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3-phase approach designed to address deadly Bypass stretch, eliminate bottlenecks at 120/99 interchange
The initial phase of the fix for the 120 Bypass/Highway 99 interchange includes 1) swinging Woodward Avenue of south to Austin Road. 2) Making the current Woodward Avenue crossing of the railroad tracks 90 degrees. 3) Building new Austin Road bridge that would cross Highway 99 and the railroad tracks. 4) A new northbound 99 off ramp for Austin Road. 5-6) Temporarily shutting down the southbound off ramp and northbound on ramp at Austin Road. 7) Building a two-lane transition from the eastbound B

The deadliest and most accident prone stretch of freeway in the Northern San Joaquin Valley as well as what is arguably the region’s most congested interchange is being addressed in a three-phase project that ultimately will cost $131.5 million in today’s dollars.

The Highway 99/120 Bypass connector project is targeted to start work in 2021.

That first phase costing $52.5 million would:

widen the connector from the eastbound Bypass to southbound Highway 99 to two lanes.

replace the existing Austin Road overcrossing with a new bridge that would also go over the Union Pacific Railroad tracks.

swing Woodward Avenue south to connect with Austin Road.

relocate the current at-grade Woodward Avenue crossing of the railroad tracks to reach Moffat Boulevard so vehicles cross the tracks at 90 degrees. This would be a new, short road that only goes from the new alignment of Woodward Avenue to Moffat Boulevard.

temporarily shut down the southbound off ramp and northbound on ramp at Austin Road and the Highway 99 interchange.

building a new northbound off ramp to Highway 99 at Austin Road.

The configuration would allow traffic to use Moffat Boulevard — which would flow under Austin Road — to access southbound Highway 99 as it currently does.

San Joaquin Council of Governments Associate Regional Planner David Ripperda provided an update on the interchange project to the Manteca Rotary Club during their luncheon meeting Thursday at Ernie’s Rendezvous Room.

Ripperda said the project had to be broken down due to its immense price tag making it the most expensive interchange upgrade ever undertaken in San Joaquin County.  He indicated SJCOG is currently working on securing all the necessary funding for  the first phase. They also will need to acquire right-of-way.

The second phase costing $26 million would:

widen the connector from northbound Highway 99 to the westbound 120 Bypass to two lanes.

add a westbound auxiliary lane on the 120 Bypass from the Highway 99 interchange to Main Street.

The third phase costing $53 million would:

add an eastbound auxiliary lane on the 120 Bypass between Main Street and Highway 99.

add a new southbound off ramp and a new northbound onramp at Austin Road.

The high cost of the third phase design is reflected in it being necessary not to impede traffic flow and create a major safety hazard from the 120 Bypass south to 99 and from 99 going north to the eastbound 120 Bypass.

In order to do so the ramp for southbound Austin would start for eastbound 120 Bypass traffic at a point near the Bypass crossing of Moffat Boulevard and the railroad tracks while  the ramp for southbound 99 traffic to access Austin would start prior to the 120 Bypass connector flyover. It would be a left lane exit.

A braided ramp system — designed on the same principle as the Interstate 680/Interstate 580 connector in Pleasanton when you are going toward San Jose — would be needed to take traffic from Austin to head onto north 99 or the Bypass. Austin traffic bound for the westbound 120 Bypass would join the Bypass after passing below Highway 99 by merging with the southbound 99 to westbound 120 Bypass ramp. The Austin Road traffic heading north on 99 would join the freeway north of the Bypass/99 interchange.

The design will allow a future carpool lane project to be built on Highway 99 through the area eventually widening the freeway from six to eight lanes.

Ripperada noted that Austin Road’s current overpass needs to be removed in order to make things work. As it now stands it cannot accommodate any additional lanes passing beneath it on Highway 99.

The design will allow both lanes on the 120 Bypass to go south on Highway 99. Improvements will be made allowing a long merging area that will end south of Austin Road.

To contact Dennis Wyatt, email