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<br />5.0 EXECUTION OF SLURRY-WALL CONSTRUCTION <br />5.1 Preparation of the Site <br />The Applicant shall prepare a temporary working surface within one percent grade along <br />the proposed slurry wall alignment. The preparation shall include stripping topsoil and <br />organic material from the site (topsoil will be stockpiled for future use), excavating or <br />filling the site with suitable materials to grade, and creating berms as necessary to <br />supply all backfill mixing operations. <br />5.2 Slurry Mixing and Hydration <br />The Applicant shall prepare slurry using a flash or paddle mixer to provide a stable <br />colloidal suspension of bentonite in water. Freshly mixed slurry shall be allowed to <br />hydrate initially in storage tanks or ponds. The slurry shall be agitated or re-circulated <br />until the bentonite is fully hydrated, based on stabilized viscosity readings, and until the <br />slurry appears homogenous. No slurry shall be made in the trench. The slurry shall <br />pass all material specifications, prior to placement. <br />5.3 Trench Excavation <br />The Applicant shall take every precaution to avoid disturbance or damage to existing <br />utilities or structures. The excavation equipment shall remain a minimum of twenty feet <br />away from overhead power lines at all times. The trench shall be a minimum of 30 <br />inches wide throughout its length and depth, and a minimum key depth of three feet. <br />Prior to backfilling any portion of the trench, the excavator shall pass its bucket along the <br />trench bottom to verify its uniformity. The toe of the excavation shall not precede the toe <br />of the backfill material by more than 200 feet, but not less than 50 feet. The trench <br />excavation shall be continuous, with a minimum overlap of 50 feet past the starting point. <br />5.4 Backfill Preparation <br />Mixing of the soil-bentonite backfill shall result in meeting the required specifications, <br />prior to placement into the trench. Backfill material shall be thoroughly mixed into a <br />homogenous mixture, free of large lumps or pockets of fines, sand or gravel. Mixing <br />techniques may include windrowing, disc harrowing, bulldozing, blading or using a pug <br />mill. Additions of dry bentonite to the mixture shall be spread over 6 to 8 inch layers <br />