Central area

Final configuration:

The SR 99 tunnel will be approximately two miles long. It will feature two 11-foot travel lanes in each direction, bordered by an eight-foot safety shoulder and a two-foot shoulder. Long, gentle curves will allow for safe sight distances. The southbound lanes are stacked above the northbound lanes, so drivers will not see oncoming traffic.

Tunnel cross-section

The tunnel will be built to modern earthquake standardsThere will be no on- or off-ramps between the two tunnel portals. In the event of an emergency, exits every 650 feet provide shelter and escape routes, while a state-of-the-art safety and ventilation system assists first responders, and fights fire and fumes. (Read more about the tunnel's safety systems in the program library.)

Current progress

Last updated: Dec. 29, 2016

At the time crews stopped for the holidays in December 2016, Bertha had tunneled 6,787 feet of her 9,270-foot journey. The machine had placed 1,035 of the 1,426 rings that constitute the new SR 99 tunnel. You can track Bertha’s progress on the Follow Bertha page.

Behind Bertha, crews build the interior structures that will carry northbound and southbound traffic. The walls and decks are built in sections, which allows crews space to work, provides concrete with time to cure, and increases the overall efficiency of the effort.