California Gulch covers about 18 square miles in Lake County, Colorado, including the city of Leadville and 11 miles of the Arkansas River. Historic mining left metals throughout the area, affecting soil, groundwater, surface water, sediment, and various waste materials. The site was placed on the National Priorities List in September 1983, and active cleanup work began in September 1988. It is one of the more advanced Superfund sites in the country in terms of cleanup progress.
The main contaminants are arsenic, cadmium, copper, lead, zinc, manganese, sulfate, and iron. These show up across multiple parts of the site. Arsenic appears in soil, surface water, groundwater, and sediment. Lead is found in residential soils, groundwater, surface water, and waste materials. Zinc and cadmium contamination extends across several operable units, especially in Oregon Gulch and Upper California Gulch.
Cleanup has addressed more than 350,000 cubic yards of contaminated soil, sediments, and mine wastes since 1995. Work has included building drainage controls to stop acid mine runoff, capping and consolidating waste piles, cleaning up residential properties, and running two water treatment plants that together process nearly 2 million gallons of surface and groundwater daily. The site is organized into 12 operable units. Nine have been partially deleted from the National Priorities List after meeting cleanup goals. Operable Unit 6, covering Stray Horse Gulch, is in active remediation and expected to finish by 2032. The Arkansas River Floodplain and site-wide water quality units remain in operation and maintenance. Human exposure is under control, and groundwater migration is stabilized with no unacceptable discharge to surface water. The most recent five-year review was completed in September 2022.
Beyond cleanup, the site has seen significant redevelopment. More than 2,300 acres opened for public recreation in 1998. The Mineral Belt Trail, a 5-mile path along the Arkansas River, opened in 2000. A sports complex built on a former zinc smelter includes a soccer field and a skate park. In 2014, part of the site earned Gold Medal Trout Waters designation, reflecting improved water quality. As of December 2024, 176 businesses on-site employ over 1,100 people and generate roughly $86.9 million in annual sales.
Community members with health concerns, especially parents of young children, should know that the EPA recommends annual blood-lead testing for children under 8, particularly those whose yard soil was not replaced during cleanup. Lake County offers free blood-lead testing at 719-486-8181. For site questions, contact the EPA's Community Involvement Coordinator. The Remedial Project Managers can also be contacted through the EPA.
