Highway 99 through Manteca is anything but appealing.Motorists whizzing by at 65 mph see a collage of decaying sound walls, the back side of aging commercial structures, and weeds.Its ugly duckling status among South County freeways will start a $496 million transformation starting next summer.When completed, it will provide Manteca with arguably the sharpest looking interchange in all of San Joaquin County plus a 13.1-mile-long landscaped corridor complete with new sound walls.The Proposition 1B project covers work between the 120 Bypass in Manteca and Arch Road at the Stockton Airport. It is made possible with a marriage of the countywide Measure K half cent sales tax and a chunk of the $1 billion state bond proceeds set aside for modernizing Highway 99 through the Central Valley.Initial work starts in the spring/summer of 2012 on adding a third lane in the center divider in each direction. The second phase is a new interchange at French Camp Road while the third phase involves a new interchange at Lathrop Road.