Drawdown of Columbia River reservoir creates problems, opportunities
VANTAGE, Wash. – Mud, lots of mud, with a river flowing through it.
Anja Reynolds gaped at an unfamiliar Columbia last week as her husband, Dave, and their three kids stretched their legs at a park near the river’s edge. The Shelton, Wash., family had stopped for a break on the six-hour drive to Spokane.
The river no longer filled the gorge at Vantage from basalt cliff to basalt cliff. Vast mudflats stretched out to the water. A “no trespassing” sign warned the family to stay off the unstable shoreline.
“I’ve seen the river a lot,” Anja Reynolds said. “This is different.”
The reservoir behind Wanapum Dam has been drawn down since late February, to relieve pressure on a crack that developed in one of the concrete supports for the dam’s spillway gates. As they pass over the Columbia on Interstate 90, people are getting a glimpse of the river not seen since the dam’s reservoir filled in 1964.
Officials at Grant Public Utility District, the dam’s owner, still don’t know what caused the crack. They’ve hired teams of technical experts and anticipate an answer in two to three weeks. Meanwhile, the utility has been working with other agencies to address impacts to migrating salmon, irrigators and public safety from the 26-foot drop in Wanapum’s reservoir levels, which could continue for some time.
“The whole event is unusual,” said Tom Karier, Eastern Washington representative to the Northwest Power and Conservation Council. “No one’s come up with a comparable example that I’ve heard of.”
As a region that depends on aging dams for electricity and other amenities, “I think we’ll learn from what happened at Wanapum,” Karier said.
The 40-year-old dam has an expected operating life of several hundred years, which is how long the concrete, steel and rebar in Columbia River dams are expected to last with proper operation and maintenance, said Thomas Stredwick, a Grant County PUD spokesman.
But Wanapum’s crack has become a case study for other dam operators and stakeholders “in the event they have to deal with a similar situation,” he said.
Water pressure from behind the dam is being studied as a possible cause for the 2-inch wide, 65-foot long fracture, which runs horizontally across the spillway structure.
Engineers have ruled out seismic activity, a settling foundation and explosions at the nearby Yakima Training Center operated by the U.S. Army as causes. The utility is drilling test holes to learn more about the fracture.
After utility officials know why the crack appeared, engineers will evaluate whether the dam’s 11 other spillway structures are at risk for fractures, said Chuck Berrie, assistant manager for Grant County PUD. A batch of bad rebar, for instance, would be a much different scenario than a structural design weakness that could affect all of the gates, he said.
The massive dam stretches 8,637 feet across the Columbia. It was never at risk for failure, Berrie said. After the reservoir was lowered, the fracture closed and the structure stabilized.
Wanapum Dam’s electrical output has dropped by about half during the drawdown. The Northwest is awash in hydropower from melting snowpacks this time of year, so the loss of electricity isn’t critical for the region. But Grant County PUD is feeling the effect of not being able to sell surplus power, Stredwick said.
Utility officials look forward to the time when they can start raising the reservoir levels. Even a partial refill would help solve many of the other issues related to public safety and fish passage, Berrie said.
Grant County PUD is paying out nearly $400,000 monthly for round-the-clock patrols to keep curiosity seekers off the newly exposed shoreline and protect Native American archeological sites. The utility is coordinating patrols with local sheriff’s departments and the state Department of Fish and Wildlife’s law enforcement.
“There’s a lot of genuine curiosity, a lot of people out looking for lost boat anchors,” Berrie said.
At least four people have gotten trapped in the soft, deep mud and had to be rescued by emergency responders, including one woman who sank up to her waist. “One step can be firm and the next you’re in silty sand,” said Kyle Foreman, a Grant County Sheriff’s Department spokesman.
Preventing looting of cultural sites is also a priority. Native Americans have lived along the Columbia for thousands of years, leaving a record of their presence through pictographs, former encampments and burial sites. Grant PUD has contracted with four archeology firms and is also working with the Colville, Yakama and Wanapum tribes to protect cultural resources, Berrie said.
The utility will also spend about $3 million to modify Wanapum Dam for fish passage and monitor how well the adaptations are working.
Spring chinook are moving up the Columbia River en route to spawning grounds, and the first fish in the projected run of 20,000 are expected to show up at Wanapum Dam this week. About 4,000 of the spring chinook are federally protected wild fish.
Behind them are about 80,000 summer chinook, 400,000 sockeye and 300,000 fall chinook – record runs that will start reaching the dam in June.
“These are great big runs,” said Keith Kutchins, policy analyst for the Upper Columbia United Tribes. “Once the salmon get here, we have to provide passage.”
The utility will pump water into the fish ladders on the upstream side of the dam, which have been affected by the drawdown. In addition, a “fish slide” will extend the ladders, so the migrating salmon don’t plunge 15 feet down to the lowered reservoir.
Chelan County PUD, which operates the Rock Island Dam 37 miles upstream, is also making adjustments to its fish ladders because of the lower river levels.
The Department of Fish and Wildlife plans to trap and truck spring chinook around the dams while hatchery-reared fish are released to test the modified fish ladders.
“The stakes are very high, especially given the number of wild spring chinook involved,” said Jim Brown, the department’s regional director.
The state Department of Ecology, meanwhile, is working with orchard owners affected by the drawdown and a smaller, related drawdown of Rock Island Dam’s reservoir upstream.
About 30 irrigators with nearly 8,000 acres of fruit trees contacted the Ecology Department seeking permits for emergency changes to their water intake systems. About half of the permits have been processed, and officials are scheduling field visits with the remaining irrigators, said Brook Beeler, a department spokeswoman.
For many members of the public, however, the drawdown’s biggest effects will be felt during the summer recreation season, said Grant PUD’s Stredwick.
The drawdown has closed boat launches and some campsites along the reservoir. During concert weekends at the nearby Gorge Amphitheatre, up to 30,000 people visit recreational areas along the Columbia, Stredwick said. Some of their favorite spots might be closed this year.
“We don’t have a timeline when the shoreline will reopen,” Stredwick said. “It’s a big concern to people who (recreate) on the river.”