Why is it necessary to close the viaduct while the machine passes beneath?

Tags: winter-closure

Keeping SR 99 open to traffic while we replace the viaduct is a top priority. Temporarily removing traffic from the viaduct while we tunnel beneath it will enable crews to monitor the structure more closely and act quickly to mitigate any settlement that may occur during this section of the tunnel drive. The short-term inconvenience of closing the viaduct will help us preserve it until we shift SR 99 traffic to the tunnel.