National Dam Inspection Program. Canonsburg Dam Number 2 (Johnsons Run Dam) (NDI Number PA 00506, PennDER Number 63-41), Ohio River Basin, Johnsons Run, Washington County, Pennsylvania. Phase I Inspection Report

摘要

Canonsburg Dam No. 2 (also known as Johnsons Run Dam) consists of an earthfill embankment 36 feet high and 630 feet long. The spillway consists of an ogee weir located at the right abutment of the dam. The crest length is 35 feet and the spillway crest is 4.5 feet below the crest of the embankment. An analysis indicated that the spillway will pass 45 percent of the required PMF before overtopping will occur. Because of a landslide on the downstream face and tension cracks and sloughing on the upstream face, the dam was considered to be in need of emergency attention. The landslide on the downstream face had occurred in May 1979 and the owner had initiated an engineering study into the necessary corrective measures. At the time of inspection, the pool was drawn down and construction modifications consisting of flattening the downstream slope and providing a drainage system had commenced. However, signs of instability of the upstream slope had only recently developed (November 1979) prior to the visual inspection on 4 December 1979. Because of these conditions the dam is considered to be in poor overall condition and is classified as being in an 'Unsafe' - 'Non-Emergency' condition.