FAIRBANKS -- A much-anticipated study on sulfolane pollution levels tends to back up the position taken by Flint Hills, concluding that a much higher level in the ground below North Pole should be considered safe than that proposed by the state.
The study says that a "reference dose" level 10 times higher than proposed by the Environmental Protection Agency in 2012 should be considered acceptable but the authors also said their confidence in the finding is on the "low end of medium." They said their recommendation would protect public health but they did not have enough information to say if further research will lead to a higher or lower reference dose.
Earlier this year the state asked a panel of Outside experts to review existing research and try to sort out the conflicting arguments about sulfolane, a chemical that has been the subject of limited research.
"The reference dose does have a big impact on the final cleanup level but it isn't the only factor. We are saying it is one more piece of information the state is considering. We have not made a determination yet regarding a revised cleanup level," said Kristin Ryan, director of the Division of Environmental Health for the Department of Environmental Conservation.
The technical document could have major implications for hundreds of property owners in the North Pole area, as it is to be a factor in setting a cleanup standard for sulfolane, but Ryan and other DEC officials said it is one piece of a complicated puzzle that the agency has been trying to sort out since the discovery of the chemical spill beyond the refinery property in 2009.
The decision on a cleanup standard, which had been expected by the end of the year, will be delayed, she said. Whatever final figure is settled on will guide cleanup plans and determine the future of assistance that has been offered to homeowners where the pollutant has been detected.
Sulfolane, a solvent used at the now-shuttered refinery since the 1980s, leaked into the ground over many years and has spread in a plume about 3 miles long and 2 1/2 miles wide. It has been found in more than 350 wells at depths as great as 300 feet. The state is in court with Flint Hills and with Williams, the company that owned the refinery during most of the years when the chemical was leaking into groundwater.
DEC had proposed a cleanup level of 14 parts per billion (about 14 drops in a swimming pool) as the standard but the owners of the refinery argued that 362 parts per billion should be considered safe. The difference is important because in most of the area where sulfolane has spread, the concentrations are well below 362 parts per billion.
Flint Hills challenged the 14 ppb level as far too stringent, arguing that several studies showed that higher pollution levels posed no health threat. The state agreed to take another look at the 14 ppb level, and the Dec. 18 report by Toxicology Excellence for Risk Assessment, an independent group of experts, was the next step in that process.
Koch Industries, owner of Flint Hills, closed the refinery last spring, citing the unknown costs of cleanup beyond the boundaries of the state's largest refinery as one of the major reasons. The facility remains in business as a fuel terminal, using products shipped to North Pole from other refineries.
The review panel included six scientists from the University of Florida, West Virginia University, the University of Cincinnati, Emory University, the EPA and the California Environmental Protection Agency.
The new report does not directly endorse the position taken by Flint Hills but it will strengthen the company argument for a more relaxed standard. It says that a 2013 study by CM Thompson and others that makes the case for allowing 10 times more sulfolane as a base for creating a cleanup target "most closely reflects the scientific panel's comments and preferences."
The TERA review added that two other studies reached similar conclusions on the reference dose. ARCADIS, a contractor hired by Flint Hills, presented evidence to back up an exposure level of .01/mg/kg/day. The Thompson study and an analysis by a Texas agency also used the .01 level, which is 10 times higher than the level of .001 used by the EPA.
Flint Hills has argued that the peer-reviewed study now endorsed by TERA reaches a conclusion on sulfolane exposure that translates to a cleanup level of 365 parts per billion. Setting the level at that number would mean that the existing sulfolane levels, at most of the 350 wells where the chemical has been detected, would not be judged a health threat.
Ryan said the assumptions used in the scientific analysis are key, adding that the 365 ppb proposal "assumes adults are consuming the water rather than children as the end point. This is significant because children consume more water per volume than adults." The TERA panel also said that the reference doses it reviewed "may or may not match" the needs of Alaska, as each study was developed by a different organization, using its own methods and for a specific purpose.
TERA held a two-day hearing in September in Fairbanks at which it reviewed evidence contained in various studies and calculations about sulfolane exposure.