Dam Failure Case Study: Langley Dam (South Carolina, 1886)

The failure of Langley Dam, located near Aiken, South Carolina, is one of the more noteworthy and surprising far field (epicentral distance ~ 176 km) effects of the M7.0, August 31, 1886, Charleston, SC earthquake. Langley Dam, a relatively small earthen mill dam, was constructed on Horse Creek circa the Civil War. Almost immediately after the earthquake shaking ceased, Langley Dam failed and the discharged water damaged two railways, which caused two separate train derailments. Two of the fatalities attributed to the Charleston earthquake were from crewmembers on the two trains. Historical accounts of the dam failure integrated with recently completed geotechnical investigations and site response modeling are used to explain the surprising failure of Langley Dam. Henry W. Grady, who was managing editor of the Atlanta Constitution newspaper, wrote an important historical account of the Langley Dam failure. Mr. Grady left Atlanta for Charleston within hours of the main shock. His detailed trip accounts provide a unique perspective on the aftermath of the Charleston earthquake. In particular, his description of the post-failure condition of Langley Dam is critical in understanding how the dam failed. The foundation conditions and geologic setting of Langley Dam, and the materials and methods used to construct the dam played key roles in its failure. Recognition of the geologic conditions that contributed to the failure of Langley Dam has implications for seismic design of modern structures in similar settings in Georgia and South Carolina.