EZA_6928East Helena environmental cleanup work completed by Montana Environmental Trust Group (METG) has been performed under EPA’s Resource Conservation and Recovery Act (RCRA) Corrective Action Program.

Background
In 1998, EPA issued a Consent Decree to ASARCO to transfer responsibility for ongoing remedial activities at the then-operating East Helena Smelter Facility (Facility) from its Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA, also known as Superfund) program to its RCRA Corrective Action program.

In 2009, METG was appointed trustee for the Montana Environmental Custodial Trust as part of ASARCO’S bankruptcy settlement. In 2012, a modification to the 1998 Consent Decree transferred responsibility for completing the RCRA Corrective Action cleanup to METG.

Initial METG Studies
Building on the Phase I RCRA Facility Investigation (RFI) and other corrective actions performed by ASARCO, METG performed a Phase II RFI to complete characterization of the Facility and surrounding, former ASARCO properties. METG also conducted an initial assessment of potential human health and ecological risk posed by Facility conditions.

These two evaluations confirmed metals from 100+ years of smelter operation were present in soil and groundwater at concentrations exceeding EPA screening levels established to protect human health and the environment.

The Cleanup & The Results

  • Significant Cleanup Completed under RCRA

    METG implemented several Interim Measures to accelerate cleanup timeframes. The Interim Measures were approved as final Corrective Measures by EPA in their July 2020 Statement of Basis. Key actions included:

    – Demolishing 60+ smelter-related buildings
    – Removing soils that were an ongoing source of contamination to groundwater
    – Consolidating ±1 million cubic yards of contaminated soil under a 62-acre evapotranspiration (ET) cover over the former smelter plant area
    – Draining two manmade lakes used for smelter process water
    – Eliminated the failing smelter dam and moving more than a mile of Prickly Pear Creek away from the slag pile into a more naturally flowing channel
    – Creating 50 acres of wetlands and expanding floodplain to 100 acres along Prickly Pear Creek
    – Removing 144,000+ tons of selenium-contaminated slag for recycling

  • Results to Date

    The Corrective Measures completed so far have reduced groundwater contamination and controlled risks to people and the environment.

    – The ET cover prevents direct exposure to contaminated soils and contaminant leaching into groundwater. Stormwater is stored in–or shed clean from–the ET cover.
    – A groundwater selenium plume migrating off-site has receded three-quarters of a mile.
    – Arsenic and selenium concentrations in groundwater have dropped by more than 50%.
    – Prickly Pear Creek now meanders naturally through remediated floodplain, habitat, and wetlands.
    – Removing the smelter dam eliminated a major barrier to fish migration between the Prickly Pear Creek headwaters and Lake Helena.

  • Ongoing Corrective Actions

    – The slag pile will be regraded and a vegetative cover will be placed over the slag to reduce the amount of precipitation infiltrating to groundwater
    – Groundwater will continue to be monitored to demonstrate conditions remain protective and contamination areas are not increasing

    Please see related fact sheets for more information about these IMs.

    EPA Citizen Guide to ET Covers
    November 2015 Fact Sheet

Since 2016, the groundwater selenium plume has receded three quarters of a mile.