National Dam Inspection Program. Hilloch Dam, NDI Number PA-00933, DER Number 23-89. Delaware River Basin. Tributary to Harvey Run, Delaware County, Pennsylvania. Phase I Inspection Report,
WOODWARD-CLYDE CONSULTANTS PLYMOUTH MEETING PA
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Hilloch Dam is a privately owned dam used for recreational purposes. The dam is in fair condition and the spillway is considered to be in poor condition. In accordance with criteria established by Federal OCE Guidelines, the recommended spillway design flood for this Small size dam and Significant hazard classification is the 100 Year Event to one-half the Probable Maximum Flood PMF. Based on the small capacity of the reservoir and limited downstream development the 100 Year Event has been selected as the spillway design flood. Hydrologic and hydraulic computations presented in Appendix D indicate the spillway structure is capable of discharging the 100 Year Event without overtopping the embankment. The spillway is therefore considered Adequate although available freeboard during the spillway design storm is limited to 0.3 feet under existing conditions. Because of the potential for property damage in the event of failure, a formal procedure of observation and warning during periods of high precipitation should be developed and implemented for this facility. This procedure should be coordinated with local authorities and should include a method of warning downstream residents that high flows are expected. In addition, an operational and maintenance procedure should be developed to insure that all pertinent items are carefully inspected on a regular basis and maintained in the best possible condition.
- Hydrology, Limnology and Potamology
- Civil Engineering