SR 99 Mining Resumes after Maintenance Stop
Seattle Tunnel Partners resumed mining July 18 following a month of routine and hyperbaric maintenance on Bertha, the TBM digging the SR 99 tunnel. Crews inspected and repaired machine components as needed during the maintenance period, which started on June 23.
The maintenance period included more than 40 shifts of work under hyperbaric conditions, changing cutting tools and performing other maintenance in the space behind the cutterhead. In all, STP changed 33 of more than 700 cutting tools.
RELATED: SR 99 TBM Reaches Half-Mile Mark
Tunnel boring is currently one-third complete. The machine is located approximately 120 ft beneath Spring Street, tunneling north toward First Avenue. At its deepest point near Virginia Street, the machine will be more than 200 ft below the surface.
STP expects to stop two more times for maintenance before they reach the future north portal, near the Space Needle.
The Washington State Department of Transportation has also recently released videos of hyperbaric work and the highway construction that is ongoing in the tunnel behind the tunneling machine.
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