Cleaning Up an Old Dump Site at El Capitan in Yosemite

The Merced Wild and Scenic River, with El Capitan in view, Yosemite National Park. NPS photo.

Some of the country's best-loved national parks hide old dump sites left by past human use. In Yosemite National Park, the National Park Service (NPS) has begun cleaning up a waste disposal area at El Capitan, paid for by the Inflation Reduction Act (IRA). The goal is to restore this part of the park to its original condition.

The cleanup

IRA funds let the NPS use its authority under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) to investigate the site and act on it:

• excavating and safely disposing of solid waste;
• testing and monitoring hazardous substances in the soil;
• treating groundwater to keep contamination from leaching into the Merced River;
• restoring the site's original watershed features and replanting vegetation.

The NPS inventory lists more than 500 contaminated and potentially contaminated sites of many types and sizes across the national park system.

How the waste got there

Yosemite Valley began drawing visitors in the 1850s. Roads into the valley brought more visitors and development in the late 1800s, and by the early 1900s there were hotels and hotel-camps, and the U.S. Army had a camp near Yosemite Creek. Records are sparse, but these establishments appear to have dumped waste in the El Capitan area from about 1905 until the 1930s. As Stephen Mitchell, former deputy lead of the NPS Environmental Compliance and Cleanup Division, put it: "Materials that came into the park that were not consumed were disposed of in the park. This was common practice for generations, until landfills were developed."

The site holds trash, glass, ceramics, automotive machinery and related waste, paint cans, 55-gallon oil drums and burned material, and hazardous metals have contaminated the soil. That threatens people and the environment, including an ancient Indian village site, groundwater and the river.

The river

The Merced River runs right beside the site. Its cliffs, waterfalls and meadows have inspired artists, photographers and writers such as Ansel Adams and John Muir for more than a century. As a designated Wild and Scenic River, it is left largely undeveloped, so its course shifts over time. "At times, the river would be extremely wild – and erode or meander into the waste disposal area, releasing both solid wastes and hazardous substances downstream," Mitchell said. The river isn't a drinking water source at or near the park, but pollution of drinking water sources farther downstream couldn't be ruled out.

The Merced River in Yosemite Valley. NPS photo.

Plants and animals at risk

Near the site grow California black oaks, culturally significant to Native Miwok and Paiute people and whose acorns feed Yosemite's animals, and live spotted bats and western mastiff bats, species of concern in California because of possible declines and vulnerability to habitat change.

Hazardous substances also move up the food chain through bioaccumulation: a worm takes up contaminants from the soil, a bird eats the worm and takes them in, and so on. "Wildlife that live in the site's terrestrial environment are most impacted," Mitchell said. "A national park isn't just about scenery — it is a living entity."

Progress

Writing in December 2024, the NPS reported that Mitchell estimated the project was nearly half done, with waste removal expected to be completed once work resumed in August 2025, after bird mating season. Crews are protecting the black oaks, keeping disturbance to a minimum, and working to keep visitors and staff safe. After the work ends, vegetation and groundwater will be monitored for three to five years to confirm the contamination is gone and plants and wildlife are thriving.

El Capitan rises more than 3,000 feet above Yosemite Valley. NPS photo / H. McClendon.

Sources

• National Park Service: "A Path to a Cleaner Yosemite National Park" (Inflation Reduction Act Powers CERCLA Cleanup Effort), by Anna Petr, December 2024.