Salt Chuck Mine, Mill Area

Site Narrative

Description

The Salt Chuck Mine is an abandoned historic gold, silver, copper and palladium mine on the southeast side of Prince of Wales Island. The site is 4½ miles from Thorne Bay, and is accessible by road, or by water.

The mine and mill operated from 1905 to 1941, processing more than 326,000 tons of ore. The mine openings are about a half mile uphill from the mill area, which is on the northern shore of Salt Chuck Bay near the mouth of Lake Ellen Creek. The remnants of at least 25 of the mill's structures are on the site.

An extensive tailings deposit of an estimated 100,000 cubic yards is located mostly in the intertidal zone south of the mill, on state-owned tidelands. Additional tailings are located in the upland area, which is managed by the U.S. Forest Service. The tailings deposits on the whole site – in the intertidal zone and the upland area – cover 23 acres.

As with other abandoned historic mines, the sources of contamination at the mill area are a result of standard practices from an era before environmental regulations, when mines operated without today's permits and reclamation requirements.

The Alaska Department of Natural Resource's Prince of Wales Area Plan identifies the area around the site as “intensive public recreation use.” The Forest Service has public-use cabins and a campground in the area, and Salt Chuck Bay is used for subsistence clamming and crabbing. Lake Ellen Creek supports five species of anadromous fish.

The U.S. Bureau of Land Management first investigated the Salt Chuck Mine's mill from 1995 to 1998. Those investigations led to a more in-depth one conducted by the Forest Service from 2002 to 2007. The Forest Service's Engineering Evaluation/Cost Analysis, which it finalized in 2010, summarized the previous sampling results.

In 2007, the DEC, Alaska Department of Health and Social Services (DHSS) and U.S. Environmental Protection Agency (EPA) reviewed the Forest Service's draft Engineering Evaluation/Cost Analysis. All three reviewing agencies agreed that the site needed additional site characterization, that all the ways people and the environment might be exposed to contamination needed to be evaluated, and that there needed to be an assessment of those exposure risks. The three agencies agreed that the additional work would provide the basis for cleanup levels that would sufficiently protect multiple uses of the land in the future.

In the spring of 2009, DEC conducted an informal sounding of public opinion about resolving lingering contamination issues and the delayed cleanup progress by giving the site Superfund status through placement on the EPA's National Priorities List. In July 2009, DEC's Commissioner Larry Hartig sent a letter on behalf of Gov. Sarah Palin to the EPA saying the state did not object to the site being placed on the National Priorities List. The EPA held a public comment period on the proposed listing.

On March 2, 2010, the EPA announced it had added the Salt Chuck Mine site to its National Priorities List. The listing makes the site eligible to receive federal funds for long-term cleanup while the EPA seeks to recover costs from the responsible parties. Community involvement and tribal participation are also an important part of the EPA's Superfund cleanup process. Background information on the Salt Chuck Mine site and other documentation is available on EPA's website for the mine.

In 2011, the Forest Service used funding from the American Recovery and Reinvestment Act, along with additional funding, to conduct a non-time critical removal action on the uplands. The Forest Service built a short road to provide access to the site, removed building debris, drums and tanks, excavated roughly 5,400 cubic yards of petroleum-contaminated soil and metals-contaminated tailings, and disposed of the excavated material in a permitted landfill out of state. The EPA collected soil, sediment, water and biota samples at the site in 2011, 2012, and 2013.  Those data were used to develop a Remedial Investigation Report, which the EPA finalized in 2018 after extensive input from the other agencies and public comments.

Public Health and Environmental Concerns

The Forest Service’s 2011 removal action in the uplands removed a significant volume of the contamination in the uplands, however some contamination remains.

In the intertidal area, the metals that were found to exceed the lowest (most stringent) screening criteria were copper, cadmium, lead, silver and zinc. Of those, copper was the only metal to exceed the next level of screening criteria (slightly less stringent than the lowest screening criteria).

(Screening criteria or levels are risk-based levels that are used initially at a site before site-specific data is available; the levels are very conservative because there are so many unknowns about the site. Once that data is collected (such as in a risk assessment), the responsible party will propose cleanup levels that use the site-specific information. DEC reviews and approves the cleanup levels – the levels that must be achieved to protect human health and the environment.)

Petroleum hydrocarbons were also found in the tailings near the former mill and are likely from historical releases. Tailings were collected from multiple locations within Salt Chuck Bay for bioassay analyses – where the laboratory monitors if polychaetes and bivalves (marine worms, and mollusks, such as clams and cockles) survive in that sediment. The tailings closest to the mill have the greatest toxicity; the polychaetes and bivalves from that area did not survive in the laboratory tests.

In general, the contaminant levels decreased as the sample locations extended into Salt Chuck Bay. The surface water of the bay showed levels of copper, cobalt, manganese and iron that are greater than the screening levels.

Butter clams, little neck clams, softshell clams and cockles were collected and the tissue was analyzed for metals. Elevated concentrations of arsenic, copper, and vanadium were found in the tissue.

Current Status

In the summers of 2021 and 2022, the EPA conducted additional sampling in the bay and conducted a treatability study. For the treatability study, a substance known as biochar was added to plots of sediment. Biochar is burnt remnants of organic material, similar to charcoal. It is good at absorbing heavy metals, and the test was intended to determine whether the amendment would reduce the toxicity of metals in the treated area of sediments. The results of this treatability study will be used in an upcoming Feasibility Study (FS) and Remedial Design process.

A FS is the next stage of the CERCLA remedial process, and EPA is beginning work on one in early 2023. This stage will begin to develop alternative remedies for the contamination, which the public will have a chance to comment on before one is selected. Remedies being considered include excavating contaminated sediments for disposal either out of state or at a purpose-built landfill nearby, capping the metals-contaminated sediments to limit environmental exposure, or amending the sediments with biochar or a similar material to reduce the effective toxicity. It is most likely that alternatives will be developed using a combination of these strategies, for example excavating the most hazardous sediments while using a biochar amendment in less contaminated areas. Once all the alternatives have been analyzed, a Record of Decision (ROD) will be issued and cleanup work will begin using the selected remedy.

Contacts

For more information about this site, contact:

Alaska Department of Environmental Conservation

• Nick Waldo, Project Manager
• nick.waldo@alaska.gov
• 907-465-5270

• Stephanie Buss, Program Manager
• stephanie.buss@alaska.gov
• 907-269-7545

U.S. Forest Service

• Linda Riddle, Alaska On-Scene Coordinator
• linda.riddle@usda.gov
• 907-586-9379

U.S. Environmental Protection Agency

• Madi Novak, Remedial Project Manager
• novak.elisabeth@epa.gov
• 503-351-4445

For more information about hazardous substances that are listed in this fact sheet and the effects of exposure to those substances on human health:

Agency for Toxic Substances and Disease Registry

• ATSDR is within the U.S. Department of Health and Human Services
• ATSDR ToxFAQs
• 888-42-ATSDR or 888-422-8737