When Arrowhead Electric Cooperative, Inc. line crews responded to a power outage in Grand Portage on the evening of Sunday, April 11, they found that an electrical transformer on a pole near the Grand Portage Trading Post was damaged and had leaked oil onto the ground. Arrowhead Electric immediately contacted the Minnesota Pollution Control Agency (MPCA) and the Grand Portage Environmental Department.
Arrowhead Electric Manager Don Stead said Environmental Troubleshooters of Duluth was contacted to assist in the cleanup.
The transformer was replaced and the electricity was restored Sunday evening Absorption pads were put in place to contain the contaminant, which was mineral oil containing a trace amount of PCBs (Polychlorinated biphenyls).
Stead said delineation of the affected area and preliminary cleanup was conducted on Monday, April 12. Amy Seitz of the Grand Portage Environmental Department said her office and Arrowhead Electric oversaw the cleanup.
“Soil removal was performed on Tuesday with 22 cubic yards of material being removed,” said Stead.
Seitz said “about two dump truck loads” were taken to a facility in Schroeder that is licensed to treat contaminated soil. The area was then filled with clean gravel. “It should not be a problem. While we don’t want to see anything spilled, this product is not extremely hazardous. It is a type 2 mineral oil with very small amount of PCBs. It is classified as less than 1 part per million,” said Seitz.
Asked for a layman’s explanation of “part per million,” Stead said in a gallon of mineral oil, that would mean a drop of PCBs.
Seitz said the oil was primarily contained under the power pole and it is believed that all of the contaminated soil has been removed. Environmental Troubleshooters took samples of the surrounding soil and Seitz said a final report would be issued soon. However, she said it is believed the cleanup was successful.
According to the Environmental Protection Agency (EPA), PCBs belong to a broad family of man-made organic chemicals known as chlorinated hydrocarbons. PCBs were domestically manufactured from 1929 until their manufacture was banned in 1979. Due to their non-flammability, chemical stability, high boiling point, and electrical insulating properties, PCBs were used in hundreds of industrial and commercial applications including electrical equipment such as transformers.
Stead said Arrowhead Electric no longer uses transformers that contain PCBs, however since PCBs were used in the manufacture of transformers, traces are still sometimes found in older transformers. Stead said if Arrowhead identifies a transformer as having PCBs, it is replaced.
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