The first components that come to mind in bridge building are the essentials: concrete, rebar and construction crews.
Equally important are aspects such as maintaining the local wildlife, protecting habitats and safeguarding the river below. With construction occurring at an ecologically sensitive stretch along Oregon’s Willamette River, the Oregon Department of Transportation (ODOT) team replacing the I-5 Willamette River Bridge between Eugene and Springfield took environmental aspects of the project into account from the start.
For this project, the largest bridge replacement in the $1.3 billion Oregon Transportation Investment Act III State Bridge Delivery Program, ODOT is using the construction manager/general contractor (CM/GC) contracting method for the first time. With CM/GC, ODOT could hire an architecture and engineering firm and retain control over design decisions, while receiving critical input from the contractor regarding construction alternatives and pricing options. CM/GC lets ODOT control costs, schedule issues and design options, adjusting the outcome as the project proceeds. CM/GC allows for innovative design enhancements and provides time for the team to gather community input. Given the complexity of this project—which involved the original I-5 bridge; the temporary bridge; and ultimately the new northbound and southbound structures—collaboration between the agency, the A&E firm and the prime contractor is essential to its success.
Unique approach
To streamline permitting for the Willamette River Bridge and the hundreds of other bridges in the bridge program, ODOT led development of a unique set of programmatic permits based on environmental performance standards to guide design and construction activities. This permitting strategy helped ODOT stay on track with timelines for the bridge work while reaching better environmental outcomes on the ground. The programmatic permits combine more than 14 separate environmental regulations into a single set of standards that meet compliance and stewardship goals.
Having taken the preliminary steps to build a bridge that will exist harmoniously with its surrounding environment, ODOT then gathered the community’s input on the project. Area residents, community stakeholders and public agencies, such as the City of Eugene Parks and Open Space, Lane County, Willamalane Parks and Recreation District, Oregon Parks and Recreation District, and the National Park Service, collaborated with ODOT to enable the agency to design and construct this major crossing while meeting the communities’ needs.
By working with local citizens, artists and architects, ODOT is integrating community input into aspects of the bridge’s design and collaborating on its defining feature: the deck-arch structure. It was important to community members that the new bridges enhance the natural beauty of this site. The graceful deck-arch design allows views of the area’s scenery to remain unhindered by the structure.
Taking it apart carefully
The deck-arch structures—separate northbound and southbound spans, side by side 16 ft apart—also will minimize disturbances to river dwellers, such as salmon and Oregon chub, as each arch touches down in the water only once in the middle of the river. The previous structure, now demolished, required five piers for support and obstructed this site’s beauty with a bulky, bulb-type I-beam structure.
The new Willamette River Bridge will not only provide open vistas for drivers and a sleek profile to passing bike riders and river paddlers, it also will improve the quality of the river habitat below.
Demolishing the original 2,000-ft-long, 50-ft-high Willamette River Bridge had the potential to be highly disruptive to water quality, while generating a large amount of construction waste. ODOT’s project team spent months planning and preparing a demolition process that greatly minimized impacts to surrounding parks and roads, ultimately deciding that excavators should pull the obsolete structure apart from a work bridge built below the existing structure.
The wood-and-steel work bridge—stretching across the Willamette River about 10 ft above the high-water mark—supported the crew and the machines used for demolition and for the construction of new bridge bents for the southbound structure. One of ODOT’s primary goals is to prevent all construction debris from entering the water, so the work bridge doubled as a containment structure to protect the river below. This work bridge will be taken apart, and the supplies yielded from its deconstruction are set to be reused on the work bridge for the northbound structure to reduce waste and cost.
The old bridge was disassembled by excavators that ran on all-natural canola oil, which reduced risk of river contamination. The leftover wood, concrete and steel from the demolition resulted in approximately 30 million lb of debris. In late February, the bridge contractors met to identify specific ways to reuse this rubble within the new Willamette River Bridge project, exploring options as varied as using it in the new bridge’s beams to creating concrete artwork for a nearby park.
Once the temporary bridge is dismantled, 50 of its salvaged concrete box girders will provide spans for a bicycle-pedestrian viaduct along the south bank of the Willamette River, adjacent to the project. The new multiuse path will improve connectivity between the cities of Eugene and Springfield and will cross creeks that will be fully restored by the end of the project.
Bring in the “bubbleator”
During construction, fish populations are required to be protected from construction noise that can negatively affect communication and migratory patterns. To muffle the noise from underwater pile driving, the contractor placed a noise attenuator (or “bubbleator”) around each pile template, designed for two piles. The “bubbleator” is a custom-made, circular device constructed of sheet metal and lined with high-density polystyrene foam. Aluminum pipes frame the piles to produce a thick wall of frothy bubbles, thus dampening sound from pile strikes. Due to its large size, the frame of these devices also serves as a safe, sturdy work platform for crews during pile driving. Hydro-acoustic monitoring on the project has shown attenuators are maintaining noise levels below required thresholds.
As construction continued, ODOT found that not only did the fish populations need protection, but so too did the local Myotis bat populations, which are declining at a rapid rate across the Northwest. Bridges are exactly the type of habitat in which bats roost, so the agency saw the Willamette River Bridge as a way to contribute to bat conservation. Because this project employed the CM/GC procurement method, designers were able to suggest that bat habitats be placed on the new bridges once construction was already under way. ODOT will build eight bat habitats, attaching two to each of the project’s bridges (northbound and southbound), as well as to the I-5 bridges over Canoe Canal, two bridges adjacent to the Willamette River Bridge. Each habitat is roughly 6 ft wide, 6 ft deep and 12 ft long and made of concrete, wood and steel.
Spreading goodwill
ODOT’s commitment to good stewardship goes beyond the environment directly surrounding this project and extends to the neighboring park lands as well. The bridge is flanked by Alton Baker Park and the Whilamut Natural Area, land covered with grass prairies, flowering plants and giant Douglas fir and oak trees. The agency plans to repave walking and biking paths for safer use and restore twice the number of native trees and plants to the area.
Monitoring and maintaining these areas will continue for at least five years after the project is complete.
Another notable improvement will be the restoration of tributaries connecting Augusta Creek and Glenwood Slough. Over the years, these upper habitats have been cut off from the river and degraded by urban development, depriving fish of access. Now, the project team is removing a concrete-lined channel, restoring stream banks with extensive native plantings and removing barriers to fish migration.
The southbound structure is now nearing completion and is expected to open for use in late October 2011. Once it opens, it will carry all traffic until the northbound bridge is finished.
Work on the second bridge is already taking place. In April, hydro-acoustic monitoring will again ensure that pile driving for the rebuilt work bridge does not disturb fish species. Once it is complete, ODOT can demolish the temporary bridge, scheduled to take place in November. The agency and its partners remain committed not only to building a safe, efficient transportation system to move people and goods through the Willamette Valley, but also to caring for and improving the natural areas that surround it.
