Keller installed large diameter shafts to an extreme depth and completed the work safely and ahead of schedule.
A 30 foot by 30-foot raw water intake tunnel was planned for Lake Travis’ new Water Treatment Plant. Keller drilled the shafts to allow pipe piles to support the structure.
The main challenge was working from an offshore oil rig-type platform, perched almost 70 feet above the water and drilling down to a final depth of 263 feet.
Using a Wirth pile top reverse circulation drill rig, Keller drilled a 12.5-foot diameter shaft 90 feet into the bedrock stratum, with an overall depth of 263 feet from the drill platform to the tip of the shaft. An IMT AF220 drill rig was used to drill 8 relief shafts, each with a 2.5-foot diameter to allow 3-foot heavy wall pipe piles to be driven 40 feet into the bedrock stratum. The installation procedures included the general contractor installing a 195 foot long, 13-foot diameter temporary steel casing through 100 feet of water and sealed 3 to 4 feet into the rock. Beneath the casing, a 90-foot deep rock socket was removed using reverse circulation drilling techniques.