Dam Failure Case Study: South Fork Dam (Pennsylvania, 1889)

DamFailures.Org is an ASDSO project that provides individual dam failure case studies and lessons learned as a resource for dam safety engineers, dam operators, owners, regulators, managers, academia and students to help prevent future incidents.

South Fork Dam was an earth- and rock-fill dam located about 8 miles east of Johnstown, Pennsylvania. Originally constructed in 1852, the dam’s primary purpose was to provide a source of water for a division of the Pennsylvania Canal. The dam was approximately 72 feet high, 918 feet long, 10 feet wide at its crest, and 220 feet wide at its base. The outlet works for the dam consisted of a stone-lined culvert with five valves for releasing varying amounts of flow as well as a spillway created by cutting into the rock along the east abutment. Though plans specified a spillway width of 150 feet, the constructed spillway only spanned about 70 feet. As a result of poor maintenance, the outlet works culvert collapsed and a portion of the dam washed out in 1862.