The Austin Dam, a concrete gravity structure, failed catastrophically on September 30, 1911, less than 2 years after its construction. Several engineering evaluations of the failure have been made since immediately following the disaster. Engineers involved in the construction of the dam recognized early on that the dam failed by sliding on its rock foundation. The dam was constructed on interbedded sedimentary rock, and its foundation was taken to a depth of approximately 4 ft (1.2 m). Although studies of the orientation of the failed blocks of the dam and other site evidence pointed to a sliding failure, no detailed quantitative studies have been done. Recent test pit excavations showed that the critical interface for sliding was a sandstone/shale contact located at a shallow depth below the base of the dam. Stability analyses based on shear-strength tests of the different interfaces of the foundation (concrete/sandstone, sandstone/sandstone, sandstone/ shale, and shale/shale) showed that the dam was safe against a bearing capacity failure, but unsafe with respect to sliding and overturning. The lowest factor of safety of 0.6 corresponded to the sandstone/shale interface, as stated above. The major factors believed to have contributed to the failure include low shear strength of the foundation materials, inadequate provisions for reducing the uplift pressure, and weak concrete. The project stands as the sixth worst dam failure in U.S. history in terms of loss of life, and this case history provides numerous lessons with regard to dam safety.

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East Branch Dam is a Pittsburgh District U.S. Army Corps of Engineers (COE) dam that nearly failed in 1957, several years after construction. The dam is a zoned embankment that is 56 m (184 ft) high and 526 m (1,725 ft) long. Its primary purpose is flood control. Following the observation of muddy water flowing from a rock drain at the downstream toe of the dam, soon after construction, emergency drilling through the embankment exposed a void that demanded lowering the pool and subsequent grouting. Localized grouting was accomplished to treat the void but did not involve a comprehensive repair of the dam. The 1957 near failure of East Branch Dam represents an excellent case history that provides dam designers and operators today insight into the mechanisms of internal erosion within an embankment dam, and it underscores the need to quickly take all necessary actions to protect the public. Since the 1957 emergency, the project has performed satisfactorily and has been closely monitored with a network of piezometers, weirs, and alignmentsettlement pins. Even though evidence of further internal erosion has not reappeared, the fundamental conditions that caused the original problem were not corrected by the 1957 emergency repairs. Recently, the dam was evaluated under the COE Screening Portfolio Risk Assessment (SPRA) program.

The City of Pittsburgh, PA is located west of the Appalachian Mountains in the Appalachian Plateaus Province. The relatively flat surface of the plateau is dissected by drainage from the three principal rivers of the region, the Allegheny, Monongahela, and Ohio. The formation of Pittsburgh’s three rivers and drainages has a long history dating back to before the Pleistocene Epoch, linked closely to the advance and retreat of continental glaciation. Western Pennsylvania is associated with the westernmost formation of the Appalachian Mountain chain with deformation in the form of a series of nearly flat-lying, gently warped Paleozoic sedimentary rocks. Rocks cropping out in the region range in age from Devonian to Permian. Pennsylvanian strata are dominated by thin cyclic sequences of sandstone, shale, claystone, coal, and limestone. Most of the geologic hazards present in the region include slope instability, expansive shales and slags, mine subsidence, acid mine drainage, pyritic acid rock and flooding. The region also has an abundance of natural resources including coal, natural gas, oil, salt, limestone, sand and gravel and water. Pittsburgh's strategic location helped shape westward expansion during the formation of the Nation, largely because of the rivers, which served as an inexpensive, yet efficient means of transportation. Infrastructure was always significant in Pittsburgh. However, the existing aging infrastructure are deteriorating. Today, Pittsburgh has transcended the legacy name, “Steel City” and has revitalized itself with nationally-recognized universities and medical centers and a resurgence in natural gas exploration. However, many environmental legacy issues still burden the area.

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