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SR-99 Bored Tunnel, Seattle, WA

Architect: HNTB Architects

General Contractor: Seattle Tunnel Partners

Completion: March 2019

Products/Services Supplied:

  • Kawneer 1600UT Curtain Wall
  • Kawneer AA425 Entrance Doors
  • Guardian Low-E Glazing by Northwestern Industries
  • Wasco Skylights

When you talk about an underground tunnel, the last thing you would expect is for there to be a large scope of glass facade involved. Although the vast majority of this project is not visible unless you travel underground, Mission Glass provided the two main spotlight features that are visible above ground; the ventilation tower enclosures at both the North and South portals.

The large yellow ventilation stacks are a prominent feature of the tunnel and were designed to be showcased. In order to do this, ultra-clear low-iron glass with a high-performance low-e coating was utilized to provide the best views possible, while also meeting energy code requirements. The curtain wall system wraps all three sides of the ventilation rooms, as well as provides daylighting to the adjacent administrative office spaces. The most dramatic views of the enclosures can be seen at night, where interior accent lighting illuminates the entire space and stands out as a decorative accent along the Seattle waterfront.

We enjoyed the opportunity to be a part of the largest (diameter) tunnel ever built, and were consistently in awe of the massive size of the aptly named "Bertha" tunnel boring machine. This will stand out as one of our more unique projects that we were able to be a part of, and will likely not have the opportunity to see anything like it in Seattle anytime in the near or distant future. The boring of this tunnel will allow the existing dilapidated SR-99 viaduct to be completely torn down, which will forever change the Seattle skyline, but also provide countless opportunities to be involved on re-building this area of waterfront.