November 14, 2007 - Bend Bulletin - Work Begins on Project to Get Fish Past the Dam
Nov 14, 2007
Work begins on project to get fish past the dam
By Kate Ramsayer / The Bulletin
Published: November 14. 2007 5:00AM PST
LAKE BILLY CHINOOK — At the northern end of Lake Billy Chinook, fed by the Deschutes, Crooked and Metolius rivers, construction has started on a structure that when assembled will be 25 stories high.
When it’s done, however, people will only see the top 5 feet. The rest of the project, a $100 million facility designed to collect migrating fish so they can be trucked downstream, will stretch down beneath the surface of the reservoir.
To build this unique structure at Round Butte Dam, for more than a year crews will use the northern section of the lake as a construction site. They’ll pound a section of the lake bottom flat, and assemble large sections of the facility on floating barges and pontoons that will tower 100 feet above the lake’s surface.
Then, once the pieces are put together, they will use cranes and underwater robotic cameras to very carefully, very precisely, sink it in the 270-foot-deep reservoir. While some parts of the structure have been used before separately, sinking the bottom structure is a unique challenge for the project managers.
“How do you control something that’s 270 feet down? It’s tough, it’s really tough,” said Steve Nichols, director of the project with Portland General Electric, which is the dam’s operator and co-owner with the Confederated Tribes of Warm Springs.
The project, part of the federal agreement that relicensed the Pelton Round Butte Dam complex until 2054, is key in reintroducing salmon and steelhead above the dams. It’s also expected to improve water quality on the Lower Deschutes.
While the old water intake facility only sucked in water from the bottom of Lake Billy Chinook to turn the dam’s turbines, the new addition will also suck in fish and water from the surface of the lake, shuttling the fish to a collection facility and directing the water through the dam.
But building a giant, underwater structure is a complex process.
The first steps of the 15-month construction period began last month, and last week, crews excavated a section of land on the west side of the dam. Although it’s a hole in the ground now, the plan is to pour 500 yards of concrete to create an anchor block that will keep the floating fish-intake facility in place.
“It has to be a very substantive structure,” Doug Sticka, project manager with PGE, said of the anchor and the bridge, which would have to withstand waves on the reservoir as well as the strong winds that come whipping down the canyon.
On the other side of the reservoir, a big crane floated on a barge, ready to start excavating rocks almost 300 feet below. That’s necessary because the bottom of the reservoir, which was surveyed with sonar and cameras on remotely operated underwater vehicles, is uneven and littered with debris like logs and old tires, Sticka said.
After using a clamshell-shaped scoop to remove those obstacles, the crews will then have the crane drop a 20,000-pound weight underwater and pulverize rocks lining the reservoir.
The goal is to create a level area where the bottom water-intake component will sit. The bits of smashed rock will be sucked up and deposited in a deeper section of the reservoir.
“We’ll just beat the rock, then suction it up,” Sticka said. “We’re just vacuuming the bottom.”
That process should take about two months, he said. And to avoid stirring up too much sediment, a concern of the Oregon Department of Environmental Quality, crews will only work when the existing water-intake facility at the dam is shut off so underwater currents are minimal.
While the work is going on, the northernmost section of Lake Billy Chinook will be off-limits to boaters and will be cordoned off.
And while crews are working on the lake, different components of the base of the new water-intake contraption are being assembled in Vancouver, Wash.
A complex base
This bottom section will weigh 1.4 million pounds and will be about 70 feet tall, Sticka said.
Beginning in January, sections of the base will be trucked down the canyon to the dam for assembly. But there’s not enough to room to build the structure on firm ground, he said. So instead it will be put together on the lake itself, supported by 18 large, reddish pontoons.
The whole contraption could reach 100 feet above the surface — an unusual sight for people fishing on the lake or bird-watching from the canyon’s edge.
When the base is completed, the floating pontoons will be moved to a precise spot in the reservoir, and the base will be lowered, 20 feet at a time, until it latches onto the current water-intake facility 270 feet below.
“The underwater construction techniques that we’re going to be using on this project are fairly unique,” Sticka said. “Parts of it have been done in other places, but the whole process of installing the bottom structure is pretty unique.”
And it’s a tremendous challenge, Nichols said, to maneuver it into place.
The contractors will use the underwater robotic cameras and sonars, but because it is so deep will try not to have to use divers, Sticka said. Once the base is latched on, crews will use hydraulic jacks to level the new piece and make sure it’s exactly where it needs to be, Nichols said.
Then, 11 pilings surrounding the equipment will be filled with cement. Slowly, the crews will drill pipes through both those pilings and 70 feet of rock below those pilings, to anchor it in place.
“Once you’ve got that done, it’s not going to move,” Nichols said.
The design of the base was the most difficult, Sticka said, because it has to hold steady with the winds, waves and the possibility of an earthquake.
And putting it in place is the most difficult part of the job, he said. “We’re going to have a big party when it’s done.”
The next piece of the complex structure is a big, 40-foot-wide, 150-foot-tall pipe that will connect the surface intake with the bottom intake. It will be assembled on a barge on the lake as well, then lowered into place on top of the base.
Topping things off will be the surface intake facility, which will take up both fish and water and then pump the small fish to a handling facility. There, the fish will be tagged by biologists before being loaded onto trucks.
The problem with the old fish-passage facility at the dam was that the surface water currents in the lake were skewed by the dam, and the fish got lost, Nichols said. With this system, taking in water from the surface creates currents that should guide the fish to the right place.
And the fish-intake facility won’t need a barge for construction, Sticka said. Instead, its floor section will be fabricated from a type of buoyant material that will support the structure and is similar to what’s used to construct floating golf greens. Like the other sections, most of it will be made off-site in smaller pieces before being assembled on the reservoir.
The whole structure is scheduled to be put together in February 2009, which would allow a few months of testing before it starts operating in May of that year.
For now, people involved with the project said it is exciting to see work actually begin after many years of planning.
“It’s a pretty nice feeling to see that after all these years of planning we finally see things happening and the project under way,” said Jim Manion, general manager of Warm Springs Power and Water Enterprises. Warm Springs owns a third of the facility, and pays for a third of the costs. The first priority for the tribes is to ensure that fish and water quality is protected, Manion said.
And because of this, staying on schedule is critical, he said.
This spring, thousands of tiny steelhead fry were released into the Metolius River. Those fish will grow in the river and reservoir for the next two years.
But come summer 2009, they’ll be ready to migrate past the dam to the Pacific Ocean.
“We’ve got fry that we released in the streams up there, and we need to have something ready for them,” Manion said.
Kate Ramsayer can be reached at 617-7811 or firstname.lastname@example.org.