The discovery of sulfolane in drinking water wells in 2009 near the North Pole Refinery, about 15 miles east of Fairbanks, has led to an extensive groundwater investigation. Flint Hills Resources Alaska, owner of the refinery, responded quickly by providing affected residents with alternate drinking water. Sulfolane is an emerging contaminant, and the long-term health effects from exposure through drinking water are not yet understood. The groundwater plume is approximately 2 miles wide, 3.5 miles long and over 300 feet deep, making it one of the largest in the state, with many private properties impacted. Currently approximately 1,500 people receive alternate drinking water supplies. For additional details, see Frequently Asked Questions.
- NTP Begins
Studies on Sulfolane: The National Toxicology Program (NTP) has initiated studies to address important data gaps regarding sulfolane exposure. Of particular concern to the Alaska Department of Environmental Conservation is the lack of information on the effects of long-term exposure to this chemical that has impacted the drinking water supplies in and near North Pole, Alaska.
A 2-year study initiated in May 2015 is evaluating the effects of long-term exposure to the solvent. The NTP studies are expected to provide a clearer picture of the risks associated with sulfolane exposure. The agency elected to study sulfolane at the request of DEC.
The Division is continuing to review a Flint Hills proposal of a 362 parts per billion cleanup level for sulfolane. At present, a cleanup level for sulfolane does not exist (see "Cleanup Level Review" below). DEC believes a comprehensive review and determination of an appropriate cleanup level cannot be complete until information from the NTP studies is available. (See a fact sheet on the NTP studies.)
Until a cleanup level is set, Flint Hills is obligated to continue to provide alternative drinking water to impacted residents. The company currently provides alternative drinking water to an estimated 1,500 people affected by the sulfolane plume. DEC will continue to work with Flint Hills to clean up contamination on the refinery property and track migration of the expanding sulfolane plume. For more information please see:
- Cleanup Level Review: Currently there is no cleanup level for sulfolane. The former site-specific cleanup level of 14 parts per billion (ppb) was revoked in April 2014 by DEC’s commissioner in response to Flint Hills' appeal of that number.
(See the Commissioner's decision - Apr. 4, 2014 --96 KB PDF) The Commissioner also asked the SPAR Division to further document the rationale and re-evaluate the information that led to the selection of a site-specific cleanup level for sulfolane.
The SPAR Division is considering all of the scientific information, including Flint Hills' proposal of a 362 ppb cleanup level.
- TERA Panel Review (summer-December 2014): In response to the Commissioner's request for a cleanup level review, and to ensure the most scientifically sound groundwater cleanup level for sulfolane, DEC sought the input of independent, national experts through a panel convened by Toxicology Excellence for Risk Assessment (TERA). TERA selected, organized, and conducted the panel discussion, choosing the members based on their expertise and screening them for any conflicts of interest. See TERA's website on the Independent Expert Peer Review of Sulfolane Reference Doses for ADEC.
The experts met in Fairbanks September 16-17 to review the available reference doses for sulfolane. A reference dose is a toxicity value and a key component used by DEC in establishing a cleanup level for the groundwater. The panel selected by TERA was comprised of national experts in toxicology, immunology, risk assessment, and contaminated sites. The public was invited to observe the two-day deliberations on relevant scientific issues related to the reference doses. This process and the results will help assure DEC utilizes the most scientifically defensible reference dose when calculating a groundwater cleanup level for sulfolane.
On December 22, 2014, TERA released their report summarizing the panel’s recommendations. DEC is carefully reviewing the report, which will be considered as part of the decision on a cleanup level for sulfolane. Click here to view the report on TERA's website.
TERA is an independent non-profit organized for scientific and educational purposes. TERA describes its mission as supporting the protection of public health by developing, reviewing and communicating risk assessment values and analyses; improving risk methods through research; and educating risk assessors, managers, and the public on risk assessment issues. For more information, please visit their website.