The actual construction of a new Interstate 5 bridge is at least a couple of years away, but bystanders will notice test pilings being driven into the Columbia River next month.
Six pilings will be driven into the river bottom while 15 gauges on the Oregon and Washington sides of the river will measure noise and vibrations. The test, which will begin the week of Feb. 7, will evaluate construction techniques intended to reduce effects on fish and wildlife.
Building the new bridge will require work platforms situated atop hundreds of pilings driven into the river bottom.
“This is a really good project to help us understand what construction will eventually be like,” said Frank Green, structures engineering manager for the bi-state Columbia River Crossing office in Vancouver.
Six circular steel columns will be driven 60 to 110 feet deep into the muddy river bottom in two locations downriver from the existing I-5 bridge, near the point where planners currently envision the new 10-lane bridge. Contractors working off a barge will hammer some pilings and push others down using a vibratory method.
The workers will test “bubble curtains” designed to deaden the noise and vibrations.
These curtains amount to a set of aluminum rings wrapped around each of the 24- and 48-inch-diameter steel pilings. Green said the rings, which are pumped full of air, should dissipate some of the noise and vibration as the pilings are driven into the bottom. One set of pilings also will be sheathed in a plastic covering.
“This project is intended to test several methods to see what kind of attenuation we can get,” Green said.
The CRC office last week awarded the contract to Tacoma-based American Construction, which submitted a winning bid of $811,204 — about 8½ percent below the estimated cost of the test.
The test will end by Feb. 28.
The $3.6 billion crossing project would replace the existing twin three-lane drawbridges with a 10-lane span, improve five miles of freeway on both sides of the river and extend Portland’s light-rail transit system into Vancouver. Project planners anticipate a three-way cost split among the federal government, the two states and local revenue generated by bridge tolls.
