A nearly 100-year-old steel-truss bridge that carries Manthey Road over the San Joaquin River in Lathrop is on track to be torn down once a new $25.9 million span is built downstream, aligned with the planned Golden Valley Parkway on River Islands. The existing bridge, built in 1926, once scored just 7.1 out of 100 in a state safety study, and city leaders are now moving to replace it rather than patch it up further.
According to the Manteca Bulletin, the steel truss bridge across the San Joaquin River on Manthey Road has stood since 1926, and a 2012 Caltrans study assigned it a sufficiency rating of 7.1 out of 100, determining it was structurally deficient and functionally obsolete. Once the new bridge is in place, the outlet reports, the century-old Manthey Road bridge will be removed. The replacement would extend south from Brookhurst Boulevard, cross the San Joaquin River on the new bridge, and connect with Stewart Road in the River Islands development.
What the New Crossing Would Look Like
The planned bridge would measure 523 feet long and 53 feet wide, per the Manteca Bulletin's reporting, a slight trim from the existing span's reported length of 539 feet. Traffic signals would be installed at the Golden Valley Parkway intersections with Brookhurst Boulevard, Sadler Oak Drive, and Stewart Road, and the project would also maintain access to Mossdale Crossing Regional Park.
The City of Lathrop, in its own environmental filing, states that the replacement bridge will be along the proposed Golden Valley Parkway alignment. Lathrop is the lead agency under the California Environmental Quality Act for the project, while Caltrans serves as the lead agency under the National Environmental Policy Act, according to the City of Lathrop's Notice of Intent to Adopt Mitigated Negative Declaration. That same document says the recirculated review presents revised and enhanced mitigation intended to reduce impacts on Swainson's hawk and the riparian brush rabbit to a less-than-significant level.
A Years-Long Environmental Review Process
City records show a Draft IS/EA for the project was circulated on September 11, 2020, and a recirculated version was later made available for public review between November 12 and December 17, 2021, with comments due by that final date. The Manteca Bulletin's account of Lathrop City Council being asked to approve an initial project study and a mitigated negative environmental impact declaration reflects where the process stands now, following that earlier review activity.
Funding and a Decade-Old Grant
The push to replace the Manthey Road bridge isn't new. The Manteca Bulletin has reported that Lathrop applied for and was granted $4.5 million in 2012 for early engineering and environmental design work, with 88.53 percent of the project's cost expected to come from the federal Highway Bridge Program.
A Regional Pattern of Slow-Moving River Crossings
Lathrop's experience building new crossings over the San Joaquin River has historically taken time. The Manteca Bulletin notes that the River Islands Parkway bridge was put in place in 2012 but was not connected to a roadway until several years later — a local precedent for how long bridge infrastructure can sit before it's fully usable.
Golden Valley Parkway's Bigger Role
Beyond replacing an aging span, Golden Valley Parkway is envisioned as a connector for Lathrop's growth. The roadway would swing through the planned River Islands employment center, where a Valley Link station for commuter rail service connecting to the BART station in Pleasanton-Dublin is planned, the Manteca Bulletin reports.
