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New Fish Protection System in Service at NYPA Plant

Photos and Captions

Stephen Shoenholz

September 16, 2008


COLONIE—The New York Power Authority (NYPA) today announced that it has installed a new fish protection system at its Crescent hydroelectric plant on the Mohawk River in an effort to further ease the way for blueback herring on their annual downstream migration to the Atlantic Ocean. 

The previous system, featuring underwater sound projectors, has been redesigned and relocated with the goal of keeping more fish away from the 11.6-megawatt plant’s powerhouse and directing them instead to a bypass atop one of its three dams.  The herring are repelled by the high-frequency sound, which is inaudible to humans. 

“We are confident that the changes will increase the system’s effectiveness,” said Gil C. Quiniones, the Power Authority’s acting chief operating officer, who noted that federal and state regulators have identified the blueback herring as the principal species requiring downstream passage protection at the Crescent plant.  “This initiative is particularly important because the herring is a major food source for recreational fish such as muskellunge, walleye and bass.”         

Dr. Dennis J. Dunning, NYPA’s administrator of aquatic programs and permits, said that in the previous acoustic deterrence system, in service since 2001, the sound projectors were installed at the headrace that directs water to the plant’s four turbine-generators.

“The water in that area moves very quickly so it was difficult for the fish to swim against the current after the sound had driven them away from the powerhouse,” Dunning said.  “Some were unable to make their way out of the headrace.  It’s likely that a number eventually became acclimated to the sound and stopped responding to it at all.”

In the new system, the sound projectors have been moved about 1,600 feet from the headrace to the entrance to a side channel in the river.  The previous configuration of nine projectors has been replaced by two groups of four new units that face in opposite directions and are mounted on a platform in the river bed.  The resulting sound field is wider than that created by the previous system, which consisted of projectors mounted at three locations. 

The sound frequency, as in the past, is between 122 and 128 kilohertz, which is similar to that emitted by dolphins and porpoises to locate herring and other fish in the ocean.  Tests by NYPA last year showed that this frequency range, at a sound pressure level of 163 decibels, consistently elicited a pronounced avoidance response from adult and juvenile blueback herring.  The sound pressure produced by the new system has exceeded that level.  

As part of the new approach, the Power Authority widened the bypass, or notch, on one of the project’s dams, in the river’s main channel, from 40 feet to 80 feet.  It also eliminated a bypass on a second dam, in the side channel.  The changes increased the flow of water through the widened bypass from 125 to 250 cubic feet per second, which should help blueback herring find that opening and thus migrate downriver more quickly.  The third dam was unaffected. 

“Our objective is to keep the herring in the main channel as they migrate down the river and to guide them toward the bypass,” said Dunning, who played a key role in the early 1990s when NYPA installed an acoustic deterrence system, the first of its kind in the United States, at the James A. FitzPatrick Nuclear Power Plant on Lake Ontario near Oswego.  “By staying in the main channel, they won’t be forced to swim against the headrace current to avoid the turbines.  We think this is the simplest, most direct way to protect the maximum number of fish.” 

The overall fish protection plan, including the revised sound projector and bypass configurations, was developed by NYPA in cooperation with the U.S. Fish and Wildlife Service and the New York State Department of Environmental Conservation and was approved by the Federal Energy Regulatory Commission. 

The Power Authority is monitoring passage rates for juvenile herring this year and will do so for adults in 2009.  It was not feasible to study the adults this year because their downstream migration was largely complete by the time the new system was in place.  The system will remain operational this year until the end of the New York State Barge Canal season in November. 

NYPA operates another small hydroelectric facility on the Mohawk River, at Vischer Ferry Dam, about 10 miles upstream from Crescent.  Although that plant also employs an underwater sound system to protect fish, no modifications are considered necessary because of the facility’s more conventional design and the absence of a side channel.

 About NYPA:

■    NYPA uses no tax money or state credit.  It finances its operations through the sale of bonds and revenues earned in large part through sales of electricity.  ■    NYPA is a leader in promoting energy efficiency, new energy technologies and electric transportation initiatives.  ■    It is the nation’s largest state-owned electric utility, with 18 generating facilities in various parts of the state and more than 1,400 circuit-miles of transmission lines.  ■   For more information, please go to

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