Table Rock Auxillary Spillway Phase 1
Kiewit completed Phase I of the new Table Rock Auxiliary Spillway, which included excavating, blasting and preparing the foundation.
The scope of work featured 254,000 cubic yards of excavation. Controlled rock excavation entailed specific requirements for blasting and mechanical ramming to achieve an undisturbed, competent pre-split face. To stabilize the pre-split walls and downstream floor, crews installed approximately 1,300 rock bolts. The 16.5-foot-long, 1.4-inch-diameter (No. 11 rebar), epoxy-coated bolts were installed on 6.5-foot centers, torqued and tensioned.
Preparation of the spillway foundation was performed in conjunction with placement of zoned embankment, which makes up the new spillway’s core. A section of the dam foundation was prepared by cleaning the embankment’s base. Cracks, clay seams and foundation deficiencies were mapped, before dental concrete was used to level portions of the floor. Once the foundation treatment was complete, the embankment was placed in a six-zone fill.
To prevent water from flowing under the base of the dam, crews placed a 1,230-foot-long by 95-foot-tall grout curtain. To construct the curtain, a line of holes was drilled and pressurized grout was forced into the rock seams. Crews completed the project in September 2000, four months ahead of schedule.