SEATTLE — Sound Transit has fallen months behind schedule in its quest to operate trains across Lake Washington by June 2023, as managers blame construction errors, a concrete delivery strike, COVID-19, frayed supply chains and even bad weather.

The 14-mile, $3.7 billion route connecting Seattle, Mercer Island, Bellevue and the Overlake area is expected to serve 48,000 daily passengers. It was approved by voters in a regional 2008 sales tax measure. This spring’s cascading project delays aren’t a total surprise, but the severity might be.

Project staff mentioned a potential start date of February 2024 in a presentation on April 26 to King County Metro Transit rail-division employees. Metro personnel operate and maintain the trains.

“That information is a bit premature,” Ron Lewis, director of design, engineering and construction management, said in an interview afterward. Lewis said he can’t provide a reliable opening date until after a new study of risk factors, which he said should be ready by June.

Sound Transit previously disclosed an estimated 48-day delay in a February progress report.

CEO Peter Rogoff frequently described the regional concrete-truck driver strike by Teamsters, as a threat to project timelines everywhere, from Lynnwood to Federal Way. The strike began Dec. 3, 2021, and lingered until April 8.

“I know the big thing for us has been that strike, that has delayed a lot of work,” board Chair Kent Keel said.

“I feel that we, as an organization, are working feverishly to keep the schedule we promised to the public. That’s the goal,” said Keel, a city council member from University Place near Tacoma. “We’re doing everything we can, but we’re facing a lot of headwinds.”

Transit board members voted April 28 to approve a $15 million contract increase to Jacobs Project Management to oversee heavy construction for the East Link project, for more months than expected.

Progress reports say the prime schedule risk involves concrete track ties where the rails curve toward International District/Chinatown Station, on the former express lanes of Interstate 90. Several of the ties, known as plinths, were built to wrong dimensions and need to be rebuilt, Sound Transit managers told its governing board in fall 2021.

Contractors in the Kiewit/Hoffman joint venture are making repairs, but those are more complex than anticipated. Extra inspections are needed to ensure workers don’t drill into previously built rebar. Some 34,600 pieces of hardware that fasten rails to the concrete ties must be removed and eventually reinstalled, said Deputy East Link Director Jon Lebo.

Some concrete contains weak spots, he said. Plinths in those sections must be grinded down and topped with polyurethane before rails can be refastened, akin to dental work. Lebo predicted repairs will be finished late this year.

About 30 repair workers could be seen April 27 from the Jose Rizal Bridge, where crews were jackhammering flawed concrete, applying fasteners to rails and arranging green rebar pieces.

In a statement on April 27, Kiewit confirmed it expects to complete the job by the fourth quarter of 2022. The company is currently paying for repairs, though spokesperson Tom Janssen referred in the statement to the “increased scope that has also impacted the scheduled completion,” which implies there may be cost disputes later.

“While some of the work is contested, we are working with Sound-Transit for a mutually agreeable path forward,” Janssen wrote.

Other contractors’ segments also fell behind, which complicates the follow-up work to install train signals. Fragile portions of Redmond Technology Station parking garage are being rebuilt at contractor expense, and even homeless encampments are mentioned as an issue. Litigation by the city of Mercer Island slowed construction at a station, the April 28 memo says.

Crews last year lost days to temperatures around 100 degrees that made work unsafe, and also to winter snows, Lewis said.

On the other hand, Sound Transit has celebrated some recent successes.

The new 1,500-stall South Bellevue park-and-ride opened in the fall, and this year, trains reached 35 mph in electric-power tests through Bellevue’s Wilburton and Spring District areas. East Link, to be shown on maps as the 2 Line, will whisk people between downtown Seattle and Redmond Technology Station in 35 minutes.

As of this week, the project remains within the overall $3.677 billion budget, with $336 million still unspent.

In the presentation shown to Metro, full-route train tests were projected to begin in August 2023, followed by simulated service (trains going at full speed and frequency without passengers) in November 2023.

Testing schedules gained importance with the Nov. 26, 2021, Apple Cup stall. Football fans streamed out of railcars after a power cord was sliced by protruding bolts, along the new Northgate extension. Sound Transit’s post-stall audit characterized the Northgate line’s 60-day testing regimen as too rushed, and said future startups must allow ample time for maintenance, training and emergency response drills. This time, train tests will go at least three months, spokesperson Rachelle Cunningham said.

They will be the world’s first to cross a floating bridge, using flexible track joints on I-90. Track ties and platforms will sit on rows of flexible seismic dampers, like those built into stadium roofs and solid-girder bridges. Engineers have pledged extra care and surveillance to guarantee trains can travel 50 mph safely.

Back in July 2020, the tunneled segment of the line in downtown Bellevue was finished by Atkinson Construction, raising hopes among supporters for an early grand opening. Sound Transit officials warned then against overconfidence.

“We can make a lot of things, but we can’t always make time,” Lewis said Tuesday. “We can take the time we need to create a quality project that will be dependable.”