It’s no secret that Lake Tahoe has a trash problem, and local nonprofit Clean Up the Lake has pulled more than 61,000 pounds of debris from the lake since 2018. But as scuba divers are limited to a depth of about 60 feet, that leaves 1,584 feet of depths the organization can’t reach. 

Enter the Restoring the Lake Depths Foundation, a South Lake Tahoe-based nonprofit using a deep-water robot to pull refuse from beneath the surface. In summer 2023 alone, the organization used the robot to pull nearly 5 tons of hazardous materials from the lake, including about 1 ton of alcohol bottles containing lead and cadmium. The rest included hundreds of action cameras and at least five camera drones with lithium batteries, plus a 16,000-pound electric boat. 

Lithium batteries contain toxic and hazardous chemicals like lead, nickel, graphite and copper. A research team in July studying water in Emerald Bay found that Lake Tahoe’s lead levels surpassed the EPA-approved limit by more than 2,500 times, partially due to deteriorating lead-based telecom cables on the lake floor. 

Aside from the human health risks posed by drinking water that contains chemicals like lead or copper, those chemicals can harm overall lake health. Lead poisoning can deplete marine species, and copper can disorient or kill freshwater fish, leading to food web interruptions and more opportunities for invasive species to take hold. Even organic chemicals in batteries, like lithium perchlorate, can lead to burning eyes and skin in both humans and animals if ingested. These chemicals can also impact marine plants, disrupting their photosynthesis cycles and germination. 

But there’s good news, at least in terms of how careful recreators are being on the lake. “It’s not a lot of litter,” says the foundation’s CEO, Scott Fontecchio. “It’s a lot of old junk and older stuff that was left there. It seems like a lot of stuff came from the ‘50s and ‘60s. Some of the boats we’ve pulled up look like they were put together with old tanks from World War II. It’s like, I can see why they sank.”

The foundation’s robot is operated remotely via a tether on a boat at the surface, with a claw that allows an operator to collect trash as deep as about 500 feet. The Restoring the Lake Depths Foundation plans to introduce a second boat with a bot that can reach depths of 500 meters (about 1,640 feet) to clean the deepest areas of Lake Tahoe, as soon as it finds a tether long enough. 

“There’s not much to it,” Fontecchio says of the current aquatic robot, which he built in partnership with Mission Robotics. “We drive it with a PlayStation controller and watch with a monitor. It’s just a battery inside a 1-by-2-foot square.” The robot also has a grappling hook to pull up bigger objects and a storage basket for collecting plastics. It can move about 4 mph underwater and see between 30 and 60 feet in either direction, depending on the water clarity. So far, the organization has covered a roughly 13-mile stretch of lake running from South Lake Tahoe to Cave Rock. 

The foundation sends the robot out five days a week in the summer and first prioritized collecting plastics, ranging from picnic tables to bottles to plastic dinghies. The robot has pulled nearly a ton of plastic from the lake this year, Fontecchio says, but the foundation is now also prioritizing batteries. “If there’s anything with a lithium-ion battery, we pull it out. We don’t wait for payment or insurance to go through,” he says. “We have to get the batteries out right away, as the slow leak can start immediately.” He says that before they were able to pull the 16,000-pound electric boat from the water, they had to test the pH of the water above it to make sure it was safe to touch. It was only a few feet below the surface, and as they stepped into the boat, “our feet were burning,” Fontecchio says. “It was super toxic.” 

The foundation has pulled items large and small from the lake. During one dive, for example, he found three GoPro cameras. “They all were still attached to the sticks,” he says, “but none had the wrist strap. So I guess it’s worth paying an extra buck for the strap.” Fontecchio has also pulled at least five drones from the lake, which he says are easy to find, as most broadcast their last location. 

He suspects he found a glass-bottomed boat once owned by William Bliss (son of famed Tahoe developer D.L. Bliss), who built it with the intention of taking tourists to view the SS Tahoe, scuttled in 1940. Fontecchio thinks that when the SS Tahoe landed in water far deeper than it was supposed to, Bliss likely scuttled the boat meant to take tourists to visit it, too. He’s also on the hunt for an airplane that crashed into Rubicon Bay in July. 

As Tahoe’s climate means scouring the lake for hazardous wastes is a summer-only pursuit, the foundation will be moving to lower elevations for winter work. It plans on cleaning Lake Oroville and Folsom Lake over the winter and using AI technology to improve the robot’s underwater recognition skills. “We’re feeding it a database of pictures of bottles,” Fontecchio says, “so it can identify the neck and learn to pick them up faster.” 

Clean Up the Lake is also working on creating autonomous bots that various marinas and environmental organizations can deploy without having a computer expert on-site, allowing trained foundation staff to control the robots’ underwater movements from afar. The foundation plans to return to Tahoe starting in April 2024 and to continue to clean areas divers aren’t able to reach. Fontecchio imagines he’ll continue to find a mix of plastics and cans, hats, empty containers and other items that have fallen off boats. 

“We’ll be looking for plastic, batteries, bottles, that kind of stuff,” he says. “Lost sunglasses. I’ll take whatever I can get if it’s crappy.”