On the water frontL.A. reservoirs emptied after high levels of contamination discovered

Amid a severe drought, two large Los Angeles reservoirs have to be drained because officials have found high levels of contamination in the water, Department of Water and Power (DWP) officials announced Friday.

Reservoirs in Silver Lake and Elysian Park were taken out of service in October when tests revealed bromate, a disinfectant byproduct that can form when treated water reacts with naturally occurring mineral bromide in sunlight. The decision means Los Angeles will lose about 600 million gallons of drinking water, enough to serve 4,000 families for a year. Long-term exposure to bromate can increase the risk of cancer. DWP officials said the bromate levels found in the reservoirs were not high enough to affect health, and there was no immediate health risk. The two reservoirs had served customers in downtown, Mid-City, and South Los Angeles, but DWP officials said that, since the bromate was found, they stopped using water from the reservoirs and instead piped groundwater or treated water directly to customers.

The Los Angeles Daily News’s Kerry Cavanaugh writes that the bromate levels did not violate state health standards, but DWP officials said they will not serve the reservoir water to any customers. Instead, they will try to find a nonpotable use for the water, such as irrigation, or dump it into the Los Angeles River. “At times of water shortage we are loathe to do that. Every drop is precious,” said DWP General Manager David Nahai. “(But) we’re going to err on the side of caution.” The 600 million gallons of drinking water, worth as much as $980,000, is the equivalent of a one-day supply for the entire city.

City Council president Eric Garcetti, who represents neighborhoods around the reservoirs, said he wants the DWP to use as much of the water as possible. “In a drought like today’s, this water can be used for all kinds of good purposes,” he said. “If we can find a way to use it for irrigation, water-treatment plants or something else, that would be my strong preference.” The reservoirs will be drained, cleaned, and refilled by 1 June to handle increased summer demand for water. The reservoirs are beloved landmarks, surrounded by popular walking trails and homes. Garcetti said he learned of the contamination last week and was disappointed that he and fellow council members were not notified earlier, but he said he was pleased with DWP officials’ response. “I don’t believe there was ever a threat to human consumption, but their quick actions ensured there wouldn’t be,” Garcetti said.

Tests in early October revealed the high levels of bromate in the water-distribution system. DWP officials said they notified state officials and traced the problem back to the Elysian and Silver Lake reservoirs, which were immediately removed from service. Of the city’s six open-air reservoirs, only Elysian and Silver Lake had high levels of bromate. State law allows, at most, an average of 10 parts per billion bromate in drinking water in a year. Tests showed bromate at 60 to 100 pbb — less than the one-day limit on bromate exposure, which is 200 ppb - and within the average annual exposure limit. Still, DWP officials said they were shocked to find bromate in the reservoirs. It was the first time regulators had seen the problem in local reservoirs, they said. The disinfectant byproduct can pop up in systems when water with naturally occurring bromide is treated with ozone. DWP reservoirs showed that bromate can also form when chlorine and naturally occurring bromide are exposed to intense sunlight. “The formation of bromate from the chemical reaction in the reservoirs was unusual and unexpected,” said Lea Brooks, spokeswoman for the state’s Public Health Department. Since the discovery, DWP water managers have been trying to understand why bromate developed. They have contracted with a laboratory in Arizona that can mimic L.A.’s intense October sunlight to discover what triggered the reaction and how to prevent it from happening next summer. “Our biggest concern is making sure this does not reoccur,” said Martin Adams, DWP’s director of water quality and operations. The DWP is also developing a plan to take the city’s last six open-air reservoirs off line.

L.A. has the nation’s largest system of reservoirs that store treated water before distribution, but federal water regulations require the city to phase those out in favor of tanks or covered reservoirs to protect drinking water from contamination. The utility must develop a plan by 2009.