The Iron Mountain Superfund site is a designated area in California that was contaminated due to mining activities. It primarily involves the remnants of mining operations that released hazardous substances into the environment, affecting soil and water quality. In 1983, the site was added to the Superfund program, which aims to clean up polluted locations in the United States. The Environmental Protection Agency (EPA) oversees the cleanup efforts, working to restore the area and protect public health and the environment from the harmful effects of the contaminants.