Keller was responsible for the excavation, survey, fabrication, and placement of reinforcing steel, handling/stockpiling of drill spoils, backfilling shafts poured below grade, CSL Testing of selected shafts, and concrete placement.

Vogtle Electric Generating Plant
Completed drilled shafts in the foreground.

The project

Vogtle Electric Generating Plant was planning to add two additional reactors, Units 3 and 4. They also needed to install two cooling towers, that were planned to be 550 feet tall and required drilled shaft foundations.

The challenge

Excavation included drilling through a porous Utley zone (marine-type limestone).

The solution

Keller installed 28 drilled shafts with 48-inch diameters and 208 drilled shafts with 72-inch diameters for both towers. The lengths varied but were 100 feet long on average (some were installed up to 128 feet deep). The work included performing a load test program for the drilled shafts prior to production, this included four lateral load tests and four axial load tests.

The general installation procedure consisted of vibrating 78-inch diameter temporary casing, up to 70 feet in length, and excavating the remainder of the shaft under polymer slurry.

Project facts


Southern Company

Keller business unit(s)


Main contractor(s)

Stone & Webster, Inc.


Shaw Constructors, Inc.