The southbound closure began at the 605 Freeway and ended at the 22 Freeway. Northbound traffic was closed at Valley View Street.
The shutdown was scheduled to last until 5 p.m. Sunday, but a Caltrans official reopened the southbound lanes by 1:45 p.m. The northbound lanes were back open around 3 p.m.
The new southbound 405 connector bridge to the eastbound 22 is already in use, so crews were working to demolish the old bridge. The work was dubbed "Bridge Bash" or "Orange Jam."
Approximately 350,000 drivers use that stretch of the 405 on a typical weekend day. Extensive publicity before the construction work appears to have convinced most drivers to stay away.
The work was done at a historic pace.
"This is the first time in the United States' history that one crew demolished a bridge of this magnitude in one shift; that is a remarkable feat," said Ted Nguyen, spokesman for the Orange County Transportation Authority.
More than 100 workers were on the job, and the cleanup was a lot shorter than expected. Most of the debris will be recycled.
The work was part of the $270 million West County Connectors project. Drivers will be able to stay in the carpool lanes when they transition from the 405, 605 and 22 freeways, easing traffic in the area.
"This will eliminate the weaving and merging between the three freeways and make for a much smoother transition for those people using the carpool connectors as well as those people that are not using them," said Nguyen.
The demolition may have ended earlier than expected, but the roadwork is far from over. The entire connector project isn't slated to be complete until 2015.