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SEATTLE — Sound Transit announced Thursday that some western Washington communities waiting for light rail service will have to wait longer, citing a myriad of issuing plaguing construction from Lynnwood to Federal Way and its eastern extension to Redmond.

The Sound Transit Board System Expansion Committee received the news in a detailed report Thursday that laid out the causes for the delay including pandemic challenges to the months-long concrete strike that ended in April. 

The report also revealed the new expected project opening timeline for the East Link and Redmond extension, Northgate to Lynnwood and Angle Lake to Federal Way extensions.

The opening of the East Link will be pushed back at least one year beyond the previously scheduled mid-2023 opening, according to the report.

The biggest challenge facing the East Link extension is the construction quality and durability concerns about plinths, or raised concrete structures, that support the tracks.

According to Sound Transit, work to fix problems with the concrete plinths on both the east and west sides of the I-90 floating bridge has led to the discovery of further issues. The contractor addressing the plinth's concerns also discovered issues with mortar pads, rebar placements and track fasteners, according to the report. Sounds Transit said the contractor is working to re-cast the plinths and address the other issues, including an emphasis on training and improved quality control.

The East Link extension launches the new 14-mile 2 Line that will include 10 new stations from Seattle to Redmond.

The delay in construction of the 3.4-mile extension to downtown Redmond is due to the concrete strike and pandemic-related impacts, power connection issues and staffing shortages, according to Sound Transit. The extension was previously scheduled for mid-2024 but will be pushed backed four to six months.

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The report said it is still too early to determine the exact delay for the extension from Angle Lake to Federal Way, but Sound Transit expects the project completion to extend into 2025, months later than its original late-2024 opening.

Sound Transit said the Federal Way extension encountered an unexpected ground instability issue in Kent, adjacent to Interstate 5.

Contractors could potentially have to redesign a segment of the line near I-5 and South 259th Place after discovering a liquefiable layer of soil, according to the report.

On July 19, a slide led to the precautionary closure of multiple southbound I-5 lanes. Sound Transit said the slope has been temporarily stabilized and that it is working with the Washington State Department of Transportation for a permanent fix. The liquefiable layer of soil may force Sound Transit to come up with a new design approach for that section of the light rail.

The 7.8-mile Federal Way extension will eventually open three new 1 Line stations in Kent, Des Moines, Star Lake and Federal Way downtown.

Completion of the north expansion from Northgate to Lynnwood may be impacted by four to six months longer than its previously scheduled mid-2024 opening date, the report said.

Sound Transit said the delayed project completion date is only slightly longer than the four-month delay caused by the concrete strike.

The 8.5-mile Lynnwood extension adds four new stations in Shoreline, Mountlake Terrace and Lynnwood and will serve both the 1 Line and the new 2 Line.

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