I-5 Antlers Bridge Replacement

The California Department of Transportation (Caltrans), in cooperation with the Federal Highway Administration, proposes to replace Antlers Bridge on Interstate 5 in Shasta County over the Sacramento River arm of Shasta Lake near the community of Lakehead. The bridge is at or near the end of its service life. In addition, a 0.4 mile section of highway south of the bridge will be realigned due to a high accident rate. Traffic will remain on the existing bridge during construction of a new bridge on a parallel alignment. New right of way will be required.

Antlers Bridge work update as of December 30, 2011

The contractor has drilled and placed concrete and bar reinforcement steel for the two pier columns at Pier 2, on the south side of the lake. Over the next several weeks the contractor will continue to place concrete forms and bar reinforcement steel for the pier table that will go on top of the two columns at Pier 2. The pier table will ultimately support and transfer the bridge and traffic loads down into the pier columns. Forming and rebar placement should be completed around the first week in January and then the contractor will begin pouring concrete into the forms.

Also on the south side of the lake is work at Pier 3. Pier 3 will have four columns. The contractor has installed a fourteen foot diameter steel casing into the ground and has begun drilling out the dirt and rock from within for the first of the four columns. Drilling will continue until they get to a depth of approximately 75’ below the lake bottom.

On the north side of the lake work continues from the contractor’s temporary trestle at Pier 5. The contractor currently has the two columns at Pier 5 above the water and is working to extend them so they can begin forming the pier table for this location next. The contractor is also working to extend the temporary trestle out further into the lake to where Pier 4 will be constructed.

To facilitate the concrete pour for the pier table at Pier 2, lane closures are expected in the north bound lanes on the south end of the project. No other lane closures are anticipated however, utility and work trucks/pickups will continue to be periodically entering and exiting the northbound lanes on the south end of the project. Please be aware and reduce speeds when traveling through the project limits.

Area Traffic Cameras and News Releases

NEWS RELEASES Antler Bridge Replacement Project Ground Breaking Celebration for Antlers Bridge Project

Form Traveler System

The Antlers Bridge superstructure, or bridge deck, will be constructed using a form traveler system similar to the one used on the Benicia-Martinez Bridge pictured here.

Both structures are segmental CIP (cast in place) balanced cantilever bridges. A cantilever is a long structure that is anchored on only one end. The cantilevers project out from opposite supporting piers and are then joined in the middle. The structures are balanced by building the segments on alternating sides. As its name implies, a segmental bridge is a bridge built in short sections, i.e., one piece at a time, as opposed to traditional methods that build a bridge in very large sections. Cast-in-place means the bridge is made of concrete and is constructed fully in its final location. This type of bridge is very economical for long spans (over 100 meters or 328 feet), especially when access to the construction site is restricted. They are also chosen for their aesthetic appeal.

The form traveler is a scaffold/formwork system that moves on rails and holds the rebar and fresh concrete as each section of the superstructure is constructed. After the concrete is cured, the completed section will support the form traveler as it is used to construct the next segment.