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<br />shall be thoroughly mixed into a homogeneous mass, free from large lumps or pockets of fines, sand, <br />or gravel. Occasional lumps of up to 6 inches in their largest dimension will be permitted. Just prior <br />' to placing, the backfill material shall have a slump of 2 to 6 inches. To this end, the material shall be <br />sluiced with slurry during blending operations. Sluicing with water will not be permitted. <br />Containment berms will be constructed where necessary to prevent slurry from entering rivers or <br />ditches or flowing across the project boundary. <br />3.08 BACKFILL PLACEMENT <br />The backfill shall be placed continuously from the beginning of the trench, in the direction of the <br />excavation, to the end of the trench. The toe of the slope of the trench excavation shall precede the <br />toe of the backfill slope so that the toe of the backfill shall not be less than 50 feet following the toe <br />of the excavation, or as required to permit proper cleaning of the trench bottom and to permit <br />inspection and measurement. Placing operations shall proceed in such a fashion that the surface of <br />the backfill below the slurry shall follow a reasonably smooth grade and shall not have hollows <br />which may trap pockets of slurry during subsequent backfilling. Free dropping of backfill material <br />' through the slurry will not be permitted. Initial backfill shall be placed by lowering it to the bottom <br />of the trenches with clamshell bucket until the surface of the backfill rises above the surface of the <br />slurry trench at the end of the trench. Additional backfill may than be placed in such a manner that <br />' the backfill enters the trench by sliding down the forward face of the previously placed backfill. To <br />accomplish this, sufficient backfill shall be piled on the edge of the existing backfill to cause a slump <br />and sliding action on the face of the in-place backfill. The backfill shall not be dropped or deposited <br />in any manner that will cause segregation. An acceptable substitute for the initial placing of backfill <br />by the use of a clamshell bucket, shall be to begin excavation at a point outside of the limits of work <br />which will provide a sufficient distance for the backfill face to form, by pushing backfill into the <br />trench, before the toe of the backfill reaches the point where the cut-off is required. <br />3.09 TREATMENT FOR TOP OF CUT-OFF TRENCH <br />' Upon completion of backfill placement, and before drying of the backfill can occur, the cutoff trench <br />shall be capped in accordance with the details shown on the drawings or as directed by the Engineer. <br />3.10 CLEAN-UP <br />After completion of the backfill and capping, all remaining excavated material and slurry shall be <br />removed and placed in thin lifts along the inside face of the reservoir and the surface shall be cleaned <br />and leveled as directed by the Engineer. Excess slurry shall be disposed of by spreading in this layers <br />on adjacent areas designated by the Engineer. No slurry shall be left in ponds, and all ponds shall be <br />pumped dry and backfilled. <br />3.11 QUALITY CONTROL <br />The Contractor shall maintain his own quality control for the cut-off wall construction under the <br />direction of a qualified Engineer. Testing requirements are summarized in Table 1 and specified <br />herein. <br />3.12 TRENCHING CONTINUITY AND KEY <br />The Contractor shall be responsible for demonstrating to the satisfactirn of the Engineer that the <br />' trench is continuous and keyed into the bedrock surface. Trench continuity shall be assured by the <br />action of movement of the trench excavation equipment such that the digging tools can be passed <br />vertically from top to bottom of the trench as well as moved horizontally along the axis of the trench <br />without encountering unexcavated material. Penetration of the bottom of the trench into the bedrock <br />07/97 Section 02168 -Page 4 of 5 <br />