The Salt Chuck Mine is an inactive former gold, silver, copper, and palladium mine on Prince of Wales Island in the Tongass National Forest at the northern end of Kasaan Bay in southeast Alaska. Elevated amounts of heavy metals from mine tailings exist in the uplands and sediments in the head of the Bay. These heavy metals may affect shellfish in areas that could be harvested by the local community. At the request of the state of Alaska, EPA added the Salt Chuck Mine to the Superfund National Priorities List in March 2010. The listing makes the site eligible to receive these federal funds for long-term cleanup of the marine part of the site. The USDA Forest Service has supplied funding for long-term cleanup of the upland part of the site.
In 2011, EPA collected many samples of mine tailings, surface water, sediments and clam tissue at the Salt Chuck Mine intertidal area. We compared our samples to EPA’s "Screening Criteria" numbers to tell us if we need to investigate more in this area. The screening criteria numbers do not necessarily mean that there is a toxic situation. We compare these numbers to our lab samples, which are usually at least 10 times lower than a toxic level, to make sure we do not miss a toxic source that could hurt people or the environment.
Out of 57 samples of sediment and tailings, half were above the screening criteria for copper and two were above the criteria for arsenic. As we expected based on historical samples, samples collected from tailings near the mill area have the highest levels of metals. We found silver and mercury in only two of the 51 samples near the mill area. All of the 31 clam tissue samples contained arsenic above screening criteria, including the "comparison samples" at Gosti Island. Only four samples were higher than the screening criteria for copper, from soft shell clams collected closest to the mill area.
EPA is conducting a Remedial Investigation to look more closely at the intertidal and upland areas to evaluate potential risk to people’s health and the environment. In 2012 and 2013, EPA collected more samples of mine tailings, soil, groundwater, upland plants, surface water, marine sediments, pore water in marine sediments, intertidal plants, and clam and crab tissue from the intertidal and upland areas of the site. A Remedial Investigation (RI) is a detailed study to find the nature and extent of contamination and the possible threats to the environment and people. Results of the RI are used to conduct a Feasibility Study (FS) to identify and evaluate options for cleanup. EPA, as the lead agency, will study the marine and upland areas with support from the USDA Forest Service, Organized Village of Kasaan, and the state of Alaska.
On May 7 and 8, 2013, EPA held town meetings in Thorne Bay and Kasaan to describe results of the site investigations that have been completed to date.