It’s been 56 years since Highway 99 – dubbed the Central Valley’s Main Street – opened as a four-lane freeway through Manteca.

Work is starting in November on the $496 million project to widen 13.1 miles of Highway 99 from the Cross-town to the Highway 120 Bypass to six lanes and replace aging interchanges.

The initial phase will involve adding a lane in each direction in the median. That work starts in November. Caltrans split the project into phases to take advantage of the fact the actual widening to six lanes did not require a time consuming right-of-way acquisition process.

The on and off ramps at Little John Creek near Stockton Metro Airport will be closed with the frontage roads converted into cul-de-sacs.

The French Camp Road replacement interchange construction will get underway in March of 2012. The third phase involves replacing the Lathrop Road and Main Street interchanges with one full standard interchange at Lathrop Road. The design work is targeted for completion in July 2012. Construction is targeted for January of 2012.

The fourth and final stage involves replacement and mitigation planting. That stage is targeted to start in December of 2015.

The phase with the biggest impact on private property is the new Lathrop Road interchange.

It would wipe out at least five businesses including an appliance firm’s warehouse, a gas station, a trailer sales, a multi-tenant business building backing up against the existing overpass and a modular home sales lot. Altogether, 24 properties will be impacted.

Most of the impacted property is on the western side of the freeway. It is the result of the need to extend Main Street north to tie into the south on and off ramps at the proposed interchange.

As proposed, the interchange would:

• realign the West Frontage Road through Delta College’s property in the northwest corner of the interchange and align it with Crestwood Avenue. Delta College is proposing developing 350,000 square feet of retail on the land.

• extend North Main as four lanes from Northgate Drive to tie into an intersection with the southbound on and off ramps at Lathrop Road. The road, designed to allow traffic to travel at 35 mph, would wipe out several older homes used for commercials purposes, the warehouse portion of Center Appliance and the small business complex built a few years ago between the existing curve and the overpass.

• provide a direct route for trucks accessing business and industrial parks that exist and are proposed between Lathrop and Manteca along the Airport Way corridor. It would also provide a direct truck route between Interstate 5 and Highway 99 in addition to the Highway 120 Bypass and French Camp Road.

• eliminate the modular home and trailer sales businesses on the southeast corner to accommodate northbound off and on ramps.

• relocate the East Frontage Road further east and extend it south of Lathrop Road behind developed parcels before curving back to the existing Frontage Road to provide access to Southland Road.

The state is picking up $282.4 million of the tab from Proposition 1B bond proceeds while Measure K – the countywide half cent sales tax – is covering the rest of the cost. If it weren’t for the Measure K sales tax San Joaquin County in all likelihood would not have secured the state bond money.