2014-12-24_REVISION - M2004051 (4)

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lumps of up to 6 inches in their largest dimension will be permitted. No frozen material, ice, or frost bearing soil shall be mixed into the backfill or allowed to be placed in the trench. Just prior to placing, the backfill 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 interfere with excavation, or as required to permit proper cleaning of the trench bottom 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 slung will not be permitted. Initial backfill shall be placed by lowering it to the bottom of the trench with clamshell or excavator 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, a lead -in trench, which will provide a sufficient distance for the backfill face to form, by pushing backfill into the trench, before the toe of the backfill reaches the point where the cut -off is required. The lead in trench shall be 1.5:1 or flatter. 3.09 TREATMENT FOR TOP OF CUT -OFF TRENCH Upon completion of backfill placement, and before drying of the backfill 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 slurry shall be removed and placed in a manner acceptable to the Owner and the surface shall be cleaned and leveled as directed by the Engineer. Excess slurry shall be disposed of by spreading in thin layers on adjacent areas designated by the Engineer. No slurry shall be left in ponds, and all ponds shall be pumped dry and backfilled as designated by the Owner or Engineer. 3.11 QUALITY CONTROL If Owner accepts Alternate Bid Item A, the Contractor shall conduct the quality control tests for the cut -off wall construction. Any deficiencies revealed by the quality control testing will be corrected immediately by the Contractor. Testing requirements are summarized in Table 1 and specified herein. Testing results shall be available for review by the Engineer on site and delivered to the Engineer on a weekly basis. If Owner does not accept bid Alternative A, Engineer shall establish quality control system above. 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 trench 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 Wattenberg Resource Pond 3 Slurry Wall Section 02168 — Slurry Wall Construction Page 4