Sylmar Gets Nation's Longest Quake-Proof Water Pipe, LADWP Says It Will Bend Not Break

Los Angeles water officials celebrated the completion of nearly 5 miles of earthquake-resistant pipeline in Sylmar this week, touting it as the longest installation of its kind in the United States. The upgrade is part of a broader push by the Los Angeles Department of Water and Power to replace aging trunk lines across the San Fernando Valley before the next big quake tests the system.

The pipeline uses specialized joints engineered to flex and move when the ground shifts during an earthquake, according to CBS Los Angeles. David Hanson of LADWP told the station that more ductile and flexible pipes are less likely to catastrophically fail and “will bend instead of break,” adding that allowing the pipe to flex makes it less likely to rupture. Those joints, known as Earthquake Resistant Ductile Iron Pipe or ERDIP, are designed to rotate up to 8 degrees and shift 1 to 5 percent axially without shearing, engaging an internal locking ring during strong shaking to keep segments from separating, according to research published on ResearchGate.

LADWP has installed more than 67 miles of the earthquake-resistant pipe systemwide since starting the program nearly 15 years ago, per the station's reporting. Trunk lines like the one in Sylmar are among the largest pipes in the city's water system, carrying large volumes of drinking water from reservoirs and other facilities into neighborhoods before it reaches distribution mains.

Why the Valley Is Ground Zero

The San Fernando Valley has long been the focus of LADWP's seismic retrofit efforts, and for good reason. During the magnitude 6.7 Northridge earthquake in January 1994, the water system recorded more than 70 trunk line damage incidents, 1,013 distribution line ruptures, and three severed aqueducts, cutting off running water to 500,000 residents and requiring $41 million in repairs, according to the Multidisciplinary Center for Earthquake Engineering Research. It took five days to restore basic service to 99 percent of customers after that quake.

LADWP first brought Japanese-engineered ERDIP technology to the United States in 2013, starting with a 1,750-foot pilot project in Sherman Oaks before expanding to a 6,500-foot installation around Northridge Hospital Medical Center in 2015, according to the Office of then-Mayor Eric Garcetti. Those early projects deliberately targeted hospitals and other critical emergency infrastructure sitting in severe liquefaction zones. In Japan, where manufacturer Kubota Corporation first commercialized the technology, ERDIP pipes have operated for more than 40 years without a single documented joint failure or break during major earthquakes, including magnitude 9.0 events, per reporting from Marketplace.

The Foothill Trunk Line's Scope

The Sylmar segment is formally known as the Foothill Trunk Line Unit 3 project, which replaces 1930s-era steel pipe with 16,600 feet, or roughly 3.1 miles, of 54-inch diameter ERDIP pipe running along Foothill Boulevard from Pacoima to Sylmar, according to LADWP. Crews used 13,000 feet of open trenching alongside 3,430 feet of tunneling to lay the new line, which upsizes the pipeline from its original 24-to-36-inch diameter to 54 inches, expanding delivery capacity while adding seismic joints across the Sylmar Fault zone. The full Foothill Trunk Line project is expected to be completed in 2032.

LADWP is also building the parallel City Trunk Line North Unit 1 project in the Northeast San Fernando Valley, installing 4 miles of 54-inch ERDIP pipe between Granada Hills and Arleta to replace a 1914 riveted steel pipeline that suffered chronic leaks. That segment runs from the Van Norman Complex to Terra Bella Street and is scheduled for full completion by 2030, per the utility's project documentation. Just days before the Sylmar celebration, the Los Angeles City Council authorized $42 million for LADWP to replace 14 miles of 1940s-era cast-iron trunk lines with ERDIP across Van Nuys, Panorama City, and North Hollywood, targeting active fault lines to protect firefighting water pressure following a magnitude 7.0-plus earthquake, according to Choseno.

A System Still Prone to Breaking

The seismic upgrades arrive against a backdrop of repeated water main failures across Los Angeles that have nothing to do with earthquakes. A 110-year-old, 36-inch trunk line beneath Sunset Boulevard in West Hollywood ruptured on July 16, spilling an estimated 17 million gallons of water and causing severe street flooding, as Hoodline reported in its coverage of a second nearby leak. Trunk lines carry drinking water directly from reservoirs, so their failures tend to be far more destructive than a typical neighborhood main break.

That break came while crews were still working nearby, and a separate main blowout hit Hollywood on July 25 near Paramount, according to Hoodline's earlier reporting. LADWP maintains more than 6,700 miles of water mainlines citywide, and more than 30 percent of its distribution pipes are over 80 years old, contributing to two to four main breaks per day systemwide. Legacy cast-iron pipes alone account for roughly 77 percent of all main leaks in the network, averaging 28.6 breaks per 100 miles annually compared to just 2.9 breaks per 100 miles for modern plastic piping.

The utility replaced over 240,000 feet of mainline in fiscal year 2024–2025, but at that pace, replacing the entire 6,700-mile network would take roughly 150 years. That math underscores the tension between the kind of proactive, decades-long seismic upgrades on display in Sylmar and the daily emergency repairs LADWP crews still perform across a system where more than a third of the pipes predate the Northridge earthquake by decades.