The district owns the shoreline behind Wanapum Dam.
Utility officials say people have been drawn to the area, which was exposed after the reservoir was drawn down about 26 feet to relieve pressure on the dam.
“There have already been incidents where people are getting stuck in the mud and need to be rescued,” utility spokesman Chuck Allen said. “We’ve seen evidence of people driving their vehicles on the shoreline and other parts that are not stable.”
From now on, only authorized personnel will be allowed access to the shoreline below the high-water mark of the reservoir, the utility said.
The 50-year-old dam is located six miles south of Vantage and the Interstate 90 bridge in central Washington.
The utility is posting signs and actively patrolling the shoreline. They say law enforcement agencies will be notified whenever anyone is observed trespassing on PUD lands.
Sections of the shoreline, including the riverbank and mud flats, are extremely unstable and pose a serious safety hazard, the utility said.
The utility is trying to determine the best way to repair the fractured spillway pier at the dam.
“The area that sustained the fracture is stable and the fracture has closed,” Allen said. “Our experts are looking at the situation to determine how it’s going to be repaired.”
Allen warned that repairing the crack is likely to be a lengthy process.
“Repairs this extensive couldn’t be made in just a few days,” Allen said.
The crack was found on a spillway pier and was about 65 feet long and about 2 inches wide, Allen said. But it is unclear how deep the crack is.
Dam officials also do not know what caused the crack, which was discovered Feb. 27, Allen said.
On Wednesday, the incident was downgraded to a “non-failure emergency,” meaning the pier is no longer considered at risk of collapsing.
The release of water that dropped the reservoir level by 26 feet relieved pressure on the dam, allowing the crack to close and a section of the spillway pier that had shifted out of alignment to return to nearly full alignment, the PUD said.
The reservoir level will remain at 26 feet below normal for the foreseeable future, the utility has said.
As a result, the dam is generating electricity at about half of its total capacity of 700 megawatts, Allen said. But it continues to meet customer electricity demands at the reduced level, the PUD said.
Power produced by Wanapum Dam, one of more than a dozen on the Columbia River, goes into the Northwest hydroelectric grid administered by the Bonneville Power Administration, a federal agency based in Portland, Ore. The Wanapum situation has not affected the grid, either in terms of power supply or rates, the BPA has said.
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