Capitol Hill Station construction

Over the next several years, Sound Transit will excavate the site for the underground light rail station and launch the tunnel boring machines that will dig the tunnels between Capitol Hill and Pine Street. A few of the major tasks are highlighted below:

Phase I: Demolition and Environmental Remediation

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Phase II: Excavation and Tunneling

Excavation

During this phase the contractor will grade the site to make it level, and begin digging out the area for the station. The excavation for the station is approximately 400 feet long, 100 feet wide, and 60 feet deep. All of the excavated dirt (also known as spoils) will be hauled away in trucks. The trucks will travel along the haul route identified by the City of Seattle - leaving the site they will travel west on Olive Way to I-5 and coming to the site they will travel east up Denny Way. The final disposal site for excavated material will be determined by the contractor. The majority of the hauling during this phase will take place during the daytime and, at times, possibly extending into the evening.
Once the excavation reaches the bottom of the station (approx. 60 feet down), a concrete slab 10 feet thick will be poured at the bottom of the excavation.

Tunnel Boring Machine

After the concrete slab is poured, the digging of the two tunnels to Pine Street will begin. A single tunnel boring machine (TBM) will be launched from the bottom of the station excavation. The TBM is scheduled to excavate an average of 40 feet of tunnel every day. As it bores through the ground, the TBM will also place the concrete rings that form the exterior surface of the tunnel. Dirt from the excavation travels through the machine and onto a conveyance system which brings it back out to the surface to be hauled away.

When the TBM reaches Pine Street, the TBM will be disassembled and transported back to the Station site, where it will be reassembled to dig the second tunnel between Capitol Hill and Pine Street. The tunneling is done in this direction because there is not sufficient room for all the equipment needed to extract the excavated dirt at Pine Street.

For safety, schedule and other reasons, the tunneling operations must continue around the clock. In order to minimize the traffic impact of the trucks hauling away dirt, most of the hauling is expected to be done in the evening and at night (7 pm to 7 am). Sound Transit has applied for a variance from the Major Project Permit in order to do the truck hauling at night (10 pm to 7 am).

Phase III: Station Construction

Business Mitigation

Sound Transit and the Capitol Hill Chamber of Commerce are committed to implement a business mitigation plan to address the local business community's needs. Sound Transit has worked closely with the Capitol Hill Chamber and business community as a whole to develop a specific plan and strategy that meet the unique characteristics of the community. Two important elements of the business mitigation plan are promoting Capitol Hill as a great place to live, work, dine, shop and visit, and providing local businesses near or adjacent to the construction site with technical training to assist them in maintaining their customer base during construction. Learn more about business mitigation >>>

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