Cascading Construction Errors Add New Delays to Light Rail Expansion

Inspectors found gaps between rails and pre-cast concrete plinths on both sides of the I-90 water crossing. They addressed the problem by installing mortar, which subsequently failed. Image: Sound Transit presentation

By Erica C. Barnett

Shoddy workmanship, the concrete workers’ strike, and the collapse of an embankment in Kent will delay the opening of the regional light rail expansion by a year or more, Sound Transit staff told agency board members on Thursday. The board already knew that a light rail extension linking Seattle to the Eastside across Lake Washington was behind schedule because of issues with concrete plinths, or track supports, installed by contractor Kiewit-Hoffman, but learned more details last week about both that construction snafu and other issues that will contribute to delays throughout the project.

The biggest potential delay involves the light-rail extension across I-90, where Sound Transit inspectors discovered problems with the concrete plinths that directly support the rails leading up to the water crossing, pre-cast concrete blocks on the bridge deck, and the nylon inserts that hold bolts in place where the rail is attached to the floating bridge itself.

“I want to be clear that as we talk about challenges and risks, we’re speaking to the ability to meet current schedules and not the ability to deliver light rail across the I-90 floating bridge,” Sound Transit’s interim CEO, Brooke Belman, said during last week’s meeting. “We are 100 percent confident in the design and operability of the segment across the floating bridge and [that we will] complete the entire alignment.”

“It was a very strange working situation for absolutely everybody, including folks who would have been on the ground looking at the work and now were required to work from home. So there were a variety of issues that led to this place where we find ourselves.”—Sound Transit deputy director Kimberly Farley

Sound Transit started unearthing problems with its I-90 crossing in 2019, when inspectors discovered that the top surface of some plinths did not connect with the rails they were supposed to be supporting. To close these gaps, Sound Transit’s Kiewit-Hoffman installed mortar between the blocks and the rails, a solution Sound Transit deputy director Kimberly Farley said the agency believed would fix the problem. Subsequently, though, that mortar failed, and Sound Transit discovered another set of problems, “including concrete placements that were too low, too high, constructed to the wrong geometry, or resulting in voids under rail fasteners,” according to a staff report.

During work to fix those construction problems, the team discovered additional issues, “such that the overall scope of the challenges has increased rather than decreased”; for example, many of the blocks had improperly installed or missing rebar, which strengthens concrete and prevents it from cracking. During this time, Sound Transit also discovered that the nylon bolt holders were stripped and decided to replace all of them. They also noticed that some of the pre-cast concrete blocks that support the rails across the bridge were cracking.

Asked why Sound Transit’s inspectors didn’t discover these problems sooner, Farley noted that much of the construction took place at the height of the pandemic, when “it was just a struggle to get everybody on site, keep the work going, and keep the protocols in place.”

“It was a very strange working situation for absolutely everybody, including folks who would have been on the ground looking at the work and now were required to work from home,” Farley continued. “So there were a variety of issues that led to this place where we find ourselves.” Earlier this year, Sound Transit hired a forensic engineer to evaluate Kiewit-Hoffman’s repairs and keep tabs on construction.

Board member Claudia Balducci told PubliCola  she was glad Sound Transit staff revealed the latest issues to the board at this stage, rather than waiting until they had come up with fixes, noting that the agency has historically had issues with transparency. Former director Peter Rogoff could reportedly be tight-fisted with information, preferring to address issues internally rather than bringing them to the board or discussing them in public. “I want that kind of transparency,” Balducci said. “I don’t want staff to be like, ‘We won’t report to the board or to the public until months later, when we have identified a problem and fully engineered a solution.'”

It could be months before the agency identifies a solution to unstable soil conditions along the alignment between Kent and Federal Way, where a 200-foot section of embankment slid nine feet earlier this year, forcing a partial closure of I-5. Originally, Farley said at last week’s meeting, Sound Transit had hoped to use timber pilings to shore up the slope, but after the slide, they went back to the drawing board. “The reason that you didn’t hear the solution [at the meeting] is because, frankly, we don’t have one yet,” Farley told PubliCola.

Sound Transit estimates the 2021-2022 concrete strike, which lasted four months, will result in delays of four to six months on other segments of the line, including the Lynnwood and downtown Redmond extensions. However, since the entire project is interconnected, Sound Transit staff said they couldn’t give a precise estimate for how long it will take to finish any specific part of the project. For example, Farley told the board last week, it might make more sense to bump the East Link extension, which includes a new operations and maintenance facility, to the bottom of the list, given the extent of the construction issues in that segment.

Balducci, who represents the Eastside on the King County Council, had an alternative suggestion: Why not build an Eastside-only rail line connecting Redmond, Bellevue, and possibly Mercer Island while waiting for Kiewit-Hoffman and Sound Transit to sort out construction problems with the water crossing? “Now that it looks like there might be a significant delay, and that delay is geographically limited to problems in construction and workmanship around the bridge, I think it’s time to look at” a temporary Eastside-only line, Balducci said.

Sound Transit’s construction update didn’t come with new cost estimates for the project. Farley said the agency will know more by the fourth quarter of this year, when it will have completed a “programmatic assessment” of the project.

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