209 Business Journal file photo
Construction is expected to begin on the 120 Bypass in spring.

The 120 Bypass — if all goes according to plan — will turn into a construction zone for the next four years starting this spring.

That’s because more than $100 million worth of interchange work has been scheduled.

*The widening of Union Road crossing the Bypass to four lanes by deploying the state’s first diverging interchange starts this spring and could be completed at year’s end as part of a $20 million plus undertaking.

*Two miles to the west work is targeted to start on building an interchange at the Bypass where McKinley Avenue crosses under the freeway. The construction timetable calls for work to be completed in spring of 2021. It has a price tag in excess of $30 million.

*The first phase of work for upgrading the 120 Bypass/Highway 99 interchange is tentatively set to start in 2021. The first phase has a $52.5 million price tag. Over all, the three-phase endeavor will cost $131.5 million.

Manteca Deputy Director of Public Works Koosun Kim provided the City Council with an update on the McKinley Avenue project in January.

The right-of-way acquisition and design work for the interchange that will open up more than 100 acres in Manteca for development in the city’s family entertainment zone anchored by Great Wolf and Big League Dreams will be completed in June. The interchange will provide access to roughly 3,000 housing units approved in southwest Manteca as well as allow access to a major employment center Lathrop has planned on the west side of McKinley north of the 120 Bypass.

It is being designed as the city’s first partial cloverleaf. But in order to save money the city is opting to build the inner ramp loops at a later date.

That means the initial construction will have all left turns from McKinley Avenue to 120 Bypass onramps go through signalized intersections just as they currently do at the Airport, Union, and Main interchanges. When the loops are completed northbound McKinley Avenue traffic will be able to get onto westbound 120 without going through a traffic signal as would southbound McKinley to eastbound 120.

It will include a separated bike path underneath the 120 Bypass that eventually will connect with the Atherton Drive bike path to provide access to Big League Dreams and the envisioned family entertainment zone.

Ultimately it will be a link in a separated bicycle pathway that loops the city going along McKinley Avenue north to connect with a path that cuts behind Del Webb at Woodbridge that crosses Union Road and ties into the Tidewater Bikeway. The Tidewater then heads south and ties in with the Atherton Drive Bikeway via Industrial Park Drive and Van Ryn Avenue.

The McKinley Avenue interchange is also part of the long-range circulation plan for Manteca south of the 120 Bypass where more than 60 percent of the city’s population is expected to be by 2040.

Once the interchange is in place, it would be possible for Great Wolf to exercise an option they have with the city to buy more land to accommodate another 200 hotel rooms. The initial 500-room indoor waterpark resort is targeted to be complete in mid-2020, a year before the McKinley Avenue interchange would be completed under the current timetable.