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Division of Spill Prevention and Response


Drinking Water Subgroup - North Pole Refinery

Goal: To ensure an alternate permanent drinking water supply for all impacted areas.

The Drinking Water Subgroup is responsible for making sure North Pole residents have a drinking water supply that meets state standards. The subgroup is also responsible for evaluating potential in-home treatment systems for impacted well owners and for overseeing the City of North Pole public water system’s routine testing.


  • The new public drinking water wells operation.
  • The City of North Pole has requested that DEC issue its final operational approval.
  • DEC’s Drinking Water Program engineers are continuing their review of the engineering plans for the wells. DEC’s final operational approval for the project is expected in the near future.
  • The new drinking water wells have been sampled each month and no sulfolane has been detected in any sample. The sampling frequency for the new wells will be reduced to quarterly for 2012.
  • The Church at North Pole, a federally regulated public water system in the plume area, elected to install the point-of-entry water treatment system being offered by Flint Hills. DEC’s Drinking Water Program engineers have issued an approval to construct the treatment system; the program issued an interim approval to operate in November 2011.


Establishing a Safe Level of Sulfolane in Drinking Water


Petroleum compounds have a number of components that can cause health and environmental effects. Sulfolane is a solvent used in the oil refining process to make gasoline. Since sulfolane has not been not a federally-regulated drinking water contaminant, neither the state nor federal government has established maximum contaminant levels of sulfolane for drinking water. The federal Agency for Toxic Substances and Disease Registry (ATSDR) has recommended 25 parts per billion sulfolane as the most protective level for drinking water. To download the report, click here.

If your water well results showed above 25 parts per billion sulfolane, we advise you not drink the water. Flint Hills is providing bottled water to all residents with impacted wells and working toward a permanent alternate water supply. The Alaska Division of Public Health will also prepare a health consultation to explain the implications of sulfolane consumption at the levels found in North Pole well water. Please feel free to contact them with your health-related concerns and questions about this site or call 907-269-8028.

Effects of Sulfolane on Human Health


The most likely way in which neighbors of the refinery could be exposed to sulfolane would be through drinking contaminated well water. Given the concentrations of sulfolane reported to date, other uses of well water such as bathing/showering, laundering clothes, and washing dishes are not likely to pose any risk to well water users. Additionally, other exposure routes such as breathing vapors or direct skin contact are unlikely because the chemical has low volatility and is not absorbed through the skin.

The health effects of sulfolane have not been studied in humans. Laboratory animals exposed to very high levels have shown changes to the liver and other organs, and the nervous and immune systems. Tests for carcinogenic (cancer) effects have not been done.


Drinking Water Monitoring


On November 11, 2009, Flint Hills began contacting residents and businesses north of the refinery to locate private drinking water which might be affected and test the water. Shannon and Wilson, a consulting firm hired by Flint Hills, has been going door-to-door since then, offering to test water from any private well in the area north and west of the refinery (the direction of groundwater flow). Flint Hills is paying for the analyses, and test results are generally available within a week of sample collection. Bottled water is provided to anyone with a private well that has been affected by the sulfolane plume.

DEC encourages neighbors to work with Flint Hills and their consultant Shannon and Wilson so that all the private drinking water wells in the potentially affected area can be found and properly evaluated. If you live in these areas and you want Flint Hills' contractor to sample your well at the cost of the refinery, please call Jeff Cook, Director of External Affairs, Flint Hills Resources Alaska, at 907-488-5104.

North Pole City water coming to consumers shows no detections of sulfolane.

During 2009, there were conflicting test results reported from laboratory analyses of city water. After additional analysis, it has been confirmed that sulfolane contamination levels in North Pole city water amount to only trace concentrations, well below the safe drinking water levels. See the complete report on the labs by clicking here ("Third party review of lab analysis...").

Click here to view maps summarizing monitoring data.

Extent of Contamination

As shown in the map below, the edges of the plume are now fairly well defined. Monitoring wells installed at Badger Road and Peridot Street and west from that intersection are clear of sulfolane but tests of residential wells in that area have shown low concentrations (below 25 parts per billion).

Click here to view maps of plume delineation.

We have no evidence that sulfolane in groundwater is spreading further or moving. The plume is driven by a source -- soil saturated with fuel from old spills at the refinery. The fuel contains sulfolane. Removing this fuel is time-consuming, but it is the most effective way to stop the sulfolane contamination. Ongoing efforts to remove this fuel from the ground are slowly reducing sulfolane in the groundwater. Work has been done on the refinery to ensure there is not an ongoing release of sulfolane, and the refinery is installing more safeguards to ensure no new future releases.

We do not expect concentrations to increase significantly in the plume area. Permanent monitoring wells have been installed to measure sulfolane monthly. This monitoring program will tell us if there is any increase or sign of the contaminant moving further.

There is also no sign that the soil in the residential areas is impacted by sulfolane—only the groundwater. We are evaluating the potential for any other sources of sulfolane contamination besides the refinery, but at this time we are certain the main source is at the refinery. We are also certain that the contaminant is moving off the refinery property in the groundwater, not the soil.

See "Report on groundwater flow" under Documents page.


Other Potential Contamination and Human Health Effects


During the summer of 2010, a Gardening Study was conducted to assess the safety of consuming garden crops grown with water containing sulfolane. The study found:


  1. Edible garden plants can take up sulfolane that is present in water. People can be exposed to (come in contact with) sulfolane by eating affected produce.

  2. Sulfolane was found in all parts of plants that were sampled (leaves, fruits, flowers, stems and roots). Results from earlier sampling suggested that sulfolane only concentrated in the leafy parts of plants, and not in the fruits, flowers, stems and roots.

  3. Based upon what is known about sulfolane, the sulfolane levels in the plants tested from these gardens are low and not likely to cause any adverse health effects. However, this sampling project was limited, and only reflects the growing conditions this past year and only the produce from the sampled gardens. The amount of sulfolane in plants could be different based on a number of factors, including the type of produce, different growing conditions (i.e. more or less rainfall), or the amount of sulfolane in the well water. In addition, scientific information on the chronic health risks of sulfolane is lacking. Due to these unknown factors, we cannot say with 100% certainty that it is safe to use sulfolane-affected water for gardening without further study; therefore, watering gardens with sulfolane-free water is preferable until more information is available.


The next steps to this study involve additional toxicology research as well as investigations into filtration systems that reduce sulfolane levels in well water. Flint Hills has offered to provide above-ground water tanks for residents to use for gardening in the interim.



Converting units of measurement


On this webpage we talk about units of sulfolane using only parts per billion, or ppb.

Micrograms per cubic liter (μg/L3) are the same as parts per billion (ppb).

Milligrams per cubic liter (mg/L3) are the same as parts per million (ppm).

To convert from parts per million to parts per billion:

Multiply the ppm concentration by 1,000. The resulting concentration is in ppb.
Example: 3 ppm x 1,000 ppm/ppb = 3,000 ppb

To convert from ppb to ppm:

Divide the ppb concentration by 1,000. The resulting concentration is in ppm.
Example: 3,000 ppb ÷ 1,000 ppb/ppm = 3 ppm

See our fact sheet Understanding Contaminant Concentrations (PDF).


For more information on the human health, toxicological, and other related reports, visit the documents page.


For more information contact Cindy Christian, Compliance Program Manager, (907) 451-2138,

Drinking Water Documents