Big spill at T.O. wastewater treatment plant addressed quickly

An equipment malfunction at the wastewater treatment plant in Thousand Oaks on Oct. 12 resulted in the discharge of 375,000 gallons of partially treated water into the Calleguas Creek, eventually ending in the Mugu Lagoon.

The wastewater had gone through every treatment step at the Hill Canyon Wastewater Treatment Plant except the last two, which involve adding and then removing chlorine for disinfection. The malfunction was caught after 35 minutes and the system immediately shut down, according to Supt. Chuck Rogers.

“As far as we know, there is no human contact with this water and no harm to the environment, to plants or creatures,” Rogers said.

Staff immediately contacted the city’s reclaimed water partners to make sure that the water wasn’t used for crops on nearby farms or to water golf courses. Reports of the spill were made to the state’s Regional Water Quality Control Board and to the county’s Environmental Health Division.

“We reviewed our procedures. We’re doing everything we can to prevent these types of situations,” Rogers said.

In fact, such spills are rare. The last time the plant experienced a spill of treated wastewater was about six years ago.

The center treats an average of about 11 million gallons of water per day generated from a combination of domestic, commercial and industrial customers. During the heavy rains last winter that figure rose to about 30 million gallons a day.

“This stuff comes in quite ugly and goes out looking beautiful,” Rogers said. “You couldn’t tell the difference between it and drinking water.”

Monitoring of the treatment process is done around the clock.

“We take great pride in our work,” Rogers said. “This is a wonderful world-class facility, so when something like this happens, we feel really badly.”

There are 14 publicly owned sewage treatment plants in Ventura County, according to Mike Byrne, supervising environmental health specialist for the county’s Environmental Health Division. He estimates that he sees about five reports of spills or clogged lines each week.

“The majority of sewage releases that occur, the city staff responds to in a timely enough manner that if it does get into the storm drain, they can get into the catch basin and clean it up,” Byrne said.

Although the Los Angeles office of the Regional Water Quality Control Board is investigating whether or not the spill was due to an operator error or an equipment malfunction, officials were pleased with the way Hill Canyon staff responded to the incident.

“These things happen very infrequently,” said Wendy Phillips, chief of Groundwater Permitting/ Cleanup. “I’m not aware of a spill of this magnitude for several years.”