St. Maries Creosote

Overview

The St. Maries Creosote site covers 13 acres along the south bank of the St. Joe River in St. Maries, Idaho, plus 3 acres of river sediments. From 1939 to 1964, the site was used to treat logs and poles with creosote, a wood preservative. That work left behind widespread contamination in soil, groundwater, riverbank soils, and river sediments. The site was proposed to the National Priorities List (NPL) on December 1, 2000, and cleanup is still active.

The EPA (U.S. Environmental Protection Agency) has identified 41 contaminants of concern at the site. These include polycyclic aromatic hydrocarbons (PAHs), a family of chemicals found in creosote, such as benzene, naphthalene, pyrene, and benzo[a]pyrene. Other contaminants include toluene, xylene, ethylbenzene, and various phenol compounds. Soil contains 26 of these contaminants, groundwater contains 37, and sediment contains 19.

Cleanup has moved through several phases. A removal action in 1999 replaced about 200 tons of contaminated soil and debris. A full remedial investigation ran from 2001 to 2007, leading to a cleanup plan finalized in a Record of Decision issued July 20, 2007. Major construction took place from 2014 to 2017 and included digging out the top 10 feet of contaminated soil, injecting grout to stabilize deeper soil down to 60 feet, dredging river sediments, and using onsite thermal desorption to destroy contamination. Upland soil cleanup is now complete and inspected quarterly. Groundwater is monitored quarterly and generally meets surface water screening criteria, though more data is still needed to confirm it reaches final cleanup levels. Groundwater at the site is not used for drinking water, and a restriction is in place to keep it that way.

Contaminated sediment remains in the St. Joe River, and the EPA is still developing a plan to address it. The most recent Five-Year Review, completed July 25, 2024, found that human exposure from soil contamination is under control but identified risk to benthic invertebrates, small organisms living in the river bottom. The EPA is also finalizing institutional controls for the upland area where some contamination was left in place. The riverine portion of the site serves as critical habitat for bull trout, and the upland portion remains vacant.

Community members can review the Five-Year Review report, which is publicly available. Questions can be directed to the EPA Remedial Project Manager. The Community Involvement Coordinators are also available.