Kraemer Selected for West Seattle Bridge Repair
In late May, the Seattle Department of Transportation announced that it had selected Kraemer North America as the contractor for the final phase of West Seattle High-Rise Bridge repairs.
The decision marks the latest in a series of on-time milestones in the ongoing effort to safely reopen the bridge.
Recent Rehab Progress
In December, SDOT reported that crews were removing work platforms from the West Seattle Bridge, marking the end of emergency measures to stabilize the structure and concluded preparations for upcoming repair efforts.
According to the Department’s blog, crews were able to successfully install and stress the post-tensioning system, use epoxy crack fillings, install carbon fiber-reinforced polymer support wrappings on sections of the structure and Pier 18’s bearing release and replacement.
In January, after work platforms were lowered crews began offsite disassembling the platforms. In addition, crews also reported that they would be finishing the last round of coating applications on the post-tensioning brackets.
Upon completing stabilization measures, SDOT announced that it had entered phase two of the project—which involves designing the full rehabilitation of the structure—and would be bringing a contractor on board. By March, the Department was noted to have reached a preliminary design milestone, a step that makes way for the selection process of a contractor.
At the time, SDOT confirmed a more accurate prediction of the costs of the rehab, which includes a total of about $72 million. On March 10, when the update was released, SDOT said that it had begun advertising a Request for Qualifications and Project Approach, initiating the process to bring a contractor on board while the project is still in its design phase—this is considered an alternate delivery method.
“Our work to reopen the bridge is on track, and we’ve made great progress to date. Simultaneously, we are continuing to implement solutions for impacted communities—including traffic mitigation, paving, detour signage, and installing safer walkways and bike lanes,” said SDOT Director Sam Zimbabe at the time.
“I am proud of the work of our teams across the department as we continue to work with urgency to restore the vitally important connection the bridge provides to our region.”
SDOT also reported that it was petitioning the United States Department of Transportation to allow the use of the city’s Priority Hire Program, since the project is federally funded. This would put an emphasis on hiring locally and putting money back into the city’s communities. Since this petition, U.S. Transportation Secretary Pete Buttigieg announced earlier this month that the USDOT would be reinstating the pilot program to allow local hiring provisions in federally-funded projects, which the City of Seattle supports through its Priority Hire and Community Workforce Agreement programs implemented in project contracts.
The federal local hire rule is currently in a 30-day public comment period.
This month’s selection of construction firm Kraemer North America as contractor now puts the rehabilitation project in motion. While the Department has reported that 2020 emergency measures have successfully halted the cracks from growing and that the structure is behaving as expected following additional stabilization efforts, it is ready to launch the project still ahead.
“The past year has been full of once in a lifetime challenges for our residents and businesses,” said Seattle Mayor Jenny Durkan. “We’re midway through this complex project and the end can’t come soon enough for everyone who’s been stretched by the emergency closure. Our new and growing construction team will work urgently to safely reopen the bridge.”
Kraemer was selected out of six firms that applied for the project. The list was then narrowed to a shortlist of three teams who were invited to interview and further demonstrate how their experience and qualifications make them best-suited for the project ahead.
“This contractor selection marks a major milestone in our work to quickly and safely reopen the West Seattle Bridge to the thousands of people who rely on it to get to work and move around the city, and to our essential freight network,” Zimbabwe said. “We closed this bridge under emergency conditions and have been working day-in, day-out to guarantee that it’s safe to use and reopen it as quickly as possible. I want to thank all the companies that threw their hat in the ring on this contract, and thank the City staff who oversaw the selection process.”
The repair contract covers both the rehabilitation of the West Seattle High-Rise Bridge and the Spokane St. Swing Bridge. For the work, SDOT and Kraemer will collaborate to identify ways to stay on schedule and find innovative solutions. In addition, SDOT and Kraemer will also be working closely with WSDOT, the USDOT and the Federal Highway Administration to advance the project and safely reopen the bridge.
“Restoring the West Seattle Bridge and the connection to Interstate 5 is important to the state’s economy and to the transportation network,” said WSDOT Secretary Roger Millar. “We are excited for the City of Seattle as they make progress to reopen the bridge and we will continue to be strong partners in addressing mobility needs across the Duwamish.”
The project is still expected to be complete in 2022.
Bridge Closure Background
Built in 1984 and envisioned to last more than 50 years, the West Seattle Bridge encompasses a six-lane cantilevered concrete structure that measures more than 150 feet high; the main span extends 590 feet long, crossing the Harbor Island and the Duwamish Waterway at the point where it enters Elliott Bay.
Over the years, the bridge has been reported to be “overused,” seeing roughly 107,000 drivers and 25,000 transit riders per day, in addition to adding on a bus-only seventh lane in the last decade. Officials have even gone on to report that the heightened usage could be a major reason for the accelerated cracking along the midspan.
While some were shocked to hear about the issue, The Seattle Times reported that SDOT had been inspecting the infrastructure every two years—as required by federal law—with engineers only noticing unusual crack patterns in mid-2019.
Prior to the 2019 inspection, the structure received a 5-merit, based on a scale of 1-9 for both superstructure condition and structural evaluation, which was reported to the National Bridge Inventory. However, the bridge also received a 69 out of 100 for its sufficiency rating, which is a federal metric that combines strength, traffic, environmental impact and navigation.
After the initial discovery, SDOT hired outside experts to evaluate the bridge, who found that the superficial cracking within the girders was actually much more serious, and in an inspection conducted in March, the issues only worsened, leading to the bridge’s indefinite closure.
In April, the Federal Highway Administration was reported to have been monitoring the situation. At the end of the month, SDOT announced that it had selected Wisconsin-based Kraemer North America to complete Phase 1 of bridge stabilization work. Work for the first phase involves the repair of lateral bearings on Pier 18. In Phase 2, Kraemer plans to add temporary external structures—otherwise known as “shoring”—and will determine in the third phase if long-term repairs are feasible.
Temporary Fix & Sensor Technology
By mid-May, the SDOT blog reported that it had been installing a new intelligent monitoring system on the structure, consisting of additional movement sensors, crack monitors and monitoring cameras. The monitoring instrumentation is expected to improve the Department’s understanding and tracking of the health of the bridge with more precision and in real time.
Around the same time that the sensors were installed, Durkan requested a failure analysis of the structure so that emergency preparedness could be improved.
Although the report was initially due by the end of April, on May 15, 2020, Greg Banks, PE SE; Lee Marsh PhD PE; Bob Fernandes, PE SE; Kare Hjorteset, PE SE; and Chad Goodnight, PhD PE, released their findings, pointing out the need for an evacuation of a long “fall zone” from the Pigeon Point greenbelt to Harbor Island, in addition to possible support solutions for the 150-foot-high main span.
While the engineers did not provide odd estimates of a potential collapse or when it could happen, they did go over two possible outcomes involving the event of a total failure or partial collapse, and another possibility involving the progression of cracks, which would then cease once the bridge stabilized itself.
According to the report, “The bridge is currently exhibiting progressive crack growth at two critical locations (Joints 38) of the four quarter points of the twin-box main span between Pier 16 and Pier 17. This is where the first failure mechanism has appeared. While a progressive failure does not mean collapse is imminent, it does illustrate an unintended redistribution of forces within the bridge that could lead to further damage.
“The cracks, without any mitigation, could stop, and the bridge could redistribute load until internal forces stabilize. However, it is not considered likely as the bridge will continue to creep (slowly deform under static load) over time and thus continue to crack.”
We have selected @Kraemer_NA to complete the final phase of #WestSeattleBridge repairs. This is one of the major on-time milestones in the ongoing effort to safely reopen the bridge on schedule in mid-2022. Find out more on our blog.https://t.co/mr5RjJrtP5— seattledot (@seattledot) May 21, 2021
In the process of completing some or all mitigation efforts, Durkan and SDOT formed a Technical Advisory Panel and a West Seattle Bridge Community Task Force. The task force includes the City of Seattle, King County, Washington State, Port of Seattle, Northwest Seaport Alliance, the United States Coast Guard and the U.S. Army Corps of Engineers. If necessary, in the event of a collapse, a unified command will be led by the Seattle Fire Department, SDOT, the Seattle Police Department and USCG.
The two advisory boards are slated to play important, complementary roles in the city’s collective effort to push ahead with the best path for the high-rise bridge, in addition to mitigating the impacts of the closure on West Seattle, the Duwamish Valley and surrounding communities.
Work began on a temporary fix for the bridge in early July, which included wrapping sections with carbon fiber reinforced polymer (CFRP) and installing post-tensioning tendons. SDOT detailed a multi-step plan for the emergency shoring that begins with reopening more than 100 traveler holes that were filled following the original construction.
The leftover holes are to be opened with water jets and aim to provide a place to fasten the hanging platforms the workers need to fasten the carbon wrap with epoxy. Carbon will also reportedly be attached inside the girders. That task was expected to start later that month and last 10 weeks.
The second stage involves stringing additional steel cables across the central span of the bridge—or post-tensioning. To anchor those cables, steel blocks will be fastened to the concrete underside. That phase is slated to be complete about two weeks after the carbon wrapping.
In the plan announcement, SDOT reiterated that a cost-benefit study by engineering firm WSP was scheduled to be completed in early fall, which would help dictate if the city should repair the bridge or demolish it.
Weighing the Options
In September, the Technical Advisory Panel released an official statement sharing that the information they reviewed indicated repairs appeared feasible and recommended SDOT continue to explore the repair option fully.
The criteria for the cost-benefit evaluation included constructability, environmental impact, equity, forward compatibility, funding, maintenance and operations, mobility, multimodality, regional business impact, and seismic resilience and safety.
However, by October, SDOT announced that its analysis was ongoing, although it had tapped HNTB to design a tentative replacement. The company’s first tasks included completing its own study to determine the type, size and location of several bridge and tunnel replacement options.
The following month, in an effort to retore traffic to its 125,000 daily travelers faster, Durkan announced that SDOT would repair the West Seattle Bridge, instead of replacing the entire structure.
Repairs are expected to extend the life of the bridge by between 15 and 40 years, using additional “post-tensioning” as its primary method for rehabilitation. The project is estimated to cost $47 million, only a fraction of what a $390 million to $522 million steel-arch replacement bridge would have been.
The decision follows Congress briefings to Durkan, which informed her that the federal government wouldn’t be acting on an infrastructure bill to make bridge grants available until mid- to late next year. However, The Seattle Times reported at the time that SDOT would still conduct a type, size and location study for an eventual replacement, which is expected to include bridge concepts and shallow immersed-tube tunnel.
In the meantime, SDOT Director Sam Zimbabwe says that the city has since hired WSP, its bridge consultant, to design the repair project following emergency stabilization earlier this year. Thus far, the firm is reported to have produced more than 400 pages of technical findings about the seismic qualities and internal girder forced of a repaired bridge.
Once the bridge is repaired, the SDOT has pledged to conduct full inspections twice a year with specialized worker-lift trucks, in addition to spending extra time on increased tensioning steel volume and to watchdog a full electronic network of monitoring devices.