Walter Yu, P.E., LEED AP

Taking Hwy 1 underground between Pacifica and Montara.

The much-anticipated Devil’s Slide tunnel project may soon reach the light at the end of the tunnel (literally). Work crews have been rotating between shifts to maintain a 24-hour production schedule.

The project moved ahead after numerous land slides in recent years that have posed a serious safety issue to drivers and cause the roadway to be closed during repairs (not to mention cost for emergency repairs).

According to the Caltrans website, the two tunnels will connect Hwy 1 between Pacifica and Montata, running about 4200-ft. (about three-quarters of a mile) in length. Construction was sequenced the two bores to be 60 yards apart so there would be no damaged between the bores due to blasting to remove rock.

The Monterey Herald covered the story in a brief article, citing project completion in fall of this year.

The project incorporates not only the tunnels but a bridge (super structure) approach into the tunnels and roadway re-alignment of Hwy 1. Inside the tunnels, electrical, metering and ventilation systems will regulate vital systems such as air monitoring for drivers.

The New Austrian Tunneling Method is used for the tunnel boring operation, relying on the strength of surrounding rock and shotcrete walls behind it to maintain the integrity of the tunnel during and after construction.

If operations run smoothly, Caltrans will indeed again be living up to its slogan of “improving mobility across California”.