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3.07 BACKFILL MIXING <br />Material from borrow shall be mixed and blended in mechanical blenders or by windrowing, disk <br />harrowing, bulldozing, b]ading or by other approved methods. Mixing and blending shall be <br />performed in such a manner as to produce the required gradation of backfill. The backfill <br />material shall be thoroughly mixed into a homogeneous mass, free from large lumps or pockets of <br />fines, sand, or gravel. Occasional lumps of up to 6 inches in their largest dimension will be <br />permitted. Just prior to placing, the backfill material shall have a slump of 2 to 6 inches. To this <br />end, the material shall be sluiced with slurry during blending operations. Sluicing with water will <br />not be permitted. Containment berms will be constructed where necessary to prevent slurry from <br />entering rivers or 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 <br />the toe of the backfill slope so that the toe of the backfill shall not be less than 50 feet following <br />the toe of the excavation, or as required to permit proper cleaning of the trench bottom and to <br />permit inspection and measurement. Placing operations shall proceed in such a fashion that the <br />surface of the backfill below the slurry shall follow a reasonably smooth grade and shall not have <br />hollows which may trap pockets of slung during subsequent backfilling. Free dropping of <br />backfill material through the slurry will not be permitted. Initial backfill shall be placed by <br />lowering it to the bottom of the trenches with clamshell bucket until the surface of the backfill <br />rises above the surface of the slurry trench at the end of the trench. Additional backfill may than <br />be placed in such a manner that the backfill enters the trench by sliding down the forward face of <br />the previously placed backfill. To accomplish this, sufficient backfill shalt be piled on the edge <br />of the existing backfill to cause a slump and sliding action on the face of the in-place backfill. <br />The backfill shall not be dropped or deposited in any manner that will cause segregation. An <br />acceptable substitute for the initial placing of backfill by the use of a clamshell bucket, shall be to <br />begin excavation at a point outside of the limits of work which will provide a sufficient distance <br />for the backfill face to form, by pushing backfill into the trench, before the toe of the backfill <br />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 cut-off <br />trench shall be capped in accordance with the details shown on the drawings or as directed by the <br />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 <br />cleaned and leveled as directed by the Engineer. Excess slurry shall be disposed of by spreading <br />in these layers on adjacent areas designated by the Engineer. No slurry shall be left in ponds, and <br />all ponds shall be pumped dry and backfilled. <br />Draft -Technical Specifications <br />01/99 Section 02168 -Page 4 of 5 <br />