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Site Cleanup and Monitoring

Updated: September 30, 2020

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 to the north-northwest. The PFAS plume appears to have a similar footprint, although the boundaries of the plume have not been fully evaluated. The former refinery’s land still contains fuel product trapped in the soil and groundwater, but these petroleum components have not migrated off the property.

Under DEC oversight in 2009, then-owner of the refinery Flint Hills Resources Alaska (FHRA) began providing affected residents and businesses with alternative drinking water solutions. 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 for 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. The expanded piped water system is expected to be complete by the end of 2020 and will provide 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.

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. PFAS was discovered beyond the former refinery’s property boundary in a 2018 sampling event. Plans are being developed for future sampling to be performed under DEC oversight.

The links below provide recent information regarding contamination off 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). The agreement includes a Potable Water Plan and Revised Onsite Cleanup Plan, described briefly below. Further information about the settlement agreement can be found at the following:

The 2017 Potable Water Plan addresses contamination off the former refinery property by providing sulfolane-free drinking water through expansion of the City of North Pole's piped water system. City water was expanded to all improved properties located within the sulfolane plume or in its anticipated migration path. Implementation of the expanded piped water system is expected to be complete by the end of 2020 and will provide permanent protection from contamination in drinking water. The plan 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, because its presence in groundwater off the former refinery property was subsequently discovered in 2018.

The 2017 Revised Onsite Cleanup Plan (ROCP) addresses contamination on the former refinery property. Administrative and engineering land use controls are used to prevent exposure to contamination remaining on the former refinery 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.

In July 2017, an onsite groundwater extraction and treatment system was phased out of operation and replaced by long-term monitoring. 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.

Groundwater monitoring performed in 2018 and 2019 demonstrated that contamination is not migrating off the former refinery property above DEC cleanup levels. Sulfolane has not been shown to be migrating off the refinery above 400 ppb.

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. See the following link for the 2015 excavation report.

Long-Term Groundwater Monitoring

Under DEC oversight, FHRA currently collects groundwater samples from wells located both on and off the refinery to monitor plume migration and sulfolane trends: 

  • Onsite monitoring results are compiled into semi-annual reports and are available on the Documents page, Onsite Plume.
  • Offsite monitoring results are compiled into semi-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.

PFAS Groundwater Monitoring

The extent of the PFAS contamination on and off the former refinery has not been fully evaluated. PFAS were discovered in groundwater off the former refinery property during a 2018 offsite PFAS 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. Plans are under development for future sampling to be performed under DEC oversight. Results from the 2018 PFAS sampling events may be found at the following:

Site Characterization

Under Alaska regulations (18.AAC 75.335), the extent of contamination is to be characterized before proceeding with cleanup at a contaminated site. 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 site characterization 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:

  • 2013 DRAFT Onsite Site Characterization Addendum Report
  • 2013 DRAFT Offsite Site Characterization Addendum Report
  • 2012 Site Characterization Addendum
  • 2011 Site Characterization Report

The extent of the PFAS contamination on and off the former refinery has not been fully evaluated. PFAS was discovered off the former refinery during a 2018 sampling event. Efforts are currently being developed to further investigate the extent of PFAS contamination both on and off the former refinery property under DEC oversight.

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

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