Hydrocutter-Excavated Slurry Wall for Center Hill Dam Foundation Remediation-Paper

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The Center Hill Dam Foundation Remediation Project addressed karst features and signs of distress that had led the U.S. Army Corps of Engineers to assign the dam its most critical safety classification. From 2011 to 2014, BAUER Foundation Corp. constructed two deep cutoff walls to stabilize the embankment and control seepage.<br /><br />The first, an encasement wall, extended through the clay embankment and into bedrock. Its main section was built from overlapping panels up to 210 feet deep and 7.4 feet wide—the widest diaphragm wall reported at the time. It was designed to support the embankment and protect it if excavation fluid was lost during construction of the second wall.<br /><br />The barrier wall formed the seepage cutoff. It extended through the encasement wall into bedrock, reaching depths of up to 307 feet, and was designed to be at least 2 feet wide. BAUER BC40 and BC50 hydrocutter systems excavated most of the walls. Real-time inclinometer and gyroscope data, combined with adjustable steering plates and cutter-wheel speeds, enabled operators to control verticality and panel orientation in challenging conditions, including hard limestone and steep soil–rock interfaces.<br /><br />The encasement wall was excavated under bentonite slurry; water was used for the barrier wall. Fluid was cleaned and recycled, and concrete was placed by tremie. As-built surveys confirmed that both walls met their stringent geometry requirements. The barrier wall’s maximum deviation from vertical was 0.56 feet, and maximum panel rotation was 3.3 degrees, within the specified limits. Minimum overlap was achieved, producing wall thicknesses greater than the 2-foot design minimum at nearly all overlaps.<br /><br />The hydrocutter’s accuracy also supported a value-engineering proposal that eliminated approximately 100 planned columns, saving the government more than $13 million. The project demonstrated the effectiveness of accurately steered hydrocutter excavation for dam remediation in complex geological conditions.

Keywords

Center Hill Dam

foundation remediation

karst features

seepage control

cutoff walls

diaphragm wall

BAUER Foundation Corp.

hydrocutter excavation

bentonite slurry

dam safety classification