When it’s completed it’ll be the first interchange of its kind in the State of California.
And on Thursday, a handful of Manteca motorists got to see firsthand exactly what the proposed diverging diamond interchange at Union Road and the Highway 120 Bypass would look like – a revolutionary design that will take traffic passing across the freeway in dedicated lanes opposite of the standard configuration.
While the design is cheaper than the inverted cloverleaf that Manteca planners originally proposed when drawing up the initial design – coming in around roughly $16 million as opposed to $30 million for the original design – it leaves a much smaller footprint than the interchange currently uses, and that will have a big impact on nearby home owners who don’t want to have their daily routine turned upside down.
According to Project Manager Matt Brogan of Mark Thomas and Company – the engineering and consulting firm hired by the city for not only this project, but also the upcoming proposal on the Highway 120/99 Interchange – because the onramps will be much closer to the actual freeway, that work can begin while the existing onramps are still being utilized, and with minimal impact to homeowners on Daniels Street who have to deal with morning and afternoon commute traffic.
Manteca had initially planned to revamp the interchange in 2009. They had begun the necessary engineering work to move the project forward until the City Council shelved it because of the downturn in the economy. When the State of California dissolved all of the redevelopment agencies throughout the state to help alleviate its own budget crisis, Manteca decided to take the $10 million that it had set aside and relaunch the idea of continuing with the project – the main reason that Union Road is being chosen over other highly-utilized highway overcrossings like Main Street and Union Road.
According to Manteca’s Public Works Director Mark Houghton, Caltrans will be coming back soon with plans on how to overhaul the existing Highway 99/120 interchange – which, like the Union Road project, will employ the services of Mark Thomas and Company – but had to focus the funds on the proposed site because they were previously earmarked for that specific location before RDA was done away with by the state.
The $5 million to $6 million needed to complete the project, he said, will come from development funds.
If the project clears all of its necessary engineering and planning hurdles – Caltrans is also involved in the project jointly with the City of Manteca – then ground could be broken as early as Fall of 2017. Planners expect about an 18-month project duration time, which will include the widening of the existing Union Road overcrossing instead of a complete tear down and rebuild – something that will save money and a significant amount of time.
The overpass is being built for the future in order to handle anticipated traffic flows down on Manteca’s arterial streets that has become the connection from the heart of the community over to the new construction south of the 120 Bypass – including Bass Pro Shops and all of the adjoining businesses.

To contact reporter Jason Campbell, email jcampbell@mantecabulletin.com or call 209.249.3544.