With cleanup efforts at the site of an electrical transformer fire in Downtown Madison expected to take up to two months, questions remain about potentially hazardous materials used to fight the July 19 blaze, which left thousands of customers without power.
Contractors for American Transmission Co., which said last week it had identified a problem with the transformer the week before it exploded, are continuing efforts to pump oil and firefighting foam out of storm sewers that empty into Lake Monona and the Yahara River.
According to the city, more than four hours passed between the time firefighters arrived on scene and the closure of the storm sewers.
But Mary Bottari, chief of staff to Madison Mayor Satya Rhodes-Conway, said high lake levels and booms inside the storm sewers and at the outfalls have contained oil and other contaminants in the storm sewer, minimizing the potential for release to surface waters and that there is no evidence yet of oil reaching the lake.
The state Department of Natural Resources confirmed there have been no reports of sheens on the water.
According to the DNR and ATC, tests have revealed the transformer oil contained no PCBs, a toxic chemical that was banned in 1979 but can be present in older electrical equipment, according to the Environmental Protection Agency.
Questions remain about the type and quantities of foam used to extinguish the fire and the levels of highly fluorinated compounds known as PFAS contained in the foam.
The Madison Fire Department has not provided records requested by the Wisconsin State Journal, but according to the DNR, firefighters applied about 55 gallons of foam along with 120,000 to 160,000 gallons of water. Bottari said the city uses foam considered “more environmentally friendly than other materials available.” The foam contains a form of PFAS known as PFHxA.
The Truax Fire Department also sent a “rapid intervention vehicle” that applied just over 4 gallons of FireAde 2000 AFFF military-grade foam mixed with about 170 gallons of water, said Capt. Joe Trovato, a spokesman for the Wisconsin National Guard.
ATC spokeswoman Anne Spaltholz said Monday that contractors have pulled about 120,000 gallons of water from the storm sewers, which is being held in tank trucks until the DNR determines the next steps.
According to the Fire Department, foam was required to extinguish the burning oil, as water alone would have caused the fire to spread.
Firefighters worked for about an hour to contain the fire, as well as a second related fire at a substation near the UW-Madison campus.
Hannah Mohelnitzky, public information officer for the city’s Engineering Division, said the fire department notified engineering of the potential storm sewer hazards at about 9:40 a.m. and that barriers were in place by about noon.
Bottari said soil, water and groundwater have been sampled for 34 PFAS compounds and that any material removed from the site will be treated to remove PFAS if testing reveals “levels of concern.”
She did not specify what that level would be.
The DNR is developing administrative rules to establish groundwater quality standards for two PFAS compounds, PFOA and PFOS, because the federal Environmental Protection Agency does not have standards for the contaminants.
The state Department of Health Services has recommended a combined groundwater enforcement standard of 20 parts per trillion for PFOA and PFOS.
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. Last week 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 on the hottest day of the year, with the heat index reaching 108 degrees.
Madison Gas & Electric, which shut down the substations for the safety of firefighters, said most service was restored by 1:25 p.m. though some problems persisted until the evening.