Case Studies

Cement-Bentonite Slurry Wall Installation and Bio-Polymer Drain A.V. Watkins Dam

Project Summary

The Willard Reservoir was constructed by the Bureau of Reclamation (BOR) from 1957 to 1964. The dam impounding the reservoir is approximately 14.5 miles long and consists mainly of sand and silty sand over soft clay. On November 2006 there was an area of concentrated seepage through the dam. Large volumes of foundation soil and embankment material had been displaced and breaching of the dam appeared possible. The local authorities and BOR took emergency actions to avoid a potential failure. In order to repair the incident area and prevent future incidents, BOR decided to install a cutoff wall and a toe drain to stabilize the dam.

Geo-Solutions teamed with Nordic Industries to build and install a cutoff wall and toe drain. The wall was a Cement-Bentonite (CB) slurry cutoff wall that was 30 inches wide, approximately 5.5 miles long, and was installed along the crest of the dam. The cutoff wall was installed to provide seepage cutoff in sandy foundation soils. In addition to the Cement-Bentonite wall, a Bio-Polymer drain was installed to dewater the original incident area during slope reconstruction at the toe of the dam. The excavation of the project was planned to take two years. To achieve higher productivity, a double shift was used for the majority of the project and Geo-Solutions and Nordic mobilized highly productive equipment and experienced personnel.

For the construction effort, Geo-Solutions provided technical assistance services to the contractor. The technical assistance included personnel, specialty equipment (including a highly productive CB slurry mixing plant), and slurry materials. Geo-Solutions provided full time supervisors for day and night shifts who supervised contractor quality control of the work as well as operation of key equipment. In addition to the supervision of the project, Geo-Solutions provided materials sampling and Quality Control testing. The custom-designed mix plant featured density monitoring and flow metering with automated electronic controls. Despite a nationwide shortage of bentonite and cement during construction, Geo-Solutions, Inc. was also able to complete the project ahead of schedule and within budget.

Instead of the original 2 year schedule, Geo-Solutions and Nordic completed the entire cutoff wall and toe drain within 5 months. The Owner was pleased with the efforts and the project was completed with no recordable accidents or injuries.

Slurry Wall Dimensions: CB wall: 1,569,741 sf, 2.5 ft wide, maximum depth of 68 ft.
Biopolymer Drain Dimensions: 500 lf, 3 ft wide, maximum depth of 18 ft.

Geo-Solutions Can Help

To download, read, and learn more about the various slurry wall sample specs and technical papers we offer online here at Geo-Solutions.com, click on the links below or to your left:

• Slurry Wall Sample Specs– Geo-Solutions provides slurry wall sample specs which can be modified for real world use on your project. Download sample specification for Slurry Wall Construction.

• Slurry Wall Technical Papers – Browse our library of Slurry Wall Technical Papers.

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