Repairs underway after century-old water main burst floods West Hollywood, opening sinkhole

WEST HOLLYWOOD, Calif. - A massive rupture of a century-old water main trunk line in West Hollywood has left emergency crews working around the clock to repair severe structural damage. 

The break sent a river of water down local streets, opened up a dangerous sidewalk sinkhole, and forced a hard closure of the iconic Sunset Strip as utility teams scramble to rebuild the pipeline.

What we know:

The incident began around 3 a.m. Thursday when a 3-foot-wide (36-inch) water main trunk line ruptured near Palm Avenue and Harratt Street. 

The pipeline, which dates back to 1916, is a riveted cast iron main that feeds major water distribution from one side of the city to the other.

According to David Hanson, interim general manager of the Los Angeles Department of Water and Power (LADWP), the flooding was triggered by a structural failure of the pipe's rivets, which caused the side of the line to peel open. 

PREVIOUS COVERAGE: Major water main break in West Hollywood floods streets, submerges cars

The resulting torrent flooded streets from Sunset Boulevard down to Santa Monica Boulevard, inundating underground parking garages and a Metro bus yard.

The rushing water pushed parked vehicles, and on Palm Avenue, a sidewalk collapsed into a sudden sinkhole, swallowing two men who fortunately did not appear to be seriously injured.

Crews working around the clock

LADWP crews stopped the surface flow by 7 a.m. Thursday by carefully turning off high-pressure underground valves. Because closing large valves too quickly can cause a shock to the system and trigger additional damage, the shutdown was a slow, deliberate process, officials said.

Crews worked through the night to completely pump out the nearly 200,000 gallons of pooled water that filled the crater. An operational 8-inch bypass line is keeping local water safe to drink for all but one customer.

Engineers determined that approximately 25 feet of the pipeline must be replaced.

Hanson said LADWP crews fabricated the replacement section from flat steel at one of the department’s facilities. The new section is expected to be transported to the site, where crews will remove the damaged pipe and begin installing the replacement.

Once installation begins, Hanson said the welding process alone will take about 16 continuous hours. Afterward, crews will gradually restore water pressure while monitoring for any additional leaks before completing the repair.

When will Sunset Boulevard reopen?

If no additional leaks are discovered once water pressure is restored, Hanson said crews hope to begin backfilling the excavation as early as Saturday.

Temporary asphalt could be in place by the end of the weekend, allowing Sunset Boulevard to reopen to traffic between Larrabee Street and La Cienega Boulevard.

Permanent roadway repairs will be completed at a later date to meet city standards.

Dig deeper:

Aging infrastructure

The ruptured pipeline highlights the challenges of maintaining Los Angeles’ aging water infrastructure.

Hanson said LADWP has an ongoing infrastructure replacement program that replaces approximately 250,000 feet of trunk line each year, with annual replacement goals continuing to increase.

He added that despite the age of many pipes, LADWP’s leak rate remains significantly below the national average.

"When we compare ourselves to other water utilities across the nation, we’re 36% lower than the national average on leaks," Hanson said.

What we don't know:

The reason why the rivets failed at that exact moment remains under investigation, though engineers noted that pressure inside regional delivery lines naturally peaks overnight when consumer demand drops.

PREVIOUS COVERAGE: Century-old water main floods West Hollywood, damages businesses as questions grow over aging infrastructure

While officials are aiming to restore traffic by the end of the weekend, it's unknown if the system will experience further complications, low pressure, or secondary leaks once the main line is fully repressurized. 

Timeline:

Thursday, 3 a.m.: The 110-year-old, 36-inch cast iron water main ruptures, causing widespread flooding and opening a sidewalk sinkhole.

Thursday, 7 a.m.: LADWP crews successfully isolate and close the massive underground high-pressure valves, stopping the active surface flow.

Thursday Night – Friday Morning: Round-the-clock pumping operations fully dewater the hole, allowing engineers to visually assess the fractured pipeline.

Friday: In-house maintenance teams deliver a custom-fabricated 25-foot steel pipe section to the site to begin a continuous 16-hour welding process.

Saturday (Expected): If welding is successful, crews will begin refilling the pipeline, gradually raising water pressure to test for integrity.

Late Weekend (Target): Backfilling of the excavation site and placement of temporary asphalt are scheduled to be completed, allowing the Sunset Strip to reopen to normal traffic.

What they're saying:

"This is a big break. We have a lot of old pipes in this area. But a break this big is exceedingly rare," said Los Angeles County Fire Department Capt. Aaron Katon.

"It was a river. I thought it was a catastrophe. I thought it must have been an earthquake. Maybe a hydrant broke; maybe all the hydrants broke," said Tehran Von Ghasri, a local resident.

"The work involves shoring to make the area safe before excavation to assess the damage to the pipe can commence. LADWP crews will continue to work around the clock until the pipe is repaired and traffic can be safely opened," said Sheri Lunn, West Hollywood Public Information Officer.

"As LADWP crews continue to work urgently to remove water to repair the pipe rupture in West Hollywood, people should avoid the area and conserve water as some may experience a loss of water pressure," said Los Angeles Mayor Karen Bass.

"You can see there was a failure of the rivets and the side peeled open, and then that's what caused the flooding," explained Hanson. "Our own folks in the house were able to fabricate this section of pipe from flat steel... Once we start to weld, it's about 16 hours of continuous welding to get the pipe in place."

Hanson also defended the utility’s proactive maintenance protocols.

"We have an infrastructure replacement plan. We replace about a quarter million feet of trunk line pipe per year... When we compare ourselves to other water utilities across the nation, we're 36% lower than the national average on leaks per hundred feet," he said.

What's next:

Once the 16-hour welding process finishes, crews will slowly reintroduce water to the 0.7-mile isolated pipeline section to bring the system back up to pressure while checking for secondary leaks. 

If the line holds, workers will backfill the hole and lay down temporary asphalt to city standards. Crews will return at a later date to execute permanent road repairs.

Los Angeles voters are expected to consider a City Charter amendment this November that would establish a mandated five-year capital infrastructure program to directly target deferred maintenance.

What you can do:

• Avoid the Area: Commuters are advised to steer completely clear of the affected West Hollywood intersections and use alternative routes.
• Conserve Water: Residents in the immediate vicinity, especially those on upper floors experiencing low water pressure, are asked to conserve water.
• File Claims: Impacted residents and business owners can visit the LADWP claims tent at 1010 Palm Ave. between 7 a.m. and 7 p.m., call 1-800-DIAL-DWP, or submit claims online at www.LADWP.com/Claims.