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By Vicky Campo, CAP Internal Communications Representative

NOTE: The Salt River Siphon is part of the engineering marvel that is Central Arizona Project. “Dewatering” – draining water from – a part of the system is quite an endeavor for an aqueduct that moves one way and is always moving water, 24 hours a day, 7 days a week, 365 days a year.

Central Arizona Project Vicky CampoAs I stepped down, one rung after another, I wondered how long it would be before I reached the bottom. I felt a slight twinge of fear with every wobble of the ladder, even though I was safely tied off. Below me was some sort of device that looked like a lighted balloon, and I could see its bright glow bend against the round walls. When I finally stepped on solid ground and was able to look around, I was astonished. I was standing in the invert of the Salt River Siphon, one of the largest steel pipes ever built by the Bureau of Reclamation. I’d be lying if I said it wasn’t eerie.

Dewatering the siphon

The Salt River Siphon hasn’t been repaired in more than 17 years. In 2009 Engineering did a partial inspection on the outlet and the inlet, and in 2016 a Reliability Cantered Maintenance Assessment was done to identify critical infrastructure--particularly the siphon. They identified needed repairs and determined the potential failure modes. As a result, an inspection was scheduled for 2018, and 2019 was slated as the year to do repairs.

“Our original plan was to do a partial blow off and just inspect the inlet and outlet. But some of our people thought the area of most concern was right underneath the Salt River, so we were able to gain support for a full dewater,” explains Phillip Pagels, Engineering Project Manager.

A full dewater allowed inspectors to see the entire siphon, thereby taking a good deal of risk out of the project, and that can reduce costs greatly.

“If we didn’t do this inspection, you might expect a 20-30% increase in the total cost. But now we are able to identify a clear scope of work, and that is always the toughest part of a project like this,” Pagels said.

Inspecting the siphon

The outage for this inspection was only three days. On Tuesday morning the siphon was dewatered, and by Wednesday biologist Scott Bryan was wrangling fish.

I joined the crews on Thursday. Retiree Rudy Gates, who led the Protective Coatings crew in the 2001 repairs, was called back as a consultant to help assess the condition of the pipe. He and Jake Pickard were the only ones on this job who had previously been inside this pipe, and they were excited to see that its condition wasn’t nearly as bad as expected.

“Jake and Rudy have seen as much of our pipes as anyone. In fact, I worked that siphon outage with Rudy in 2001, so I’ve been in there several times myself. There has been some discussion about the rough condition that siphon must have been in, but I think in general, what I got from both Jake and Rudy, was, no, not at all. In fact, it looked pretty darn good,” said Bob Moody, Director of Field Maintenance. 

Repairing the siphon

The outage for the Salt River Siphon repairs will be six weeks later this fall, during which crews will work around the clock. CAP will provide a support role for the 2019 inspection and dewatering, but the contractor will be responsible for most of the work. They will do the full dewater, provide safety support, remove the old coatings and apply the new, and perhaps even provide a third-party inspection company. CAP inspectors will be there as well as part of the team.

At the same time, another portion of work will be happening just downstream at the Salt Gila Pumping Plant where CAP crews will be dewatering the forebay and removing the sediment. It’s a lot to accomplish in six weeks.

For me it was a remarkable experience, and I’m hoping to go back in the pipe later this year!

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