Construction crews pour sections for new deck on Sunset Bridge as part of the I-405 Sepulveda Pass Improvements Project.

Marking a new phase in the bridge rebuilding effort for Sunset Bridge, work crews will complete pouring the bridge’s new southside deck which spans the the 405 freeway Wednesday night, August 31.

Work will require the closure of southbound I-405 for 1.75 miles between the Sunset offramp and Wilshire Boulevard in the early morning hours Thursday.  See details in latest construction notice.

The Sunset Bridge itself will be closed from 10 p.m. to 6 a.m. Street and freeway traffic will be detoured for one night only to parallel streets and next available on-ramps to get around the closures.

By now, these types of freeway closures are pretty routine. Not to be confused with a multi-day, bi-directional freeway closure like that which occurred last July during Carmageddon weekend, these type of closures happen on only one side of the freeway at a time and are over and done within a few hours, usually between midnight and 5 a.m.  They are reserved for major construction work to preserve public safety.

Just last week, work crews closed the northbound I-405 to pour bridge decking over the northbound 405, and last Monday workers closed Sepulveda Boulevard for similar pouring work.

The Sunset Bridge was the project’s first major bridge demolition activity when work began in July 2010. Back then, heavy construction equipment progressively demolished sections of the south side of the bridge over five nights, which constituted the public’s first real-world experience with major freeway construction impacts for the 405 carpool lane project.

Since then, the domino of bridge demolition work has fallen on the Skirball Center Drive Bridge and, most recently, the Mulholland Drive Bridge. All bridges have to be completely rebuilt one side at a time to accommodate an extra traffic lane on the northbound I-405 and to improve mobility of traffic with standardized lanes and shoulders.

Sunset bridge work sheds some light on what the public can reasonably expect for other bridge rebuilding work over the next two years. It is one of three bridges to be rebuilt as part of the I-405 Sepulveda Pass Improvements Project.

Here’s a quick summary of prior Sunset bridge rebuilding work, and what’s next:

Sunset bridge construction crews have spent the last year excavating new bridge footings, building bridge abutments and columns, framing the new bridge, setting new girders, performing utility relocation, installing rebar supports, and laying the new bridge deck.

Because the south side of the bridge contains a 36-inch water line, workers must first tie in the line to the DWP water line at Sunset and Church Lane.

Next crews will have to raise the intersection at Sunset Boulevard and Church Lane to meet the raised elevation of the bridge – which is approximately three feet taller than the existing bridge to create more clearance for vehicles passing underneath.  That work will require a 14-day closure of the eastbound Sunset Boulevard to southbound I-405 on-ramp in late September.  Other 14-day closures also will be required in September for intersection reconstruction work.

From now until October, crews also will continue to work on civil improvements, including curb, sidewalks, railing, street and traffic lights.  Construction crews have already started rebuilding sidewalks and curbs on Sunset and Church Lane and are also rebuilding the bus stop there.

Next they will perform utility work on the bridge to ensure the catch basins and storm drains are working properly, as well as perform work on relocating a Chevron utility line on Sepulveda Boulevard.

Once all civil improvements have been made and the approaches to the bridge have been raised to its new elevation, crews can then reconfigure traffic lanes on Sunset Bridge and move those lanes over to the south side.  Traffic will be moved over onto the reconstructed side of the bridge in October.

Later this year, the contractor plans to begin the demolition process all over again on north side of bridge.  The north side of the bridge is expected to be rebuilt in a 12-month period.

Work will be phased in and crews will work day and night to complete work by the project’s opening date of 2013.