Honeydew Bridge Replacement Project

Humboldt County Public Works has completed design, obtained the necessary permits and funding has been allocated. Advertisement is planned for early 2024 with Phase 1 construction in 2024 followed by Phase 2 of construction in 2025.

The Honeydew Bridge was constructed in 1920 as a single-lane bridge with two steel Camelback truss spans. The bridge is supported by a reinforced concrete pier and wing abutments on spread footings. The bridge has timber decking and rails. The total bridge length is 386 feet and the vertical clearance is 14 feet. The bridge is posted to limit truck and bus speeds to 15 miles per hour.

The bridge is classified as functionally obsolete due to geometric constraints, and is incompatible with modern highway use and the need for conveyance of heavy equipment and fire equipment. Projects to widen the existing bridge or increasing its vertical clearance are technically infeasible. The overall sufficiency rating based on a July 15, 2014 inspection by Caltrans Structure Maintenance and Investigations was 13.3. The bridge is considered deficient due to its age, deteriorated condition, elevated maintenance costs, and seismic susceptibility.

The truss structure has repeatedly been struck and damaged by oversized vehicles. Several main truss members and portal cross frames have been replaced, typically with plug welding. The truss portion of the bridge was last painted in the mid-1970s. The County does not have funding for a bridge painting program. The maintenance needs of the bridge are high due to its age, design, and materials of construction.

The County proposes to replace the bridge with the objective of providing a bridge that meets modern highway standards and can serve the local and regional transportation needs. The proposed project will replace the existing single-lane steel truss bridge with a new two-lane bridge. In addition, the roadway approaches on both ends of the new bridge will be widened to accommodate two 12-foot wide lanes, 4-foot wide shoulders and 3-foot wide unpaved shoulders.

Humboldt County Public Works retained Morrison Structures, Inc. to prepare a Bridge Type Selection Study (January 2013) to assist in the County’s selection of bridge type for a replacement bridge. Morrison Structures developed the type selection study based on using the existing alignment and providing a clear roadway width of 26 feet (two 12-foot travel lanes with two two-foot shoulders). The County has not made a determination on the design type for the new bridge. This decision will be made during the preparation of the Environmental Impact Report for compliance with the California Environmental Quality Act.

Construction is expected to require two seasons due to the amount of work to be performed and the limited allowable work period. Foundations and support walls for a new pier (or piers) and the south abutment would be constructed in the first season. This will require water diversion and excavation of channel sediment. A detour would not be required during the first season. Detour construction, dismantling and removal of the existing bridge, and construction of new piers, abutments, superstructure, and approaches would be performed during the second season. Work during the second season will require erection of falsework and temporary support bents. 

The detour road will be built over a low water crossing on the Mattole River, approximately ½-mile downstream from the bridge. The existing bridge will be dismantled using a crane to remove the steel truss sections and excavators with demolition tips to break apart the piers and abutments. The existing bridge pier in the river channel and both abutments will be completely removed and pile supports will be excavated and cut off at a minimum of 5-feet below the surface. All bridge, abutment, and pier debris will be removed from the streambed using heavy equipment.

Consideration of bridge replacement began in the early 1970s. Initially there was interest in re-locating the bridge to allow re-aligning the approach road on the north side, in order to bypass several hillslope curves. A total of ten alternative routes were assessed. Based on this initial assessment, the preferred location for a new bridge alignment was located approximately 1,800 feet downstream of the existing alignment. The primary rationale for this selection was meeting the objective of straightening the alignment of the approach road to the north. In the late 1970s, the County acquired right-of-way for a new approach road on the north side of the Mattole River through dedication on a subdivision map. Right-of-way was not secured on the south side of the river. Funding to pursue this option was not secured and project development was discontinued.

In 1997, the Humboldt County Board of Supervisors passed a resolution stating the intent to replace the bridge based on its lowered sufficiency rating. The low rating was based on a history of incidents in which oversize vehicles had hit and damaged the structure, as well as the overall deteriorating condition of the bridge.

In 2011, Humboldt County Public Works initiated technical studies and engineering design for bridge replacement. This work included updated hydraulic analysis, geotechnical evaluation, and preliminary design for the bridge and road approaches. 

From 2012 through 2022, continued work with the environmental and design phases occurred which included further public scoping, preferred alternative design type options and completion of the joint EIR/EA. Humboldt County Public Works, with assistance from their consultants, applied for and received the necessary permits for the Project. Additionally, during this time, the Right-of-Way phase included working with landowners on construction easements and the proposed detour crossing location.

In 2023, final design plans were completed, necessary permits and approval were obtained, and all construction easements were granted. The project is schedule for bidding and award in early 2024 with a planned 2-season construction beginning in 2024 and ending in late 2025.

In 2003, Caltrans determined that the Honeydew Bridge was eligible for listing on the National Register of Historic Places under Criterion C, which specifies structures that “embody the distinctive characteristics of a type, period, or method of construction.”  Caltrans identified the bridge as an “excellent example” of a rare and significant bridge type from the early 20th century.  The Camelback truss design was an innovation that allowed for longer spans with less material to reduce overall construction costs.  The 2003 report stated that three bridges of this type currently exist, and the Honeydew Bridge has a substantially longer span than the other two remaining examples.  The bridge had previously been evaluated in 1986 and had been rated as not eligible for National Register listing.

Members of the Honeydew community have expressed appreciation for the aesthetic and historic character of the bridge.  The geometric patterns of the truss structure and the bridge’s rustic nature contribute to its representation of an earlier era.  While the basis for the bridge’s eligibility for listing on the National Register of Historic Places is tied specifically to the engineering design aspects of the bridge within a state context, the community’s attachment to the bridge is primarily based on aesthetics and general historical character.

Humboldt County retained JRP Historical Consulting, LLC (JRP) and the Humboldt State University Cultural Resources Facility to perform the evaluation and documentation required under Section 106 of the National Historic Preservation Act and the applicable guidelines and procedures developed by Caltrans.  A Historical Resources Evaluation Report, Historic Property Survey Report, and Archaeological Survey Report were prepared in 2013.