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.
Northwest of Mill Creek Road, RDU 3 – Smelter Hill Uplands addresses the area surrounding the Anaconda Reduction Works facilities located southeast of the city of Anaconda. There is mixed land uses within the 3,354 acres that comprise RDU 3, including residential and open space. Due to its size, RDU 3 was divided into three work areas based primarily on land ownership.
Given its close proximity to the Washoe Smelter and the Anaconda Reduction Works facilities, the soils and waters of RDU 3 were more significantly impacted by smelter fallout than other areas within the Anaconda Smelter NPL site. It was determined that remediating surface soils to comply with state and national standards was technically impracticable within specific areas of RDU 3 – Smelter Hill Uplands. Under the 2011 amendment to the Anaconda Regional Water, Waste & Soil (ARWWS) Operable Unit (OU) Record of Decision (ROD), the EPA incorporated these lands into the Smelter Hill High Arsenic Area (HAA), which allows for higher arsenic concentrations in surface soils as well as ground and surface waters. Atlantic Richfield Company and Anaconda-Deer Lodge County own the properties included in the Smelter Hill High Arsenic Area. Land use and development restrictions were instated to minimize human and wildlife exposure to contaminants of concern.
Development of remedial designs for RDU 3 – Smelter Hill Uplands was completed in 2013. These designs required the reduction of surface soil arsenic levels to current open space/recreation standards – where practicable – through the installation of protective vegetative covers. This process includes tilling with lime and soil amendments; leading to the ultimate establishment of a self-sustaining, diverse plant species. Approximately half of the total acreage within RDU 3 required remediation. Remedial action has been taken, but is still ongoing within RDU 3 – Smelter Hill Uplands.
RDU 3 – Smelter Hill Uplands is drained by four tributaries of Mill Creek including Lost Horse, Lapilli, Silver and Cobble Creeks. Therefore, surface soil contamination is transferred to surface water runoff. Remedial designs were developed to divert this contaminated runoff to the Opportunity Ponds Waste Management Area (WMA), thereby minimizing human exposure and contaminant transfer to adjacent soils/waters.
The remainder of runoff from RDU 3 drains into Mill Creek. Additionally, a watershed that drains to the City of Anaconda and Sheep Gulch is located in the western portion of RDU 3 – Smelter Hill Uplands. A Storm Water Runoff Control Plan for Best Management Practices (BMPs) was developed for these areas to minimize human and environment exposure to contaminants. In addition to the Storm Water Runoff Control Plan, plans for long-term monitoring and weed spraying have been developed for all of RDU 3 – Smelter Hill Uplands. Additionally, plans to ensure the preservation of identified historic features within RDU 3 are included in remediation designs.
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.