What appears to be an explosive invasion of tiny black orbs is actually one small part of the solution to Los Angeles’ four-year drought. Colloquially called “shade balls,” these 36 cent buoyant spheres are a part of a $34.5 million water quality protection project by the Los Angeles Department of Water and Power (LADWP).

The department deployed the last 20,000 of the approximately 96 million shade balls this past week. The simple technology helps prevent water contamination and evaporation. According to NPR, LADWP General Manager Marcie Edwards applauded the innovative alternative to a dam and tarp solution, which would have cost a whopping $300 million. “This is a blend of how engineering really meets common sense,” Edwards told NPR. “We saved a lot of money; we did all the right things.”

The 4-inch-diameter polyethylene balls, produced by California startup XavierC, help slow evaporation and are chemically coated to block ultraviolet rays that can potentially cause a chemical reaction that could produce the cancer-causing chemical bromate. The hollow, water filled plastic spheres are expected to save 300 million gallons of water annually, enough to quench the thirst of 8,100 individuals a year.