Bertha moving underneath Seattle’s Showbox
That rumble on First Avenue in downtown Seattle may not be the latest concert at The Showbox. Rather, that’s where Bertha is pushing forward, constructing the SR-99 tunnel.
At this point, Bertha should be about 192 feet below the surface. It has moved 4,239 feet from its start and has constructed a total of 644 concrete rings to form the tunnel. That places it roughly in the middle of First Avenue between Union and Pike Streets.
On that block, above Bertha, is The Showbox, Seattle’s legendary performance space. The building that houses the stage was built in 1916 and is of masonry construction, according to King County records. Across the street is a 76-unit condo building built in 1985, as well as a 60 unit building for low-income senior housing. Farther to Bertha’s left is the southern stretch of Pike Place Market. The world’s largest boring machine will soon pass to the right, and well below, the famous gum wall.
This is all within Zone 6 — out of 10 zones — that Bertha is moving through. Within this zone, between Bertha and the surface, is a railroad tunnel built in 1904. There is also a main sewer line that runs between downtown and the West Point Treatment Plant.