To untangle the current condition of the dams at Redridge takes a bit of a history lesson.

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 emergency spillway on 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 in the 1890s 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.

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. Concrete was still used for the foundations, as the dam is considered a “gravity dam”, held in place by its own weight rather than anchors in bedrock.

From Clarence J. Monette’s “Redridge and its Steel Dam” 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.

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 and 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 short of coming over the road.

When the steel dam was initially drained isn’t noted by Monette or other sources, 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.

Photo provided by Barbara Koski Water flowing over the top of the Redridge steel dam in April of 1941.

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 would not 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.

This article is part of a series on local dam conditions.

Part 2: Click here