Fish collection system goes online
By Holly M. Gill
At the Pelton-Round Butte Dam, fish seem downright eager to pass through the new fish transfer system.
One yearling spring Chinook salmon was so anxious to head for the ocean that it traveled at least 160 miles in just over five days.
“I don’t think you could get a canoe down there that fast,” said Don Ratliff, senior aquatic biologist for Portland General Electric, which operates the dams.
The smolt was among among about 200 which have found their way into the new $108 million fish passage system since it became operational Dec. 2. The fish are tagged with a Passive Integrated Transponder, which lets biologists know when they pass through dams, and then released below the reregulating dam, about 10 miles downstream.
“One went through the Bonneville Dam — about 110 miles down the Deschutes, and about 50 miles down the Columbia — in 5.2 days,” said Jim Bartlett, fish passage lead for PGE.
The fish passed through The Dalles dam before reaching Bonneville, he said last week, noting, “By chance, they had their full flow bypass working and detected our fish. That fish could be in the ocean right now.”
Although December is early for fish to begin migration since the peak season is from March to July, they weren’t surprised to see the system being used.
“We turned it on Dec. 2, and started getting chinook and sockeye smolts. Most of the fish have been healthy and beautiful,” he said.
Officials from PGE and the Confederated Tribes of Warm Springs, which is a one-third owner in the hydroelectric projects, had expected the “selective water withdrawal tower” to be operational in April 2009, in time for the migration season.
Instead, on April 11, as workers were slowly floating the top section of the system toward the massive underwater column, the 40-foot diameter conduit collapsed, with part floating to the top of the water and the remainder dropping to the bottom of the reservoir. Since then, contractors have worked nonstop to repair and replace parts to get the facility up and running.
Barnard Construction, of Bozeman, Mont., and Dix Corp., of Spokane, Wash., made the repairs and salvaged about 300,000 pounds of steel out of the reservoir above the Round Butte Dam, according to Chad Croft, project manager for PGE.
“They reused most of it,” he said, noting that repairs were completed in early November, and it took a month to put together.
“The reconstruction of the tower section took a little bit longer this time, because we modified construction techniques and sequence, and the modifications were based on the incident,” Croft said.
Three separate analyses of the root cause of the collapse were conducted, but Croft said PGE is not commenting on the causes since other parties may be involved in litigation.
“Since we went operational, we haven’t had any major problems,” he said. “There have been minor equipment control or operational issues, but it’s operating very well and it hasn’t affected our ability to generate electricity.”
The Round Butte Dam is capable of generating about 340 megawatts of electricity, the Pelton Dam, about 110 megawatts, and the reregulating dam, about 15 megawatts.
Last week, officials had two small problems on their hands: a broken pipe — from the below-zero temperatures earlier in the month — and a dead bull trout, which was sent to a pathologist to determine the cause of death.
“It’s all part of the game,” said Bartlett, who is excited to be a part of the new facility. “It’s really one of a kind.”
The new fish passage system was designed for two primary purposes: to restore fish runs, and to improve the water quality.
“The main thing we’ve accomplished with this new facility is to extend the intake of the dam to the surface of the reservoir,” said Ratliff. “The water leaves Lake Billy Chinook naturally, like it would at Suttle Lake.”
Ratliff explained that before the tower was completed, water left the reservoir through a pipe at a depth of about 240 feet, where the water is colder.
“Normally, if a river is coming through a lake, it comes in off the mountains, and runs off at the lowest elevation,” he said. “Fish migrating know how to get out of the lake; they don’t know how to swim down to the bottom.”
Soon after the dam was constructed in 1964, it became clear that the first attempt at a fish passage system — with a gondola for upstream migration, and an intake and collections system for the downstream trip — had failed.
The problem was that fish from the three rivers which form the reservoir — the Metolius, Deschutes and Crooked rivers — were confused by the different currents and temperatures, and were unable to reach the collection facility.
As a result, a hatchery was built below the dams to replenish the fish supply in the Lower Deschutes River.
Ratliff compared the reservoir and 40-foot diameter pipe to a bathtub and drain. “We put a pipe in that drain, and extended it up to the surface. Now fish can find moving water on the surface.”
Fish are drawn into two V-shaped 40-foot deep, 30-foot wide intakes near the surface. Screens on the sides of the intakes drain the water, but keep fish moving through the system, where they are sorted by size, to keep the larger fish from eating the smaller ones.
Last week, after three weeks of operation, 190 Chinook salmon had been collected. “Everyday, we take the fish that we caught that day and let them go below the reregulating dam,” Ratliff said.
So far, most of the small fish seem to be entering the system in the evening, he noted. “I think that they wait until dark so they’re not as vulnerable to predators.”
“It’s all designed to catch and process and truck 7,000 of these small salmon a day at the peak,” Ratliff said.
The system was also designed to modify water temperatures as the warmer surface water flows down the vertical conduit to generate power, blends with the colder subsurface water, and is sent through the historic power tunnel.
Over time, Ratliff said, “The water in the reservoir is going to get colder. The top 10 to 15 feet is going to be the same, but below the thermal cline, it’s going to be about 46 degrees. It used to be 54 degrees.”
“In the spring, it will be colder in May and June than it has been,” he continued. “In July, August and September, swimmers won’t notice any difference — except the water should be cleaner.”