Sunday, April 21, 2024

EPA wants to delete a portion of Libby Superfund site from Superfund list

by The Western News
| February 27, 2024 7:00 AM

The U.S. Environmental Protection Agency (EPA) and the Montana Department of Environmental Quality are seeking public to comment on a proposal to delete Operable Unit 5 (OU5) of the Libby Asbestos Superfund site from the National Priorities List. 

Comments will be accepted through March 18.

Operable Unit 5 includes the former Stimson Lumber property, now home of the 400-acre Kootenai Business Park and multiple businesses. 

The Libby Asbestos Superfund Site was added to the Environmental Protection Agency’s Superfund list in 2002 due to asbestos contamination that resulted from the vermiculite mine and associated facilities operated by W.R Grace from 1963 to 1990.

Gold miners discovered vermiculite in Libby in 1881. In the 1920s, the Zonolite Company formed and began mining the vermiculite. In 1963, W.R. Grace bought the Zonolite mining operations. The mine closed in 1990.

While in operation, the Libby mine may have produced 80 percent of the world's supply of vermiculite. Vermiculite has been used in building insulation and as a soil conditioner. Unfortunately, the vermiculite from the Libby mine was contaminated with a toxic and highly friable form of asbestos called tremolite-actinolite series asbestos, often called Libby Amphibole asbestos (LA). 

EPA’s investigation determined LA to be present in air (indoor and outdoor ambient), vermiculite insulation and bulk materials, indoor dust, soil, water, animal and fish tissue and various other media.

According to the EPA, Operable Unit 5 was cleaned up in 2016 and does not require additional cleanup as previously completed actions are considered protective of human health and the environment. Operable Unit 5 is co-located with the Libby Groundwater Superfund site where cleanup is ongoing and that site is not affected by the proposed OU5 partial deletion.  

A partial deletion is part of the Superfund process used to remove a section, or operable unit, of the site from the NPL when no additional remediation is expected. The area will continue to be subject to operation and maintenance activities, including regular reviews for protectiveness. 

The EPA, in consultation with the state Department of Environmental Quality, will continue to address contamination concerns at remaining Operable Units of the Libby Asbestos site, which includes the former mine site.  

The proposal to delete OU5 is available online at

Those interested may comment on the proposed partial deletion of OU5 using the following methods: 

- Online by following instructions for submitting comments at the link listed above;

- By email to: 

- By mail to: Dania Zinner, U.S. EPA, Region 8 (SEM-RB), 1595 Wynkoop Street, Denver, Colorado, 80202-1129 

For more information, visit the Libby Superfund site webpage at