LADWP accelerates $300m trunk line replacement after catastrophic Sunset Boulevard rupture

LADWP accelerates $300m trunk line replacement after catastrophic Sunset Boulevard ruptureFollowing a 17-million-gallon spill in West Hollywood, the Los Angeles Department of Water and Power is fast-tracking a 6.33-mile pipeline replacement project to mitigate the risks of aging, century-old infrastructure.

A 36-inch riveted steel pipeline dating back to 1916 ruptured on July 16, spilling 17 million gallons of water and requiring a complex nine-day repair effort.

LADWP is splitting the long-term replacement project into two units, accelerating the design completion of the $139 million Unit 1 to the first quarter of 2027, three years ahead of the original schedule.

The utility plans to detour the new alignment off Sunset Boulevard and utilize earthquake-resistant ductile iron (ERDI) pipe to enhance seismic resilience.

LADWP is increasing its in-house large-diameter pipe construction crews from three to five to help reach its target of replacing 3.5 miles of trunk line annually.

Acoustic sensors and expanded leak-detection crews are being deployed to proactively identify vulnerabilities across the utility's 63 miles of riveted steel trunk lines.

The Los Angeles Department of Water and Power (LADWP) is significantly accelerating its planned replacement of the Sunset Boulevard trunk line following a major rupture on July 16 that flooded West Hollywood streets with 17 million gallons of water. The incident has prompted utility leadership to expedite the $300 million replacement of the 110-year-old infrastructure. The failure occurred on a 36-inch riveted steel segment of the trunk line originally installed between 1916 and 1924. Cesar Rubio, a water system director at LADWP, reported that the initial leak was detected at 3:55 AM. Over a nine-day emergency response, crews isolated the segment, dewatered the excavation, and installed a 25-foot replacement section. However, the century-old pipe continued to leak in subsequent days, ultimately forcing the department to implement a contingency plan to permanently isolate the compromised segment. Root cause analysis revealed extensive external corrosion and wall thinning, though the internal cement mortar lining installed in the mid-20th century remained intact. Originally, the 6.33-mile replacement of the Sunset trunk line was scheduled to complete design in July 2031, with construction spanning from 2032 to 2036 at an estimated cost of $280 million. In response to the failure, LADWP Water System Director Gregory Reed outlined a new strategy dividing the project into two accelerated units. Unit 1 will address a three-mile stretch in West Hollywood. Currently at 45% design, the unit's design completion is being accelerated to the first quarter of next year—a three-year acceleration from the original timeline. Unit 1 is estimated to cost $139 million. Unit 2, covering the remaining 3.4 miles in the City of Los Angeles, is at 30% design, with completion targeted for spring 2028 at an estimated cost of $162 million. The total project cost is now estimated at $300 million. The new alignment will detour off Sunset Boulevard and utilize earthquake-resistant ductile iron (ERDI) pipe to enhance seismic resilience. In the interim, LADWP is taking immediate steps to stabilize the system. Crews have already reconnected five fire hydrants to an adjacent 8-inch main. By December 2027, the utility plans to install approximately 6,600 feet of new 16-inch ERDI pipe to replace the existing 8-inch main, increasing fire protection and flow capacity. A permanent regulator station will also be installed on Larrabee Street. The incident has underscored the urgency of LADWP's proactive asset management. The utility maintains 547 miles of trunk lines over 20 inches in diameter, including 63 miles of highly vulnerable riveted steel pipe. The department targets a 100% 50-year replacement cycle, aiming to replace 3.5 miles of trunk line annually. To support this, LADWP is increasing its in-house large-diameter pipe construction crews from three to five. Additionally, the utility is expanding its acoustic leak detection program, which currently surveys 43 miles of pipe annually and has identified 93 hidden leaks to date. For the Sunset trunk line specifically, sound-based sensors are being tested to monitor 3.6 miles of pipe. The department's aggressive mainline replacement program has already driven its leak rate below 15 leaks per 100 miles, which is 36% below the national average.