Trancas Bridge

This was to replace a bridge over Trancas Creek on the Pacific Coast Highway (PCH) near the world-famous Zuma Beach. The existing structure was over 100 years old prior to reconstruction, which necessitated the replacement. 

Need 

The existing bridge structure faced severe structural deficiencies and did not have a channel size to meet the water flow requirements of a 100-year storm, making this infrastructure upgrade a critical requirement for the historic PCH. Prior to reconstruction, the outflow of Trancas Creek led to flooding in the area. 

Work 

• Cast-in-steel-shell piling supporting cast-in-place columns, pier caps, and abutments. 
• 100 precast prestressed voided slabs, with cast-place-deck placed on top. 
• Channel restorations with native planting. 
• Utility relocations. 
• Fiber reinforced deck roadway concrete.  
• Rock slope protection structures on each abutment.

Challenges Met

Despite the bid-build contract, the team brought our project-first, collaborative mentality to the project to ensure its success in the face of many obstacles. As the bridge is at a critical choke point on the coastline of Malibu, work was completed in two stages in order to allow traffic to continue flowing. 

Shortly after contract execution, there was a year-long delay due to uncompleted third-party utility relocations. The team partnered with the State to begin early procurement and submittals to limit material escalations.  

The deep foundation PDA test piles failed the initial testing, resulting in an entire redesign of the foundation. To offset this, foundation work was accelerated by welding Stage 1 and Stage 2 pile together to comply with the new longer pile design. Working with Caltrans, the team modified material lengths and welding locations to expedite the overall process for Stage 2 construction.   

Coordination with agencies was crucial as heavy rainfall and tidal action transformed the seasonally dry Trancas creek into an active river and tidal lagoon for two years. Progress was successful through the implementation of work berms, temporary creek protection decking, floating snap dock work platforms, gravity piped diversion systems, and the installation of infiltration ponds. None of these construction techniques were part of the original scope but emerged through collaboration between Stacy Witbeck, Caltrans, and other agencies committed to advancing the project.