Over 90 Million Plastic Balls To Protect The City Of Los Angeles

Over 90 million plastic balls cover the Los Angeles Reservoir in the Sylmar area of Los Angeles Wednesday, August 12, 2015. The city has completed a program of covering open-air reservoirs with floating “shade balls” to protect water quality. Photos by Damian Dovarganes/AP Photo

The 4-inch-diameter plastic balls block sunlight from penetrating the 175-acre surface of the reservoir, preventing chemical reactions that can cause algae blooms and other problems.