OLEM/OSRTI

Washington, DC 20460

NATIONAL PRIORITIES LIST (NPL) 

***Proposed Site*** April 2016 

ARGONAUT MINE Jackson, California 

Amador County 

 Site Location:

The site is located within a residential area in the city of Jackson, Amador County, California. 

 Site History:

The Argonaut Mine was a historic hard rock gold mine that operated from the 1850s until 1942. The Argonaut Mining 

Company operated the mine and dissolved in 1948. At the stamp mills (known as the Mill Area), raw ore was processed 

and mercury was amalgamated to extract gold from the crushed ore. The mine tailings were transported and disposed of in a 

valley located approximately 1⁄2 mile south of the stamp mills (Tailings Area). The site includes impoundments, buildings, a 

mine shaft and headframe, earthen tailings dams, a 100-year old concrete dam (Eastwood Multiple Arch Dam), and an old 

cyanide plant.

 Site Contamination/Contaminants:

Soils in the Tailings Area and in residential properties adjacent to the Tailings Area are contaminated with arsenic, lead and 

mercury. Wetland sediments in the Tailings Area are also contaminated with arsenic and mercury. 

 Potential Impacts on Surrounding Community/Environment: 

Many residential properties have been built on top of or adjacent to the former mine processing areas. The Argonaut High 

School is located approximately 250 feet to the west of the Tailings Area and Jackson Junior High School is 550 feet to the

east of the Tailings Area. Residents and children are exposed to soil contaminated with high levels of arsenic, lead and 

mercury. There are wetlands located within the Tailings Area and intermittent wetlands within the Mill Area which flow 

into Jackson Creek. In addition, an engineering study of the Eastwood Multiple Arch Dam has shown that the dam is

structurally unstable. If there is a breach or dam failure, significant damage and possible injuries or loss of life could occur.

 Response Activities (to date):

In March 2015, the EPA removed approximately 1,872 cubic yards of highly contaminated soil from a vacant lot located at 

the corner of Argonaut Lane and Pioneer Street. The contaminated soil was transported to a five acre parcel within the 

Tailings Area where a repository was constructed, capped and hydro-seeded. In July 2015, the EPA removed approximately 

1,014 cubic yards of arsenic-contaminated soils from 11 residential properties near the Tailings Area, and from an 

embankment at the Jackson Junior High School’s athletic field. The embankment at the Jackson Junior High School was

capped and a fence was installed to protect the cap.

 Need for NPL Listing:

The state of California referred the site to the EPA in 2013 to assist with response actionsin the Tailings Area. None of the

former corporate owners or operators are financially viable and there are no viable successors. NPL listing will allow for a 

thorough investigation and cleanup of the site to protect the surrounding communities from exposure. Other federal and/or 

state programs were evaluated, but are not viable at this time. The EPA received a letter of support for placing this site on 

the NPL from the state of California.

[The description of the site (release) is based on information available at the time the site was evaluated with the HRS. The description may 

change as additional information is gathered on the sources and extent of contamination. See 56 FR 5600, February 11, 1991, or 

subsequent FR notices.] 

For more information about the hazardous substances identified in this narrative summary, including general information regarding the effects of exposure to these 

substances on human health, please see the Agency for Toxic Substances and Disease Registry (ATSDR) ToxFAQs. ATSDR ToxFAQs can be found on the Internet 

at http://www.atsdr.cdc.gov/toxfaqs/index.asp or by telephone at 1-888-42-ATSDR or 1-888-422-8737.