$100M plan revealed for better fish passage at Mactaquac dam
John Chilibeck Legislature Bureau
FREDERICTON - Scientists are recommending NB Power spend about $100 million on improving fish passage if it rebuilds the Mactaquac Generating Station.
Allen Curry, a director at the Canadian Rivers Institute at the University of New Brunswick, is one of a dozen senior researchers hired by the public utility to write a series of reports on what would happen to the St. John River’s ecosystem if it goes ahead with rebuilding, refurbishing or taking down the station.
The easiest way to give fish free passage would be to knock the entire structure down, including the dam. But Curry said if the station near Fredericton were rebuilt, NB Power could introduce better systems to help fish circulate more freely in the river, something most species haven’t been able to do since the late 1960s, when the dam was erected.
“We’re providing conceptual ideas around what’s the appropriate fish passage for the St. John River,” Curry said in an interview Tuesday. “As you can imagine, for every species, they need something that’s different. So what we’ve tried to do is put together a package for NB Power that will tell them for the 55 fish species, here are a set of solutions to get them up the dam and a set of solutions for getting them down.”
When the 670-megawatt station was built, conservationists of the era, most notably author and naturalist George Frederick Clarke, warned the dam would destroy one of the world’s greatest salmon runs.
In response, NB Power created a fish collection system below the dam that captures wild Atlantic salmon and gaspereau migrating upriver. The fish are then hoisted onto trucks and moved behind the dam. Curry said the results of the experiment, which includes a salmon hatchery and gene bank run by the federal Department of Fisheries and Oceans, have been mixed.
Gaspereau have prospered in the lake-like environment created by the headpond behind the dam. But the salmon haven’t fared as well. At one time numbering in the tens of thousands, they have been reduced to a few hundred returns a year, although it’s possible other factors such as climate change, pollution, ocean-net fishing, seal predation and aquaculture could also be contributing to their demise.
Other important fish species, such as short-nosed and Atlantic sturgeon, have been blocked from reaching the upper part of the river entirely. While their population numbers are good in the lower reaches, it’s thought they would do even better if they had free reign in the St. John. The large, ancient fish species is threatened or extinct in American rivers south of New Brunswick.
Fish that migrate downriver have to go through the station’s turbines and endure a large free fall, often injuring or killing themselves in the process.
“As part of the solution you’d have fish lifts, like a big elevator for fish,” Curry said. “The eel species need a special ladder and ramp you’d have to build into the facility. And you may have to keep doing some trapping and trucking for other fish. So the solution is going to have to be some combination of all these ideas. It’s not as simple as building a big fish ladder. The dam is too high.”
NB Power has presented four options for Mactaquac, which will reach the end of its service life by 2030 because of deteriorating concrete.
The first three options would cost billions of dollars, even though no firm estimates have been publicly released.
They include building a new generating station, removing all structures to allow the river to return to its natural flow, or leaving the dam in place but without power generation. It has also considered making big repairs that could prolong the life of the station to about 2068, its original, 100-year service life.
The rivers institute began looking at the three original options in 2013 and by the end of this year will have delivered 45 separate reports to NB Power, at a cost of more than $6 million.
The scientists have not recommended what option would be best for the environment because there are too many factors involved. Instead, they have tried to explain what’s most likely to happen if NB Power pursues any single option.
For instance, while many fish would benefit from having a free reign in the river, there’s also worry that invasive species would extend their reach.
Ravenous muskie have already colonized the upper reaches of the St. John, destroying native fish species. The large, pike-like fish was introduced to the river’s headwaters by the Quebec government in the 1970s to lure more anglers, with unintended consequences. Researchers have already found some of the muskellunge downstream of the dam, raising serious concerns.
Rainbow trout that have escaped from stocked ponds and hatcheries in the upper portion of the river would also likely inundate the lower reaches if the dam were removed.
Of all the options in front of NB Power, the worst for fish passage would be to refurbish the existing facilities or shut the generator down and leave the dam in place.
“The current fish passage system isn’t very functional,” Curry said. “We know from every dam around the world that’s had to be retrofitted for fish passage, you can’t achieve the efficiency you’d like to have, because you’re confined by all the existing facilities. So if you’re going to keep the site as a dam, building new is always the best option.”
Fish swimming downstream at Mactaquac are forced to go through sluice gates and endure an enormous free fall, potentially killing or injuring themselves. Photo: daily Gleaner archive