Structure C on the Federal Way Link project required problem-solving due to tough ground conditions.
Photo courtesy of Sound Transit

Sound Transit opened the first 6.5-mile, eight-station segment of its $3.67-billion East Link Extension in April, connecting South Bellevue and the Redmond Technology Center east of the city. The floating bridge component, which features the world’s first installation of light rail track on such a structure, is nearly complete. The Federal Way Link extension, a nearly 8-mile, three-station alignment via mostly elevated tracks between the airport and Federal Way, is slated to open in early 2026.

Sound Transit is steadily extending light rail north, south, east and west, opening new stations every few years to form a 116-mile regional system by 2041. ST2, approved in 2008 for the $18-billion, 15-year plan, is followed by ST3, approved in 2016 for the $54-billion plan. Mestas says the leadership transition is ongoing, as is the agency’s quest to keep improving through one-on-one sessions with industry, working with other area public agencies on timing of procurements and working with the Design-Build Institute of America to train people on collaborative delivery methods.

“There is a shortage of labor in the region,” Mestas says. “The ability for contractors to meet project labor agreement local hire goals is really hard. We are looking at how to partner with apprenticeship programs more robustly.”

Three current projects wrapping up soon—the Lynnwood, Federal Way and East Link extensions—highlight the ongoing success of Sound Transit’s efforts to be an owner of choice through overcoming construction challenges ranging from unexpected ground conditions to concrete strikes and the pandemic.

Doug Glaser, executive vice president with Kiewit, has worked with the agency for almost a decade, including on the three jobs. “Everybody’s evolved over this time frame as more and different procurement types come in,” he says. “It’s working pretty good.”

The $1.4-billion Federal Way Link project is Sound Transit’s largest design-build job to date.
Photo courtesy of Kiewit

Floating Innovation

For the East Link extension, crews with the joint venture of Kiewit and Hoffman have wrapped up installation of eight “track bridges” that will allow transition of 300-ton light rail vehicles onto the nearly mile-long Homer M. Hadley floating bridge, which already carries Interstate 90 traffic across Lake Washington to points east of Seattle.

British engineer Andy Foan came up with the concept of 43-ft-long curved platforms that sit on double-pendulum bearings, allowing the rail to act like a continuously variable-radius track panel. Atop the bearings, a curved wing element connects to a hinge that allows the rail to stay on plane, even as the lake moves the bridge horizontally or vertically. Movement pushes on the hinge, and the bearings self-level the rail for continuous alignment (ENR 12/11/17 p. 14).

The pandemic and a 2022 concrete driver strike have pushed the opening to 2025, says Jon Lebo, Sound Transit executive project director. The work is deployed under the construction manager-general contractor method (general contractor-construction manager in local parlance).

The specialized track attachments will minimize weight and isolate stray current from the electric system that powers the trains. Crews post-tensioned the bridge pontoons, a process that reinforced the concrete and high-strength tensioned strands and cut off concrete guardrails to save weight, says Lebo. “Post-tensioning helps reduce wear and tear from the lake and storms,” he says.

At 3,600 ft, project officials believe this post-tensioning job includes the longest continuous tendons in the world. Crews worked inside the individual cells of the bridge, each about 30 ft by 15 ft by 15 ft, core-drilling roughly 2,500 holes below the water line to create a path for the continuous tendons and the ducts that encase them. Trolley systems transported 600-ton hydraulic rams inside the bridge structure to stretch the strands to 22 lineal ft during a weekend shutdown of the bridge.

Almost 9,000 specially engineered and constructed lightweight concrete blocks are affixed to the bridge deck using a specialized epoxy. The bearings allow for motion under the platform while ensuring ties remained a constant distance apart.

“The challenges of putting light rail on a floating bridge was realized very early on by the Washington State Dept. of Transportation and Sound Transit,” says Matt Barber, supervising engineer with WSP. “Sound Transit committed to full-scale prototype testing.” Two track bridges were fabricated and shipped to the Transportation Technology Center in Pueblo, Colo. “Sound Transit shipped rolling stock there so that actual trains and suspension systems could be tested,” Barber says.

The new Lynnwood light rail extension entailed paralleling and crossing over Interstate 5.
Photo courtesy of Sound Transit

In addition to testing several installation methods, the team had to determine “what we could and couldn’t do on the bridge according to the time of year,” says Jason Acres, vice president and director of operations for project and construction management for the West with Jacobs, the project construction manager. “During preconstruction, we did a mock-up of the unique track attachment.”

Now the team is “spending time on detailed measurements on where the track bridges sit right now versus alignments so that the bridge can behave as intended,” adds Jason Ruth, Jacobs vice president and director of operations for transportation in the Northwest. “Even a quarter of an inch anomaly is a problem. It’s like building a Swiss watch—you have to be precise.”

When completed, the extension will provide light rail service 14 miles from downtown Seattle to Mercer Island, downtown Bellevue and the Overlake area of Redmond via I-90. Passengers will be able to travel from Mercer Island to the University of Washington in 20 minutes, from South Bellevue to Sea-Tac Airport in 50 minutes and from Redmond Technology to Bellevue’s downtown in 10 minutes.

“It is a critical link for the community,” says Dave Bowman, Kiewit construction manager. ‘We worked with Sound Transit, WsDOT and stakeholders around the clock for several months to complete this critical link while retaining service.”

Acres, who has worked with the agency since 2008, notes its evolution of using alternative project delivery first on stations and maintenance buildings, then to heavy civil. “There’s a big effort [by Sound Transit] to understand the issues we have and to continue to be a good client.”

Public art is a significant component of all new Sound Transit stations.
Photo courtesy of Sound Transit

A Fix on Federal Way

That effort paid off when the design-build team of Kiewit and Parsons Corp. encountered unexpected ground conditions while building the Federal Way Link Extension project, a 7.8-mile extension of the Link light rail line that includes three elevated stations and three parking garages. At $1.4 billion, it is Sound Transit’s largest design-build contract to date.

In November 2020, Kiewit submitted notice of a potential differing site condition at the Structure C bridge area midway through the alignment. Investigations determined that the soil had the potential to liquefy, causing the adjacent slope to fail and slide into the guideway. The simple span bridge structure included in the original design would not meet design requirements.

“Kiewit decided to design the solution,” says Dan Novakovic, technical manager with AtkinsRéalis, which provided project management services for the project. Working with McNary Bergeron & Johannesen as construction engineer, the team selected a rigid-pier bridge option designed to slide along bearings and stay operable during a seismic event.

Then, a 200-ft-long landslide occurred while crews were installing timber piles to stabilize slopes. The team pivoted to a bridge option with a 500-ft main span and 250-ft back spans, built with the balanced cantilever method, which avoided the need for piles in the poor soil altogether.

“Structure C posed a tough condition, but we came up with a solution together,” says Glaser.

Divers were enlisted to pull out rebar after a foundation casing got stuck last year, says Michael Jellison, a Sound Transit construction manager. He notes that the box segments vary in depths from 15 ft up to 27 ft, with a width of 30 ft. “It’s a substantial bridge,” he says.

The agency worked with Kiewit to reach a change order of $109 million—still within the budget—with substantial completion by November 2025. Linneth Riley-Hall, Sound Transit’s Federal Way executive project director, notes that the project winds not only through residential areas, alongside a busy highway and a landfill, but is adjacent to a Washington State Dept. of Transportation highway project.

The extension will provide light rail service south from Seattle-Tacoma International Airport (SeaTac) to Des Moines, Kent and Federal Way in King County, largely running parallel to Interstate 5. The project is funded partly by a $629.5-million TIFIA loan from the U.S. Dept. of Transportation and a $790-milllion grant from the Federal Transit Authority.

This year, the project was the seventh in the nation to receive the Envision Platinum designation from the Institute for Sustainable Infrastructure—and the second such designation for Sound Transit. The design-build contract had stipulated the project attain at least Envision Gold. Social impacts, community context (such as preserving a view of Mount Rainier from stations), stormwater treatment and pedestrian-friendly measures during construction all contributed to the rating, according to the institute. Local art is also a major component of all the projects, including the Lynnwood extension.

Lynnwood Link involved two general contractor-construction manager teams and extends the system 8.5 miles north.
Photo courtesy of Sound Transit

Sharing a Sandbox

The four-station Lynnwood Link Extension will extend the Link light rail transit system 8.5 miles from Northgate Transit Center in Seattle north to Shoreline in King County and on to Mountlake Terrace and Lynnwood in Snohomish County. It received a $657.9-million TIFIA loan and a $1.17-billion Full Funding Grant Agreement.

The extension involved two general contractor-construction manager teams. Skanska’s approximately $800-million contract includes 3.8 miles of guideway that links the cities of Shoreline, Mountlake Terrace and Lynnwood to north of Seattle, two elevated stations and a five-story parking garage at the Lynnwood Transit Center. A Stacy and Witbeck/Kiewit/Hoffman joint venture partnered in an approximately $900-million contract to build 4.8 miles of a double-track extension in a narrow corridor parallel and adjacent to Interstate 5. It includes about 1.9 miles of elevated guideway with direct fixation track and 3 miles of ballasted track in an at-grade guideway on retained cut and fill.

“We did preconstruction for three years, got into construction in 2019 and were in ramp-up mode—then the pandemic hit,” says Andy Auxier, regional manager with Stacy and Witbeck. Just as work began to ramp up again, the concrete strike happened. “We had to send people home since there was no concrete for four months.”

Once work began again, “we knew we were up against it schedule-wise,” he recalls. With Skanska and Mass Electric, the systems contractor, “we had three teams locked in a room and looked for opportunities to get the systems work started before [construction] was 100% complete. We overlapped schedules.”

Crews were squeezed between the I-5 and residential areas, which required massive retaining walls. “Getting access into the jobsite was challenging,” Auxier adds. “Almost half of it is aerial.” Once the guideway was completed, “we met daily with the systems contractor to get them ‘squeezed into the sandbox.’”

Josh Pategas, Sound Transit’s deputy executive project director, notes that crews had to build a temporary trestle over a wetland with oscillating drill rigs and cofferdams. A cast-in-place overpass required some 200 shafts, up to 10 ft in diameter and some 80 ft deep. “There are miles of retaining or fill wall” due to the often steep slopes, he adds. “Soil nail walls, MSE walls, some cast-in-place gravity walls.”

Randy Harlow, Sound Transit executive project director, adds that the agency and teams worked to overcome a big potential cost and schedule overrun with value engineering. For example, “We relocated one garage to the north side of I-5 and examined means and methods for the overpass.”

Thorvaldur Konradsson, Skanska project executive, notes that rain, snow and wildfires also posed challenges in 2022. “One end of our job would be under the limit” for air quality while “the other end was over the limit. So do we shut the entire job down or half the job? We invested in air-quality monitors approved by OSHA and established our own perimeters.”

When one soil nail wall collapsed, “we backfilled it immediately, drove soldier piles with lagging and moved on. We had to be innovative in resequencing.”

Rain at one point hit during a concrete pour for a five-story parking garage’s ramp, he recalls. “We spent countless evening meetings figuring it out,” he says. “We got through it and opened the garage 15 months before revenue service as planned.”

The team had a staffer dedicated solely to community outreach, he notes. “It took a year to get people used to us, but the outreach was amazing,” he adds. Moreover, the three contractor teams collaborated constantly. “If we ran out of ballast, we could call [the Stacy & Witbeck-led team] and ask for some,” he says.

Structure C on the Federal Way project is a cast-in-place segmental structure.
Photo courtesy of Kiewit Infrastructure West

Moving Forward

Sound Transit is already looking forward with a $54-billion program to come. Mestas expects that will expand as the agency envisions increasing to 91 miles from 83 miles of commuter rail, 45 miles of new bus rapid transit and five lines of light rail. “First out of the gate will be the West Seattle Link extension program,” she says. “We will do design procurement first for design-build items such as tunneling.”

The extension adds 4.1 miles of light rail service from SODO Station to West Seattle’s Alaska Junction neighborhood, including four new stations. Also in planning is the Ballard Link Extension, which would add 7.1 miles of light rail service from downtown Seattle to Ballard’s Market Street area, including a new downtown Seattle rail-only tunnel. It would include nine new stations between Chinatown-International District and Market Street.

Sound Transit will consider progressive design-build and construction manager at-risk as additional tools for project delivery. “What will work look like, what will be different so it’s easier to chase the work? Clarity of risk, scope—we’re working on that now,” says Mestas. The agency will also pursue high-tech tools for geotechnical investigations and digital twins, she adds.

Jeanine Viscount, WSP principal project manager, notes that the agency began trying APD in the mid-2000s. “Right now they are in the design-build phase, but are moving toward progressive design-build.”

Ronald Wong, executive vice president with PGH Wong Engineering Inc., one of the agency’s consultants, notes that it runs multiple lessons-learned workshops on various aspects of construction. “They don’t just do lip service,” he says. “They’ve very open to ideas. If something makes sense, they’ll use it.”

He adds: “Nobody ever says, ‘that’s not my problem.’ That goes a long way.”