A week after a 93-yr-old water trunk line rupture in Los Angeles sent an estimated 20 million gallons of water gushing over the UCLA campus and Sunset Boulevard, the city's Dept. of Water and Power crews have finished work on getting the pipe back in service.
"The cause of the break was pipe corrosion and structural problems with the Y-juncture," says Joe Castruita, LADWP director of the Water Distribution Division. He says when the burst 30-in., riveted steel pipe was originally installed in the 1920s; engineers did not support Y-junctures with steel plates like is common practice today. "It would be engineered and welded differently by today’s standards to stabilize the pipes."
The break happened at the juncture of two water trunk lines that met at a Y-joint. To fix it, crews removed and replaced 76 ft of the old pipe and added two new 4,000-lb, 36-in.-diameter butterfly valves to the system.
"What makes this somewhat different from an inline pipe failure was that there were three intersecting points that had to be connected," says Castruita. "This required our engineers and welding team to design and construct the repair segments on site. This required hundreds of fabricating and welding hours to complete."
The end result was a new, reinforced T-juncture, which LADWP says saved time and increased the structural integrity of the pipe and connections.
To get to the ruptured trunk line, crews excavated the 56-ft by 40-ft work site around the pipe and shored it with an 8,000-lb shield to protect workers and to help stabilize Sunset Boulevard, which has since re-opened. Once the pipe was fixed they filled in the excavation pit with roughly 400 tons of sand and 540 tons of crushed aggregate base.
When the pipe ruptured on July 29, the deluge took the LADWP nearly four hours to get under control. Jim McDaniel, a DWP senior assistant general manager, said the delay was mainly due to crews having to battle rush hour traffic and then deal with the powerful 30-ft tall spout and a resulting 20-ft-wide sinkhole on Sunset Boulevard, while trying to locate the shut-off valves.
"All valves are mapped and locations are identified by measurements when installed," says Castruita. "Our field crews have this information available to them at all times. Turning off the water flowing to the site required the manipulation of up to 11 valves. Crews had to do this in a calculated manner to avoid further problems in the water system. Note that some of these valves required hundreds of turns to shut and in most cases have to be exercised open and shut to gain isolation in the system."
LADWP spokesperson Joseph Ramallo says crews had to be extra careful when shutting down the high-pressure line so as to not rupture other pipes, or lose pressure in the system. “Loss of pressure would have resulted in a water quality problem that likely would have triggered a widespread boil water notice. It was a very complex shut down job,” he says.
The last water trunk line break in Los Angeles was in 2009 in Coldwater Canyon, but smaller water main leaks and breaks occur on average approximately 3-4 times a day across the City, says Castruita.
"This rate is significantly lower than industry standards and reflects that L.A.’s water system is fairly tight," he says. "The rate of leaks and pipes has also dropped significantly. Comparing water main breaks in 2013 to 2006, water main leaks and breaks have been reduced by 37%."
Breaks and leaks may be down, but Mark Gold, acting director of the Institute for the Environment and Sustainability at UCLA, still calls the Los Angeles water conveyance infrastructure "incredibly old" and says roughly one quarter of the city's water pipes have been around for at least a century.
"L.A.'s water infrastructure crisis is a classic case of 'out of sight, out of mind.' If the public and city leadership can't see the problem, then it often gets ignored for years, if not decades," he says. "Perhaps this high profile water infrastructure failure will finally lead to larger investments in the near future."
Besides a nightmare for Westwood commuters, the water break also resulted in the flooding of UCLA’s famed Pauley Pavilion sports facility with about 10 inches of water, and the stranding of more than 900 cars in underground parking structures. LADWP spokesperson Jane Galbraith says damages, insurance claims and repair costs won’t be determined for quite some time.
This mainline pipe that burst handles an estimated at 75,000 gallons per minute at its peak. The water comes from Upper Stone Canyon Reservoir at the top of the nearby Santa Monica Mountains. LADWP delivers about 500 million gallons of water to customers each day.
