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National Dam Inspection Program. Old DAM (NDI ID Number PA-499), Ohio River Basin, St. Patricks Run, Washington County, Pennsylvania. Phase I Inspection Report.

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The Old Dam is an earth embankment. As it presently exists, the embankment is approximately 130 feet long with a maximum height of 38 feet from the downstream toe and a minimum crest width of approximately 8 feet. Review of the design drawings indicates that the embankment as built was 235 feet long. It appears that during the reconstruction of U.S. Route 22, which is approximately 200 feet downstream from the crest of the dam, a significant fill was placed on the left abutment, reducing the embankment to its present length. The flood discharge facilities for the dam consist of a combined primary and emergency spillway located on the left abutment looking downstream. The overflow structure of the spillway is a 49-foot-wide stone overflow section which discharges initially into an earth channel and then into a trapezoidal concrete discharge channel which terminates at a point approximately 200 feet downstream from the toe of the dam in line with the right abutment. The outlet works for the dam as designed consisted of a 24-inch cast-iron pipe through the embankment equipped with a masonry intake structure at the upstream and and a valve at the downstream toe of the embankment. However, presently it appears that the inlet structure has collapsed and now is a mound of rubble. The owner reported that the valve at the downstream end of the outlet pipe has been dynamited in an attempt to drain the lake. The downstream end of the pipe could not be located. It apparently discharges under the surface of the pool of water at the downstream toe of the dam. The dam has no operable emergency drawdown facilities. Author

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  • Civil Engineering

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