It’s part of a $34.5 million project to protect the city’s water supply from the sun.

No, the folks at Las Virgenes’ municipal water district in Los Angeles are not making the world’s biggest ball pit in this mesmerizing video from June.

What’s being dumped from the back of the truck are “shade balls”—hollow, plastic balls measuring 4 inches in diameter that, as the name suggests, block sunlight. They cost 36 cents each, but to the city of L.A., they’re worth much more.

Local news outlets in L.A. reported Monday that 20,000 balls were released into a reservoir at the Van Norman Complex in the Sylmar area of the city. With that move, city officials completed a $34.5 million project that dumped 96 million balls into four reservoirs to protect what’s left of the city’s drinking-water supply.

For a city facing one of the worst droughts in U.S. history, the sun is a tough adversary. Not only does it evaporate millions of gallons of precious water, but it can also cause chemical reactions that make the water unsafe to drink. That’s where the shade balls come in.

The balls float at the surface of the reservoirs to form a cover that prevents sunlight from triggering a reaction between bromide (found naturally in ground water) and chlorine (added to kill bacteria)—which forms carcinogen bromate. They’re expected to last for 10 years and save 300 million gallons of water from evaporating each year. That’s enough drinking water for 8,100 people.

About the Author

Most Popular

  1. Two women at a bar with a bottle between them.
    Life

    The Particular Creativity of Dense Urban Neighborhoods

    A new study finds evidence that Jane Jacobs was right about the dynamic and innovative qualities spurred by living in dense, urban neighborhoods.

  2. Design

    Why Amsterdam’s Canal Houses Have Endured for 300 Years

    A different kind of wealth distribution in 17th-century Amsterdam paved the way for its quintessential home design.

  3. Charts

    The Evolution of Urban Planning in 10 Diagrams

    A new exhibit from the San Francisco Planning and Urban Research Association showcases the simple visualizations of complex ideas that have changed how we live.

  4. Design

    Before Paris’s Modern-Day Studios, There Were Chambres de Bonne

    Tiny upper-floor “maids’ rooms” have helped drive down local assumptions about exactly how small a livable home can be.

  5. photo: Developer James Rouse visiting Harborplace in Baltimore's Inner Harbor.
    Life

    What Happened to Baltimore’s Harborplace?

    The pioneering festival marketplace was among the most trendsetting urban attractions of the last 40 years. Now it’s looking for a new place in a changed city.

×