Reservoirs Banned as Tap Water Source

New federal water quality rules announced Thursday are forcing Los Angeles to take its historic network of reservoirs out of use, ultimately costing the city water department billions of dollars and changing the way it stores and distributes water.

The long-anticipated regulations are among a series of rules aimed at reducing harmful chemicals that can form during disinfection and at guarding against a parasite that caused a lethal disease outbreak in the Midwest a decade ago.

“These important new regulations are the fruit of years of hard work and collaboration across the drinking water community,” U.S. Environmental Protection Agency Administrator Stephen L. Johnson said in a Washington teleconference. “Together, we have created two proactive, science-based safeguards that will protect public health.”

Los Angeles water officials have been preparing for the requirements for years and have begun to convert the city’s treated water storage system to comply. Most reservoirs in the country are filled with untreated water and will not be similarly affected.

The new rules, which tighten standards for disinfection byproducts, are expected to cause about 70% of the nation’s water systems to change their treatment methods, either by using less chlorine or by switching to methods that don’t rely on chlorine. The byproducts, which are suspected carcinogens, are formed when chlorine and other disinfectants combine with naturally occurring organic matter in the water.

The Metropolitan Water District of Southern California is embarking on an $856-million conversion of its five treatment plants to use ozone instead of chlorine to purify drinking supplies. Two plants have already made the switch and the others will make the change by 2010. “We started planning for these rules 15 years ago,” said Bart Koch, chemistry unit manager at Metropolitan’s water quality lab.

In Los Angeles, which operates the largest open-reservoir system of treated water in the country, dating to the 1920s, the regulations are having a much more tangible effect. “We cannot have open reservoirs,” said Pankaj Parekh, director of water quality compliance for the Los Angeles Department of Water and Power. “That’s a huge deal for us.”

Under the new standards, the DWP, which already uses ozone for primary treatment, has to switch its secondary treatment chemical in the reservoirs from chlorine to chloramine. And in the sunlight of an uncovered reservoir, chloramine promotes potentially harmful algae growth.

Four of the DWP’s 10 open reservoirs -- the two Hollywood reservoirs, Encino and Stone Canyon near UCLA -- are no longer being used for drinking supplies and will be kept filled with untreated water for emergency use, such as firefighting. The fate of the remaining six is being worked out with local communities. Some could be converted to recreation fields, others maintained with shallow water to retain the appearance of a reservoir. “In Silver Lake, we know the residents care about a lake,” Parekh added.

To make up for the lost reservoir storage, the city is building underground tanks, installing larger-capacity distribution pipes and routing water directly from its main treatment plant in Sylmar to customers. All told, the work will cost an estimated $3.5 billion, Parekh said.

The second EPA rule requires utilities to monitor for levels of cryptosporidium, a water-borne parasite found in human and animal waste that caused an unusual outbreak of disease in Milwaukee in 1994 that killed 100 people. If high levels are found, water systems will have to undertake more sophisticated treatment.

“This is a precautionary step that the water community is taking,” said Tom Curtis, deputy executive director of the American Water Works Assn., whose members serve 80% of the American population. “But it would be hard to say in a scientifically credible way that there is really a problem now.”