About five years ago the Los Angeles Department of Water and Power (LADWP) dumped 400,000 black “shade balls” into the Ivanhoe Reservoir. The reservoir is one of the two concrete basins that are collectively known as the Silver Lake Reservoir in the Los Angeles neighborhood that bears the same name-Silver Lake.
The shade balls are similar to the type you would find in the ball pit of a Chuck E. Cheese’s (hollow and plastic) except obviously far less colorful and their purpose is for science not merriment.
They were placed in the water to act as a relatively inexpensive and safe floating barrier to prevent a chemical reaction between bromate and chlorine caused when California’s perpetual sunlight hits the water. This particular pairing could cause cancer if the bromate was allowed to reach high levels.
While there was only a slim chance Los Angeles residents could get cancer from the water officials decided to go with the balls while the Headworks Reservoir- an underground reservoir that will replace the existing basins for potable water- is being built.