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l 3-2 l - • 23, 1982. Final grading and site clean-up were completed on August 27. 1 Equipment used during slurry wall and pump-back system construction included: o FMC Link-Belt LS-7400 backhoe o CAT-DSK dozer o JD 690-B backhoe o JD 544-B front end loader o Utility/fuel truck o Pumps - B+S 8 hp - Gorman Rupp Co. pump 14C2-F3L - Gorman Rupp Co. pump 16C2-5034 3.2 SLURRY WALL AND EMBANKMENT , The slurry wall vas constructed in the location shown in Figure 2. The location and length of the slurry wall vas chosen in the field to maximize the amount of seepage intercepted. In preparation of the actual excavation, a construction pad vas built of compacted fill •along the proposed axle of the slurry wall. This pad vas also part of the retention embankment across the ~• valley. The grades along the top of the pad were an average of 2-1/2 percent and all less than 4 percent. Station numbers were Snstituted along the construction pad to facilitate all measurements. Station numbers began with Oi00 on the vest abutment and proceeded eastward extending approximately 430 feet to Station 4+30. (see Figure 2). The bentonite for the wall vas mixed into slurry form and stored on-site prior to placement in the trench. Approximately 48.5 tons of premium grade, 124 pounds/barrel yield, Wyoming bentonite were delivered in two truck-loads. Mixing with pond eater occurred on the crest of the lower tailings pond. The resultant slurry was pumped to a holding pond just upstream of the proposed slurry wall location. Mixing produced a 1/44 second viscosity bentonite with an approximate specific gravity in the range of 1.06 to 1.08. A 35-Foot reach, FMC Link-Belt backhoe vas used for trench excavation. Excavation began from Station 0+00 and proceeded to Station 0+50 on the western portion of the embankment. The drill rig was operating on the eastern ~• D~~~1®T~ _.