Libby Ground Water Contamination

Overview

A lumber and plywood mill operated in Libby, Montana from 1946 to 1969, using creosote, pentachlorophenol (PCP), and other chemicals to treat wood. Spills and poor disposal practices left behind contaminated soil and groundwater. EPA added the site to the National Priorities List (NPL) in September 1983. The site is now managed in two operable units (OUs), each targeting a different part of the problem.

Contaminants affect both soil and groundwater. Groundwater contains volatile organic compounds including benzene, toluene, xylene, and tetrachloroethene, along with heavy metals such as arsenic, lead, chromium, and zinc, and polycyclic aromatic hydrocarbons (PAHs) including naphthalene and pyrene. PCP and other chlorinated compounds are also present. Soil holds PAHs, dioxins, dibenzofurans, and heavy metals. Benzene is a known human carcinogen. Dioxins can cause cancer, reproductive and developmental problems, immune system damage, and hormone interference. People can be exposed by eating, drinking, or touching contaminated soil or groundwater.

OU1 addressed the immediate risk of people drinking contaminated well water. An interim remedy completed in November 1986 paid residents to switch to municipal water and established a city ordinance banning new drinking or irrigation wells within city limits. OU2 covers broader soil and groundwater cleanup. Construction ran from October 1989 to September 1993 and included soil excavation, treatment, and groundwater extraction. For the deeper lower aquifer, EPA determined in 1993 that full cleanup was technically not feasible and switched to institutional controls and monitoring instead. International Paper, the current responsible party, completed a focused feasibility study in 2018 for the upper aquifer. EPA finalized an amended cleanup decision in April 2020, selecting enhanced in-situ bioremediation (treating contamination in place using microbes), monitored natural attenuation, updated cleanup standards, and continued institutional controls. All elements of the upper aquifer remedy are expected to be in place by fall 2025.

Human exposure is currently considered under control, according to EPA assessments. A city ordinance prevents new well drilling, and a deed restriction on the former International Paper property limits activities that could disturb contaminated areas or active treatment zones. Operation, maintenance, and groundwater monitoring are ongoing. A combined remedial investigation and feasibility study for OU2 is estimated to be completed between September and November 2026. The most recent five-year review was completed in July 2025. The site has not yet been deleted from the NPL.

Redevelopment is active at the Kootenai Business Park portion of the site through the EPA's Superfund Redevelopment Initiative. Community members can review site records at the Lincoln County Library in Libby or the EPA Superfund Records Center in Helena.