MATTOLE RIVER BRIDGE

MCI was awarded the Mattole River Bridge Replacement Project by the County of Humboldt in 2024. The existing bridge, originally constructed in 1920, no longer met current California bridge safety standards or lane width requirements.

The original structure was a two-span Camelback truss bridge spanning 375 feet. It featured a single traffic lane with a timber deck and was one of only three remaining Camelback truss bridges in California at the time of its replacement.

To safely complete the project, MCI installed a temporary detour bridge downstream of the existing structure, allowing traffic to continue while construction progressed. During the first year, crews completed the bridge substructure. In the second year, the temporary bridge was reinstalled, and each span of the original bridge was removed using a 350-ton crawler crane.

Following demolition, MCI immediately began constructing the remaining concrete components of the new bridge before installing the 15 steel girders that support the bridge deck. Due to the size and design of the structure, the concrete deck was placed in three separate pours.

The completed bridge measures 30 feet wide and 385 feet long, providing a safer and more durable crossing that meets modern transportation standards.

Despite extremely limited environmental work windows, MCI completed the project without any negative environmental impacts and finished construction several months ahead of schedule.