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A hometown newspaper with a local office, local owners & lots of local news
At the century mark, it's a first
Work is ongoing this summer on replacing gates that hold back water near the Scanlon hydroelectric power dam run by Minnesota Power. The dam, built in 1923, is getting its first major overhaul since it was first installed.
Gates at the Scanlon dam that have been in place for a century are being replaced with new, specially fabricated gates (pictured).
Project manager Zac Blair, a Minnesota Power engineer, said he drew "the A-team" with J.F. Brennan's crew of seven or eight people to refurbish the dam in Scanlon. The Scanlon hydroelectric infrastructure was built in 1923. Most of what's being replaced dates back to then, with some concrete repairs over time, and one gate having been recently refurbished that is not being replaced. Some minor concrete repairs are also being done this time.
J.F. Brennan employees do much of their work on a barge that floats behind the Scanlon dam. The barge is also home to a large crane during the construction.
Crossing the St. Louis River on Minnesota Highway 61 in Scanlon offers a glimpse of a construction crane and a handful of workers crawling over one of the neighborhood dams.
Even in the rain, the marine contractors from J.F. Brennan can be seen wearing yellow slickers.
They've been working on a $3 million Minnesota Power project since May. It's aimed at replacing seven of eight gates on what is the east channel dam, built 100 years ago.
"Hydro dams are long-lasting, forever assets," said Nora Rosemore from atop the operators' deck of the dam. "If you keep it up, this dam could be here forever."
Rosemore is the hydro manager for Minnesota Power, and is proud to proclaim the company as the state's largest hydroelectric power producer, part of its renewable-sourced energy production that makes up half of the company's portfolio.
The east channel gates are unlike the dam on the other side of the island, where water passes through turbines to produce electricity.
"All that generation and those generators, that's on the other side of the river at the Scanlon hydro plant," Rosemore said. The east channel gates are generally closed, and function during high flow events, like last spring's melt, when water was rushing at 20,000 cubic feet per second. Or during the flood of 2012, when water coursed down the river at 55,000 cubic feet per second. As it is right now, waterflow is 500 cubic feet per second passing into the power plant, which is capable of handling roughly 2,000 cubic feet per second. Anything beyond that requires the waste, or spill, gates to be opened, and water passed through so as not to overflow the dam and risk catastrophic failure.
"They are not used often, but they are critical to have," Rosemore said of the east channel gates. "They're for when we've got a lot of water we've got to pass down river."
Rosemore was joined on a tour of the ongoing dam work by project manager Zac Blair, a Minnesota Power engineer, who said he drew "the A-team" with J.F. Brennan's crew of seven or eight people.
"They're a national marine contractor, and they've worked with Minnesota Power on the hydro system for a lot of years," Blair said.
Replacement of each gate takes about a month, putting estimated completion sometime in October, Blair said. In the meantime, he and the contractors are working on two gates at a time, fully replacing them with new, black-painted steel gates. At 15 feet wide and 7,500 pounds each, the gates are shaped like roll-top desk covers. Each comes with a new hoist which requires a manual operator to roll the gates up so that water can pass beneath them.
"You can see the black marks on the concrete," Rosemore said, pointing below the operators' deck. "That's where the gate rides up."
The gates are being fabricated at Northshore Steel in Two Harbors. To access the gates, bulkheads are set in front of each gate pier and the workspace is dewatered behind the bulkheads using pumps. Contractors are able to disassemble the old gate and fix any concrete that needs restoration before installing a new gate.
"Things are going well," Blair said. "We're doing two gates at a time. As we're installing the first gate, we're demo-ing the second gate."
The Scanlon hydroelectric infrastructure was built in 1923. Most of what's being replaced dates back to then, with some concrete repairs over time, and one gate having been recently refurbished that is not being replaced.
"They knew what they were doing when they built capacity for this flow," Rosemore said of last century's contractors.
Scanlon is part of the St. Louis River Project, the area of Minnesota Power's hydro network that also includes the dam at Knife Falls north of Cloquet, Thomson dam and Fond du Lac dam in Jay Cooke State Park.
Power generated in Scanlon hits the local grid and flows to where it's needed, Rosemore said.
Projects like the gate replacements are long-planned, part of the company's 10-year plan.
"It's investments like this where we're ensuring dam integrity, so we don't have (failures)," Rosemore said. "We're making sure it withstands what Mother Nature gives us."
From atop the walking deck above the dam, one can see water seeping through the old, closed gates.
"It's a little bit, right?" she said. "This water could be going through the generators right now, but it's being wasted. It's time to clean it up and get new gates."
Minnesota Power filed a letter of intent to apply for funding with the U.S. Department of Energy in hopes of recouping up to 30 percent of the project costs via the $110 billion Infrastructure Investment and Jobs Act passed in 2021.
"That funding window just opened," Rosemore said. "We're doing the project regardless, because it needs to be done. But if we can offset customer costs ... we're pursuing that."
Future work targeting the Scanlon dam will come next summer, when one of three power generating turbines at the hydro plant is ticketed to be replaced.
Rosemore praised the overall efficiency of the network.
"But after something
is 100 years old," she
said, "it's time to invest in that infrastructure and rebuild it."
