The East Helena landscape is dominated by the ±16-million-ton pile of slag that occupies almost half of the former ASARCO smelter property. Slag is the stony, black byproduct of smelting, which occurred for more than a century at the East Helena Site. The Montana Environmental Custodial Trust (Custodial Trust) has been pursuing options for repurposing slag and continually evaluates how slag contributes to groundwater contamination.

The slag pile consists of fumed and unfumed slag. Unfumed slag has value for secondary metals recovery, including zinc. In late 2020, METG, as Trustee of the Custodial Trust, entered into an agreement with international metals trader Metallica Commodities Corp. Metallica planned to crush and transport 2 million tons of unfumed slag over 5 years to a purchaser in South Korea.

Montana Rail Link began constructing a new rail siding in late 2020, and the slag repurposing project began in 2021. Metallica transported crushed slag by rail to Vancouver, B.C., and then by ship to Korea Zinc, one of the world’s largest zinc smelters.

So far, Metallica has transported almost 145,000 tons of slag. Still, supply chain and transshipping issues caused Korea Zinc to terminate its contract with Metallica in June 2024, pausing the project. To resume slag removal, Metallica or METG need to find a new slag purchaser and resolve transshipping issues.

In December 2024, METG distributed a community survey to provide updates and to get resident input on the future of the slag recycling and capping. See survey responses here.

Unfumed slag in the upper part of the pile currently contributes about 75 percent of the selenium loading to groundwater at the Site. EPA has approved the final remedial action at the former smelter, which entails grading the remaining slag pile and capping it with a vegetated soil cover. This is the final remedy for groundwater, as proposed in the Corrective Measures Study (CMS).

This aerial figure illustrates parts of the slag removal process at the East Helena Site.

Removing the “upper lift” of the slag pile will eliminate the last major source of selenium and will ultimately reduce the pile’s height by over 50 percent. The slag recycling project will result in cost savings on regrading and capping. Sale proceeds will go into the East Helena cleanup account for future cleanup work at the Site.

For more information on the slag project, see our update/community survey.
See our 2021 fact sheet here.

This page was updated in April 2025.