C150009 Project Completion Summary

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, . . . . . ~ . ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ t . t t t t t t t . . . . t t t t t t t t t t t t . 2.0 SPILL WA Y/OUTLET STRUCTURE CONSTRUCTION SUMMARY The concrete spillwayloutlet structure was founded on undisturbed claystone bedrock. All excess water and degraded bedrock material was removed before the base slab was poured. Reinforcing rebar was placed in the excavated foundation with bent bars extending into the structure walls. A six- inch PVC waterstop was cast into the foundation around the base of the spillway shaft walls. The new spillway structure has 12-inch thick walls with two layers of rebar reinforcement. The wall reinforcement was tied to the foundation reinforcement. A 42-inch RCP inlet pipe was cast into the southerly outlet works shaft wall, and the 30-inch diameter ductile iron pipe was cast into the northerly spillway shaft wall. Two rebar hoops were placed around each of the pipes. Waterproofing material was placed on the outside face of the spillway shaft walls up to the highwater line (gauge height 9.7) of the reservoir. Both shafts contain manhole steps for access should any inspections or maintenance need to be performed. All exposed corners were chamfered. A 30-inch by 30-inch Waterman Series S-3000-F-Y self-contained square, medium duty sluice gate, with a handwheel operator, was installed between the spillway and the outlet shafts. The gate frame was sealed against the northerly outlet shaft wall using non-shrink grout and a thin layer of epoxy. The gate was field tested for leakage, and met the leakage standard in the project specifications. Hot dipped galvanized trash racks and grates were bolted to the top of the spillway structure. A three and one-half foot, locking chain link fence was placed around the spillway structure to help prevent uncontrolled access. A staff gauge was placed on the inside of the west wall of the outlet shaft with 0.00 gauge height corresponding to the invert elevation of the outlet pipe. 3.0 OUTLET WORKS PIPE CONSTRUCTION SUMMARY The existing outlet works structure was removed, and the dam embankment was breached. The excavated embankment soils were stockpiled for reconstruction ofthe dam. All organics, large rocks, and tree roots greater than one-inch in diameter were removed before the eKcavated soils were stockpiled. The outlet works pipe is composed of four sections (74 feet) of ductile iron restrained joint pipe placed at a 0.3 percent grade. The outlet pipe was cast into the northerly spillway shaft wall on the upstream side of the dam, and into the reconstructed concrete headwall of the outlet channel on the downstream side of the dam. A 12-inch thick reinforced concrete cutoff wall was constructed at outlet works Station 0 + 88. The cutoff wall extended a minimum of 24 inches out from the outlet pipe. A non-reinforced concrete cradle was placed to the pipe springline. Four sacrificial anodes were placed at outlet works Station 1 + 14. All of the pipe sections were connected with two bond wires. Soil under the concrete cradle was excavated to bedrock. Soil placed beneath the concrete cradle was compacted to a minimum of 98 percent of the maximum dry density as determined by the Standard Proctor test as described in ASTM D698. Soil used in the dam embankment reconstruction over the pipeline was compacted to a minimum of 95 percent of the maximum dry density. FINAL CONSTRUCTION REPORT - Davis No.1 Dam Outlet Works and Spillway Rehabilitation -2- May 2001 !:\OO57 _059.mjb\Conslruction Report\Construction.rpt.wpd