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Division of Spill Prevention and Response Contaminated Sites

Site Cleanup and Monitoring

Updated: May 8, 2023

Overview

Contamination associated with historical oil refining activities at the former North Pole Refinery (now Marathon Terminal), located about 15 miles east of Fairbanks, has affected groundwater used as a source of drinking water in the North Pole area. The refinery operated from the late 1970s until it shut down in 2014. In 2009, the industrial solvent sulfolane, which was used in the refining process, was detected in drinking water wells off the former refinery property. In 2018, per- and polyfluoroalkyl substances (PFAS) used in fire-fighting foams on the former refinery were detected in groundwater off the property. The sulfolane groundwater plume is approximately 2 miles wide, 3.5 miles long and over 300 feet deep, and continuing to migrate gradually northward. The PFAS plume appears to have a similar footprint, although the boundaries of the plume have not been fully evaluated.

On the former refinery, fuel product remains trapped in the soil and groundwater. Groundwater monitoring through 2022 has shown no evidence of petroleum compounds migrating off the property above State cleanup levels. Sulfolane continues to migrate beyond the property line below levels allowed under the 2017 settlement agreement (400 parts per billion).

In response to the sulfolane contamination, the refinery’s then-owner Flint Hills Resources Alaska (FHRA) began providing affected residents and businesses with alternative drinking water solutions in 2009. They also began sampling and other activities to find out how far the sulfolane had spread. Sulfolane was found to have impacted approximately 350 drinking water wells. FHRA provided affected properties with either connections to city water (if available), bulk water tanks, bottled water, or point-of-entry (POE) treatment systems to remove sulfolane from their well water. Properties in a “buffer zone” beyond the sulfolane plume were provided interim bottled water to protect against possible migration of the sulfolane. Sampling conducted in 2018 showed that the alternative water solutions that provided protection from sulfolane were also protecting residents from PFAS in their well water.

In February 2017, the State of Alaska, FHRA, and the City of North Pole reached a settlement agreement to expand the City’s piped water system to all improved properties located within the sulfolane plume or in its anticipated migration path. By the end of 2020, all eligible property owners were offered connection to the service and able to phase out the use of contaminated groundwater wells. Most property owners were eligible to connect at no cost, depending upon the land’s location and improvement status. The expanded system provides permanent protection from contamination in drinking water.

Long-term groundwater monitoring continues off the former refinery property to track the sulfolane plume’s migration and concentrations for protection of properties developed in the future or ones located beyond the expanded piped water area. On the former refinery property, groundwater monitoring is used to track sulfolane and petroleum concentrations.

On the former refinery property, a multi-year investigation to evaluate PFAS levels in soil, groundwater, and surface water began in 2020 under DEC oversight. The investigation is continuing in 2023. PFAS is a component of aqueous film-forming foams (AFFF) used to extinguish fires. Fire training and other activities on the former refinery included extensive use of AFFF, which contaminated soils and groundwater.

The links below provide recent information regarding contamination off the former refinery property.

The links below provide recent information regarding contamination on the former refinery property.

Cleanup and Monitoring

Current cleanup and monitoring activities are governed by the terms of a February 2017 settlement agreement between the State of Alaska, the City of North Pole, and the then-owner of the former refinery, Flint Hills Resources Alaska (FHRA), along with subsequent 2020-2022 work plans prepared by Williams Alaska Petroleum, Inc. (Williams), a previous owner of the former refinery. Further information about the settlement agreement can be found at the following:

The settlement agreement includes a Potable Water Plan and Revised Onsite Cleanup Plan, described briefly below.

The 2017 Potable Water Plan prepared by FHRA, addresses contamination off the former refinery property by providing sulfolane-free drinking water to properties within the sulfolane plume or its anticipated migration path through expansion of the City of North Pole's piped water system. By the end of 2020, all eligible property owners were offered connection to the service and able to phase out the use of contaminated groundwater wells. Most property owners were eligible to connect at no cost, depending upon the land’s location and improvement status. The expanded system provides permanent protection from contamination in drinking water.

The plan also includes long-term sulfolane groundwater monitoring requirements for protection of properties beyond the expanded piped water area until the plume meets a cleanup level to be set by the State of Alaska. PFAS is not addressed in the 2017 Potable Water Plan; it was discovered in groundwater off the former refinery property in 2018.

The 2017 Revised Onsite Cleanup Plan (ROCP) also prepared by FHRA, addresses petroleum and sulfolane contamination on the former refinery property. Administrative and engineering land use controls are used to prevent exposure to contamination remaining on the property. Long-term groundwater monitoring is used to ensure that contamination in groundwater is not migrating off the former refinery above DEC cleanup levels. For sulfolane, which does not have a cleanup level, offsite migration is not to exceed a concentration of 400 parts per billion.

Groundwater monitoring performed in 2018 through 2022 shows no evidence of contamination migrating off the former refinery property above DEC cleanup levels. Monitoring indicates sulfolane is migrating off the former refinery property at concentrations below 400 micrograms per liter (µg/L).

Williams Groundwater Monitoring: In 2020, Williams, a previous owner of the former refinery, began performing the offsite sulfolane monitoring. Williams prepared a work plan - "2020 Offsite Sulfolane Plume Monitoring Plan; City of North Pole and Surrounding Area," monitored sulfolane concentrations off the former refinery in 2020 and 2021, and reported the results.

Long-Term Groundwater Monitoring

Under DEC oversight, FHRA currently collects groundwater samples from wells located on the former refinery, and Williams collects groundwater samples from wells located off the former refinery to monitor contaminant plume migration and trends.

  • Onsite monitoring results are compiled into annual reports and are available on the Documents page, Onsite Plume
  • Offsite monitoring results are compiled into annual reports and are available on the Documents page, Offsite Plume
  • Maps of the results of groundwater monitoring are posted on the Maps page, with the most recent at the top

After completion of the 2022 monitoring, Five Year Reviews of the results will be completed under DEC oversight, and changes to the monitoring program may be recommended, if appropriate. The Five-Year Review for onsite monitoring is available and posted on the Documents page. DEC is still reviewing this report. The Five-Year Reviews will be posted to this website when available.

PFAS Groundwater Monitoring

The extent of the PFAS contamination on and off the former refinery has not been fully evaluated. Site characterization activities were performed in 2022 to evaluate PFAS on the former refinery property (see Site Characterization, this page). PFAS were discovered in groundwater off the property during a 2018 investigation. Follow-up activities included an evaluation of uptake of PFAS into garden produce irrigated with PFAS-contaminated groundwater, and sampling of three rainbow trout collected from Kimberly Lake, northwest of the former refinery. Results from the 2018 PFAS sampling events may be found at the following:

Historical Onsite Cleanup Activities

A groundwater extraction and treatment system operated for many years on the former refinery property until it was phased out of operation and replaced by long-term monitoring in July 2017. The treatment system was initially installed in the 1980s to remove free petroleum product from the subsurface. The system was expanded and upgraded several times over the years to capture and treat contaminated groundwater. After sulfolane was discovered off the property in 2009, the system was significantly expanded to capture sulfolane before it migrated beyond the property boundaries. During its years of operation, the treatment system removed thousands of pounds of sulfolane and petroleum from groundwater, thereby greatly reducing the amount of sulfolane migrating off the refinery property. Limited sampling showed the system also removed some PFAS from the groundwater. Petroleum constituents have not been shown to have migrated off the property. Contingencies are in place to resume active treatment if the Plan goals are not met.

Historically, contamination present in some accessible portions of the former refinery property was removed through excavation and offsite disposal. In 2015, three soil excavations were performed to remove soil contamination from the former refinery property, including the removal of PFAS-contaminated soil from the former fire training area.

Site Characterization

Under Alaska regulations (18.AAC 75.335), the extent of contamination at a contaminated site is to be characterized before proceeding with cleanup. The site characterization requirements generally include investigation activities to determine the types of contaminants present, the source areas, possible risk to people and the environment, the possible need for interim cleanup actions, and the extent of the contamination both horizontally and vertically. The site characterization reports include an evaluation of potential cleanup activities that may be appropriate at the site. More information on the State of Alaska cleanup process is available at the links below:

Multiple site investigations were performed on the North Pole Refinery, beginning in the 1980s, but the 2009 discovery of sulfolane beyond the refinery property instigated a new round of intensive efforts. Investigations of soil and groundwater were performed onsite to evaluate the source and extent of the sulfolane and PFAS contamination, and to refine the understanding of the nature and extent of petroleum contamination. Offsite investigations assessed the size and boundaries of the sulfolane groundwater plume. Hundreds of monitoring wells were installed, and thousands of groundwater samples were collected. The most recent and complete characterization reports are listed below and found on the Site Characterization portion of our Documents page:

The extent of PFAS contamination on the former refinery has not been fully evaluated. A multi-year site characterization of PFAS in groundwater and surface water began in 2020 under DEC oversight. The 2020 characterization focused on groundwater sampling from existing monitoring wells. Results showed PFOS and PFOA above DEC cleanup levels in some portions of the former refinery and suggested that additional characterization activities were warranted. The investigation continued in 2022, with a soil investigation and additional groundwater and surface water monitoring.

Other project documents and reports on site investigation and remediation are available on the Documents page.

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Department of Environmental Conservation

Mailing Address:  P.O. Box 111800
Juneau, Alaska 99811
Location:  410 Willoughby Avenue, Juneau