The canal conundrum
Decisions to repair or remove will both take time
September 15, 2022 | View PDF
LEABURG: Early in 1927, when the Eugene Water & Electric Board decided another power source was needed it didn't plan 10,000 years in advance. Nor did the utility have to consider what natural disasters might occur in the next million years. Today, though, potential seismic or mega-flood events are part of the design requirements mandated by the Federal Energy Regulatory Commission (FERC).
2022 marks 95 years since EWEB made the decision to build the Leaburg hydroelectric project. It is also a time when the useful life of the facility has run out. Choices for its future range from full modernization to minor upgrading as well as the possible removal of all structures.
This December, EWEB commissioners are planning to choose one of four options that will range between $179 million to $257 million. Any decision will come with requirements for decades of consultations involving a wide range of agencies and interest groups - all monitored by FERC.
"Regardless of what alternative the board chooses we are going to need a FERC license," according to Mark Zinniker, the utility's generation engineering manager. He estimates issues raised during those discussions would likely be resolved by 2028 or '29.
From there the timeline would likely extend another 5 years before the final plan is actually implemented and the physical work gets underway. Adding all that together - people could expect the Leaburg project to be back in service, continue to only act as a channel to transport rainwater, or be completely removed - by 2035 or 2037.
Underlying issues involve how the project was originally built. In some places, the levees that form the canal channel are up to 50 feet tall. Material to build them was taken from the surrounding landscape which in some places has led to structural deficiencies.
EWEB had always kept an eye on seepage, which is considered to be normal in similar structures. But over the last 15 years, the seepage had tripled. In 2018 FERC ruled the canal had to be dewatered because of the possibility of dangerous breaches in some sections.
Any rebuilding would involve replacing the sand, gravel, and cobbles used in areas like Cogswell Creek and the Ames reach with higher-strength materials. But in addition, Zinniker says the dimensions would also have to be increased.
An updated canal would have a much broader base with shallower slopes. In some areas, like near the Greenwood Drive/Hwy. 126 intersection, that wider design could cause problems.
At Greenwood, Zinniker said, "the canal is butted right up against the highway and the highway is butted right up against the river."
The solution calls for constructing a structural concrete flume with reinforced steel to no longer rely on the earthen embankment.
Other changes from the original design address potential hazards, The Leaburg and Walterville projects went through FERC relicensing in 1997. Seismic issues weren't on most people's radar. "At that point, the Cascadia Subduction Zone wasn't seen as a problem," Zinniker says. "now we understand it's quite active and that the magnitude of an earthquake that could happen is much greater."
Soil testing in 2018 also showed the banks can't handle earthquakes, leading to a FERC requirement that they are beefed up.
Zinniker said the agency is also requiring that all high-hazard projects include design elements that address a probable maximum flood. "It's a detailed recipe for a probable maximum flood that in western Oregon generally equates to a 1-in-a-million flood event. That's what they expect us to be able to deal with. It's challenging."
To ensure the canal isn't overwhelmed, it's likely a solution would involve the creation of an additional spillway to handle the increased water volumes.
People can comment on the different proposals for the canal until October 10th. Also that month, EWEB's staff expects to provide the Board of Commissioners with a complete draft of their assessments of the alternatives.