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Tests show low levels of PFAS after Madison substation fire; high concentrations of less-studied compounds

Tests show low levels of PFAS after Madison substation fire; high concentrations of less-studied compounds


Lab tests have shown low levels of hazardous chemicals in water pulled from the storm sewers near the site of a July 19 transformer explosion on Madison’s Near East Side.

Highly fluorinated compounds known as PFAS, an ingredient of foam like that used to fight the fire at Madison Gas & Electric’s Blount Street substation, were found in water pulled from city storm drains at levels below the state’s proposed limits for groundwater, according to a report filed with the Department of Natural Resources.

But the tests showed high concentrations of a less toxic — but also less studied — variant known as 6:2 Fluorotelomer Sulfonate (6:2 FTS).

“It’s difficult to draw definitive conclusions” from the preliminary tests, said Nate Willis, a DNR wastewater engineer who specializes in PFAS compounds. “All the levels we saw are below the (Department of Health Safety’s) groundwater recommendations.”

However, Willis said further testing will be required to determine if any of the hazardous compounds made their way into the groundwater.

Explosion and fire in Downtown Madison
Explosion and fire Downtown
Firefighters battle blaze and explosion Downtown
Explosion and fire Downtown leaves thousands without power
Explosion and fire Downtown leaves thousands without power

The tests were conducted for an environmental contractor hired by American Transmission Company, which owned the transformer and is responsible for the cleanup, which is expected to continue through mid-August.

Samples were taken the day of the fire from catch basins inside the substation site and just outside at the corner of East Washington Avenue and Livingston Street as well as from water collected directly from the site.

There were no samples taken where the storm sewers empty into the Yahara River and Lake Monona, but Willis said there was no indication that the materials made it that far and that concentrations would likely be lower than those near the site.

There were also no tests performed on water from a substation near the UW-Madison campus where a second fire occurred minutes after the first, where Willis said firefighting foam was not used.

According to ATC, cleanup of that site was completed about a week after the fire.

PFAS refers to a group of chemicals found in firefighting foam and other products that studies have shown may increase people’s risk of cancer and affect cholesterol levels, childhood behavior, the immune system and the ability to get pregnant.

The DNR is working to establish groundwater quality standards for two such compounds, PFOA and PFOS, and the DHS has recommended a combined groundwater enforcement standard of 20 parts per trillion (ppt).

The highest concentration of either chemical found was 13 ppt, in water collected from the surface. The highest concentration in combination was 15.7 ppt, from the same sample.

But there were concentrations as high as 230 ppt of the 6:2 FTS compound found in foam used by the Madison Fire Department, which the city has called “more environmentally friendly.”

Maria Powell, president of the Midwest Environmental Justice Organization, says that label is misleading.

Maria Powell


“Lack of studies does not mean lack of risk — it just means we don’t know as much,” Powell wrote in an email to the city. “This does not deem them ‘environmentally friendly’ or safe for humans.”

The Madison Fire Department said Wednesday that incident reports for the fires will not be completed for another five weeks.

According to the DNR, firefighters applied about 55 gallons of foam along with 120,000 to 160,000 gallons of water. In addition, the Truax Fire Department applied just over 4 gallons of military-grade foam mixed with about 170 gallons of water.

ATC said environmental contractors have also recovered about 120,000 gallons of water and foam, which the company said will be put through a carbon filter before it is released back into the environment.

According to ATC, of the 18,000 gallons of insulating oil in the transformer, roughly 15,000 gallons have been recovered.

Willis said the DNR believes most of the other 3,000 gallons were burned in the fire.

ATC, which maintains high-voltage lines for moving electricity over long distances, says it continues to investigate the cause of the blast, which it believes was the result of a mechanical failure.

The company said final results of the investigation will be released “within the next few weeks.”

The company said it had previously identified a problem with a component, but did not complete a follow-up inspection before the explosion, which was reported just before 7:40 a.m. on July 19.

No injuries were reported, but the fires left about 13,000 homes and businesses without power for hours on a day when the heat index reached 109 degrees.


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