Additional nighttime I-405 freeway closures are planned beginning Monday, Oct. 31, for 12 nights as construction crews for the I-405 Sepulveda Pass Improvements Project demolish the northern side of the Sunset Boulevard bridge in West Los Angeles.

During this demolition activity, only one side of the freeway will be closed at a time for a distance of up to one mile in the bridge area. All demolition work and associated closures will be conducted during nighttime hours, with the bridge, freeway and local streets reopened in time for daytime traffic.

Ramp closures on the Sunset bridge will start as early as 7 p.m. Freeway lane closures will start as early as 10 p.m., with full directional freeway closures between 12 a.m. and 5 a.m. weekdays, and 12 a.m. and 7 a.m. weekends. Street closures will be in place from 9 p.m. to 6 a.m.

Below is a schedule of planned demolition activity, freeway and street closures and recommended detours (Detour maps are available at metro.net/405):

The bridge’s columns and bents are anticipated to be demolished from Wednesday, Nov. 9 to Friday, Nov. 11, 2011. Demolition of the bridge’s abutments will follow at a later date. Demolition work will be followed by approximately 12 months of north-side bridge reconstruction.

To maintain motorist access in the area, Sepulveda Boulevard will NOT be closed at the same time as freeway closures. Pedestrians will be rerouted to an area outside the construction zone. Traffic control officers will be on site to help direct traffic. Additionally, emergency access will be maintained on the bridge at all times.

The replacement of the entire bridge is required to build a new high-occupancy vehicle lane on the northbound I-405 between I-10 and U.S. 101. Bridge columns will be repositioned to accommodate the additional freeway lane created by the project.

Demolition of the southern side of the bridge was completed in July 2010. Since that time, construction crews have reconstructed the bridge’s southern side and its street approaches. The demolition and reconstruction process will now be repeated for the north side.

When complete, the expanded, seismically enhanced Sunset bridge will be widened by approximately 30 feet and contain two additional lanes to improve area traffic flows. Southbound freeway ramps also will be widened to accommodate a greater number of vehicles, which will help reduce local street congestion.

Sunset bridge, like the project bridges at on Mulholland and Skirball Drive, will be demolished utilizing large hoe rams that chip the concrete bridge side into small pieces that fall onto a dirt pad on the freeway. The concrete materials and rebar are then hauled away for recycling.

The $1 billion project, a joint partnership between the Los Angeles County Metropolitan Transportation Authority (Metro) and the California Department of Transportation (Caltrans), will create a 10-mile carpool lane on the northbound I-405, the last remaining gap in the I-405 carpool lane network between Orange County and the San Fernando Valley. Additional project benefits include greater ramp capacities at key locations, widened overpasses, widened and seismically updated bridges and new landscaping within the project area. For additional project information and ongoing construction updates, visit www.metro.net/405 or call the project hotline at 213-922-3665.