Overall water quality not compromised, but customers are being notified
By Miriam Raftery
Photo: When completed in 2008, the Twin Oaks Valley Water Treatment Plant was the largest submerged membrane water treatment plant in the world and the first treatment plant built by the San Diego County Water Authority.
July 10, 2019 (San Diego) -- A malfunction at the Twin Oaks Valley Water Treatment Plant resulted in a citation from the state Division of Drinking Water due to a two-day failure of one of its systems that kills harmful organisms. The plant provides water to water districts across San Diego County including East County, but the County Water Authority assures that water in regional pipelines continued to be safe for all uses due to additional treatment processes.
The malfunction lasted about 15 hours on April 21-22, when ozone dosage levels in the plant fell below state-mandated levels because a valve failed to fully open. Ozone is a common disinfectant used in water treatment systems to kill bacteria and other organisms. To be effective, water must be in contact with the proper dosage of ozone for specific amounts of time.
CH2M Hill/Jacobs operates the Twin Oaks plant under a contract with the Water Authority, but the citation was issued to the San Diego County Water Authority as the plant owner and permit holder. This is the first citation issued at the Twin Oaks plant in more than a decade of service.
When completed in 2008, the Twin Oaks Valley Water Treatment Plant was the largest submerged membrane water treatment plant in the world and the first treatment plant built by San Diego County Water Authority.
“Corrective actions were taken immediately, and the lapse was reported to state regulators. The contractor has updated its operational procedures and installed additional monitoring equipment to prevent similar problems in the future,” the CWA states in a press release.
If there had been a water quality emergency, the public would have been notified immediately. After the citation was issued on June 4, the Water Authority says it worked closely with impacted member agencies to follow state-manded noticing requirements.
“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 Water Authority. “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.”
That process involved identifying and notifying all customers who may have received water from the Twin Oaks plant during the April 21-22 incident. Affected agencies are Carlsbad Municipal Water District, Helix Water District, City of Oceanside, 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, City of San Diego, Vallecitos Water District, and Valley Center Municipal Water District. Notices in English and Spanish are being mailed to potentially affected customers this week.
The notices include a hotline number that Water Authority set up to address questions from the public at (858) 284-4142. In addition, the Water Authority has provided online resources at www.sdcwa.org/water-quality. Those resources include a map of affected areas searchable by address, the official public notice, the formal citation by the state and frequently asked questions.