San Diego County Water Authority Treatment Plant Cited for April Error

By on July 13, 2019
San Diego County Water Authority

The Twin Oaks Valley Water Treatment Plant (TOVWTP), operated by the San Diego County Water Authority (SDCWA), experienced a malfunction for some 15 hours on April 21-22. Ozone dosage levels in the plant fell below state-mandated levels when a valve failed to fully open. The state Division of Drinking Water (DODW) issued a citation, though the water in the regional pipelines continued to be safe for all uses due to additional treatment processes that the TOVWTP had in place.

The Twin Oaks plant is operated by CH2M Hill/Jacobs under a contract with the SDCWA. However. the citation was issued to the San Diego County Water Authority as the plant owner and permit holder. This is the first citation issued to the SDCWA’s Twin Oaks plant in its more than a decade of service.

Ozone is a common disinfectant used in water treatment systems to kill bacteria and other organisms. To be effective, the proper dosage of ozone must be in contact with the water for specific amounts of time to achieve the state-mandated safety levels. The lapse of approximately 15 hours was reported to state regulators and corrective actions were taken immediately.

“This was an unfortunate event, and we’ve put new procedures and equipment in place to ensure it doesn’t happen again,” said Sandy Kerl, acting general manager of the SDCWA. “We are committed to maintaining the high levels of safety and reliability we’ve achieved over more than 75 years of service to the San Diego region.”

In order to prevent a similar problem in the future CH2M Hill/Jacobs has updated its operational procedures and installed additional monitoring equipment. Had the malfunction caused a water quality emergency, the public would have been notified immediately.

After the DODW citation was issued on June 4, the SDCWA began working closely with impacted member agencies to follow state-mandated noticing requirements. That process involved identifying and notifying all customers who may have received water from the Twin Oaks plant during the April 21-22 incident.

Agencies who may have been affected include the Carlsbad Municipal Water District, Helix Water District, Otay Water District, Padre Dam Municipal Water District, Rainbow Municipal Water District, Ramona Municipal Water District, Rincon del Diablo Municipal Water District, Vista Irrigation District, Vallecitos Water District and Valley Center Municipal Water District as well as the cities of Oceanside and San Diego.

The SDCWA is mailing notices – in both English and Spanish – to potentially affected customers during the week of July 8. The notices include a hotline number that has been established to address questions from the public at 858-284-4142. In addition, the SDCWA is providing online resources at These resources include a map of affected areas searchable by address, the official public notice, the formal citation by the state and a frequently-asked-questions piece.