As you progress along the foundation of the Redridge Dam, you drop level after level via a series of concrete staircases built into the floor. It’s about 30 feet from the gorge rim where the dam’s wing sections are, to the river level where the main center section sits. As you take the plunge, the superstructure of the dam opens up around you and encompasses all of your vision. The sun disappears behind the dam’s steel face and the roar of water starts to permeate your senses. The roar are from yet another design feature of the dam that sets it apart from its siblings- discharge pipes.
Other steel dams were built as weirs – or overflow dams. When the water got too high in the reservoir it simply flowed over the top of the structure and into the river beyond. This was not the case at Redridge, where a total of three systems were in place to deal with excess water. First was the 350 foot spillway and waste weir we featured earlier. Second was the installation of a series of “steel standards” (thanks to reader Dave Freeze for the info) set atop the header wall discussed in part 1 of this series. These were set below the crest level of the dam and could be used to relieve pressure on the dam in a stop-gap measure. Then there was the third method, the installation of four 24″ discharge pipes within the foundation of the dam here at the center section (see in the diagram above).
The flow through these pipes was controlled in one of two ways. First was the use of sliding doors over the pipe openings at the reservoir. These were operated by a set of controls accessed from the Trestle above the dam. The control rods for those doors can be seen on the face of the dam, rising up towards semicircle shields just below the valves in the photo above. (the valves themselves can just barely be seen above the level of the water as well) The discharge pipes were also controlled by a series of flow valves in the pipes themselves, accessed through recesses in the central section’s foundation.
The discharge pipes, although unique, are not the big draw down here in the center section of the dam. That honor belongs to the sheer scale of what stands above you. Here the dam’s outer steel wall soars 74 feet above your head, held in place by a series of immense beams. Everything seems large than life in this section; from the massive concrete footings on which those beams sit to the oversize bolts and nuts holding them in place. Unlike the wing sections, the wall here is held up by two support beams, each with their own dedicated footings. Let’s take a look at some details.
Mid way up the steel plating lie the connections to the support beams for the middle section of the dam. The lower beam drops down to a foundation, while the upper beam ties across the the second set of beams supporting the upper portion of the dam.
Besides the main support beam and the cross tie, the center section of the dam is tied down with the use of long steel rods driven into the foundation. These rods are set in groups of two, and you can make out one set here just below the joint. The foundation along the steel wall here rises up a good 30 feet to meet the plating just a few feet below this point.
The two sets of support beams – one for the middle section of the steel plating and one for the upper section – are tied together by a set of three cross beams. These beams all meet here at the center point of the main support beam. The connection here seems to rely on a steel flange on which the other three beams are rived to. (reminds me of a slot A to tab B type of connection).
At the footing for the middle section support beam (the beam on the left here), is shared by a cross beam that drops down from the main support beam. They are further tied down by metal rods driven down into the concrete foundation.
Here is another view of the same connection, but from the opposite angle. The support beam from the middle section seems to have been sat in a metal bracket, on which the cross beam is rived to.
A shot of the main support beam as it meets its footing. As this shot clearly shows this beam is massive. You can clearly see the large rods attached to the beam that are driven down into the concrete in order to keep the beam from kicking out.
Finally back to where we started, a damaged control to the flow valves in the discharge pipes. These sit in recesses in the foundation, and were once used to close up the flow valves down in the pipe. Copper Range attempted to open these valves further but the controls were frozen in their positions after a half century of neglect. Instead they cut large holes in the dam’s steel plating.
Information found in this series comes primarily from “A Narrow Window of Opportunity: The Rise and Fall of the Fixed Steel Dam” by Terry S. Reynolds published in The Journal of the Society for Industrial Archeology (Volume 15 Number 1) in 1989. Other information and photos were taken from the Redridge Dam HAER report at the Library of Congress and a contribution from reader Dave Freeze.