On Thursday, March 12, 2009, the Licensee’s representative informed the FERC regional office that during the ongoing activity for the installation of the new authorized Unit No. 1, they discovered a void under a portion of the existing concrete penstock section (the penstock for unit 1 was part of the original project for future expansion) The void was found when leakage was observed upon initial filling of the penstock which was subsequently dewatered; and cores were taken under the Unit 1 concrete penstock. The void is about 2 feet deep under the central section of the penstock but rapidly decreases. The licensee is going to investigate the other four unit penstocks to find if there are voids under these penstocks. The intake structure has sheet piling around it which provides seepage control, but the penstock apparently lost part of its support and the Licensee wants to make repairs as soon as possible. As the intake is at the downstream end of a 3,000 foot-long headrace canal that starts at the dam, it does not seem that the void presents an immediate dam safety issue. No other anomalies have been observed by the Licensee. The Licensee has hired a consultant to review the situation and provide a plan for repairs. The project dam is a concrete buttress structure, 80 feet high and 1,500 feet long with a small uncontrolled gravity spillway at fixed crest elevation 349.60 feet with flashboards that bring the normal pool to elev. 353.3 feet. The dam is located on the Upper Hudson River in Saratoga County, NY, north of Albany. The reservoir has a surface area of 350 acres with a gross storage capacity of 9,150 acre-feet at a normal pond level of 353.3 feet. The dam is classified as having a high hazard potential.
Failure Mode
Loss of support due to a void under the penstock
Effect
Storage Lost
Fatalities
0
Remedial Action
The licensee hired a consultant to develop plans for repairs.
