Date: Tuesday September 16 and 17, 2014
Location:  University of Alaska, Fairbanks

The Alaska Department of Environmental Conservation (ADEC) tasked Toxicology Excellence for Risk Assessment (TERA) with conducting an independent, expert peer review of the available reference doses (RfDs) for sulfolane. The sulfolane RfD will be used by ADEC to develop cleanup levels for groundwater in North Pole, Alaska.

The peer review meeting was held September 16 and 17, 2014 in Fairbanks, Alaska. 

The purpose of the peer review meeting was to have the experts evaluate and discuss the RfDs and reach conclusions based on the available science; the discussions will be limited to the panel members.   Those wishing to submit written comments on scientific issues or data related to the RfDs were invited to do so.  These written comments were provided to the panel for their consideration and posted on this web page. 

Draft Peer Review Meeting Agenda

Review Materials Provided to the Expert Panel

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Description of the Peer Review Meeting Process

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Submitted Technical Scientific Comments

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Background Information

The discovery in late 2009 of sulfolane (2,3,5-tetrahydrothiophene-1,1-dioxide; tetramethylene sulfone; CAS No. 126-33-0) in drinking water wells near the North Pole Refinery, about 15 miles east of Fairbanks, Alaska, has led to an extensive investigation of contaminated groundwater.  Sulfolane is an industrial solvent used to remove the aromatics from the naptha during gasoline production.  Sulfolane has a low vapor pressure, suggesting it has low volatility; however, it is highly soluble in water.  The chemical is listed as a high-production-volume chemical by the Organization for Economic Cooperation and Development and by the United States Environmental Protection Agency.

Through 2013, Flint Hills Resources of Alaska (FHRA), the current refinery owner, has provided 305 long-term alternate water supplies at 285 properties in the affected area. ADEC is currently in the process of setting a groundwater cleanup level protective of residential consumption of groundwater containing sulfolane. As part of that review, ADEC has tasked Toxicology Excellence for Risk Assessment (TERA) with conducting an independent, expert peer review of the available chronic, oral reference doses (RfDs) for sulfolane.

Site characterization activities during 2000 to 2002 identified sulfolane in onsite groundwater monitoring wells.  It is believed to come from leaks from the wastewater stream containing sulfolane, as well as fuel spills.  Spills of pure sulfolane are also probable.  At the time of the review, the plume was nearly 2.5 miles wide and 3 miles long.  Flint Hills Resources of Alaska, the current refinery owner, responded to offer all affected residents and property owners an alternate drinking water source. ADEC is currently in the process of setting a groundwater cleanup level protective of residential consumption of groundwater containing sulfolane and homegrown produce watered with sulfolane-impacted water.  Site characterization activities in 2011 through 2013 continued to fill in the data gaps on and off the refinery property necessary to assist with the long-term monitoring, evaluation, and potential remediation of the sulfolane plume.

For additional background on the site, please refer to ADEC’s project website at http://dec.alaska.gov/spar/csp/sites/north-pole-refinery/ .