The closure is part of a $277 million project that will link car pool lanes and ease traffic on the 405, 22 and 605 freeways. During this part of the closure, crews will rebuild a connector road and add a carpool lane. The entire project is expected to be completed in 2014.
The route is one that is heavily used in the evening, so drivers are being asked to use surface streets as an alternate.
Caltrans has set up several detours. Drivers will be able to exit the 605 and take surface streets through Long Beach, Rossmoor and Seal Beach to reach the 405, or they can exit at Katella Avenue, go right on Los Alamitos Boulevard/Seal Beach Boulevard to get the southbound 405.
The connector is set to reopen Aug. 15.
Other freeways in Norwalk and the San Gabriel, Antelope and San Fernando valleys saw closures starting Sunday. Also, "Ramp Jam" continues in Westwood, with ramps between the northbound 405 Freeway and westbound Wilshire Boulevard out of commission until further notice.
City News Service contributed to this report.