The big switch into the State Route 99 tunnel is right around the corner, but not before several tests are carried out.
Thousands of tunnel components and 90 interconnected systems must be tested before the tunnel opens to ensure that the roadway is safe for traffic to move through.
Back in March the physical roadway inside the tunnel was finished, and since then crews have been conducting multi-layered tests of operational and safety systems in the tunnel, like individual sprinkler heads as well as entire sprinkler systems.
Several tests have already been conducted. However, there are plenty of more tests to go, and soon both the tunnel and viaduct will be closed as on-ramps are rerouted into the tunnel.
The tunnel could open by October.