Hayward Baker Inc. (HBI), North America’s leader in geotechnical construction, recently completed remediation work on the Lake Manatee Dam located in Manatee County south of Tampa, Florida. The nearly 50-year-old dam, constructed of sandy soils with a clay core, serves as a freshwater reservoir for 300,000 area residents.
During annual inspections significant erosion observed and supplemental subsurface investigations revealed a compromised dam core with areas of permeable soils, allowing excessive seepage through and under the dam, which threatened major flooding and depletion of the water supply if left untreated.
Priority remediation goals implemented included reestablishing seepage control via a new cutoff wall within the existing dam embankment and beneath the service spillway.
The scope of the remediation work ultimately consisted of a 3,300 feet long, nominal 2 foot thick cutoff wall to maximum depths of 105 feet below the current crest elevation. The cutoff wall required a minimum of 5 feet embedment into a deep underlying low permeable clay layer. The design required that the wall have a very low permeability of 1x10-6 cm/sec.
Emergency priority Phase I goals of remediation included reestablishing seepage control within the dam embankment and beneath the service spillway. To achieve this, HBI worked closely with the client, Manatee County, and its consulting engineer, AMEC, to develop a plan to achieve the goal.
As the focal point, HBI designed and constructed a Trench cutting Remixing Deep (TRD) cutoff wall located on the north and south sides of the spillway. The 105-foot-long chainsaw-like TRD vertical cutter was inserted vertically in segments by the crawler machine until the design depth of the wall was reached. The base crawler rig then moved along the planned wall alignment as the cutter post cut and mixed the soil with a cement binder constructing the wall in place.
Find more details and photos of Hayward Baker's Dam Rehabilitation Project.
Source: Hayward Baker
Source: Hayward Baker
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