Jackson Shutdown Provides Chance for Intake Gate Inspection

A recent planned shutdown at the Jackson Hydroelectric Project gave the PUD a rare chance to inspect the intake gate for the Culmback Dam in Spada Lake. The gate, which is responsible for helping control water flow into the tunnel, hadn’t been assessed in almost 20 years.

Months of planning went into the project, which had to be completed while water levels in Spada Lake were low. It took seven hours to fully raise the 90-foot gate out of the water, which was brought up about 10 feet at a time. The gate was then analyzed to make sure it was still working properly and well-maintained.

“It’s the only mechanism that can hold off water from flowing into the tunnel if there’s any rupture in something downstream,” said Scott Spahr, the PUD’s Manager of Generation Operations and Engineering. “This is what needs to work properly to make sure we can keep water from the tunnel and keep it from flooding.”

Culmback Dam’s intake gate passed its inspection with flying colors. All of the seals and stainless-steel components were in working order.

“I think the whole group was really impressed with the condition of that gate,” said Jessie Pittis, who works as a Generation Superintendent. “I feel confident that it can protect our employees, the citizens of Sultan and all our resources up there. You get nervous because you dewater that tunnel, and you put folks behind that gate and that’s their only safety net. It really instilled confidence in the group.”

“The PUD has a tremendous responsibility to ensure that these systems function properly and are reliable should they be called upon in an emergency,” added Eric Schneider, Principal Engineer and one of our dam experts. “It is important to stay on top of everything, especially those elements that we rely on for dam safety. I think the entire team was l impressed with the gate’s condition after being submerged for 42 years in Spada Lake.”

The group plans to continue to keep an eye on the intake gate, along with the rest of Culmback Dam. Discussions are underway to determine how long the interval should be between regular inspections.

“There were a number of recommendations that came out of the inspection,” said Robin Berry, an Engineer who worked extensively on the project. “That was the main objective, to see the condition of the gate and make sure it’s still functioning. There’s stuff to monitor and maintain and supervise. We’re in the process of figuring out do we pull it up again in 5, 7, 10 years? It’s just deciding the timing.”

But everyone agreed that the gate remains in great working order.

“It looks great for 40 years old!” Scott said. “But something happens at middle age, when you start to need some more maintenance. It just needs some small things.”