The Interstate Bridge Replacement Program will study the possibility of building a new drawbridge over the Columbia River, program officials said Friday.
The “movable span” option, which came at the request of the Coast Guard and federal government, will be explored in addition to the program’s original plan of a fixed-span bridge with 116 feet of vertical clearance.
The program will study both a lift span like the current Interstate 5 Bridge and a bascule bridge like the Burnside Bridge in Portland.
Program Administrator Greg Johnson said he believes a fixed-span bridge will ultimately end up spanning the Columbia.
He said a movable span would likely cost $500 million more than a fixed-span bridge and noted that the Columbia River Crossing project received a record of decision from the Federal Highway Administration and Federal Transportation Agency for a fixed-span bridge with the lower river clearance.
“I would be totally shocked if we can’t get to a fixed-span,” Johnson said.
Johnson said a drawbridge is being examined as a design option for the final bridge as opposed to an alternative. Other design options include the possibility of adding a second auxiliary lane or whether northbound and southbound traffic lanes should be stacked like Portland’s Fremont Bridge, or arranged side-by-side like the current I-5 Bridge.
Although the Coast Guard permitting process has changed, Johnson said, nothing has changed from a river user perspective. The users who need more than 116 feet today are the same who agreed to 116 feet of vertical clearance after reaching an $86.4 million mitigation agreement during the Columbia River Crossing process.
In the Coast Guard’s preliminary determination in June 2022, the agency pointed to the trend of vessels requiring more than 160 feet of vertical clearance coming to the Portland/Vancouver area, pointing to two examples of such ships docking in Portland and said that the trend is likely to continue east of the I-5 Bridge.
The Coast Guard cited the MV Navios Unite, a container ship that transited to Portland in March 2022 with a vertical clearance of approximately 166 feet, and the Caribbean Princess cruise ship that arrived in the spring of 2022 with a vertical clearance of about 183 feet.
Johnson said both vessels were bound for locations downstream from the Interstate 5 Bridge.
“While it may be true that the river navigation and business usage along the river in the larger metro area has changed, the navigation needs under the Interstate Bridge have not, according to our analysis,” Johnson said. “The vessels referred to in the Coast Guard’s (preliminary determination) did not travel under the Interstate Bridge.”
Johnson does not believe the study of a moveable span bridge will impact the program’s schedule of receiving a record of decision before the end of 2024. A separate team of WSP and Parametrix engineers will examine a drawbridge.
“(A drawbridge) has been looked at before,” Johnson said. “We’re going to leverage that work and put the latest thinking toward technology on a moveable span and configuration of a moveable span to know the impacts of it.”
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