On Monday, DWP officials and Los Angels Mayor Eric Garcetti supervised the release of the last 20,000 “shade balls” into the Los Angeles Reservoir in Sylmar, marking the end of adding 96 million of the balls to the facility.
Created by biologist Brian White, shade balls are used to keep the water in the shade, thereby cooling it. They also will reduce evaporation, saving 300 million gallons of water each year, and protect the water from sunlight that could catalyze a chemical reaction between bromite in the groundwater and the chlorine used to disinfect the water for drinking. That reaction could engender the creation of bromate, a suspected carcinogen. In 2008, after high levels of bromate were found in the Silver Lake and Ivanhoe reservoirs, the DWP started adding shade balls to the Ivanhoe reservoir. The Upper Stone, Elysian, and Ivanhoe reservoirs all contain shade balls.
The L.A. Reservoir, measuring 175 acres, contains over 3.3 billion gallons of water. Because of its size, it was infeasible to use a protective cover, and the cost of using two covers was estimated at $300 million, according to The Los Angeles Times. It cost $34.5 million to add the 96 million balls to the reservoir; Artisan Screen Printing made 89.6 million of the balls, XavierC LLC supplied the rest.
The 4-inch-diameter shade balls, made from high-density polyethylene, are covered with carbon black to protect them from UV light. Bloomberg reported that Ed Osann, a senior policy analyst at the Natural Resources Defense Council, said that the chances of the shade balls releasing any toxic materials into the water supply are slim. The city claims that adding the shade balls to the reservoirs has cut water use by 15% in the last two years. The manufacturers of the balls say they should last roughly 25 years.