Long-smoldering underground fire at landfill near Pasco is out

A fire that began smoldering underground at the Pasco Sanitary Landfill in November 2013 has been extinguished and steps have been taken to make sure another fire does not start, according to the Washington State Department of Ecology.

Data collected for six months from temperature probes has shown no evidence of the fire. In addition, wells installed to check for indications of combustion, like carbon monoxide, show the fire is out, said Chuck Gruenenfelder, site manager for the Department of Ecology.

The wells were drilled where the fire was known to have burned and in other areas to make sure there was no trash burning undiscovered elsewhere.

“We don’t see anything out there,” he said.

The next step in the landfill’s cleanup will be the release of a draft study to guide the selection of a cleanup plan for the landfill. About 32 businesses and government agencies, including Franklin County, are potentially liable for the cleanup.

The 250-acre landfill just east of Pasco city limits near the intersection of Kahlotus Road and Highway 12 is a federal Superfund site. It no longer accepts waste.

The underground fire at the landfill was persistent, but small. It covered an area at most about 30 feet by 30 feet.

The fire was burning in an area of the landfill where tires and municipal waste compacted into bales were buried.

State officials were concerned about what else was buried at the landfill. Next to the bales of household trash and fires were an estimated 35,000 drums of solvent and paint sludges and cleaners.

The landfill also has 11,000 tons of sludge from paper manufacturing and residues from the disposal of 3 million gallons of plywood resin waste, lime sludge and bulk liquid waste. Almost 5,000 drums of herbicide manufacturing waste were removed in 2002.

Water was not considered to extinguish the fire because it could carry contamination down through the soil and pollute the groundwater.

The initial plan was to place soil on areas where the ground had settled, and cracks and smoke appeared to smother the fire. Attempts in December 2013, April 2014 and May 2014 failed.

Next the parties potentially liable for the landfill’s cleanup were required by the state to inject liquid carbon dioxide under pressure into the ground to cool the waste and displace oxygen feeding the fire.

It had some success, but obstructions in the ground kept the liquid carbon dioxide from spreading throughout the smoldering trash. Probes being used to track the fire showed that temperatures that initially dropped rose again.

It took boxing in the fire with underground walls 35 feet deep and then mixing the smoldering trash with grout to finally put it out.

In some places, the fire was in the upper 10 to 15 feet of the landfill, but in other places, it was smoldering 25 to 30 feet deep.

The containment box built around the fire was about 60 feet wide and 40 feet wide. Within it, the waste was dug up and sorted.

Large, combustible items like tires and woody debris were taken to a landfill near Boardman, Ore., where they were disposed of using modern and safe methods.

Waste with hazardous chemical characteristics was taken to a chemical waste disposal site at Arlington, Ore. Some metal was recycled.

The remaining waste, mostly smaller pieces of debris, was mixed with a slurry of soil, cement and clay so it would be unlikely to catch fire again and reburied within the barrier wall.

“Our belief is this is a very isolated incident,” Gruenenfelder said.

As a precaution, an additional 300-foot-long underground barrier wall has been built of a similar mixture of soil, cement and clay to separate the household bales area of the landfill from the industrial waste area where solvent and paint sludges are buried.

This story was originally published June 5, 2016 at 7:31 PM with the headline "Long-smoldering underground fire at landfill near Pasco is out."