will <br />meet the specification requirements. Additional bentonite may be added <br />to the slurry, to increase the density or viscosity, as needed. The slurry <br />will have a minimum viscocisty of less than 40 seconds as measured with <br />a Marsh Funnel; a filtrate loss of less than 20 cubic centimeters in 30 <br />minutes at 100 psi; and a pH of 6 to 8. These requirements will be tested <br />a minimum of 1 to 2 times per shift and at least once for each batch of <br />slurry that is prepared. <br />B. The slurry mixture in the trench will have a unit weight not less than 64 <br />pcf and not greater than 85 pcf. The sand content for the slung mixture <br />will not exceed 20 percent of the mixture, or as approved by the Engineer. <br />The slurry level will be maintained at least 3 feet above the ground water <br />elevation and will not be more than 2 feet below the top of the working <br />platform. The slurry density will also be at least 15 pcf less than the <br />backfill unit weight. If the slurry mixture density exceeds the maximum <br />weight, the excess solids will be removed by desanding, or the slurry <br />replaced with fresh slurry. <br />C. The slurry mixed with backfill material will be taken from the trench or will <br />meet the requirements for slurry introduced into the trench. <br />