National Dam Inspection Program. Rossiter Dam (NDI I.D. PA-1080, DER I. D. 032-019), Ohio River Basin, Straight Branch Run, Indiana County, Pennsylvania. Phase I Inspection Report

Based on the evaluation of existing conditions, the condition of Rossiter Dam is considered to be unsafe/nonemergency due to a seriously inadequate spillway capacity. The overall condition of the dam is considered to be poor. The spillway structures have partially collapsed and the dam is overgrown with large trees and thick brush, precluding a complete inspection. The spillway capacity was evaluated according to the recommended criteria and was found to be seriously inadequate. According to the recommended criteria, small dams in the high hazard category are required to pass from one-half to full Probable Maximum Flood (PMF). In view of the small size of the dam, one- half of the PMF was selected as the spillway design flood. Flood discharge capacity was evaluated according to the recommended procedure and was found to pass 20 percent of the PMF without overtopping the embankment. Since the spillway capacity is less than 50 percent of the PMF and results of a breach analysis indicate that the potential loss of life and downstream damage would be significantly increased due to a dam failure, the spillway is classified to be seriously inadequate. (Author)