What's Floating in LA's Water? 96 Million Black Balls (And Here's Why)

Imagine standing at the edge of a massive reservoir and watching millions of small black balls roll down a concrete slope, splashing into the water below. One after another, they tumble in, creating waves of bouncing spheres until the entire surface of the water looks like the world's biggest ball pit. This isn't a scene from a science fiction movie. It actually happened in Los Angeles in 2015, and the reason why is more fascinating than you might think.

A Reservoir Turns Black

On August 10, 2015, the Los Angeles Department of Water and Power (LADWP) released the final 20,000 shade balls into the Los Angeles Reservoir, bringing the total to 96 million balls. The event made headlines around the world. News crews filmed the balls cascading into the water while then-Mayor Eric Garcetti looked on. Within hours, the reservoir's sparkling blue surface had transformed into a sea of black.

But why would anyone dump nearly 100 million plastic balls into drinking water? The answer involves chemistry, California's worst drought in recorded history, and a creative solution to a dangerous problem that most people had never heard of.

The Real Reason: A Chemical Threat

While many news reports focused on saving water during California's drought, the primary reason for the shade balls was actually about preventing a toxic chemical from forming in the water supply. The chemical is called bromate, and it's classified as a carcinogen, meaning it can cause cancer.

Here's how bromate forms: Los Angeles gets some of its water from Northern California. This water naturally contains small amounts of a substance called bromide. When water treatment facilities add chlorine to kill bacteria and make the water safe to drink, the bromide doesn't go away. Usually, that's not a problem. But when sunlight hits water that contains both bromide and chlorine, a chemical reaction occurs. The result is bromate, which is definitely something you don't want in your drinking water.

The Los Angeles Reservoir is huge and sits out in the open, exposed to intense California sunshine for hours every day. Before the shade balls, sunlight was constantly triggering this chemical reaction, creating bromate in the water that would eventually flow to people's homes.

Blocking the Sun

The shade balls work through a surprisingly simple principle: they block sunlight from reaching the water. Each ball is about four inches in diameter (roughly the size of a grapefruit) and is made of high-density polyethylene plastic with added carbon black, which gives them their distinctive dark color. The carbon black isn't just for looks. It protects the plastic from breaking down under constant sun exposure.

When 96 million of these balls float on the surface of a reservoir, they create a protective layer that blocks about 80-90% of the sunlight. No sunlight means no chemical reaction. No chemical reaction means no bromate. Problem solved.

This wasn't Los Angeles's first time using shade balls. The city had actually started experimenting with them back in 2009, when about 400,000 balls were placed in the Ivanhoe Reservoir. When that test worked well, city officials decided to scale up the solution for the much larger Los Angeles Reservoir.

The Drought Factor

While preventing bromate was the main goal, the shade balls came with another benefit that became especially important in 2015: they reduce water evaporation. California was in the middle of a severe drought that had lasted for several years. Reservoirs were running low, and every drop of water mattered.

In the hot Los Angeles sun, water evaporates from open reservoirs at a surprising rate. The shade balls, by covering the water's surface and keeping it cooler, significantly reduce this evaporation. The LADWP estimated that the balls would save about 300 million gallons of water each year. To put that in perspective, that's enough water for about 8,100 people for an entire year.

During the 2015 release event, Mayor Garcetti highlighted this water-saving aspect. "In the midst of California's historic drought, it takes bold ingenuity to maximize my goals for water conservation," he said. The timing couldn't have been better for a project that both protected water quality and conserved a precious resource.

The Science of Shade Balls

Each individual shade ball is hollow and filled with water, which makes it heavy enough to stay stable on the reservoir's surface even when it's windy. The balls are designed to last about 10 years in harsh outdoor conditions. They're also BPA-free and meet strict safety standards for contact with drinking water.

When all 96 million balls are floating together, they create a dynamic, shifting blanket across the reservoir. The balls move with the water's currents and bump against each other, but they stay tightly packed enough to block most of the sunlight. From an airplane, the reservoir looks like a giant black oval, a stark contrast to the surrounding landscape.

The balls also help keep birds and other wildlife away from the water, and they reduce the growth of algae, which needs sunlight to thrive. These were added bonuses that made the shade balls even more valuable.

But Wait: Is This Really a Good Idea?

Not everyone was convinced that shade balls were the perfect solution. Some environmental scientists raised concerns about using millions of plastic balls, even if they were solving an immediate problem.

First, there's the issue of producing 96 million plastic balls in the first place. Manufacturing that much plastic requires petroleum and energy, which contributes to carbon emissions and climate change. Some critics argued that the environmental cost of making the balls might outweigh the benefits of saving water.

Second, what happens when the balls reach the end of their 10-year lifespan? That's 96 million plastic balls that will eventually need to be disposed of or recycled. Even if they can be recycled, the process uses energy and resources.

Third, some researchers questioned whether the evaporation savings were as significant as claimed. A 2015 study suggested that in some conditions, the shade balls might not reduce evaporation as much as other methods, like covering the reservoir with a more permanent structure.

Finally, there were concerns about whether the plastic itself might leach chemicals into the water over time. The LADWP insisted that the balls were thoroughly tested and met all safety standards, but some skeptics remained unconvinced.

Alternative Solutions

If shade balls aren't perfect, what are the alternatives? There are a few other ways to prevent bromate formation or reduce evaporation:

Covered Reservoirs: Some cities build roofs or covers over their reservoirs. These structures completely block sunlight and prevent evaporation, but they're extremely expensive to build and maintain.

Underground Storage: Storing water underground keeps it dark and cool, but again, this requires massive infrastructure investments and isn't practical for existing above-ground reservoirs.

Different Treatment Methods: Water treatment facilities can adjust their processes to reduce bromide levels before the water reaches open reservoirs, but this can be technically challenging and expensive.

Floating Covers: Some reservoirs use large floating covers made of materials like plastic or fabric. These can be effective but are also costly and require maintenance.

For Los Angeles, shade balls offered a relatively quick and affordable solution that could be implemented in an existing reservoir without major construction. At about 36 cents per ball, the total cost was around $34.5 million. While that sounds like a lot, it was far less than building a covered reservoir, which could cost hundreds of millions of dollars.

The Big Picture

The story of the Los Angeles shade balls is about more than just 96 million black spheres floating in water. It's about the complex challenges cities face in providing safe drinking water to millions of people while also conserving resources and protecting the environment.

It's also a reminder that solutions to modern problems often require creative thinking. Who would have guessed that the answer to a toxic chemical problem would look like the world's largest collection of ball pit balls?

The shade balls represent a type of solution called "geoengineering on a small scale." Instead of trying to change the water's chemistry or rebuild the entire water system, Los Angeles found a way to work with what it had by simply blocking sunlight with floating balls. It's not perfect, but it works.

What Happened Next?

Since their 2015 debut, the shade balls have continued doing their job in the Los Angeles Reservoir. The water quality has remained good, and the balls have held up well under constant sun exposure. Other cities around the world have taken notice and considered using shade balls in their own reservoirs, though not all have followed through.

The project also sparked conversations about water management, climate change adaptation, and creative problem-solving in the face of environmental challenges. In a time when climate change is making droughts more common and water resources more precious, cities everywhere are looking for innovative ways to protect and conserve their water supplies.

The 96 million black balls in Los Angeles might look strange, but they represent an important lesson: sometimes the best solutions to complex problems are simpler than we think. They just need to be creative, practical, and willing to look a little unusual.

Sources

1. Los Angeles Department of Water and Power (LADWP) - Official information about the shade ball project and water quality protection

2. News coverage from major outlets including CNN, The Guardian, and local Los Angeles media from August 2015

3. Scientific studies on bromate formation in drinking water reservoirs

4. Environmental research on the effectiveness and environmental impact of shade balls

5. California drought data and water conservation initiatives from 2012-2017