An inside look at a District 2 bridge

By Haleigh Pike
District 2 public information officer

The Antlers Bridge, which carries Interstate 5 traffic over the Sacramento River Arm of Shasta Lake, is one of the largest bridges in District 2, but there is one more thing that helps it stand out that many don’t know about. You can go inside it!

The first of its kind in District 2, the Antlers Bridge was constructed to include an enclosed box girder that is essentially a tunnel that runs right under the surface of the bridge deck, allowing easier access for inspections and repairs. Inside the enclosed box girder is a crane, hoist and lighting system, installed to help make inspections and repairs easier during the bridge’s 100-year design life.

For 74-years, the former 1,328-foot-long Antlers Bridge carried traffic but its active fatigue cracks and degrading deck made the bridge an annual drain on the State’s maintenance resources, including the District 2 Bridge Crew. In September of 2016, the original bridge was retired and traffic was moved to the new 1,942-foot-long bridge which was constructed adjacent to the old bridge.

The District 2 Bridge Crew inspects the Antlers Bridge every two years but additional inspections are occasionally required if the crew is notified of issues with the 16 seismic monitors placed throughout the bridge structure.

According to Chris Traina, Chief of the Division of Engineering Services, these monitors are maintained and operated by the California Geological Survey (CGS)through an interagency agreement between Caltrans and the Department of Conservation. In addition to providing information following earthquakes in ourarea, CGS also “pings” the sensors monthly to ensure everything is in working order.

Another aspect to inspecting the bridge is ensuring all the internal equipment is operating correctly including the crane, hoist and lighting. This requires the assistance from an electrician, which is not usually required for a bridge inspection.

Overall, the new Antlers Bridge requires significantly less maintenance resources and according to Billy Shakespeare, the District 2 Bridge Crew Supervisor, all maintenance will be easier as well. “The old Antlers Bridge was a fracture critical structure with a lot more maintenance to perform on the steel rivets, bolts, and components needing replacement as they fatigued butwith the way the new bridge was constructed, eliminating the streel truss support, we’re spending a lot less time on this bridge and do not expect it to require significant maintenance over the years,” said Shakespeare.

The Antlers Bridge was completed in 2016 and this historic project was celebrated by installing a time capsule, with photos and personal items from those involved in the construction of the bridge, within the enclosed box girder. The capsule is scheduled to be opened in 2043, 100 years from the completion of the Shasta Dam.