NPL Partial Site Deletion Narrative

Idaho Pole Co.

Bozeman, Montana

On January 31, 2020, the EPA partially deleted the surface and unsaturated subsurface soils portion outside of the
4.5 acre Treated Soils Area of the Idaho Pole Co. site located in Bozeman, Gallatin County, Montana from the
National Priorities List (NPL). Any remaining contaminated soils, sediments and groundwater at the Idaho Pole
Company site as well as the 4.5 acres within the Treated Soils Area will remain on the NPL.

The Idaho Pole Co. site covers approximately 87 acres near the northern limits of Bozeman. The Idaho Pole
Company (IPC) was a wood treating facility that started operations in 1945 using creosote to preserve wood.
Initially, site operations consisted of immersion of the end of the poles into a butt vat of heated creosote solution.
In 1952, a full-length vat was installed and IPC switched to pentachlorophenol (PCP) for wood treatment until
operations ceased in 1997. The full-length vat was decommissioned in 1979. The bottom of the vat had corroded
and an unknown amount of wood treating fluid had leaked into the underlying soil and groundwater for an
unknown period of time. System operations also resulted in the occasional spilling of heated wood treating fluids
on nearby soils. The site was listed on the NPL on June 10, 1986. In the fall of 1997, IPC announced that it would
terminate all wood treatment operations.

The EPA issued a Record of Decision (ROD) in 1992 selecting a remedy for soil and groundwater at the site. This
remedy was based on the assumption that IPC would continue wood treatment operations. Explanations of
Significant Differences (ESDs) were issued in 1996 and 1998 to document changes to the selected remedy. The
selected soil remedy was implemented between July 1995 and October 2002. The remedy included construction
of a lined land treatment unit (LTU) and a retention pond to collect any runoff from the LTU; excavation of soils in
the accessible areas of the site, as well as de-rocking and transportation of excavated soils in the LTU. The soils
were treated in the LTU until ROD performance standards for PCPs and polynuclear aromatic hydrocarbons (PAHs)
were met. Treated soils were then placed in the excavated areas on-site and covered with clean soil.
Approximately 14,000 cubic yards (cy) of contaminated soil were placed in the LTU in 1995. The soils were
excavated from six areas at the site and were treated in the LTU by tilling, irrigation and nutrient addition with a
retention pond collecting any excess water, which was subsequently treated in the groundwater recovery system.
In 1999, an additional 5,000 cy of impacted soils were loaded on the LTU for treatment. Once treatment was
complete, the LTU was decommissioned and closed in accordance with an EPA-approved closure plan. The soil
remedy is protective of human health and the environment because no exposure pathways exist. The treated soils
were placed above historic groundwater levels; have clean soil on top as cover; and institutional controls are in
place to restrict land use in the 4.5 acre Treated Soils Area. The institutional controls restrict new construction
and excavation on the 4.5 acre area where treated soils were placed. The use of groundwater is also restricted on
the IPC site and nearby residential properties to prevent consumption of groundwater and protect the
groundwater remedy.

The EPA and the state of Montana, through the Montana Department of Environmental Quality have determined
that all appropriate response actions under CERCLA, other than maintenance of institutional controls and five-
year reviews, have been completed for the soil component of the remedy at the Idaho Pole Company site.
Therefore, the EPA is deleting the surface and unsaturated subsurface soils portion outside of the 4.5 acre Treated
Soils Area of the Idaho Pole Co. site from the NPL. The remaining contaminated saturated soils, sediments and
groundwater at the site as well as the 4.5 acres within the Treated Soils Area will remain on the NPL.

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