Cleanup and restoration efforts continue in the aftermath of a large fire that broke out last week at a Puget Sound Energy (PSE) substation in Redmond off of Willows Road.

Martha Monfried, director of corporate communications for PSE, said Wednesday it will be a few weeks before the utility’s investigative team determines what caused a high-voltage transformer — filled with 15,000 gallons of non-toxic mineral oil — to go up in flames at the Sammamish substation just after noon June 16.

Mineral oil — approved by the FDA in personal care and cosmetic products, as well as for an additive for food — is used as a coolant and conductor for all PSE transformers, Monfried said.

Monfried said PSE will have final cost estimates of the damage caused by the fire next week, saying that “the transformer alone costs $3 million and $1 million more in equipment to install.”

There will be additional costs in the cleanup and transformer replacement efforts, Monfried said.

The state Department of Ecology was at the substation last Friday, advising contractors doing cleanup, but are no longer on site.

PSE’s environmental consultant, Geo Engineers, Inc. along with PSE environmental and engineering teams are leading the cleanup and replacement project, along with providing regular reports to Ecology, according to Larry Altose, spokesman for Ecology.

Some mineral oil from the transformer and foam used to douse the the fire did enter the storm drains that eventually lead to a creek that feeds into the Sammamish River, a major habitat for salmon.

In total, crews have recovered 60,000 gallons of liquid — water, oil and foam — as part of the cleanup effort, Altose said.

But some quick thinking by responding fire officials minimized the potential environmental damage, Altose said. He added that officials are estimating that about 1,000 gallons of transformer oil and foam spilled into a nearby bioswale — a drainage ditch that helps filter polluted stormwater before entering a drain that feeds into a nearby creek.

Soon after arriving at the site, fire officials instructed the City of Redmond public works department to close off the link between the bioswale and the storm drain. The drains were blocked off and cleaned, therefore minimizing the spill into the nearby creek, Altose said.

“The spill got into the bioswale and it stopped there,” Altose said. “That avoided a huge oily, foamy mess that would have been pretty substantial. It could have been environmentally damaging to organisms that live in the river.”

Monfried agreed, saying shutting off the link to the storm drain “was quick thinking” and “good teamwork.”

As water and foam spilled into the bioswale while firefighters contained the fire, crews, using vacuum trucks, sucked the liquid out of the bioswale into a large tanker, according to Monfried.

With the environmental impact minimized, crews are now focusing on testing the affected landscape and extracting the contaminated soil near the transformer and the bioswale, according to Randy Walls, PSE project manager.

“They are going to dig until there are no traces of oil,” said Wall, who added that a soil testing lab was to be set up at the site today (June 22) to improve the efficiency of the project. In addition, the project calls for building a new transformer pad, installing the new transformer and rebuilding the horizontal structure above the transformer, according to Monfried.

The toasted transformer (above) was moved off its pad on Saturday and Sunday. Then today (June 22), crews were to begin jackhammering the existing pad and removing the contaminated soil around the pad, Walls said.

A new pad will be built and the new transformer (left) — a spare one that was being stored at the Sammamish substation — will be put on the new pad by July 9 and will be energized by the end of July, according to Walls.

Monfried said it was the first transformer fire at PSE in at least 40 years, but she did say a breaker caught fire at the Sammamish substation in January 2000. Last Friday’s fire belched a large plume of black smoke, which could be seen from miles away, but thanks to some quick-thinking teamwork, the environmental impact was minimized, Monfried said.

The fire caused power outages throughout the region to approximately 25,000 customers, but power was restored within three hours. “It’s remarkable we were able to get people back in three hours,” Monfried said.

“Now we have to check everything, put it back together and make it better than it was before,” Monfried said.