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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Sound Transit's construction started on Capitol Hill in February 2009 with the demolition and environmental clean-up of the site. This part of the project included: removing hazardous materials from buildings, clearing trees, demolishing and removing existing buildings, installing "soil nails" beneath the Bonnie Watson Parking lot, and paving and fencing all three construction sites. Salvage and recycling have been a very important part of Sound Transit's work at the Capitol Hill Station site. During demolition the contractor recycled 2,890 tons of bricks, wood, metal and other building materials from Capitol Hill that would otherwise have gone to the landfill. More information on the types of materials recycled is here >>>

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Phase II: Excavation and Tunneling

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Denny Way Closure A portion of Denny Way between Broadway and 10th Ave. will be closed to traffic for approximately 6 years while the light rail station is under construction (see map ). The construction wall surrounding the work site will be extended across Denny, preventing public access to that portion of the street. A gate at either end of the road will allow construction vehicles into and out of the site. Construction walls One of the first tasks the contractor will undertake is to construct a portion of the walls that will surround the construction site for the next 6 years. The wooden walls are expected to be between 8 feet high facing Broadway and up to and 24 feet high facing 10th Ave. The final height of the wall is subject to further design work. Sound Transit will be working with the community and local artists to design graphics for the exterior surface of the walls.

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

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Before the TBM has completed the second tunnel, another contractor will begin building the internal structure of the station - floors, stairs, mezzanines, elevators, etc. - and the three above-ground entrances to the station. Pedestrian Tunnel An underground pedestrian tunnel will provide direct access from the west entrance (next to Seattle Central Community College) to the mezzanine level of the rail station. While this tunnel is under construction, a portion of Broadway will be reduced to one lane in either direction, with no on-street parking. The pedestrian tunnel construction will take approximately six months, and will probably be one of the last activities in the 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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