TARZANA : Leaking Water Tank Declared Unusable

An estimated 800,000 gallons of water has leaked from a 4-million-gallon water tank in the hills of Tarzana since Thursday, forcing the Los Angeles Department of Water and Power to declare it unusable, DWP officials said Monday.

Although inspectors did not find structural cracks in the Corbin water tank near Mulholland and Greenbriar drives after the Jan. 17 Northridge earthquake, officials now speculate that the temblor or an aftershock damaged a drainage valve.

Water “has been seeping out for a while,” said Joey Castruita, a DWP supervisor. About 20% of the tank’s capacity, or 800,000 gallons, has leaked since the damage was discovered, he said. But he said an unknown amount of water may have leaked before then.

“It is kind of surprising,” said Scott Munson, a DWP waterworks engineer. “But lots of little, weird things happened during the earthquake.”

Munson said the steel tank, which is 156 feet in diameter and 30 feet tall, was “one of our better, newer tanks.” It was built in 1987.

Once the leak was discovered, he said, no water was pumped into the tank, and most of the remaining water flowed into the city’s water system as planned.

The underground location of the tank hindered workers from immediately stopping the leak.

“There is no way to drain the water or stop the leak without extensive excavation to the hillside,” Castruita said. “We would have had to dig too deep.”

The tank is now empty and will be repaired next week. It served the area of Mulholland Drive to the north, Wells Drive on the south, Winnetka Avenue to the west and Alonzo Drive to the east.

Residents are now being served by the Nogales Pump Station in Tarzana, and Castruita said there should no change in service. The tank is designed to drain into a natural waterway along a canyon, Castruita said.