When complete in June 2013, the bridge south of Paradise Road will better withstand an earthquake.
"There's a lot of work going on to stabilize the abutments," said Collin Yerzey, project design manager for the city of Modesto. "They're putting in deeper piers on either side of the existing piers."
The bridge will remain two lanes, but there will be more room for pedestrians and bicyclists.
"Before, it didn't meet the current acceptable pedestrian traffic width," Yerzey said. "We're bringing it up to standards."
The 625-foot span was built in 1960. A study conducted after the 1989 Loma Prieta earthquake found that it could be weakened if sandy soil under the Tuolumne River is liquefied during an earthquake. In 2009, the city approved a $357,450 contract for Dokken Engineering of Folsom to update the plans and position the city to secure state and federal grants. The city was awarded $10.75 million in funding for the project last year.
Plans call for widening the bridge from 34 to 69 feet, with 12-foot pedestrian walkways on each side. Concrete barriers will protect people crossing on foot or bicycle.
Workers also will replace a line that delivers water to south Modesto.
Traffic continues over the bridge during the work, though it may occasionally be reduced to one lane.
Yerzey said his department will send out regular updates, which will appear in the "Road Work" column Mondays.