New power supply should help keep North Blenheim dam safe in future floods
NORTH BLENHEIM Efforts to open up spillway gates to protect a Schoharie County dam should be less complicated in the future once the New York Power Authority completes a project to add a redundant power supply to its hydroelectric facility on the Schoharie Creek.
Despite a power outage and the failure of a backup generator, NYPA staff were ultimately able to get all three Tainter-style gates opened up at the Blenheim-Gilboa Pumped Storage Project during Tropical Storm Irene, relieving pressure on the earthen dam that holds back the facility’s 5 billion-gallon lower reservoir.
During the disaster, they had to drag a backup generator to the gates and use an electric drill on each of the gates to get them opened.
Staff were put in a harried position when the water began to rise so fast it threatened to overtop the earthen dam, a major threat to its stability.
The gates opened several feet until, all of a sudden, everything stopped.
The gates were powered by a nearby National Grid electricity line, which like many throughout the Northeast went dead during the throes of Irene.
Crews hooked up the facility’s emergency generator to get the job done, and that generator failed about three hours later, leaving the gates only partly opened.
The backup generator and a power drill, added to quick thinking on the part of staff, likely saved the dam and prevented a disaster in downstream communities that would take on a sudden rush of water were the dam to fail.
The Federal Energy Regulatory Commission this month received plans for a redundant power supply to operate the spillway gates. Work on the project is under way, NYPA spokeswoman Maura Balaban said.
There are three gates that open outward on the dam to release water. Those, as well as valves at the spillway, are powered by the local electricity distribution system “which can be vulnerable to disruptions,” Balaban said in an email.
NYPA is installing a new power supply line from the powerhouse at the foot of Brown Mountain to the dam. It will be safely buried underground.
Balaban said the new power line will provide electricity not only to the Tainter gates but also to the valves, using power from NYPA’s high-voltage transmission lines.
Though they had difficulty getting the gates opened, NYPA staff were able to operate pumps in another section of the hydroelectric plant.
The pumps are employed to send water back up to another 5 billion-gallon reservoir atop Brown Mountain.
The facility, situated downstream from New York City’s Schoharie Reservoir and Gilboa Dam, creates electricity by sending water from the upper reservoir down massive tubes and into turbines.
The water then spills into the lower reservoir and gets pumped back up to the upper reservoir using low-cost electricity available during times of low usage.
NYPA staff during Irene began pumping water up to the upper reservoir, ultimately limiting the amount of water that surged through the Schoharie Valley.
Balaban said installation should be complete in 2014.