The Marshall Fire as seen from the City of Boulder on Dec. 31, 2021. Credit: John Herrick

Update: As on Jan. 14, state health officials have not found any evidence of contamination in Superior’s drinking water in concentrations exceeding federal health standards. Read our latest story for more information on post-fire water quality concerns.

The Colorado Department of Public Health and Environment will review water samples to determine whether last week’s Marshall Fire could have caused long-term contamination to drinking water supplies. 

The blaze left nearly 1,000 homes and businesses destroyed and thousands of residents displaced. For those able to return to their homes, the Town of Superior and City of Louisville are asking them to boil their water or use bottled water until further notice. 

Boiling the water is intended to kill bacteria that entered the drinking water system due to the fire. Fire-fighting depletes water levels and fires damage water mains. Pressure inside the water system drops as a result. When that happens, plumbing pulls in bacteria.

The state health department said it plans to review samples to determine whether toxic chemicals emitted from burning homes were also drawn into the system to contaminate drinking water. This includes volatile organic compounds (VOCs), such as benzene, which can cause nausea and vomiting from short-term exposure and, over time, cancer. 

In the aftermath of California’s 2017 Tubbs Fire and 2018 Camp Fire, researchers found toxic VOCs in drinking water systems at levels exceeding federal health standards. In some cases, unhealthy chemicals were detected months after the fire had passed. 

‘It is prudent to be cautious’

It’s unclear whether water supplies in and around the Marshall Fire burn area will be similarly affected, according to Fernando Rosario-Ortiz, director of environmental engineering at the University of Colorado Boulder. 

But, he added, “It is prudent to be cautious that a possibility of contamination exists based on what we’ve seen. It is also prudent to do some testing to make sure the water is safe for the communities to drink.” 

The full impact of the Marshall Fire, the most destructive in Colorado’s history in terms of property damage, remains unknown. County officials said they are patrolling the burn area with cadaver dogs in search of two missing people. Officials said the cause of the fire is still under investigation. 

Water quality issues may be yet another lasting impact of the Marshall Fire well after the smoke has cleared. 

Alex Ariniello, the director of the Department of Public Works and Utilities for the Town of Superior, said the town plans to flush the water system and lift the boil water advisory as soon as Friday. 

Boiling water and flushing systems are not certain to remove VOCs from the water. A July 2020 study published in AWWA Water Science found benzene levels exceeding California’s health standards lingered for months in water supplies even after flushing. 

Heated, burned or melted plastic pipes can cause chemical contamination, too, according to the study. Plastic pipes can trap the toxins and release them over time into the water, the researchers said. 

Ariniello said the town uses plastic PVC pipes for main lines and copper pipes to service buildings. He said the town has shut off services to homes completely destroyed to prevent contaminated water from coming back into the system.

The researchers said officials should issue a “strict ‘Do Not Use’ water order” to protect public health following a wildfire in an urban area. 

But local officials said they are restoring utilities, including water service, to get residents displaced by the fire back into their homes as soon as possible. Many have been staying at hotels or with friends or family. Earlier this week, two dozen people were still staying at the Red Cross emergency shelter in Lafayette.

Ariniello said he didn’t want to sensationalize the risk to residents. 

“We’re really worried about getting word out and getting people overly excited about something like that,” he said.

Ariniello said the state health department plans to review more than a dozen water samples and will determine when the water is safe to drink. 

A spokesperson for the state health department said it anticipates receiving the first water sample test results this week, including sample results for VOCs. 

Erin Garcia, a spokesperson for the department’s Water Quality Control Division, said in an email to the Boulder Reporting Lab that it considers boiled water safe to drink. Garcia said preliminary test results for the Louisville indicate that VOCs are not present in the city’s drinking water system. 

“If VOC sample results were above drinking water standards, we would take additional action and notify the public accordingly,” Garcia said.

Half the state lives in fire-prone areas

The impact of wildfires is more obvious when ash-laden runoff from burn scars turns rivers black than when chemicals contaminate underground water lines. 

“The fact that questions about chemical contamination cannot be answered with a lot of details at this point means that there’s a lot of research that needs to be done,” said Rosario-Ortiz, of CU Boulder. 

He added, “We know, sadly, we’re going to have more of these situations in the near future.” 

Nearly three million residents — about half the state population — live in areas at risk of wildfires, according to state foresters. That number is growing, too, they said. Experts also expect climate change to increase the prevalence and severity of fires in the wildland-urban interface

Residents can get free water at the Louisville Public Library and the Louisville Recreation & Senior Center until potable water is restored, according to the Boulder Office of Emergency Management. The YMCA of Northern Colorado and the Disaster Recovery Center, both in Lafayette, are also providing residents with free bottled water. 

John Herrick is a reporter for Boulder Reporting Lab, covering housing, transportation, policing and local government. He previously covered the state Capitol for The Colorado Independent and environmental policy for Email: