Established in 1998, the Anaconda Regional Water, Waste & Soils (ARWWS) Operable Unit (OU) is the largest and most diverse Operable Unit in the Anaconda Smelter NPL site. As a result, the OU was separated into fifteen Remedial Design Units (RDUs) based upon factors such as location, source and type of contamination, and remedial needs. Click here for more information about the ARWWS OU.

RDU 11 – Cashman Concentrates included two separate stockpile locations: Smelter Hill Concentrates, located south of the East Anaconda Rail Yards; and the Skykomish Concentrates, located at the Cashman Mill near Skykomish, Washington. The concentrates stored in these stockpiles were created from Berkeley Pit ores using a flotation process at the Anaconda Company Weed Concentrator in Butte, Montana. The resulting concentrates contain economically recoverable amounts of precious and base metals. Approximately 10% of the content of these concentrates is copper. Additional contents include lead, zinc, cadmium, silver, gold and arsenic. Concentrates were originally transported to the Anaconda Smelter Hill site and stored in holding pits. The Smelter Hill facility housed approximately 18,000 – 20,000 tons of materials

As a result of their economic value, the concentrates of RDU 11 were deemed a product rather than a waste by the EPA for a term of five years from the date of issuance of the Anaconda Regional Water, Waste & Soils (ARWW&S) Operable Unit (OU) Record of Decision (ROD), which was signed in September of 1998. In 2003, five years later, these materials were considered waste and subject to remedial action as is written in the ARWW&S OU 1998 ROD as well as below. Remedial action taken during the five year period that these concentrates were considered a product rather than a waste included minimizing erosion and further release of contaminants into the environment, establishing stormwater Best Management Practices (BMPs), as well as installing fencing to prevent human/wildlife exposure.

In the autumn of 2003, prior to the demolition of the Smelter Hill facilities, the concentrates – now considered waste rather than product – were transported to the two stockpile locations. The majority of materials, 16,000 – 18,000 tons, were relocated to the East Anaconda Yards, while the remaining 2,000 tons of materials were shipped to Skykomish, Washington to be processed so that precious and base metals could be recovered. This processing, however, did not occur. The Skykomish concentrates were eventually returned to Anaconda, Montana via railroad and later hauled to Montana Resources (MR) in Butte, Montana for processing and metal recovery. Materials excavated from the Anaconda Smelter Hill site that had little economic value were consolidated and disposed of at a waste treatment, storage and disposal facility in Oregon.

Remedial action within RDU 11 – Cashman Concentrate also included the removal and disposal of contaminated soils beneath the original stockpile on Smelter Hill. Impacted soils were removed to a depth of six inches and capped. Excavated soils were consolidated in the Opportunity Ponds (see RDU 8). All required remedial action for RDU 11 has been completed.

Visit the Superfund Library, located on the Arrowhead Foundation’s website, to review documents and research regarding the Anaconda Smelter NPL site. Additional information can also be found on the EPA’s website.