Construction is officially underway on the long-awaited replacement for the Hills Ferry Road Bridge, marking a critical step in ensuring safe and reliable access across the San Joaquin River for decades to come.
Stanislaus County, working in collaboration with Merced County, the California Department of Transportation (Caltrans), and the Federal Highway Administration (FHWA), has embarked on a major infrastructure project to replace the aging bridge, which has long been plagued by seismic vulnerabilities and scour concerns.
Originally built in 1961, the current bridge has served as a vital connector between Interstate 5 and Highway 99, linking the towns of Patterson and Los Banos. The structure, spanning 647 feet and comprised of 18 reinforced concrete spans, replaced a 1901 wood trestle and steel swing-span truss bridge downstream. However, over time, the bridge has faced significant challenges. Seismic activity poses a threat due to subsurface liquefaction and lateral soil spreading, while accelerated bank erosion and deep scour at several piers have raised alarms about its long-term safety. Emergency repairs in 2020 offered temporary relief, but extensive studies determined that a full replacement would be far more cost-effective than retrofitting the existing bridge.
The new bridge design promises enhanced safety and functionality, addressing these critical deficiencies while minimizing environmental and land-use impacts. The replacement structure, measuring approximately 750 feet in length, will feature five spans supported by reinforced concrete piers and abutments. With a usable roadway width of 34 feet, including wider shoulders and lanes, the bridge will accommodate the region's growing traffic demands—projected to exceed an average daily traffic (ADT) of 5,310 vehicles.
County staff opened bids for the construction of the Project on March 4, 2024. The bids came in substantially higher than the programmed amounts. Staff requested and received approval for additional federal funds. On June 25, 2024, the Stanislaus County BOS approved a contract with the low bidder, Golden State Bridge, Inc., in the amount of $24,764,304. The total estimated construction costs are as follows: Construction Contract: $24,764,304 Contingency (10%): $ 2,476,430 Construction Engineering (15%): $ 3,714,646 Total: $30,955,380.
Federal Highway Bridge Program will fund 88.53% of the federally-participating cost of the Project or $26,467,801. The remaining 11.47% would normally be the responsibility of the local agency; however, this project will receive $1,213,331 of Prop 1B Local Seismic Safety Retrofit Program (LSSRP) funds to offset a portion of the local match requirement. The remaining local match requirement for this project which will be split equally between Stanislaus and Merced counties is $2,215,853 or $1,107,927 each.
Key upgrades include a raised profile to improve flood resilience and a realignment of Hills Ferry Road that shifts the crossing northward to allow seamless construction without disrupting existing traffic. Once the new bridge is completed, the old structure will be dismantled, with foundations removed to standard depths and asphalt concrete cleared from the remaining embankments.
The revamped Hills Ferry Road Bridge is set to become a modern lifeline for the rural communities it serves. As Stanislaus County takes the lead on the environmental compliance process under the California Environmental Quality Act (CEQA), while Caltrans handles the National Environmental Policy Act (NEPA) process, the project is supported by a mix of federal, state, and local funds, including the FHWA Highway Bridge Program and State of California Local Bridge Seismic Retrofit Account.
The proposed construction is expected to be completed in less than two full construction seasons, with a timeline ranging from 15 to 24 months. In Stage 1, the construction of the two-lane replacement structure will begin north of the existing crossing during the initial “in-water” work window, typically lasting from June 15 to October 31. Concurrently, western and eastern approach roadways will also be constructed. Traffic operations will remain on the current two-lane bridge during this phase, although temporary disruptions—particularly near the eastern approach—may occur as the new alignment is tied into the existing roadway.
Once Stage 1 is complete, traffic operations will transition to the new alignment and replacement structure, paving the way for Stage 2. During this phase, the old bridge and required elements will be removed, with embankments left intact to provide added protection during high river flows. Seasonal constraints and environmental considerations may extend removal into a second “in-water” work window, resulting in a total construction duration of less than 21 months.
After the new bridge is open to traffic, the existing bridge would need to be removed. For portions of the bridge that are not over water during the removal period, those segments would likely be demolished using hydraulic breakers attached to excavators and the debris would be collected after it falls to the ground. For portions to be demolished over water, the demolition would likely be done from another work trestle built upstream of the old bridge or by working from the deck of the old bridge and working backwards during the removal. Removal methods would depend on whether concrete debris would be allowed to fall in the water or not.
As the project takes shape, residents on the Westside can anticipate a safer and more resilient crossing over the San Joaquin River, designed to meet modern standards while preserving the vital link between communities and commerce for years to come.
