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.. ~ . material shall have a slump of 2 to 6 inches. To this end, the material shall be sluiced with slurry during blending operations. Sluicing with water will not be permitted. Containment berms will be constructed where necessary to prevent slurry from entering rivers or ditches or Flowing across the project boundary. 3.08 BACKFILL PLACEMENT The backfill shall be placed continuously from the beginning of the trench, in the direction of the excavation, to the end of the trench. The toe of the slope of the trench excavation shall precede the toe of the backfill slope so that the toe of the backfill shall not be less than 50 feet following the toe of the excavation, or as required to permit proper cleaning of the trench boom and to permit inspection and measurement. Placing operations shall proceed in such a fashion that the surface of the backfill below the slurry shall follow a reasonably smooth grade and shall not have hollows which may trap pockets of slurry during subsequent backfilling. Free dropping of backfill material through the slurry will not be permitted. Initial backfill shall be placed by lowering it to the bottom of the trenches with clamshell bucket until the surface of the backfill rises above the surface of the slurry trench at the end of the trench. Additional backfill may than be placed in such a manner that the backfill enters the trench by sliding down the forward face of the previously placed backfill. To accomplish this, sufficient backfill shall be piled on the edge of the existing backfill to cause a slump and sliding action on the face of the in-place backfill. The backfill shall not be dropped or deposited in any manner that will cause segregation. An acceptable substitute for the initial placing of backfill by the use of a clamshell bucket, shall be to begin excavation at a point outside of the limits of work which will provide a sufficient distance for the backtill face to form, by pushing backfill into the trench, before the toe of the backfill reaches the point where the cut-off is required. 3.09 TREATMENT FOR TOP OFCUT-OFF TRENCH Upon completion of backfill placement, and before drying of the backtill can occur, the cut-off trench shall be capped in accordance with the details shown on the drawings or as directed by the Engineer. 3.10 CLEAN-UP After completion of the backfill and capping, all remaining excavated material and slurty shall be removed and placed in thin lifts along the inside face of the reservoir and the surface shall be cleaned and leveled as directed by the Engineer. Excess slurry shall be disposed of by spreading in this layers on adjacent areas designated by the Engineer. No slurry shall be left in ponds, and all ponds shall be pumped dry and backfilled. 3.1 I QUALITY CONTROL The Contractor shall maintain his own quality control far the cut-off wall construction under the direction of a qualified Engineer. Testing requirements are summarized in Table I and specified herein. 3.12 TRENCHING CONTINUITY AND KEY The Contractor shall be responsible for demonstrating to the satisfaction of the Engineer that the trench is continuous and keyed into the bedrock surface. Trench continuity shall be assured by the action of movement of the trench excavation equipment such that the digging tools can be passed vertically from top to bottom of the vench as well as moved horizontally along the axis of the trench without encountering unexcavated material. Penetration of the bottom of the trench into the bedrock shall be demonstrated by observation of the cuttings removed from the trench and the action of the excavating tools on the bedrock surface. 3.13 SLURRY AND BACKFILL O I /99 Section 02168 -Page 4 of 5