O.C. Water Main Rupture Blamed on Worker Error

Operator error and computer-system flaws caused the massive water main failure that disrupted water supplies in December to more than 700,000 customers in southern Orange County, water officials said Monday.

An inspection of the 26-mile pipeline also uncovered possible evidence of corrosion in the prestressed concrete segments of the water main, similar to defects that led to ruptures at other water agencies across the nation.

While corrosion was not a factor in the December rupture, the finding has created “some cause for concern,” said Jill T. Wicke, manager of water systems operations for the Metropolitan Water District.

The district will conduct a detailed inspection of the pipeline in early February, a year ahead of a planned inspection, and shut down the main for a week, Wicke said.

The closure is not expected to cause any disruptions in water service for residents, since county water agencies will be asked to store additional water supplies beforehand, agency officials said.

Investigators found that an employee in the MWD’s Eagle Rock operations center caused the Dec. 13 rupture by using incorrect procedures in opening and then shutting flow valves while sending water to the Santa Margarita Water District, Wicke said.

By closing two valves too quickly, the operator caused a backward surge in water pressure that exceeded the pipe’s capacity. The pressure blew out a 10-foot section of the buried concrete and steel pipe on the outskirts of Irvine, Wicke said.

About 5 million gallons of water, along with chunks of concrete, churned up from 25 feet underground in a torrent of water that flooded over Portola Parkway and nearby strawberry fields.

Crews worked around the clock to replace 60 feet of damaged pipe, and the main was back in operation within eight days. Drought-like water restrictions were imposed throughout south Orange County during the water crisis. The repairs cost about $650,000, Wicke said.

Wicke presented the four-page report on the findings of the investigation to members of the MWD’s board of directors on Monday morning. The report confirmed the MWD’s preliminary inquiry released in late December.

The MWD is considering possible disciplinary action against the operator, said MWD spokesman Bob Muir. The possible punishment could range from a reprimand or additional training requirements to dismissal, depending on the employee’s past performance and culpability in the incident, Muir said.