Martin-Marietta Aluminum Co.

Overview

An aluminum smelter operated on this 305-acre site in The Dalles, Oregon, from 1958 to 1987. Improper waste disposal and treatment activities spread contamination across 28 areas of the property. EPA added the site to the National Priorities List in 1986 and selected a cleanup plan in 1988. The site has since been deleted from that list, and as of 2018 it achieved ready-for-anticipated-reuse status.

Eight contaminants of concern were identified at the site. Arsenic was found in sludge and soil. Cyanide and cyanide compounds contaminated leachate, groundwater, and solid waste. Fluoride turned up in groundwater, leachate, soil, solid waste, and sludge. Polycyclic aromatic hydrocarbons, or PAHs, were found in soil, leachate, sludge, and solid waste. Sodium contaminated solid waste, sludge, leachate, and groundwater. Sulfate appeared in leachate and groundwater. All of these contaminants are tied to Operable Unit 1, which covers site control activities.

Cleanup construction ran from 1989 to 1994. Workers excavated cathode waste, capped a 15-acre landfill holding about 200,000 cubic yards of waste, covered two sludge ponds, treated groundwater, and collected landfill leachate. Nearby water wells were abandoned, and groundwater users were connected to the City of The Dalles water supply system. In 2012, removal actions addressed toxic, asphyxiating, and explosive gas releases, and crews repaired fencing and signage around capped areas. The most recent five-year review, completed in May 2023, found the remedy protective in the short term. Human exposure is under control and contaminated groundwater migration has stabilized. To ensure long-term protection, EPA recommended adding deed restrictions on three parcels along River Road to limit use of the S Aquifer.

A remedial investigation for Operable Unit 1 is currently underway, with completion estimated between June and August 2028. A feasibility study and final remedial action for that unit are planned for the same general timeframe. The City and Port of The Dalles are exploring industrial or commercial redevelopment of the site, contingent on the ability to move or consolidate landfilled materials. As of December 2024, one business operating on the site employed 60 people and generated roughly $30.8 million in annual sales.

Community members with questions can contact the EPA Remedial Project Manager or the Community Involvement Coordinator.