Department of Water and Power workers are emptying out bales of plastic balls in the Ivanhoe reservoir in Los Angeles on Monday, June 9, 2008. Department of Water and Power released about 400,000 black plastic 4-inch balls as the first installment of approximately 3 million to form a floating cover over 7 acres of the reservoir to protect the water from sunlight. When sunlight mixes with the bromide and chlorine in Ivanhoe’s water, the carcinogen bromate can form. (Irfan Khan/AP)

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