Rebuilding Dams in The Sand Hills: Challenges of Seepage Control and Embankment Stability-Video

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Video Summary

The presentation covered the rehabilitation of Langley Pond Dam on the South Carolina–Georgia border. Built in the 1860s, the 35-foot-high earthen dam had a long history of seepage and internal erosion. Investigations found very loose, permeable “sugar sand” in the embankment, as well as timber structures and voids beneath the old spillway.<br /><br />Reconstruction included a 65-foot-deep cement-bentonite slurry wall keyed into low-permeability residual soil to control seepage. Late in construction, very soft peat, clay, organics, and loose sediments beneath the upstream cofferdam created a stability risk. Rather than mobilize specialized equipment, the team adapted the slurry-wall equipment to build seven stronger, roughly 25-foot-deep shear walls beneath the upstream slope.<br /><br />The project demonstrated the value of CPT investigations, careful field observations, and adapting available equipment to address unexpected conditions efficiently. The seepage barrier has helped mitigate problems that had persisted for decades.

Keywords

Langley Pond Dam

seepage control

slurry wall

dam rehabilitation

CPT investigations