National Dam Inspection Program. Hemlock Lake Dam (NDI I.D. PA 00571, PA DER 45-258). Delaware River Basin, Tributary of Pohopoco Creek, Pennsylvania. Phase I Inspection Program,
O'BRIEN AND GERE ENGINEERS INC PHILADELPHIA PA
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Hemlock Lake Dam is an earth embankment about 450 feet long and 27 feet high. An ungated overflow spillway is located at the right abutment. A paved roadway has been constructed on the dam crest and a bridge has been constructed over the spillway. The dam was constructed in the early 1950s to provide a lake for recreational purposes. Hemlock Lake Dam has a maximum storage capacity of 117 acre-feet and a maximum height of 27 feet. The dam is classified as Small size. Due to the potential for excessive property damage and the loss of more than a few lives in the damage center which consists of 5 houses with door sills as low as 5 feet above the stream bed located within 1,500 feet downstream of the dam, the structure classified as a High hazard. Examination of the results of the hydrologic and hydraulic analyses indicates that the spillway is capable of passing approximately 26 of the Probable Maximum Flood PMF without the dam being overtopped. The selected Spillway Design Flood SDF for this Small size, High hazard potential structure is the PMF. The water surface elevation at the damage center is 2.4 feet higher for the breach condition than for the non-breach condition. The spillway is classified as Seriously Inadequate, Unsafe, Non-Emergency since breaching of the dam significantly increases the downstream hazard potential. Based on visual observations and a review of the information obtained from the Pennsylvania Department of Environmental Resources DER, Hemlock Lake Dam appears to be in poor condition.
- Hydrology, Limnology and Potamology
- Civil Engineering