Preliminary results from a U.S. military analysis show high levels of groundwater contamination at the Air National Guard Base in Sioux City. Authors of the report suspect toxic chemicals known as PFAS could be migrating off site. The substances are thought to be from the use of certain firefighting foams that have been used at the base.
Preliminary results from a series of soil and water tests conducted at the Air National Guard Base seven miles south of downtown Sioux City show chemicals known as per- and polyfluoroalkyl substances, or PFAS, are seeping into the soil, sediment, surface water and groundwater. According to the 70-page Air National Guard report, at some testing sites analysts found PFAS concentrations at a level that could impact human health.
Analysts found the amount of PFAS in the groundwater at one hotspot near the base’s main hangar is more than 100 times the health advisory set by the federal government. According to U.S. Environmental Protection Agency guidance announced in 2016, PFAS in drinking water should not exceed 70 parts per trillion. According to the report, analysts detected levels of 8,610 parts per trillion at one groundwater well. Six out of the eight groundwater wells tested showed levels above the EPA health advisory, and one of two surface water samples was also above the limit.
David Cwiertny heads the Center for Health Effects and Environmental Contamination at the University of Iowa and reviewed the report. He called the results “concerning."
“Those levels at the high end of what was found are notable because it will make cleanup more challenging and it will make it more likely that there are levels that we might need to be concerned about further away from those points and potentially off the base,” Cwiertny said.
The PFAS class of chemicals includes thousands of individual substances. PFOA and PFOS are the most studied of the group and exposure to the chemicals has been linked to increased risk of kidney and testicular cancers, immune issues, fertility problems and hormonal changes.
According to the analysis, the Sioux City base doesn’t use the groundwater for drinking. But the report authors say chemicals are likely drifting off site. Groundwater in the area is thought to flow generally to the southwest.
“PFOS/PFOA compounds are likely migrating offsite given their presence and magnitude near the Installation boundary,” the report reads. The report authors also called for further testing on the base and off, recommending "sampling of upgradient and downgradient off-Base monitoring wells to better define the upgradient source of PFAS as well as PFAS concentrations that have migrated off Base."
The base, located near the Sioux Gateway Airport, is approximately two miles east of the Missouri River. The report notes there are no public water systems within a one mile radius of the base, but there are 189 private wells within that area, and the city of Sergeant Bluff is served by municipal water supply wells located approximately one mile east of the base.
A spokesman for the Iowa National Guard said in a written statement that the agency is “committed to protecting human health” and “ensuring safe drinking water."
“Additional tests and monitoring are needed to determine the impact, if any, on the local community. Site inspections are an ongoing process that can last several months or longer,” said Lt. Col. Michael Wunn in a written statement.
If contamination is found off-base, Wunn said the agency will respond to it.
“If these inspections indicate potential pathways to off-base drinking water supplies, the Iowa Air National Guard will expand the site inspection footprint and may conduct additional tests if necessary. Once these inspections are complete, the Iowa Air National Guard, in conjunction with the U.S. Air Force, will take action to reduce any potential risk to local communities,” Wunn’s written statement reads.
Staff at the Iowa Department of Natural Resources are reviewing the report and have said they will supply more information as it’s available.
The PFAS class of chemicals are used in a slate of household and consumer products, including cleaning products, non-stick cookware, fabrics, and food wrappers. They are also found in fire suppressing foams known as AFFF that have been widely used at military installations, fire training centers, airports and certain manufacturing sites.
According to Wunn, the Iowa National Guard has “already taken action to prevent any future impact by replacing legacy fire suppression systems that used these potentially harmful compounds.”
Plumes of PFAS contamination are being identified across the country. The analysis of the Sioux City Air National Guard Base is part of a nationwide review conducted by the U.S. Air Force. Similar testing has been done at the Air National Guard Base in Des Moines.
While researchers have demonstrated potential public health risks associated with PFAS exposure, the EPA has not yet set a federal regulatory limit that is enforceable by law. EPA Acting Administrator Andrew Wheeler announced last week the agency plans to begin the process of setting such a limit, called a maximum contaminant level or MCL by the end of the year.
Currently, the EPA has only issued voluntary recommendations. At the state level, there are no mandatory screenings for PFAS in public or private water supplies in the state of Iowa. But other states are setting their own internal monitoring levels and mandating testing of drinking water supplies.
Between 2013 and 2015, the Iowa DNR participated in testing for six PFAS chemicals at some 57 public water systems across the state and did not detect the contaminants. But critics say focused testing at suspected release locations could expose further contamination.
Cwiertny says more testing is needed at the Sioux City base to confirm the nature and extent of the contamination.
“As the report concluded, more testing, more work needs to be done to try to characterize the full extent of which chemicals are there? At what levels? And then where they might be encountering vital resources like wells that might be used for private water supplies,” he said.
A finalized report on the PFAS testing conducted at the Sioux City base is expected to be finished this April.