Waste and Underground Tank Management Bureau

Burlington Northern & Santa Fe Railway (BNSF)
Former Tie Treating Plant
Paradise, Montana
(BNSF Paradise Site)


Site Location Map

Paradise, Montana

BNSF Paradise Surface Impoundment Prior to Cleanup
Surface Impoundment Prior to Cleanup


BNSF Surface Impoundment after Excavation of Sludge and Contaminated Soil
Surface Impoundment after Excavation
of Sludge and Contaminated Soil


BNSF Land Treatment Area
Land Treatment Area

Click on Photo to Enlarge


The BNSF Paradise Site is located on the northern bank of the Clark Fork River, approximately 2.7 miles downstream of the confluence with the Flathead River, approximately 0.75 miles downstream of the town of Paradise, Montana.  This site was used for creosote treatment of railroad ties from 1908 until 1982, when the plant was destroyed by fire.  BNSF is still the owner of the majority of the property.

During operation of the tie treating plant, railroad ties were treated with creosote at elevated pressures and temperatures in the treatment building.  Wastewater containing creosote was discharged through a buried pipe into a surface impoundment located southwest of the former plant site.  The impoundment is a former channel of the Clark Fork River and was used during plant operations as a sedimentation basin for recovery and reuse of creosote.

Freshly treated ties were transported to the drip track area west of the treatment building where they were allowed to drip onto the underlying track and soils.  The depress track, located south of the drip track, was used to remove the treated ties.

Creosote is produced from coal tar: polycyclic aromatic hydrocarbons (PAHs) are semi-volatile organic compounds that generally account for 85 percent (by weight) of the chemical constituents of creosote.  Creosote is denser than water and when it is released to groundwater is typically collects at the bottom of aquifers.



Under the Montana Hazardous Waste Act (MHWA) and the Resource Conservation and Recovery Act (RCRA), the State of Montana issued a hazardous waste permit to BNSF in 1988 to allow storage of hazardous waste in an on-site waste pile unit, to allow treatment of contaminated soil in an on-site land treatment unit (LTU), and to provide requirements for closure of the surface impoundment. 

In addition, the Environmental Protection Agency (EPA) issued BNSF a permit under the Hazardous and Solid Waste Amendments to RCRA which required BNSF to investigate site-wide contamination, as opposed to the specific areas regulated under the State’s permit, and develop a corrective action plan to clean up any contamination from past operations at the site.  The corrective action process consists of several stages of investigation and clean-up.

In 2000, Montana Department of Environmental Quality (DEQ) obtained oversight for facility-wide corrective action from EPA.  Hazardous waste permits (both state and federal) are issued for a ten-year period and may be renewed at the end of that period.  The BNSF hazardous waste permit was reissued by DEQ in 2001 and includes requirements for the operation of a Corrective Action Management Unit (CAMU).  The CAMU consists of a product recovery system to recover creosote from the groundwater, and operation of the land treatment unit (LTU), which allows BNSF to treat remediation waste.  The permit also includes requirements for continued maintenance of the closed surface impoundment and waste pile, and for facility-wide corrective action. 

On July 26, 2006, the hazardous waste permit was modified to include requirements for an Alternate Concentration Limit (ACL) to address dissolved-phase groundwater contamination.  The modification also includes requirements for land use controls to ensure groundwater use and soil disturbance will be controlled, and to include requirements for tank storage of creosote collected from the product recovery system prior to off-site disposal.



Contaminated Soil:

In 1989, EPA identified 22 potentially contaminated areas at the Site which required some degree of investigation and remediation.  As part of site characterization, a site-specific baseline risk assessment was conducted for the Paradise Site.  Through the risk assessment study it was determined that the limit for acceptable human health exposure for soils in an industrial setting was 40 ppm of carcinogenic PAHs .  In 2002, areas where surface soil exceeded the determined 40 ppm standard was excavated to 2 feet below ground surface.  The excavated areas were then backfilled with clean soil and seeded.  Approximately 4,870 cubic yards of soil was excavated, and was placed on the LTU for treatment.

Contaminated Groundwater:

Subsurface conditions at the Site have been investigated through extensive groundwater monitoring and on-going corrective action soil characterizations.  Monitoring shows that groundwater has been impacted by creosote constituents in free-phase, residual phase, and dissolved phase. 

Free Phase (DNAPL):

Creosote is a dense non-aqueous phase liquid (DNAPL).  When creosote is released to subsurface soils it migrates downward and slightly outward.  After reaching the water table, creosote will sink because it has a density slightly greater than water.  Since most of the constituents in creosote are essentially insoluble, creosote usually remains as a separate liquid phase (free phase) when it is in contact with groundwater.  Additionally, the rate of free phase creosote movement is many times slower than that of water.

Extensive groundwater monitoring and investigations has shown that creosote has pooled at the bottom of the aquifer beneath the surface impoundment and former retort area.  Free phase creosote is estimated at 94,000 gallons.  Recovery of free phase product in the surface impoundment and former retort area has been ongoing since 1996.   


Although creosote tends to stay in free phase and pool at the bottom of the aquifer, some of the contamination does dissolve and migrate in the aquifer.  Groundwater data indicate that the dissolved PAH plume fluctuates throughout the year, but generally has not increased in size since the initiation of monitoring in 1986.  The observed static extent of the PAH plume and the distribution of dissolved oxygen concentrations suggest that intrinsic biodegradation of the plume is occurring.  Monitoring wells continue to be sampled at the Site to ensure dissolved phase PAHs are not increasing in concentrations or migrating off-site.

Residual Creosote:

As the creosote migrates downward in the subsurface some of it becomes trapped in the soil pore spaces as “residual saturation”.  Creosote at residual saturation will not flow through the pore spaces and cannot be removed from the soil pores by groundwater pumping.  Residual creosote at the Site is estimated at 1,050,000 gallons.



An Alternate Concentration Limit (ACL) has been established for the Paradise Site and permit requirements were added to the hazardous waste permit on July 26, 2006.  ACLs are contaminant concentrations that, based on the site specific risk assessment, have been determined to not pose a substantial hazard to human health or environmental receptors (given exposure pathways and other factors).  At the Paradise Site, given the nature of creosote, it is technically impractical to achieve the existing groundwater protection standards established by the State (Circular DEQ-7).

A network of monitoring wells has been selected to evaluate PAH concentrations in the groundwater.  Wells are situated along the downgradient boundary of the Site and within the areas of contamination.  Groundwater samples are taken from wells along the boundary of the site semi-annually, and are taken from wells within the areas of contamination annually.  Groundwater samples are analyzed to ensure PAH concentrations do not exceed the established ACL limits.



Due to the nature of creosote and its interaction with the subsurface, the volume of recoverable creosote mass in the subsurface is quite small (2 to 6 percent).  The estimated maximum volumes of recoverable creosote at the Site are 8,500 gallons from the surface impoundment area (out of an estimated 494,000 gallons), and 38,500 gallons from the former treatment area (out of an estimated 650,000 gallons).  Actual recoverable volumes may be significantly less.  The estimated total remediation time frame is approximately 300 years.



Groundwater monitoring and sediment sampling near the Clark Fork River have demonstrated that subsurface contamination does not appear to impact the river.



DEQ requires that BNSF establish land use controls to further ensure prevention of potential future exposure to contamination.  Required land use controls include compliance with the DNRC Controlled Groundwater Use Area designation, deed restrictions, restrictive covenants, notice to any potential successors of the title in the property, engineering controls, notice to DEQ prior to any land transaction, and annual land use control notification to DEQ.



Environmental Indicators (EIs) are used by EPA to determine if contamination is being mitigated at or from facilities.  There are two EPA EI’s:  1) “Human Health Exposures Under Control”, and 2) “Migration of Contaminated Groundwater Under Control”.  Currently, Human Health Exposures are Under Control and Migration of Contaminated Groundwater is Under Control.



Throughout the cleanup process, the DEQ will keep the public informed through notices of public meetings and public comment periods in area newspapers.  In addition, the hazardous waste operating permit and other pertinent information about the project are maintained at the Plains Public Library.



DEQ Contact: 
Ann M. Kron, Environmental Science Specialist
Montana Department of Environmental Quality
P.O. Box 200901
Helena, Montana 59620-0901
e-mail: akron@mt.gov


Plains Public Library
108 West Railroad
Plains, Montana