Here is the press release from Metro:

The I-405 Sepulveda Pass Improvements Project contractor plans to fully close the southbound I-405 between Santa Monica Boulevard and National Boulevard in West Los Angeles on the following dates and times to facilitate the installation of a full-span freeway overhead sign and to conduct other roadway construction activities at the freeway median:

• From midnight to 5 a.m. on the nights of:
  • Monday, March 17, to Thursday, March 20
  • Sunday, March 23
  • From midnight to 6 a.m. on the nights of:
    • Friday, March 21 and Saturday, March 22

Other Closures:

• Lanes will begin to close at 10 p.m.
• Ramps will begin to close at 7 p.m.
• Southbound Santa Monica on-ramp
• Southbound Sunset on-ramps
• Southbound Wilshire on-ramps
• Southbound I-405 to eastbound I-10 connector
• Southbound I-405 to westbound I-10 connector

Detour: From the southbound I-405, exit at Santa Monica Boulevard, turn left to eastbound Santa Monica Boulevard, turn right to southbound Sepulveda Boulevard, turn right to westbound National Boulevard, and turn left on to the southbound I-405 on-ramp on National Boulevard.

What to expect:

• Work is dependent on favorable weather conditions.
• Emergency access will be maintained at all times.
• For a listing of daily closures and latest updates visit our website at www.metro.net/405 or follow us on twitter: www.twitter.com/I_405 and Facebook at www.facebook.com/405project.