Officials announce the 405 reopening at a news conference Sunday morning. Photo by Luis Inzunza/Metro.

With work on tearing down the southern half of the Mulholland Drive Bridge complete, Los Angeles Mayor Antonio Villaraigosa announced Sunday that the 405 freeway over the Sepulveda Pass will begin reopening about 11:30 a.m. Sunday, more than 17 hours before the scheduled reopening at 5 a.m. Monday.

“Not enough is said about the people of Los Angeles when they come together and decide they have to work together to make something work,” said Mayor Antonio Villaraigosa, thanking area residents for staying off local roads and preventing the massive traffic jam some feared would result from the 405 closure this weekend.

“Thank you to the people of this area who have put up with and will continue to put up with this construction project for a couple more years,” said Supervisor Zev Yaroslavsky, whose district includes the construction site. “They have been very patient with us and we thank them and we do not take their patience for granted.”

Metro will continue to offer free service on the Red and Purple line subways, the Orange Line busway and 25 other bus lines for the remainder of Sunday.

The work to take down the southern half of the bridge began when the freeway closed at midnight Friday — a closure that attracted national media attention because of the region’s dependence on the road. The final column supporting the north side of the bridge was toppled earlier this morning and cleanup of the freeway then kicked into high gear.

The work was done by contractors hired to work on the project – Kiewet and the Penhall Company.

Traffic on the Mulholland Drive Bridge will be moved to the remaining northern half of the bridge for the next year while the southern half is rebuilt. The northern half of the bridge will then be torn down next year in a similar exercise that will also require the 405 to be entirely closed.

The bridge is being rebuilt and lengthened as part of the I-405 Sepulveda Pass Improvements Project, which is widening the freeway to add a carpool lane to the northbound side of the 405 between the 10 and the 101 freeways. The project is also upgrading on- and off-ramps in the area and rebuilding three bridges over the freeway — the Sunset, Skirball and Mulholland structures.

The 10-mile carpool lane is projected on average to save motorists who use the carpool lane about 10 minutes of travel time.

The project is scheduled to be completed in 2013.