In Northern California's San Joaquin County, the San Joaquin Council of Governments (SJCOG) is leading the highway-to-highway State Route 99/120 Connector Project, marking the first time in its history that SJCOG is leading a construction project.
The project is a major infrastructure initiative designed to enhance safety, improve traffic flow, and reduce congestion in the Northern California megaregion by improving the critical highway-to-highway link between State Routes 99 and 120. By adding lanes, improving ramps, and upgrading nearby streets, the project aims to facilitate smoother and safer travel for residents, workers, and freight, all while reducing greenhouse gas emissions and enhancing air quality in the Central Valley.
Westbound State Route 120 connects State Route 99 with Interstates 5, 205, and 580, as well as the San Francisco Bay Area, while eastbound State Route 120 from State Route 99 leads to the Sierra Nevada, Yosemite National Park, and U.S. Highway 395. The nearly 425-mile State Route 99 passes through major California cities, including — among others — Bakersfield, Fresno, Madera, Merced, Modesto, Manteca, Stockton, Sacramento, Yuba City, Chico, and Red Bluff.
“This project is absolutely vital for the people who live, work, and play here,” said Christina Fugazi, Stockton Mayor and SJCOG Board Chair. “It is a gateway to jobs, education, entertainment, adventure, services, and more. More than 180,000 vehicles move people and goods through the interchange every day. Not only is it near some of the fastest growing cities in California, it opens up travel throughout Northern California, from the San Francisco Bay Area to the Sierra Nevada and up and down the state, from Red Bluff to Bakersfield.
“This major transportation hub serves cities which are home to an array of logistics and fulfillment centers. Those businesses depend on the interchange and the region’s transportation system to get their goods to customers. It’s also located in the San Joaquin Valley, known by some as the 'Breadbasket of the World' for its vast agricultural output of products that must also get to market.”
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The State Route 99/120 Connector Project is being completed in two phases.
“Two primary elements of the first phase are the added lane to the eastbound State Route 120 connector ramp to southbound State Route 99, and the new, longer Austin Road overpass south of the connector ramp that will span the added lane and nearby Union Pacific Railroad tracks,” said Ryan Niblock, SJCOG Deputy Director of Programming and Project Delivery. “Other work included building a new surface street and improvements to existing surface streets with new lanes and signal lights, streetlights, intersections, sidewalks, curbs, landscaping, and other infrastructure — to allow traffic to flow more safely and smoothly to and from the interchange.”
The second phase of the project will reconstruct the interchange to relieve one of the California Department of Transportation (Caltrans) District 10’s top traffic congestion and safety bottlenecks on the State Highway System. During the second phase, crews will:
- Construct a two-lane northbound State Route 99 to westbound State Route 120 connector structure and auxiliary lanes
- Relocate the Austin Road northbound on-ramp and build braided ramps between the Austin Road on-ramp and State Route 120 connector
- Widen State Routes 99 and 120 for auxiliary (or merge) lanes and improve interchange to remove conflicts due to weaving traffic
- Upgrade signing, striping, lighting, and drainage to be consistent with Caltrans standards
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Groundbreaking on the project was in July 2024. The first phase of the project is expected to be completed by summer 2026, and design for the second phase is expected to be completed in late 2028 or early 2029. The construction for the second phase is dependent on funding but could start in 2029.
The San Joaquin Council of Governments is the planning, financing, and coordinating agency for the San Joaquin region, overseeing transportation, housing, and habitat conservation. SJCOG is a joint-powers authority with a board of directors comprised of elected representatives from Escalon, Lathrop, Lodi, Manteca, Mountain House, Ripon, San Joaquin County, Stockton, and Tracy.
SJCOG’s responsibilities include managing the Measure K transportation sales tax program, collecting county demographic and economic data, airport land use planning, affordable housing initiatives, and regional air quality. SJCOG partners with a network of local governments, private organizations, and community groups to deliver local, state, and federal programs that support the streets, roads, highways, public transit, and other transportation resources.
SJCOG, as the project sponsor, has taken on the role of lead agency for the first time since its founding in 1968.
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“Because the highway-to-highway State Route 99/120 Connector project is so important to the region — to traffic safety, people and goods movement, the economy, air quality, and more — we absolutely wanted to have our hands on the wheel of this project to expedite it throughout the process,” Fugazi said. “We wanted to create the very best highway construction experience from conception to completion.”
The project owners are Caltrans and the City of Manteca. General contractor on the project is Teichert Construction. Project design was developed by the Mark Thomas & Company Inc. engineering firm. The construction engineer is WSP USA Inc.
“Mark Thomas worked collaboratively with SJCOG, Caltrans District 10, Union Pacific Railroad, San Joaquin County, and the City of Manteca on the design, development, and approvals required for the project,” said Matt Brogan, Principal and Executive Vice President of Mark Thomas. “This work began back in 2015 with the development of the environmental document and project report, which completed approvals for the overall interchange complex. The final designs and right of way acquisitions for the first phase began in 2018, and the project advertised for construction in early 2024. Through the final design phase, Mark Thomas worked closely with all stakeholders to address design challenges and develop the final construction documents.”
Funding for the first phase of the project comes from a combination of sources, including Measure K (the half-cent sales tax managed by SJCOG for transportation improvements in San Joaquin County), the State Transportation Improvement Program, Caltrans’ State Highway Operation and Protection Program, federal COVID-19 relief money, and the federal Highway Infrastructure Program.
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The cost of the first phase is an estimated $77.5 million. The second phase is currently estimated to be around $144.67 million.
First phase construction included adding a lane to the SR 120 Connector to SR 99 and work to improve East Woodward Avenue and railroad crossings at that location.
“The most visible milestones for the first phase obviously have been the dismantling of the Austin Road overcrossing of State Route 99 and the rebuilding of the new, longer bridge,” Fugazi said.
“We also constructed a new street to help traffic circulation,” Niblock added. “The half-mile Singh Street, named to honor a common and well-recognized surname in Manteca, was built between Austin Road and East Atherton Drive to ease detours needed for the project.”
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Reinforced concrete paving for the widening of the eastbound State Route 120 connector to southbound State Route 99 has also been completed. Once opened, the additional lane will allow for traffic to efficiently merge to southbound 99 and ease traffic congestion on eastbound 120.
“Almost all of the major roadwork along the existing frontage roads and city streets has been completed, along with the erosion control measures to prevent stormwater quality issues,” said Michael Saunders, Senior Project Manager for Teichert. “As the bridge nears completion in the early spring, the northern end of the bridge approach will be constructed to final grade under traffic control closures to complete the overpass. An asphalt overlay will also be placed on north- and southbound State Route 99 in the springtime.
“The contractor, construction manager, owner, and all other stakeholders have worked together throughout the project to avoid potential schedule impacts due to staging and utility conflicts. For example, the team revised the construction staging sequence to avoid potential schedule impacts from working around the railroad and existing underground utility lines and made design changes to allow for work to be completed around and under existing overhead electric utility lines.”
A major component of the Connector Project is the new Austin Road Bridge, according to Niblock.
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“The 1950s-era Austin Road overcrossing just south of the State Route 99/120 Connector ramp is being replaced with a longer bridge to span the added State Route 99 lane and nearby Union Pacific Railroad tracks,” he said. “Removing the old Austin Road bridge was necessary to span the new lane and tracks, and to better align with improved surface streets and intersections on either side of State Route 99. ... Nighttime work to remove the 1950s-era Austin Road overcrossing over State Route 99 required various lane closures and detours to ensure the safety of motorists and our crews.”
Figures provided by SJCOG illustrate the size and scope of the work:
- 4,319 cubic yards of structure excavation
- 2,524 cubic yards of structure backfill
- 437 drive piles with a total end-to-end length of 4 miles
- 19,688 linear feet of furnish piling
- 7,760 cubic yards of concrete to rebuild the bridge/overpass
- Nearly 2 million (1,904,639) pounds of reinforcing steel (rebar)
- 1,180 headed bar reinforcements
- 34,472 pounds of miscellaneous metal
- 2 acres of bridge deck supported by the girders
- 63 girders — 115 to 159 feet long with a total end-to-end length of 2 miles
“All the foundation work and precast girders for the Austin Road overcrossing have been set,” Saunders said. “The permanent steel decking is being installed along with the rebar for the bridge deck. The bridge deck construction is continuing, along with the construction of concrete barriers on the bridge.”
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“There were several challenges to raising the nearly 160-foot-long precast girders,” Niblock added. “We had to lower the grade of Moffat Boulevard to improve the alignment with nearby intersections and then use a two-crane multistep process to raise the girders under Pacific Gas and Electric powerlines, which had to be de-energized. It took tremendous planning, collaboration, and coordination with our partners to put the girders in place.”
“We knew that the Austin Road overcrossing would be closed for 16 months or so, but we did as many things as possible to help to lessen the impact on traffic and maintain the safety of motorists and our crews,” Fugazi said. “Much of the work on the interchange, Austin Road bridge, and surface streets was intentionally scheduled at night, so there would be limited impact on traffic.”
“Communicating to travelers also helped a lot,” Niblock said. “As you might expect, there are lots of bright orange signs, electronic signs, and other measures used to alert motorists of upcoming work zones and detours. We also used SJCOG’s website, text messages, emails to critical stakeholders, and notifications to subscribers, social media, and even the City of Manteca’s Nextdoor platform to tell people about the work, closures, and detours.”
- Project Sponsor: San Joaquin Council of Governments
- Owners: Caltrans and the City of Manteca
- Participating SJCOG Member Cities: Escalon, Lathrop, Lodi, Manteca, Mountain House, Ripon, San Joaquin County, Stockton, and Tracy
- General Contractor: A. Teichert & Son Inc., dba Teichert Construction, Sacramento, California
- Designer (Engineer): Mark Thomas & Company Inc., Sacramento, California
- Construction Manager (Engineer): WSP USA Inc., Sacramento, California
- Bridge Subcontractors: Myers and Sons Construction LLC, Sacramento, California
- Crane Company: Bigge Crane and Rigging Company, San Leandro, California Photos courtesy of San Joaquin Council of Governments
