The cause of a fire that broke out in the northeastern section of the Juniper Ridge Landfill on Monday, May 15, 2023, is unlikely to be determined. Credit: Linda Coan O'Kresik / BDN

The cause of Monday night’s fire at the state-owned Juniper Ridge Landfill in Old Town may never be identified, according to the Maine Department of Environmental Protection.

The fire started on the landfill’s northeastern slope, Maine DEP spokesperson David Madore said Wednesday. DEP officials visited the site Tuesday morning.

“It is doubtful that the cause will be discovered because of the effort needed to put out the fire,” he said.

Firefighters fought the blaze Monday from about 8 p.m. to midnight. Workers from landfill operator Casella Waste Systems and two construction companies continued moving dirt to the site into the morning hours to prevent the fire from reigniting, Casella spokesperson Jeff Weld said.

Determining what caused the blaze and the state’s assessment of the site after it was extinguished comes amid ongoing concerns about the landfill, including a sludge crisis in February. While worries from nearby residents about the landfill’s effects on their health and the environment are not new, the fire is making some demand answers from Casella and the state.

The state will not monitor air quality because there are no longer emissions now that the fire is out, Madore said.

The fire and movement of waste and soil might have harmed the landfill’s gas infrastructure, which is now being evaluated, he said.

Water runoff from firefighters went to an internal collection system, Madore said, and there is no evidence of contaminated water leaving the site or traveling to the Penobscot River. Soil used to extinguish the fire remains in the landfill cell, he said.

Don’t Waste Maine — a group advocating for policies that protect people from the harmful effects of landfill, sludge disposal and other operations — hopes the fire was a wakeup call for the state and Casella.

On Tuesday night, members held a news conference at the Alton home of Laura and Harry Sanborn, who live down the street from the landfill, where they raised concerns and pressed for more oversight. Members wanted answers about what caused the fire and potential health risks.

They called for an effective plan in response to future events like the landfill fire, and more effort from the state to work with the Penobscot Nation, among other requests.

During an uncontrolled burn, contaminants such as carbon dioxide, particulate matter and dioxins are released into the air, said Jean MacRae, an associate professor of civil and environmental engineering at the University of Maine.

Dioxins take a long time to break down once they’re in the environment. They are highly toxic and can cause cancer, reproductive and developmental problems, damage to the immune system and can interfere with hormones, according to the United States Environmental Protection Agency.

Generally, uncontrolled burning is not good, but landfill fires tend to become problematic when they last a long time and continue to smolder, MacRae said.

“It depends on how much [pollutants] got released, how long the fire went on, how much wind was blowing,” she said, along with factors such as temperature and the size of the fire. “That affects the concentration of where the fire is, and the concentration and how long people were exposed would determine the degree of toxicity.”

Maine DEP staff members are expected to return to the landfill on Thursday for a previously scheduled meeting about construction, and they plan to conduct a follow-up assessment of the site.