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We have not yet analyzed Dr. Bardet’s findings but look forward to doing so.

LADWP’s internal investigation explored current watering restrictions as a possible factor, however, our investigation found the data on effects of outdoor watering restrictions to be inconclusive. The data on cast iron pipe corrosion proved far more compelling and definitive.

The Department believes corrosion is the indisputable and primary factor in most of our water main breaks, including those from last September. We believe Dr. Bardet’s findings will support this position.

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 increased severity of the breaks in the weeks that followed.

Cast iron pipes comprise 70% of our system’s pipes and, mirroring that, nearly 70% of the breaks discussed occurred on this type of pipe.

As cast iron pipes are most prone to break due to corrosion and other factors, the operational changes implemented for the City Trunk Line repairs took an increased toll on those cast iron pipes. In the Department’s internal report, these operational changes were found to be a contributing factor in the uptick of main breaks that followed the trunk line rupture.

Breaks on cast iron pipes typically take the form of longitudinal and somewhat lengthy splits, resulting in larger leaks that can lead to increased damage to the street surface, hence the perceived increase in severity of main breaks in September 2009.

The break on the City Trunk Line required the operation of 26 gate valves to redirect water in order to isolate the broken segment and make the necessary repairs. Other operational changes were also necessary to maintain pressure and flow in areas supplied by the City Trunk Line, placing undue stress on weaker pipes in our system and accelerating possible ruptures that otherwise may have occurred later.



Q: What is LADWP’s main break activity today?
A: Following the uptick in main breaks of September 2009, LADWP experienced a decline in both the frequency and the severity of water main breaks, with most breaks or leaks requiring small spot repairs, not full replacements. That trend continues today as the number of main breaks occurring in our system returned to an average of about four small leaks or breaks each day a rate that is well below the national average.

Q: How does LADWP’s water distribution system compare to other systems across the nation?
A: The system has an average of 19.85 leaks and breaks per 100 miles of pipewell below the national average of 25 per 100 miles of distribution pipe.