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Shade balls are small plastic spheres floated on top of a reservoir for environmental protection and to slow evaporation.
Contents
Also known as bird balls, they were developed initially to prevent birds from landing on toxic tailing ponds produced by mining operations. They have been used by airports to prevent birds from being attracted to drainage ponds and thus risking collisions with planes.
Usage by LADWP
Starting in mid-2008, the Los Angeles Department of Water and Power deployed about 400,000 of these devices in the Ivanhoe reservoir with the main objective of preventing the formation of a carcinogenic chemical, bromate, which forms when naturally occurring bromine reacts with chlorine in the presence of sunlight. In the original release by the LADWP, there is no mention of water conservation as an objective, and the project was planned for a five year life span, until a Griffith Park project was completed. However, the reduction in evaporation led to a saving of more than a billion gallons of water in one year.
In 2014 and 2015, the LADWP deployed 96 million shade balls on its largest reservoir in response to the United States Environmental Protection Agency's surface water treatment rule, which requires large reservoirs to be covered. The LADWP claims that in addition to reducing evaporation, they will also reduce UV radiation by-products and algae growth.
Construction
The shade balls used in the Los Angeles project are made of high-density polyethylene (HDPE) with carbon black additive to protect the plastic from ultraviolet radiation. Adding carbon black also prevents the formation of bromate, which causes stomach problems when water contaminated with it is consumed.
They are about 4 inches (10 cm) in diameter, and partially filled with water to avoid being blown by wind. HDPE plastic is commonly used for food and beverage containers as well as water distribution pipes.