The Flue Dust Operable Unit (OU) was the second remedial action to be taken in the Anaconda Smelter NPL site by Atlantic Richfield Company. A by-product of the smelting process, flue dust is the finely divided metal or metallic compounds that escape with the flue gases of a smelter or metallurgical furnace. Flue dust contains high levels of metals such as copper, arsenic, cadmium, and lead.

Until 1976, flue dust was generated from reverberatory furnaces, lower temperature processing furnaces used for metallic ores, and reprocessed on-site to recover arsenic. Ore processing operations changed in 1976, where after flue dust was generated from an electric furnace, collected in a bag house, pelletized, and limed (treated with lime to reduce acidity) to produce scrubber sludge.

Remediation of the Flue Dust OU took place between 1992 and 1994. Flue dust materials were treated using on-site cement or silicate based stabilization and disposed of in an on-site engineered repository. Over 648,000 cubic yards of flue dust were excavated, treated, and storaged. Long-term monitoring plans and institutional controls were established to prevent human and wildlife exposure to the treated flue dust. Additionally, storm water controls were created to protect all lands affected by the flue dust.

Since completion of remedial action in 1996, the repository continues to be monitored with active maintenance (leachate collection and disposal, vegetation repair, and ground water monitoring). Site access is controlled through fencing, gates, and security patrol. Future actions include the continued monitoring of the repository under the Smelter Hill Facility RDU (RDU 14) of the Anaconda Regional Water, Waste & Soils (ARWW&S) Operable Unit.

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.