Carmageddon: A Breakdown of How The Mulholland Bridge Will be Broken Down
Yeah, the 405 freeway is closing from the 10 to the 101 this weekend. But the meat and potatoes of Carmageddon really comprises only about four lanes or so of width -- the Mulholland bridge.
California DOT The Mulholland Bridge.
To widen lanes and make way for a new bridge they're taking the old thing out, and not, as Metro says, in a "Vegas-style" flash of explosives. Rather, in an anticlimactic, un-Michael Bay-like process, they'll be chipping away at the circa-1959 bridge with ... jackhammers. No 'splosions.
In an effort to satiate your thirst for all things 'geddon, the L.A. Sheriff's Department sent out this Metro rundown of what exactly will be happening to the bridge while your car overheats on Sepulveda. Fascinating:
The iconic three-span box girder bridge, standing tall between the canyon vistas connecting San Fernando Valley suburbs with urban Los Angeles' Westside for more than 50 years will see its southern side steadily chipped away over 53 hours, not 53 seconds. The demolition will be accomplished utilizing the relentless "tat-tat-tat" of jack hammers mounted on heavy equipment, not dynamite.
Besides the sound of demolition in the immediate area, the I-405 in this corridor will be silent for the first time in 50 years.
Kiewit Infrastructure West, the project's contractor, has been working on aspects of the demolition plan for over a year, and has developed a timeline for the 53-hour demolition which breaks work activity into precise, 15-minute increments.
The contractor will know exactly where it must be in the work schedule in order to safely reopen the freeway for early morning rush hour traffic Monday, July 18. The demolition plan has been meticulously reviewed and approved by project partners Caltrans and Los Angeles County Metropolitan Transportation Authority (Metro), and is considered the best demolition method available. Throughout the weekend, the contractor will look for opportunities to expedite the schedule.
The demolition timeline will begin Friday evening, July 15 when work crews begin closing freeway on- and off-ramps between the I-10 and U.S. 101 as early as 7 p.m. to prevent additional vehicles from entering into the closure area.
Crews will then begin closing freeway lanes one by one on both sides of the freeway at 10 p.m. in order to achieve a full freeway closure by midnight. The Mulholland Bridge also will be closed. Mulholland Bridge Demolition Work Will be a Meticulous, Painstaking Process.
The area surrounding the Mulholland Bridge will be lit up like the Astrodome utilizing two very large light plants and about 12 regular light plants. Staged in nearby project construction yards and other areas, 15 pieces of heavy construction equipment (with another five on standby) and an army of 100 demolition workers and support staff will be poised to begin their precision operation.
Starting at 12 midnight, trucks will begin to haul dirt onto the 405 freeway underneath the Mulholland Bridge to form a cushion four feet high on the freeway roadbed. The dirt will catch falling debris and prevent concrete pieces from damaging the freeway lanes.
At approximately 2 a.m. Saturday morning, workers will use a large diamond-bladed saw to cut the bridge top deck and soffit to safely demolish the southern half while keeping the northern half structurally sound. Workers also will cut slots in the southern side of the bridge to quicken the demolition process. During demolition work, workers will perform vibration monitoring and other tests to ensure the structural integrity of the northern side of the bridge is retained at all times.
At approximately 5 a.m. Saturday morning, as many as four "hoe rams," or rolling jack hammers of various sizes will begin to chip away at the south side of the bridge.
Approximately 4,000 tons of concrete will be removed in the first phase of demolition work.
Two Hoe rams will be stationed on the bridge deck starting in the center working toward each end. Once they have reached the ends of the bridge, two hoe rams will begin to work on the ground also starting in the center and working toward both ends. These giant and powerful demolition machines will deliver between 1,200 and 7,500 foot-pounds of power to break away concrete from the bridge. This compares to 90 foot-pounds delivered by a common hand-held jack hammer. Operators in these machines will be able to deliver between 300 and 600 blows per minute on the concrete decking to break pieces into sizes no bigger than a basketball or microwave oven which can then be easily hauled away from the demolition site.
So that's what all this hype was about? Yep.