The Redridge steel dam from downstream. While the six holes cut through the dam can be plainly seen draining water from the reservoir, the actual outlet pipes are near the surface of the river below. Joshua Vissers/Daily Mining Gazette
This story was originally published by the Daily Mining Gazette.
The world’s longest steel dam, at Redridge, isn’t even registered as a dam anymore. Its outlet pipes are as open as they’ll get, and six large holes have been cut in its face to act as an emergency spillway. The registered dam at Redridge is actually the rock and timber dam 200 feet upstream, which is now more than 120 years old and still holds back a reservoir of about 74 acres of water back from Lake Superior.
To untangle the current condition of the dams at Redridge takes a bit of a history lesson.
A 1972 photo of the timber crib dam built in 1894. Much of the timber portion visible here was removed in 2005, lowering the level of the reservoir. Provided by Barbara Koski
The first dam, made of rock fill and timber, was built in 1894 by the Atlantic Mining Company to provide water for stamp mill operations. It consisted mostly of mine rock, supported by a timber structure that supports and protects it from erosion as water spills over the top. The dam was originally constructed with two cast iron pipes to release water, but according to modern inspection reports, all sign of them has disappeared as of 1979.
Because the government had told them that they had to stop dumping stamp sands into the Portage Canal, stamp mills had started moving to the Lake Superior Shore. This increased the demand for water at Redridge, and the Atlantic and Baltic mining companies agreed in 1900 to build a larger dam there to supply both company’s operations.
A photo from during the Redridge steel dam construction by workers from the Wisconsin Bridge and Iron Company and Prendergast & Carson. Bill Brinkman’s father was a worker on the project. Provided by Bill Brinkman via Barbara Koski
A breakdown of costs from the first year of the steel dam’s construction. Final costs for the dam were about $150,000. Adjusted for inflation, that’s about $4.5 million today. From Clarence J. Monette’s “Redridge and its Steel Dam”
The new dam would be built of steel, largely because it was easier to move the required steel to Redridge’s remote location than concrete or other building material. Steel dams can also be built faster, and are more resistant to frost and ground settling, important considerations for Copper Country’s long winters.
The steel dam at Redridge was only the second dam of this type built in the world, and at 464 feet long, it was the first of any significant size. When the steel dam was completed in 1901, it inundated the timber dam, hiding it below 20 feet of water. The new impoundment was roughly twice the size of the first dam’s.
Stamp mill operations ceased in the 1920s, but the dam was left standing, largely intact.
In spring of 1941, water came over the top of the steel dam when, according to local historian Clarence Monette, beaver dams upstream broke, sending a torrent of water and debris at the dam. While the steel structure held, severe damage was done to the spillway on the west side of the main structure, breaking open the gates that restricted flow out of the reservoir.
Water flowing over the top of the Redridge steel dam in April of 1941. Provided by Barbara Koski
Debris flowed down the spillway and became lodged in the culverts below the road to Freda and Beacon Hill. Water began building up between the dam and the road. The road was nearly washed out, but the water stopped and began receding about two feet from coming over the road.
When the steel dam was initially drained isn’t noted by Monette, but other dates suggest it would have been around 1950 or 1951. This once again revealed the timber crib dam, and since then the two dams have each held back some of the Salmon Trout River.
In 1979, the dam was owned by the Copper Range Company. Concerned with the lack of an emergency spillway and the ability of the aging structure to hold full capacity during spring thaws, they cut four large holes in the steel section of the dam to act as a new spillway. Later, when the initial holes proved insufficient to keep the reservoir drained, two more holes were cut.
While nobody has reported seeing the steel structure overtopped by water since the holes were cut, there are other issues. The dam was originally designed so that water flowing over its top wouldn’t erode the base of the dam itself, but that design didn’t include six 4-by-8 foot holes in the middle of the steel face of the structure.
By the beginning of the new millennium, the Redridge dams were owned by Stanton Township and roughly as you see them today, with a couple exceptions. Under recommendation from the then-Department of Environmental Quality, the upper, timber portion of the older, earth-fill dam was removed in 2004, lowering it by about 13 more feet.
”The Redridge Dam is in fair condition,” the inspection reports from 2005 and 2014 say. “There were no deficiencies observed during the inspection that would lead to failure of the dam.”
The inspector went on to recommend the removal of trees and shrubs on the dam embankments, the continued planning for the repair or removal of the earth and timber dam, and the development of written plans for operation, maintenance, and emergency action.
That might still be the condition of the dams today, if it weren’t for the heavy rains of Father’s Day 2018.
“The best we can tell, the water went up about two-thirds of the dam,” Stan Vitton said.
Stan Vitton, civil and environmental engineering professor at MTU, leans on one of Redridge dam’s supports, which swings freely after taking damage in the 2018 floods. Behind him, water continues to rush over the concrete base of the dam, eroding it. Joshua Vissers/Daily Mining Gazette
Vitton is a professor of civil and environmental engineering at Michigan Technological University. He grew up on the Keweenaw Peninsula and is now part of a group of locals working to preserve the Redridge steel dam as a national landmark.
During the Father’s Day event, water rushed over the earthen dam, and culverts under the road to Freda were temporarily plugged, building pressure against the road’s embankment. Vitton believes the steel dam is the only thing that kept the road from being washed away.
“The steel dam became something of a baffle,” he said.
Even though the dam had six 4-by-8 holes that let water pour through, it was still holding back a significant amount of the flow, too. Enough to, Vitton thinks, keep enough pressure off the road to save it.
The steel dam, however, didn’t escape unscathed. Not only did a significant amount of the concrete base behind the dam get eroded away by the torrent of water and debris, but one of the major steel supports was broken completely loose of its concrete mount. Left to deteriorate, these significant structural deficiencies will lead to the eventual failure of the dam.
If the dam did fail, Chris Van Arsdale has a plan. An Emergency Action Plan, to be specific.
Van Arsdale is the Emergency Management Coordinator for Houghton and Keweenaw Counties. His full-time job is to keep the EAP updated with emergency contacts, available resources, and important considerations for every kind of emergency imaginable for Houghton and Keweenaw counties.
“It’s not so much like “do this” it’s more like “should you do this”, or “have you considered this?’” Van Arsdale said. “In the moment, these might not be obvious things to think about.”
He said that open-endedness is to keep the plan, and the people using it, flexible and responsive to unanticipated situations.
While some dam failures would require an immediate public notice component to the plan, in Redridge’s case, Van Arsdale doesn’t think it would help much. The proximity of the dam to Lake Superior means the very few people in the floodplain would be aware of the problem well before any warning message could be arranged and sent. But there are other considerations.
“The big one would be access for fire and EMS… to the homes south of there,” Van Arsdale said.
Depending on the details of the situation, options include logging and ATV trails, a temporary replacement culvert, ferry boat service, or an emergency temporary bridge called Acrow Bridge.
The EAP is not available to the public, both because of the personal contact information included, and because the detailed information about public infrastructure and emergency response is something sought after by terrorists.
The 2018 damage to Redridge is not being left to further decay, however.
Copper Country’s infrastructure took a heavy damage during the 2018 Father’s Day flooding. Among the repairs still being made are those to Redridge’s steel dam.
Stan Vitton, a professor of civil and environmental engineering at Michigan Technological University, is a key member of the Redridge Dam Revitalization Project. The group, led by Ken Vrana, is working to save the Redridge dams for several reasons.
“The dam has historic value, number one,” Vitton said.
The steel dam was listed in the National Registry of Historic Places in 1992. Vitton also thinks the steel dam helps the resiliency of the road downstream in situations like the Father’s Day flood.
Images showing the Redridge dam reservoir in June of 1938 (above) and 2020, showing the difference in the reservoir’s size after it was lowered twice-- around 1950 when the steel dam was opened, and in 2004 when the top of the timber and rockfill dam was removed. EarthExplorerer.com and Google Maps
“The dam, in my opinion, retained enough water to keep the road from failing,” he said.
Marvin Heinonen is the supervisor of Stanton Township, which currently owns the dam. According to him, the dam is also a popular recreation spot for hikers, picnicers and especially fishermen. Steelhead congregate below the dam, and above the dam is entirely free from sea lamprey (first observed in Lake Superior in 1938), making it a good brook trout habitat.
After the damage to the steel dam made it less stable, Vitton, Heinonen and others worked with the Federal Emergency Management Agency to get grant money made available under the disaster declaration. They were approved for two projects. One to clear debris and repair damage to the drainage pipes, and $270,000 to refinish the cement, and stabilize the loose steel support.
The logs and other debris have been removed from the dams and moved away from the reservoir already, but the work on the cement and steel has yet to begin.
“We’re going to put it out on bids and that concrete is going to be beefed up so that we don’t have any issues in the future,” Heinonen said.He expects the repairs to keep the dam in safe condition for at least another 30 years. Local residents have talked about putting in picnic tables, benches or trash cans, but the township has not felt the investment would last.“People just don’t take care of equipment,” Heinonen said.
The remote location of the dam makes any kind of regular patrol to prevent theft or vandalism unlikely as well. Instead the township plans to, for the time being at least, leave the area around the dam to nature.
“We’re going to leave it just like it is for now,” Heinonen said.