Underground water pipes in Los Angeles have suffered significantly more "major blowouts" in the last three months, officials confirmed Tuesday after analyzing dozens of ruptures, some of which flooded streets, damaged vehicles and buildings and created a sinkhole so big that it almost swallowed a firetruck.
And the city's engineers don't know why.
It could be fluctuating temperatures. It could be a statistical anomaly. It could be something else.
"It's strange," said William Robertson, general manager of the Bureau of Street Services, which repaves the ruined roads after the water recedes. "The thing that is puzzling is they are so spread out . . . all over the city. You can't link them to anything."
What Department of Water and Power officials can say with certainty is they want more money to fix the problem and plan to ask for a water rate hike. The blowouts underscore the fact that the city's aging water system, which has 7,200 miles of pipe and moves 600 million gallons of water a day, needs an upgrade, officials said.
"This all requires a lot of money," said Jim McDaniel, head of the city's water system.
But some City Council members, who would have to approve any rate increase, did not appear convinced.
"They have to make a case for that," said Councilwoman Jan Perry. She added that she is concerned about the rise in blowouts. "We have to get to the cause," she said. "People can get hurt. Property can be lost."
Los Angeles' water system was put in place by William Mulholland, who figured out how to tap water from the Eastern Sierra and the Owens Valley and designed an aqueduct system that let it flow to Los Angeles on the force of gravity alone.
The influx allowed the semi-arid Los Angeles to boom -- and subdivisions marched outward in the 1920s and the years just after World War II.
The system remains a marvel to many engineers and still sends water over the Santa Monica Mountains from Sylmar to San Pedro using gravity. But parts of it are now almost 100 years old, and many of the pipes are wearing out. At the same time, new water quality standards are requiring the DWP to cover many reservoirs at great expense.
The age of the pipes has long been a concern to engineers and officials at the DWP, but most Angelenos were unaware of the urgency until earlier this month.
On Sept. 5, a 95-year-old trunk line ruptured under Coldwater Canyon Avenue, sending a torrent of mud and water shooting 10 feet into the air and then into the streets of Studio City.
Less than 72 hours later, a broken main created a sinkhole in Valley Village -- and nearly consumed a fire truck that responded. Days later, another broken main flooded Melrose Avenue near Fairfax High School.
And on Tuesday there was another on Exposition Boulevard, which caused officials to close the thoroughfare between Crenshaw and Degnan boulevards and cut off water to several businesses.
DWP officials say the number of leaks was not out of the ordinary.
City pipes fail about 1,400 times a year, a rate per mile of pipe that is actually much lower than in other big cities.
But what is unusual is the increase in "major blowouts" in which pavement is ruptured and the leak causes problems.
McDaniel said that there have been 13 such incidents in the first 14 days of this month. By comparison, there were 13 in all of September 2006, 17 in September 2007 and 21 last year. July and August saw a similar jump, he said.
"At this time, I don't have a definitive cause," he told DWP commissioners Tuesday.
To fix the system, officials last year persuaded the City Council to approve a water rate increase of about $2 per month per customer. That will allow the DWP to spend about $1.3 billion over the next five years.
But officials would like an additional $1.4 billion to accelerate the replacement of water mains and to make other water quality improvements.
"We need to have a conversation with the people of Los Angeles if we're going to enlarge and accelerate the program, which is what we'd like to do," said DWP General Manager H. David Nahai.
DWP officials have proposed additional rate increases for 2010 and 2011.
Times staff writer Robert Lopez contributed to this report.