'Fish window,' other issues complicate work on transit crossing
by: Courtesy of Portland-Milwaukie Light Rail Project 
A rendering shows how TriMet’s completed transit bridge will look from the Eastbank Esplande near the Oregon Museum of Science & Industry.

A one-page application to the U.S. Department of the Army was all it took in 1912 to build the Steel Bridge over the Willamette River.

Nearly 100 years later, TriMet has spent about three years obtaining 34 permits and approvals from several government agencies for the planned $134 million transit bridge over the river between South Waterfront and the Oregon Museum of Science and Industry.

Construction officially begins this week, with a groundbreaking ceremony. Work on the bridge is expected to be completed in fall 2015 as part of the 7.3-mile Portland-to-Milwaukie light-rail line.

That pile of permits and approvals needed for the project dramatizes how much more complicated major infrastructure work has become in the past century. Most of the permits are required to reduce potential environmental damage - especially in the Willamette River that is home to endangered fish species.

'It's a lot of work, but the result is a healthier river both during and after the construction,' says TriMet Project Manager Robert Barnard.

Many of these permits and approvals are related to two large piers that will be built in the river to support the bridge. Two barges, each with two derricks, already are anchored near the west and east banks of the crossing to begin the work. They are clearly visible from OMSI and where an elevated roadway is being built for the west end of the bridge.

Because of federal requirements, work in the water to build the piers can only occur each year between July and October - informally called the 'fish windows.'

To meet the requirement, TriMet will stagger the in-water work for four years. Two oval-shaped retaining walls, known as cofferdams, will be constructed during the next four months near the west and east banks of the river. They will create two gaps in the river where the piers will be built. When the cofferdams are completed, the in-water part of the work is considered finished and construction inside them can continue year-round.

That work involves cleaning the river floor, filling the cofferdams with sand and rock, and driving six pilings through to bedrock. After the pilings are sunk, they will be capped with concrete.

The bridge's support towers will be built on top of the caps. The bridge will then be built in stages from the towers, supported by both permanent and temporary cables allowing the deck to connect in the middle and along both banks by 2015.


Tribune Photo: Christopher Onstott • Two barges with two derricks each are stationed in the Willamette River to build the piers that will hold the towers to support the coming transit bridge.

Mitigation costs

Removing the cofferdams when the piers are complete is considered in-water work. So is the installation and removal of connecting trestles. All of that work will be completed during the following three annual fish windows.

To obtain the permits and approvals, TriMet has been required to deal with practically every level of government. Federal agencies include the Federal Emergency Management Administration, the Federal Transit Administration, U.S. Fish and Wildlife, the Army Corp of Engineers, the National Oceanic and Atmospheric Administration and the U.S. Coast Guard. State agencies include Oregon's Department of Transportation, the Department of Environmental Quality, the Department of Fish and Wildlife, the Department of State Lands, the Oregon Marine Board and the State Historic Preservation Office.

The Port of Portland also was involved. The city of Portland issued more than eight permits and approvals for the project.

When completed, the bridge will carry MAX trains, buses, the Portland Streetcar, pedestrians and bicyclists across the river between east and west Portland. The MAX extension will run from the southern end of Portland State University to downtown Milwaukie through inner southeast neighborhoods and along Southeast McLoughlin Boulevard (Highway 99E).

The total cost of the Portland-to-Milwaukie light-rail line is estimated at nearly $1.5 billion. That includes $1.46 million to mitigate environmental damage from the bridge construction, despite all the permits and approvals that have been obtained.

Live and time-lapsed video of the bridge construction can be seen on TriMet's website,

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