The water level behind the hydroelectric dam, six miles south of Vantage and the I-90 bridge, was lowered 26 feet after a two-inch-wide crack was discovered in the dam last Thursday.
The dam is still operating, but at about half capacity, according to a statement posted Wednesday on the website of the Grant PUD, the Ephrata-based utility that operates the dam.
The power produced by the 50-year-old dam, one of more than a dozen on the Columbia, goes into the Northwest hydroelectric grid administered by the Bonneville Power Administration, a federal agency based in Portland.
The Snohomish County Public Utility District buys about 80 percent of its power from BPA. And the PUD, which serves all of Snohomish County and Camano Island, is BPA’s biggest customer.
The Wanapum situation has not affected the system at large, either in terms of power supply or rates, said BPA spokesman Mike Hansen.
“There does not appear to be any impact on the ability of the federal Columbia River power system to meet energy demand in the region,” Hansen said.
However, if the Grant PUD continues to be unable to produce power at the usual level, electricity rates might be affected, according to Hansen.
Three of the dam’s 10 turbines were already down for maintenance and replacement. While the dam is capable of generating 700 megawatts — enough for about 525,000 homes — it’s now producing about 360 megawatts, according to the Grant PUD.
The utility also operates Priest Rapids Dam, 18 miles downriver from Wanapum.
“We are delivering power to our customers and ensuring that any power demands will be met,” Grant PUD spokesman Chuck Allen said.
The crack was discovered when curbing along the top of the dam was seen to be out of alignment. Divers subsequently found the two-inch-wide crack running about 65 feet horizontally near the bottom of the dam.
With the weight of the water relieved, the crack has closed to about an inch wide and the dam appears stable, according to Wednesday’s statement. After the water level was lowered, the damaged section of the dam moved an inch back upstream.
Other measures were taken to ensure public safety. The Wanapum Heritage Center and the day-use park at Wanapum Dam remain closed and boat ramps in the area were closed due to low water levels.
Besides the public-safety implications, there could be economic ones as well if Wanapum’s power-generating capacity remains below normal for too long.
The Columbia River Treaty with Canada calls for a certain amount of hydroelectric power from the U.S. to be sent to Canada in exchange for the downstream generating capacity that is created by three dams in British Columbia. Those dams enable flows to be controlled to produce more power during dry times of year.
In exchange, the U.S. gets flood control and the remaining generating capacity.
Three utilities in central Washington, including Grant PUD, are responsible for sending 27 percent of that power to Canada, Hansen of the BPA said. If they can’t meet their obligation, the BPA would have to pick up the slack, he said.
“How we would get paid back — we are still looking into that,” Hansen said.
Allen said a team of the Grant PUD’s engineers, with experts from the Federal Energy Regulatory Commission and other consultants, are inspecting the dam to come up with a repair plan.
Bill Sheets: 425-339-3439; firstname.lastname@example.org.
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