Humboldt County, Williams Creek Bridge Replacement
The Williams Creek Bridge on Grizzly Bluff Road is a forty (40) foot long, single span concrete T-beam structure with concrete abutments that was originally constructed in 1920. The Williams Creek Bridge is located about one-half mile east of the City of Ferndale, California, and provides access across Williams Creek for farmers and local residents travelling between Rio Dell, Waddington and Ferndale. The existing bridge has extensive cracking in the abutments, wingwalls and concrete railing due to settlement and errant vehicles. The primary reason for replacing the Williams Creek Bridge is to provide a road crossing that meets modern highway design standards and accommodates local and regional transportation needs. The existing bridge is 97 years old and is beyond the end of its service life. The bridge exhibits signs of significant structural fatigue (sufficiency rating of 44); does not comply with modern geometric and seismic standards; lacks standard shoulder width; and is unsafe for pedestrians.
The proposed replacement bridge type will be a single span cast-in-place pre-stressed concrete voided slab, widened to meet current County standards. The new bridge will be longer to decrease the height of the bridge abutments and reduce creek channel constriction which will help prevent debris buildup and channel scour due to flow constriction during large storm events. The new bridge will be 60 feet long with an overall structure width of about 36 feet, including two 11- foot lanes, two 5-foot shoulders, and it will have two concrete bridge rails with tapered metal beam guard rail approaches. The construction work to be done includes, without limitation, demolition of the existing concrete bridge, installation of a temporary detour, temporary stream diversion, driving steel H-piles, constructing abutments, constructing falsework and voided slab bridge structure, grading and widening the roadway, stream channel grading, installing rock slope protection around the abutments and graded stream channel, erosion control and revegetation planting and roadway paving, striping and revegetation monitoring. Bridge construction is expected to take one hundred and twenty-five (125) working days to complete, or about six (6) months and the revegetation monitoring will continue for five (5) years after the project is completed.