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For the better part of a day this April, water passing through one of San Diego’s main drinking water treatment plants wasn’t fully treated to remove viruses and the parasite Giardia before reaching taps across parts the county.
For the better part of a day this April, San Diego’s main drinking water treatment plant wasn’t doing everything it was supposed to do to kill viruses and a nasty parasite known as Giardia before reaching taps across parts of the city, North County, East County and South Bay.
State regulators said it’s “likely” that the problem didn’t create a public health threat and that the water eventually met state safety standards before it left the plant. That’s because the water is treated several different ways, and only one treatment process partly failed. The water was still disinfected with other chemicals.
Water quality testing also didn’t show any problems with the water itself. The county, which monitors disease outbreaks, did not see any meaningful increase in illnesses, like Giardia, that untreated water would have caused.
But the problem was enough for the state’s Division of Drinking Water to cite the San Diego County Water Authority for failing to follow proper treatment techniques on April 21 and 22.
The Water Authority disclosed the citation this week.
Because the problem wasn’t considered a public health emergency, the Water Authority didn’t have to immediately notify the public. If there had been an emergency, the Water Authority said it would have notified the public immediately.
State regulations give agencies 30 days to notify the public of non-emergency citations. The citation was issued on June 4.
“Because this event impacted multiple member agencies it required extensive coordination to prepare for the notification,” the Water Authority’s operations director, Jim Fisher, said in a statement to Voice of San Diego. “In addition, the Water Authority requested a four-day extension to issue the notification on July 8 so that customers would not receive it over the holiday weekend.”
The April risk, however small, is an extraordinary one for a water supplier as large as the Water Authority. The Water Authority imports water into San Diego from Northern California and the Colorado River and then sells that water to cities and local water agencies across the county.
The largest water agencies tend to be the safest, since they are well-funded and closely watched.
The citation appears to be the first issued to the Water Authority since at least 1995, said Sean Sterchi, the top drinking water regulator for the San Diego region.
On Monday, the Water Authority said it had a hotline to handle questions from the public. It also released a map showing which areas received some of the affected water and said it will be sending notices to all potentially affected customers this week.
The problem appears to have begun around 8:30 p.m. on Sunday, April 21, when demand for water from the Twin Oaks Valley Water Treatment Plant in San Marcos went from 54 million gallons per day to 68 million gallons. The plant is designed to treat up to 100 million gallons a day, though in recent years part of the plant has gone unused because of low demand.
Before it’s sent to taps, water passing through the plant is supposed to come into contact with ozone, a disinfectant used to kill pathogens. The plant has two “ozone contactors” and the second one is supposed to be used when flows exceed 55 million gallons per day. But a valve failed to open, so too much water kept going to the first.
The problem was discovered at 12:50 p.m. on April 22. That day, the plant’s staff contacted state regulators to report the problem.
The private engineering firm Jacobs operates the plant for the Water Authority.
In a letter to state regulators, a Jacobs official said an employee did not visually monitor valves to ensure that the system was working, among other issues. The company said it is taking measures to prevent future problems.
“Until the event of April 21 2019, this procedure had functioned without incident,” Jacobs plant manager Brian MacDonald said in an April 25 letter to Sterchi.
The citation is also the first in the plant’s history.
“This was an unfortunate event, and we’ve put new procedures and equipment in place to ensure it doesn’t happen again,” Sandy Kerl, acting general manager of the Water Authority, said in a statement. “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.”
A Water Authority map showing what customers may have been affected is a patchwork of places that only make sense to people who understand how water is piped around the region.
The Water Authority sells two kinds of water: treated water, which has been cleaned up for drinking; and raw water, which comes from a river or reservoir and is not yet fit for human consumption. Water treatment plants make the raw water drinkable.
The Water Authority resells some water that has already been treated by another agency, the Metropolitan Water District of Southern California, and it also treats its own water to sell. It also sells raw water to some places, like the city of San Diego, that have their own treatment plants.
During the April incident, water from Twin Oaks reached city customers, though other parts of the city were receiving city-treated water.
The Olivenhain Municipal Water District in Encinitas has its own treatment plant and said none of its customers received any poorly treated water.
The Water Authority incident comes at a delicate time for the region. Right now, the city of San Diego is working to build a water treatment facility that would take sewage and make it drinkable. Scientists who have reviewed the plan in depth say it is safe, but a breakdown in normal water treatment processes shows that even tried-and-true treatment processes can falter.
Water quality issues are rare for most urban Californians. Though, in recent years, San Diego residents have worried about the danger of lead in their water following the discovery of leaded water at area schools. Water officials across the region say that lead comes from customers’ own property, where old metal lines and plumbing is deteriorating in homes, offices and schools and that there is not lead in the overall water supply. That said, city officials admitted late last year that they could be wrong about that and that several thousand city-owned pipes may contain lead.