State Superfund Program| Joslyn Street Tailing Facility | Helena, Montana| Public Notice

July 02 2026

The Montana Department of Environmental Quality (DEQ) has published an Explanation of Significant Differences (ESD) document for the Joslyn Street Tailing (JST) State Superfund Facility. The purpose of the ESD is to identify a change from the Record of Decision (ROD) that DEQ proposes to integrate into the JST Facility cleanup plan. The ESD verifies that this change to the cleanup plan is protective of public health, safety, and welfare and the environmental and complies with environmental laws.

Background:

On November 12, 2019, DEQ selected the final cleanup remedy for the JST Facility with the publication of the ROD. The selected remedy included soil excavation and off-site disposal at a licensed landfill, monitoring natural attenuation for groundwater, long-term monitoring, and institutional controls (ICs). BNSF Railway (BNSF), the lead liable person, has performed all excavation and disposal work required in the ROD except on BNSF properties where the excavations were either constrained by digging into the BNSF rail line or potentially damaging the on-site repository. To address these areas, DEQ is outlining the use of a remedial alternative detailed in the ROD: a low permeability clay cap with a cover system within the ESD.

The low permeability clay cap with a cover system will be composed of two feet of soil that includes: a geotextile material, low permeability clay layer, backfilled soil material, and a vegetative cover. This system will be placed over, and around, the remaining areas where site specific cleanup levels (SSCLs) are exceeded. This remedy modification will be combined with engineering and institutional controls, i.e. fencing and deed restrictions, to ensure the low permeability clay cap and cover system is not disturbed or compromised. Once completed, this remedy will prevent direct contact exposure to soils that exceed SSCLs and limit infiltration through the soils, thus, limiting leaching of soil contamination to groundwater.

Next Steps:

With the finalization of the ESD, BNSF will develop a work plan to implement this remedy modification to the specific areas where construction constraints were encountered. DEQ anticipates these actions to occur in 2026 or early 2027. There are also areas of the Facility that still require backfilling. That work is anticipated to occur in 2026. BNSF is required to control weeds and revegetate all areas where excavations have occurred and backfill placed. Ongoing monitoring activities, including groundwater monitoring and vegetation surveys will continue to ensure the implemented remedies are successful and metals concentrations in groundwater decrease.

For More Information:

If you have any questions, please feel free to reach out to the DEQ State Superfund Project Officer for the JST Facility, Robert Roll: 406-444-6438, RRoll@mt.gov.

Associated Materials:

Accommodation statement

The department will make reasonable accommodations for persons with disabilities who wish to participate in this public participation process or need an alternative accessible format of this notice. If you require an accommodation, contact the department no later than 5:00 P.M. on August 7, 2026, to advise us of the nature of the accommodation that you need. Please contact the Department of Environmental Quality at P.O. Box 200901, Helena, Montana 59620-0901; phone (406) 444-6438; or e-mail RRoll@mt.gov.

Tags: Cleanup and Public Notice