Brookfield Renewable Constructs Nature-Like Fishway to Transport Migratory Fish Species
For hydropower facilities, protecting the environment and aquatic life is a top priority. How fish will move through their structures is just one aspect of environmental protection they need to consider. Traditionally, fish move through ladders or elevators, which have proven to be successful and effective means of fish passage. New technology, however, has eligible hydro generators considering fishways, which provide a more-natural fish passage option.
When it came time to relicense its 28.6-megawatt Oswegatchie River Hydroelectric Project, Brookfield Renewable was committed to improving the fish passage systems on its Eel Weir and Heuvelton Dams — two of company’s six hydropower developments on over 90 miles of the Oswegatchie River in St. Lawrence County, N.Y. After careful review, the company installed innovative fishways at both dams, which use the natural terrain of the river and shoreline to emulate natural river channels that accommodate a broad range of fish species and sizes. They also provide a riffle-pool habitat for many aquatic organisms.
“Fishways aren’t possible everywhere because of the variance in design and the complexity of
construction for them to ultimately be viable for fish passage,” says Brookfield Renewable’s Director of Stakeholder Relations, North America Andy Davis. “But if you have the right scenario, fishways are ideal because fish aren’t taken through the stresses of an elevator, ladder or other unnatural feature.”
The fishways would restore a historic migratory route for many fish species — connecting the Saint Lawrence River to upstream spawning and riverine habitats on the Oswegatchie River. For American Eel, the fishways would connect the habitat for growth to their spawning grounds. The fishways would also allow for the travel of Lake Sturgeon, Walleye, Bass, Mooneye, Pike, and minnows upstream or downstream to meet their seasonal spawning, feeding, or overwintering habitat needs.
Construction of the fishway for the Eel Weir Dam began four years ago. The method is so new that the project represented the first fishway installed in New York and the second in the entire Northeast. There were no established guidelines for construction, so it required high levels of planning, consulting, and ingenuity.
Brookfield Renewable planned to excavate bedrock to develop natural weirs and pools. During excavation, the team found the bedrock had a compressed strength greater than 40,000 psi — leaving conventional hoe-raming to break up bedrock ineffective. Then the team tried to break up bedrock using bentonite slurry, which also did not work. So the team approached the Federal Energy Regulatory Commission, which approved carefully blasting the area to break up rock where needed while leaving the surrounding areas undisturbed — a successful method that allowed construction to continue as planned.
The fishway also needed to function during high-flow conditions, which required Brookfield Renewable to install weir stones large enough to stay stationary during flooding. Weir stones also were placed into flood flow channels outside the fishway to create conditions that would provide upstream passage when water levels are high. Construction on the Eel Weir Dam fishway was completed in October 2015.
Then construction started on the Heuvelton Dam fishway, which needed to be built outside of the existing river channel because there was no established instream natural gradient. To create the needed gradient and flow velocities, a series of channels, weirs, and pools were constructed in the channels. Because the fishway needed to be constructed onshore, it needed to take into account the constraints of existing and future structures such as a substation, distribution line poles, roads, private building, and a recreation area.
Given that Heuvelton Dam is located in the center of Heuvelton, N.Y., Brookfield Renewable worked closely with town officials to ensure the city and its residents would be happy with the finished product. As a result, the company has plans to install benches, fishing access sites, and other public features.
“We had a great consultation process with the municipality and the residents that will be looking at this every day and will be affected by its use — we consulted them before we broke ground,” Davis says. “We have neighbors who live just feet away from the fishway and tourists who will come to town and see the facility.”
Construction of the Heuvelton Dam fishway began in 2017 and finished in late 2018. So far, the results have been promising.
Brookfield Renewable was able to measure the early success of the Eel Weir fishway by using fall and spring sampling, as well as monitoring 40 hours of dawn and dusk video. Testing found nearly 600 fish representing nine species moved through the fishway over five days in the fall of 2017. In the spring of 2018, more than 2,000 fish representing 14 species were recorded over five days.
Brookfield Renewable’s efforts were honored by the National Hydropower Association, which awarded it with a 2019 Outstanding Stewards of America’s Waters award in the Recreational, Environmental, and Historical Enhancement category.