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. A man walks his dog on a hilltop overlooking San Francisco in the early morning hours on Mount Davidson.
    Equity

    When Millennials Battle Boomers Over Housing

    In Generation Priced Out, Randy Shaw examines how Boomers have blocked affordable housing in urban neighborhoods, leaving Millennial homebuyers in the lurch.

  2. Life

    Amazon HQ2 Goes to New York City and Northern Virginia

    After Jeff Bezos set off one of the highest-profile bidding wars in modern history, Amazon picked two East Coast cities for its new headquarters. The surprise extra: There's something in it for Nashville, too.

  3. A photo shows the Amazon logo on a building.
    Amazon HQ2

    Amazon’s HQ2 Spectacle Isn’t Just Shameful—It Should Be Illegal

    Each year, local governments spend nearly $100 billion to move headquarters and factories between states. It’s a wasteful exercise that requires a national solution.

  4. A photo of a resident of Community First Village, a tiny-home community for people who were once living in homelessness, outside of Austin, Texas.!
    Design

    Austin's Fix for Homelessness: Tiny Houses, and Lots of Neighbors

    Community First! Village’s model for ending homelessness emphasizes the stabilizing power of social connections.

  5. Cyclists and walks use a trail beside Lady Bird Lake in Austin, Texas.
    Life

    HQ2 Is Only Part of the Story of Big-Tech Expansion

    Amazon HQ2 may be split between superstar cities, but San Francisco’s big tech firms are starting to expand into smaller, non-coastal places.