Hayward Baker has successfully completed geotechnical remediation work on the Lake Manatee Dam in Manatee County, south of Tampa, Fla. It took 10 months to complete the project, all while operation of the reservoir was maintained.

“We found Hayward Baker to be a quality partner in this endeavor,” says Mark Simpson, Manatee County Water Division Manager. “We had a relatively short time to correct some major weaknesses in a critical piece of infrastructure, and HBI was able to overcome some substantial issues to get the job completed.”

The construction of a new cutoff wall within the existing dam embankment and beneath the service spillway helped re-establish seepage control. The project involved a 3,300-foot long nominal 2-foot thick cutoff wall. It reaches maximum depths of 105 feet below the current crest elevation. The wall called for a minimum of 5 feet embedment into a deep underlying clay layer of low permeability. The wall’s permeability is 1x10-6 cm/sec.

The 50-year-old structure, which serves as a freshwater reservoir, had experienced a great deal of erosion. Its core was compromised with areas of permeable soils that allowed a lot of water to seep through and underneath the dam. Before Hayward Baker’s rehabilitation efforts, the threat of major flooding and depletion of the water supply was serious.

To install the Trench cutting Remixing Deep (TRD) cutoff wall, a 105-foot long chainsaw like vertical cutter was used. It was inserted vertically in segments by a base crawler rig until desired depth was reached. Then the crawler machine traveled the planned wall alignment as the cutter post cut and mixed the soil with a cement binder constructing the wall.

The TRD wall connects to a jet grouted cutoff wall beneath the spillway, constructed by Hayward Baker. Drill steel was advanced to the maximum treatment depth. Then high velocity jets of cement slurry at the tip of the drill steel mixed with the soil, creating soil-cement columns as the drill steel was withdrawn.

The project was a joint venture of Hayward Baker, Manatee County and its consulting engineer, AMEC.

“The depth, performance requirements and constraints of the project made this a perfect candidate for our TRD and jet grouting techniques,” says Curtis Cook, vice president of Hayward Baker. “As a specialty contractor, it is professionally fulfilling to have the full range of tools to help clients solve difficult geotechnical issues — and an added pleasure to be able to work with the professional team of Manatee County and AMEC.”

Hayward Baker has worked in ground modification and site improvement for 60 years, and offers a range of foundation support and rehabilitation services. For more information, visit www.haywardbaker.com.