Madison Mayor Satya Rhodes-Conway has asked American Transmission Co. for more details about the cause of a July transformer fire and why the utility didn’t shut it down sooner after problems were detected.
ATC issued a news release Wednesday saying an internal investigation showed a voltage regulator — known as a “load tap changer” — failed, igniting combustible gases inside the 138-kilovolt transformer around 7:40 a.m. on July 19 at the Blount Street substation.
The explosion rocked Downtown Madison, snarled traffic and left thousands of customers without power on the hottest day of the year.
Cleanup efforts continue as environmental contractors work to determine the extent of contamination from hazardous chemicals in foam firefighters used to extinguish the blaze. Tests showed elevated levels of the compounds, known as PFAS, in water samples from Lake Monona.
In a letter sent Thursday to ATC president and CEO Mike Rowe, the mayor said she met with ATC’s environmental director on Aug. 5 but received “few answers” and was told a detailed report would be available in a week.
Rhodes-Conway said ATC refused to turn over a copy of the completed report Thursday, ”indicating that the press release released this week by ATC was sufficient.”
Crediting firefighters, police and other municipal workers for ensuring no lives were lost, Rhodes-Conway said “the public deserves to see the full investigative report without further delay.”
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According to its news release, ATC was aware of a problem with the transformer and was monitoring it in the days leading up to the explosion. ATC said it had planned to shut it down on July 22 for a “detailed internal inspection.”
The mayor said the news release only raises more questions, such as why ATC waited to shut down the troubled transformer, which was near a gas station, whether anyone has been held responsible, and what steps ATC has taken to prevent something similar from happening.
Rowe responded Friday with a letter saying, “We are taking what steps we reasonably can to avoid a similar failure elsewhere on the ATC system, taking what we now know and applying it.”
“We have completed a review of test results of other transformers around the system as well,” Rowe wrote. “While we follow industry practices, we commit to revising internal procedures as to transformer diagnostics and responding to anomalies to continuously improve maintenance practices. We are working on a corrective action plan to attempt to avoid a reoccurrence.”
Rowe said several company directors are available to meet with the mayor to answer any questions.
Rhodes-Conway called the response “wholly inadequate.”
“They did not turn over the investigative report, and they did not even address the questions I raised in my letter,” she said. “It makes you wonder what they are not telling us. It is nice of them to offer me a meeting, but it is the public that deserves answers. We are still awaiting the full report.”
Wisconsin Public Service Commission spokesman Matt Sweeney said ATC has yet to provide regulators with a copy of the report and that PSC staff plan to meet with the utility in the coming weeks to discuss it.