DIAPHRAGM WALLS FOR SEEPAGE CONTROL AND REMEDIATION: A COMPARISON OF THREE CASE HISTORIES-Paper

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The paper describes three U.S. Army Corps of Engineers dam-remediation projects, showing how seepage-control and soil-improvement methods were tailored to site conditions and performance requirements.<br /><br />At Tuttle Creek Dam, Kansas, 351 transverse shear walls were installed near the downstream toe to reinforce liquefiable foundation soils and reduce earthquake-induced deformation without blocking underseepage. The walls were excavated by clamshell and filled with self-hardening slurry (SHS). A specially designed mix achieved the required strength; core tests recorded an average unconfined compressive strength (UCS) of 357 psi, exceeding the 300-psi target.<br /><br />At Herbert Hoover Dike, Florida, an SHS cutoff wall was built through variable soils and limestone to address risks from internal erosion and piping. Clamshells removed upper organic and fill materials, while a hydromill excavated deeper soils and rock. The resulting wall met specified strength and permeability criteria, and testing confirmed continuity and homogeneity across more than 7 miles of construction.<br /><br />At Bolivar Dam, Ohio, a deep seepage barrier was required through the upstream slope, including sections embedded in bedrock. Because the depth, rock conditions, and high strength requirements made an SHS wall unsuitable, the contractor selected plastic-concrete panels excavated using clamshell and hydromill equipment. Extensive quality-control testing confirmed the wall’s continuity, strength, and low permeability; measured UCS averaged about 1,300 psi, and permeability was well below the specified limit.<br /><br />Across all three projects, performance specifications, carefully selected construction techniques, purpose-designed materials, and rigorous quality assurance were central to success. The authors conclude that no single method suits every dam: solutions must be adapted to the geology, construction challenges, and required performance of each site.

Keywords

dam remediation

seepage control

soil improvement

U.S. Army Corps of Engineers

Tuttle Creek Dam

Herbert Hoover Dike

Bolivar Dam

self-hardening slurry

plastic-concrete panels

quality assurance