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120/99 work will alter southeast Manteca roads
bypass art

The first phase of a $131.5 million project targeted to break ground next year to address safety and traffic flow issues at the 120 Bypass and Highway 99 interchange will also bring significant changes to city streets.

It includes:

*Redoing the Woodward Avenue connection to Moffat Boulevard so it intersects with Moffat Boulevard at closer to a 90 degree angle. Traffic signals would also be included.

*Replaces the at-grade crossing of the railroad tracks at Austin Road as part of the new bridge overcrossing of Highway 99.

*Swings Woodward Avenue to the south to connect directly with Austin Road.

And even though the southbound off-ramp and northbound on-ramp at Austin Road will be closed for at least 10 years while funding is secured for the third phase, the Caltrans improvements to city streets will have significant positive impacts on traffic in southeast Manteca.

*The four-way stop at Austin and Moffat is eliminated. That — along with the temporary closure of the southbound Highway 99 off-ramp to Austin Road — will eliminate the long traffic back-up on Moffat Boulevard heading toward Modesto. While the additional southbound transition lane from the eastbound 120 Bypass to southbound Highway 99 is expected to take pressure off Moffat by reducing people taking shortcuts, long-term growth is likely to replace the congestion with more vehicles.

*The city is expected to pay — with probably an advance loan or some other type of assistance from the San Joaquin Council of Governments — so Caltrans will replace the existing bridge across Highway 99 at Austin Road with four lanes instead of two. That would open up more of southeast Manteca to development.

It would also position the Austin Road interchange to possibly be the southernmost interchange in Manteca along Highway 99 for use at least for a four-fifths loop road of Manteca instead of the city ultimately pursuing an interchange connecting Raymus Expressway to Highway 99. Such an interchange has been pegged at $100 million plus due to the need to bridge the railroad and shift Highway 99 to the east. The cost would be all on the city’s dime which is why the previous council dropped it from the traffic circulation plan.

Raymus Expressway — as it is unfolding in various approved subdivisions at the city’s direction even though no official alignment has been adopted — will ultimately connect with Austin Road. In doing so it will cross Main Street and a future extension of Atherton Drive north of Sedan Avenue.

The Manteca City Council on Tuesday when they meet at 7 p.m. at the Civic Center, 1001 W. Center St., will consider an agreement with Caltrans that is a precursor to the project getting underway.

 That first phase of the Caltrans project costing $52.5 million would also build a new northbound off ramp to Highway 99 at Austin Road.

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 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.

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 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.

Austin Road’s current overpass needs to come out 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