New York Power Authority

Eel Passage Facility

Summary

When the New York Power Authority received a federal license in 1953 to build its first generating facility, known today as the St. Lawrence-Franklin D. Roosevelt Power Project, it set a new standard in hydropower development by including an unprecedented degree of conservation and recreational features in its plans. In 2003, the St. Lawrence-FDR project again broke new ground when it received a new 50-year license for its use for an innovative, collaborative approach to relicense the Project. Following that achievement, the Authority continued to set the standard in its collaboration with the U.S. Fish and Wildlife Service (FWS) and the New York State Department of Environmental Conservation (DEC) for a state-of-the-art passage facility at the Project’s Robert Moses Power Dam for American eel migrating upstream to the Upper St. Lawrence River and Lake Ontario.

Designing the passage facility required not on a state-of-the-art ladder section for eels to climb, but also a practical and innovative solution to the challenge of delivering eels from the top of the Dam to a safe release location upstream. Although an upstream delivery system of eels has never been used, the Authority and its design team successfully designed and tested such a system which included a passage pipe and a receiving basing in the River. In its first year of operation, all aspects of the fishway performed almost flawlessly; all eels that ascended the ladder on the Dam successfully swam through the passage pipe. With a total of 8160 eels completing the journey through the facility and a similar number using the ladder on the Canadian portion of the Dam, the number of eels passing upstream doubled in 2006. The outstanding performance of the state-of-the-art facility was celebrated by the Authority, FWS, and DEC in mid-summer as they gathered at the Dam to mark its success and to look forward to years of providing safe upstream passage for an increasing number of eels.

Background

Breaking ground in 1954, over 6,000 construction workers took five years to build the 912-MW St. Lawrence-Franklin D. Roosevelt Power Project, part of the joint United States-Canadian effort to create the International Power Project and the associated ST. Lawrence Seaway. Forty years later, the New York Power Authority, owner of the American portion of the International Power Project, organized a much smaill team of staff members to relicense its flagship hydropower facility, whose 50-year license was set to expire in 2003.

Drawing on concepts championed by the National Hydropower Association and the Hydro Reform Coalition, the Authority developed an innovative strategy for early and active public participation in the complex task of relicensing the Project for the 21st century. The resulting Cooperative Consultation Process (CCP) involved about 100 stakeholders across a wide cross section of public and private interests. The CCP team met regularly to identify issues, resolve their differences, and reach consensus on issues ranging from environmental impacts to socioeconomic concerns. Their efforts culminated in the Comprehensive Relicensing Settlement Accord, which recommended specific terms of the Project’s new license to the Federal Regulatory Commission.

While production of reliable hydroelectric energy provided many benefits, it also brought environmental consequences, including blocking the movement of your American eels migrating from the Atlantic Ocean to the upper St. Lawrence River and Lake Ontario. Mitigation to this impediment was provided in the 1970’s when Ontario Hydro (now Ontario Power Generation), the owner of the Canadian half of the International Power Project, installed an eel ladder on its portion of the Dam. The need for additional passage at the Dam was an issue raised by the U.S. Fish and Wildlife Service (FWS) and the New York State Department of Environmental Conservation (DEC) during the CCP relicensing process.

The need for additional passage facilities was affirmed through studies that demonstrated the there were a substantial number of eels on the American side of the Dam and that many of these eels did not move to the eel ladder in Canada. The Authority, FWS, and DEC agreed that another eel ladder would provide an opportunity to increase upstream eel passage.

Challenge

The Authority began planning the new fishway by reviewing the performance of the ladder on the Canadian side of the Dam and an eel ladder installed in 2000 at Hydro Quebec’s Beauharnois Power Dam near Montreal. While the experience at these ladders provided valuable information for design and on seasonal and daily periods of eel movement, an unexpected issue was discovered. Almost half the eels that successfully climbed the ladder on the Canadian portion on the Dam fell back below the Dam, presumably through the turbines. This fall back indicated that a ladder to carry eels above the international Dam was not enough. Its was necessary to release eels at a location where they would be less likely to fall back through the turbines. The challenge ws two fold – find a safe release location and design the system to deliver eels to it.

Innovation

The location of the safe release point was determined by a study in which tagged eels were released at various locations upstream of the Dam and then were trapped downstream of the Dam to see what proportion fell back through the turbines. The study showed that the fall-back rate decreased to approximately 6% at a release location 980 ft. upstream of the Dam, with only slightly lower fall-back rates at release pointes still farther upstream. Based on this information, this location was selected for the release of the eels.

Several methods were considered for a system to safely deliver eels to the release location. A pipe was judged to be the simplest and most cost-effective method, but a pipe had never been used to move eels over a distance of 980 ft. The Authority assessed the feasibility of this approach with a 100-ft test pipe with initial testing attempting to flush them through with high flows. Despite the belief that juvenile eels are not thought to be strong swimmers, the eels readily swam against all but the highest velocities (5.9 feet per second) and were not effectively washed through the pipe with the flow. Undeterred, the biologists realized that they could use an eel’s natural inclination to swim into a current by reversing the direction of flow in the pipe thereby allowing eels to swim through the pipe. When the flow direction was reversed, all test eels swam against a relatively low flow and successfully passed through the pipe.

With this information in and working with engineers and biologists at FWS and DEC, the Authority and its design team of engineers from C&S Engineers (Syracuse, N.Y.) and eel biologist from Milieu, Inc (LaPrairie, Quebec) completed design of the fishway. It consisted of five distinct elements: a ladder that provides the pathway for the eels to ascend to the top of the Dam, a collection hopper that provides a transition to a passage pipe, the passage pipe that provides a transition to receiving basin, and a receiving basin in the River that provided a safe haven for eels after passage through the facility before they return to the river. Detailed descriptions of these five components are provided in Section 5.

During design, the team uncovered yet another challenge in the upstream delivery system. The receiving tank’s two functions – supplying a steady flow to the passage pipe and allowing eels to move from the pipe to the receiving basin – required an effective separation of two separate flows into the tank; a 0.71 cubic feet per minute flow released at the top of the ramp that leads to the receiving basin and the 10.95ft3/min flow introduced into the bottom of the tank for the passage-pipe flow. For eels to find the much smaller flow from the climbing ramp, it was necessary to eliminate cues provided by the flow for the passage pipe. This was accomplished by delivering the greater flow through an inclined porous false perforated plate in the bottom in the receiving tank. This porous plate physically separated eels from this flow and dispersed it through a large enough area that it minimized any flow cues.

Results

Completed in June 2006 at a cost of approximately $2 million, the facility began to operate on July 1. All components of the fishway performed exceptionally well, with nearly 100% availability through the four-month period of eel migration. During its first year of operation, a total of 8060 eels completed the journey through the facility. With a similar number using the ladder on the Canadian portion of the Dam, the number of eels passing upstream doubled in 2006.

The fishway’s operational success was mirrored by its effectiveness in passing the eels as demonstrated by equipment throughout the facility that monitored the movement of tagged eels. As expected, monitoring shoed that eels successfully climbed the ladder, typically in approximately 60 minutes. For the upstream delivery system, monitoring showed that every eel that climbed the ladder successfully moved through the passage pipe, typically in about 30 minutes, and successfully reached upstream waters. One eel moved through the entire facility in 36 minutes! Furthermore, eel fall back through the turbines was below 2%, less that the 6% estimated from the release-location study. This success validated the design of the facility, especially the unique elements for the upstream delivery system, and surpassed the expectation of even the most optimistic member of the design team.

The Authority is extremely pleased that years of study and careful planning have resulted in a fishway that performed almost flawlessly during its first year of operation. The outstanding performance of this state-of-the-art facility allowed the Authority, FWS and DEC to gather at the Dam in mid-summer to celebrate its success and to look forward to years of providing safe upstream passage for an increasing number of eels.