RDU 13 – Old Works

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 13 – Old Works is located northeast of Anaconda in the area previously occupied by the Upper and Lower Works smelting operations. Encompassing 2.2 square miles, RDU 13 is near the Old Works golf course and Arbiter Plant. Portions of RDU 13 exist within the Old Works Waste Management Area (WMA). The Old Works WMA was defined in the 1998 Anaconda Regional Waters, Wastes & Soils (ARWWS) OU Record of Decision (ROD). The Waste Management Area includes floodplain wastes, heap roast slag, the Red Sands portion included in RDU 13, and the Old Works High Arsenic Area. The primary contaminants of concern (COCs) in the Old Works WMA are cadmium, copper, zinc, and arsenic. The WMA encompasses a total of 2.4 square miles.

In addition to RDU 13, remedial concerns within this region are also addressed in the Old Works/East Anaconda Development Area (OW/EADA) Operable Unit. Final remedial action for contaminated soils and waste materials are addressed as part of the OW/EADA Operable Unit as illustrated in the 1994 OW/EADA OU Record of Decision (ROD). Final groundwater and surface water remedial action was deferred from the OW/EADA OU to RDU 13 – Old Works of the ARWWS OU.

RDU 13 was divided into six subareas based on waste types and historical smelting operations. These subareas include:

Subarea 1, encompassing approximately 160 acres, contains historical and culturally significant structures of the Upper and Lower Works. Some of these historical features were left in place, while all other waste sources were capped and structures demolished. Structures that were demolished include concentrators, boiler houses, “slum” houses, flues, among others. Demolition led to the creation of eight waste piles within subareas 1 and 2, which were later graded and capped.

Subarea 2 spans 235 acres within the Warm Springs Creek floodplain. Waste materials, both from smelting operations and demolition, were the primary remedial concern in this subarea. Waste materials included heap roast slap, waste piles (demolition), and floodplain wastes. These materials were graded and capped.

Subarea 3 includes approximately 140 acres containing residential areas (Teresa Ann Terrace and Cedar Park Homes), commercial buildings (Anaconda Industrial Park), the southern portion of the Warm Springs Creek floodplain, and the Charlotte Yeoman Complex (baseball/softball). Remedial action within Subarea 3 addressed floodplain wastes in the northern portion of the subarea.

Subarea 4 is the largest of the six subareas, encompassing 430 acres. This subarea contains the Red Sands, Arbiter Plant, and Anaconda Wastewater Treatment Plant. The Arbiter Plant tailings ponds, bunker, and Old Works tailing ponds were previously included in this subarea; however, these were removed during the Accelerated Removals Expedited Response Actions that took place between 1992 and 1993.

Subarea 5 is adjacent to the eastern boundary of Anaconda and the northern boundary of the Smelter Hill Facilities Area (RDU 14). Historically, this area served as the main entrance to Smelter Hill. This subarea is part of the Smelter Hill WMA and, therefore, remedial action after 1998 within this subarea is not addressed in RDU 13. Subarea 5 contains the East Anaconda Yards and a public park, Benny Goodman Park. The East Anaconda Yards contained Washoe Works acid and brick plants, both constructed in 1910, as well as the Bradley Ponds flue debris material. The brick plants produced both building bricks and high-grade silica firebricks used in the reververatory furnaces. The acid plant produced sulfuric acid used in the flotation and leaching processes, and the treatment of phosphate rock at the phosphate plant. Adjacent to the black slag pile, the Bradley Ponds were used for the disposal of scrubber sludge and flue debris generated at the smelter. In 1970, demolition activities began in the East Yards and were completed in the 1980’s. Much of the subarea was capped with 1.5 feet of borrow materials and vegetation. Remedial action associated with the Bradley Ponds was completed in 1994 under the Flue Dust OU. Wastes from the Bradley Ponds were removed, Stabilized, and placed in the Flue Dust Repository on Smelter Hill. This subarea is part of the Smelter Hill WMA and is not included in the RDU 13.

Subarea 6 contains the Drag Strip, which spans 268 acres. Remedial action in this subarea took place as part of OW/EAD OU.

Remedial goals for RDU 13 – Old Works were to return useable ground waters to beneficial use where practicable. When restoration of ground water was not practicable, remedial action was taken to prevent transfer of contamination to underground aquifers and storm water aquifers. Groundwater sampling determined elevated levels of cadmium, copper, zinc, and arsenic within RDU 13 – Old Works. These samples have been taken periodically from April of 1985 to the present. There are approximately forty wells within RDU 13; however, not all of these wells are currently monitored. It has been determined that these elevated concentrations in the groundwater are a result of the infiltration of precipitation through waste materials prior to remedial action. The implementation of remedial actions within RDU 13 – Old Works has resulted in a minimizing of further contamination of groundwater, as evidenced by collected samples.

Visit the Superfund Library, located on the Arrowhead Foundation’s website, to review documents and research regarding the Anaconda Smelter NPL site. The 2010 Final Design Report (available online) provides further information regarding the remedial concerns and action for RDU 13 – Old Works. Additional information can also be found on the EPA’s website.