Report: Rationing caused water main breaks

LOS ANGELES With residents restricted to watering only two days a week, pressure fluctuated in the city's 7,200-mile water system, straining aging and corroded cast iron pipes until they burst, said University of Southern California civil engineering professor Jean-Pierre Bardet, who led the team of scientists and private-sector analysts.

The experts reported back to a city council committee Tuesday on their investigation of last summer's series of water main breaks that damaged several homes, turned city streets into rivers and produced a huge sinkhole that nearly swallowed a fire truck.

Water pressure fell significantly on Mondays and Thursdays, the days when homeowners were allowed to water their lawns, after the rationing program started in June, the report said.

The report recommended reworking the city's water conservation plan to avoid sudden variations in water pressure.

Bardet suggested adjusting the rationing schedule so residents in homes with odd-numbered street addresses can water their lawns on a different day than residents with even-numbered addresses.

The team found that 90 percent of the ruptures happened in cast-iron pipes that were already corroded, but water temperature and internal pressure changes also contributed to the failures.

Department of Water and Power officials said they have not yet analyzed the team's findings.

The DWP's internal investigation considered the watering restrictions as a factor but was inconclusive, officials said in a statement. The department's study found that cast iron pipes, which make up 65 percent of the city's 7,200 miles of water distribution system, were to blame for the ruptures.

"The data on cast-iron pipe corrosion proved far more compelling and definitive," the statement said.

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