Priest Rapids Dam passes major safety inspection

MATTAWA — A comprehensive safety assessment of the structure at Preist Rapids Dam determined the dam met standards that will allow it to keep operating safely. That was the conclusion of a report released by Grant County Public Utility District officials.  

“No conditions were found that would require immediate remedial action to protect the safety of the project. We did not identify any other items that require follow-up action,” according to a letter from the Federal Energy Regulatory Commission, the agency that oversees dam safety and licensing.

“That’s language that we love to see when they come and inspect,” said Zach Ruby, PUD chief dam safety engineer.  

Results of the assessment, along with recommendations from a separate required inspection, were presented to PUD commissioners at the Jan. 14 meeting.  

Repairs are scheduled in 2026 for a spillway joint at the dam that first attracted attention about seven years ago. It was one of the repairs identified in the report.  

Ruby said PUD engineers already knew the anchor project would be required and planning and design are underway. Utility district engineers also are working on a second project, an ongoing assessment of the bank on both sides of the Columbia River.  

The “disbonded” spillway joint was first discovered in 2018 when Grant County Public Utility District officials evaluated the structure. That followed the discovery of a crack in the spillway at Wanapum Dam that took about a year and $86 million to repair. 

The initial investigation concluded the pieces don’t fit together as tightly as they once did, according to previous reporting in the Columbia Basin Herald, which resulted in a leak.  

Christine Pratt, PUD public information officer, said the disbonded joint will be reinforced with what are called anchors. Holes are drilled through the structure into the bedrock, then cables are dropped into the holes and anchored in cement or similar material. The cables are stretched and the holes are filled. 

Ruby estimated that the actual construction, when it starts, would take about two years to 18 months.  

“Right now, there’s still a lot of permitting going on, and getting contracts in place. The design has been submitted to FERC,” he said.  

Utility district officials will be reevaluating a section of the riverbank on the Yakima County side in 2025. Most of that embankment was reinforced after an analysis was conducted that determined the embankment could crumble in the event of a big earthquake, magnitude 6 or greater on the Richter scale 

The section that wasn’t reinforced might not present the kind of risk originally thought, Ruby said – which the inspectors pointed out. Utility district engineers already planned to take a second look at that section, he said.  

The Grant County riverbank, Ruby said, might need some reinforcement. The PUD is required to analyze the risk of dam failure, he said, any and every possible kind of failure. That analysis suggested a possible risk along the Grant County side in the case of an earthquake.  

“We were already working on this one, so we were aware of it,” he said.  

Utility district engineers will be doing some drilling along the embankment to determine the scope of the problem, he said. That work will begin in 2025.  

Ruby said FERC requires major inspections every five years, alternating between the very detailed comprehensive assessments and one that’s less detailed, Pratt said. The Energy Regulatory Commission conducts safety inspections each year.