More than 100 water main ruptures that occurred throughout the city between July and September last year were likely the result of a two-day-a-week water-rationing program that placed stress on the city’s aging water system.

A water main rupture in the 200 block of S. Irving Boulevard was one of several that occurred after water rationing regulations were enacted. (photo by Edwin Folven)

The finding was contained in a report released Tuesday by an independent group of scientists who were analyzing the cause of the numerous water main ruptures that began occurring after the water-rationing program was implemented on June 1. The program, which was launched by Mayor Antonio Villariagosa, allows residents to only water their lawns and gardens on Mondays and Thursdays.

The study, which was led by Dr. Jean-Pierre Bardet, chairman of the University of Southern California’s Department of Civil and Environmental Engineering, concluded that watering restrictions allowing residents to water only on Mondays and Thursdays caused drops in pressure on those days. On days when people were not allowed to water, the pressure went back up, placing stress on old cast iron pipes and causing them to rupture. The independent study was convened by Villaraigosa and the Los Angeles City Council. Between July and September last year, 101 water pipe breaks occurred, compared to 42 during the same period in 2008.

“The investigation team’s findings reveal a connection between the city’s water rationing program and the increase in pipe breaks during the summer of 2009,” Bardet wrote in the report. “These findings conclude that the sudden change in water pressure in the system, attributable to the water-rationing program, had a negative effect on cast iron pipes with lower fatigue resistance…especially corroded cast iron pipes.”

Officials from the Los Angeles Department of Water and Power (LADWP) declined to comment on the independent report, but issued a statement outlining that the utility also had investigated the cause of the water main ruptures, and the possibility that they were being caused by the water-rationing program, but the findings were inconclusive.

“The department believes corrosion is the indisputable and primary factor in most of our water main breaks, including those from last September,” according the LADWP statement. “It is the department’s position that the operational changes to accommodate city trunk line repairs resulted in ruptures on mostly cast iron mains, which accounts for the severity of the breaks in the weeks that followed.”

Trunk lines are the main arteries in the LADWP’s water system. The LADWP conducted major work on trunk lines last summer, and had to divert water from pipes that were being repaired, causing stress on the pipes to which the water was diverted. Since the trunk line repairs were completed around the end of September, the proliferation of water main ruptures subsided, according to the LADWP. The utility currently experiences approximately four ruptures per day, which is considered average, according to the statement.  The water system is comprised of more than 7,200 miles of pipe.

Some members of the Los Angeles City Council disputed the LADWP’s findings, including City Councilmember Paul Koretz, 5th District, who said he wants the water-rationing program re-evaluated. Some of the most high-profile water main ruptures occurred in Koretz’s district, including one on September 5 in Coldwater Canyon that resulted in numerous homes being flooded and major repairs to the street. Three days later, another water main ruptured in Valley Village, causing a large sinkhole that temporarily swallowed a city fire engine. City Councilmember Jan Perry, 9th District, who chairs the council’s Energy and Environment Committee, said the water –rationing plan may need to be changed.

“The DWP will respond in 30 days with their implementation strategy based on the independent steering committee report on water system breaks during the summer of 2009 in Los Angeles,” Perry said. “Based on the recommendations presented by Dr. Bardet, it appears that there is a need for more aggressive pipeline repair and replacement, and an adjustment in the schedule for watering to address the issue going forward.”

The independent study outlined some solutions, including allowing watering for residents with even-numbered addresses on even-numbered days, and vice versa for residents with odd-numbered addresses. Bardet also recommended that aging pipes be replaced more frequently.

Inquiries to Villaraigosa’s office regarding possible changes to the water-rationing program were not returned, and the city council has not scheduled a date to review the findings of the ireport. More than 108 lawsuits have been filed against the city for the water main ruptures last summer.