The days are numbered for the notorious traffic snarl on the eastbound 120 Bypass that worsens as you near the Highway 99 split.

The Manteca City Council when they meet Tuesday at 6 p.m. will be asked to approve a series of documents that will help “T” up a groundbreaking next spring of the first phase of a three-part, $131.5 million upgrade of the 120 Bypass and Highway 99 interchange and the nearby Austin Road interchange.

The project is also designed to address an issue that makes the traffic delays trivial.

That’s because it is aimed at addressing the fact you are seven times more likely than the national average to get into a crash on the 120 Bypass than in a typical segment of freeway in California.

The $52.5 million initial phase will essentially address the safety issue first. It involves adding a second southbound transition lane to Highway 99 and replacing the Austin Road overcrossing to allow it to happen.

The existing Austin Road overcrossing built in 1955 does not have enough space beneath it for additional lanes needed to make the 120/99 interchange work as well as ease congestion on Highway 99.

The Austin Road interchange will be demolished and replaced with a four-lane overcrossing that will have the capacity to accommodate future growth in southeast Manteca.  

The replacement bridge is more expensive than a typical interchange because it will also solve another Manteca problem. It will clear the railroad tracks — in a fashion similar to Jack Tone Road at Highway 99 in Ripon.

It will reduce the number of at-grade crossing on the Union Pacific main line from nine to eight along the tracks passing through Manteca.

The first phase will include reconfiguring Woodward Avenue, its crossing of the Union Pacific Railroad tracks, and constructing a new connector road from Austin Road to Woodward Avenue.

 The first phase improvements will also:

 * temporarily shut down the southbound off ramp and northbound on ramp at Austin Road and the Highway 99 interchange for a number of years.

*build 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.

The second phase costing $26 million would:

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

*convert the existing structure crossing Highway 99 to the 120 Bypass to two lanes.

*construct a new separation structure to serve eastbound 120 Bypass traffic to the northbound Highway 99 connector ramp.

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

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

The third phase costing $53 million would:

*restore the southbound off ramp — if it ends up being closed in the first phase — by constructing a grade-separated braided ramp to eliminate weaving with 120 Bypass merging traffic.

*construct the entrance ramp from Austin Road to northbound Highway 99 and to the westbound 120 Bypass as a loop ramp that will separate traffic movements to Highway 99 and the 120 Bypass.

*relocate the northbound Highway 99 exit ramp to Austin Road to accommodate the loop onramp.

*relocate the Highway 99 frontage road for about 0.8 miles.

*add an auxiliary lane in each direction on Highway 99 from the 120 Bypass to about 1.7 miles south of Austin Road by shifting the median away from the Union Pacific right-of-way and relocating the frontage road.

*add an auxiliary lane in the existing median of the eastbound 120 Bypass from Main Street to Highway 99 to provide a dedicated lane to connect to the new 120/99 separation structure.

The high cost of the third phase design is reflected in the necessity 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.

To contact Dennis Wyatt, email dwyatt@mantecabulletin.com