The deadliest and most destructive wildfire in California history, November's Camp Fire, killed 85 people and destroyed 87 percent of the 10,480 buildings in the mountain town of Paradise.
Once home to 27,000 residents, about 1,500 people and 1,300 structures are all that's left in Paradise. Those remaining are plagued with another problem only known to have happened one other time: wildfire-caused contamination of the drinking water system.
The carcinogen benzene and other volatile organic compounds (VOCs) somehow got into Paradise's drinking water system, which is made up of 172 miles of water mains and 10,500 service lines.
Built with a variety of materials, the Paradise system conveys water by transmission, distribution and secondary mains made mostly of asbestos cement but also PVC, concrete, steel, cast iron and ductile iron. The mains then connect to service lines made mostly of copper and high density polyethylene but also steel, PVC and polybutylene.
The possible roles played by the different pipe materials in the tainted water system have been assessed by local, state and university experts but to no certain conclusion.
"The science of wildfire-driven VOC contamination of a water distribution system is new, not completely understood, and an area of ongoing research," says a 74-page recovery plan of the Paradise Irrigation District (PID), which operates the damaged system.
A lot of the research is still unfolding in Paradise, where results of the PID's initial round of water samples were described as "jaw-dropping" by a member of California's Water Resources Control Board. About 32 percent of the 500 water samples detected benzene at an average level of 27 parts per billion. California's drinking water standard is one ppb while the federal standard is five ppb.
PID tested for VOC contamination because benzene had been detected one other time in the drinking water of a fire-ravaged area. That was 100 miles away in Santa Rosa, where the October 2017 Tubbs Fire burned 3,100 homes in a matter of hours.
An oft-cited theory in both incidents is that the contamination happened when first responders and residents fought the firestorms. The excessive demand of fire hoses and garden hoses drew heavily from the water system and it depressurized, which created a vacuum effect that sucked in a toxic combination of gases from the fires.
"Some of those VOCs can end up adsorbing [soaking] into the walls of the pipe in the water distribution system," the PID recovery plan says, noting this can happen with any type of pipe material.
Once VOCs are adsorbed in pipe walls, they later desorb into the water in the pipe. To restore potable water service, PID will take thousands more water samples, replace contaminated service lines and flush contaminated mains at a cost of $53 million. The work will take two years.
In the meantime, residents will continue using bottled water for drinking, brushing teeth, making ice and preparing food. They also have been advised not to use hot water or swimming pools or let pets and livestock consume tap water.
Officials at two plastic pipe trade groups said they had never observed similar situations occurring in water distribution systems until the Santa Rosa and Paradise wildfires. They call the depressurization theory reasonable but dispute some other findings.
"The most plausible explanation is that the water mains became depressurized due to the extremely high water demand associated with fighting the fires. There were likely breaches of the service lines inside buildings, allowing combustion gases, including benzene, to be drawn into the distribution system," Bruce Hollands, executive director of the Uni-Bell PVC Pipe Association, said in an email.
Based in Dallas, Uni-Bell represents PVC pipe producers.
Tony Radoszewski, president of the Irving, Texas-based Plastics Pipe Institute, said the devastation to homes, offices and the overall community provided many sources of contamination.
"Just look at the building materials and contents of a house and yard, including trees with sap that have all sorts of organic compounds," Radoszewski said in a phone interview.
"That fire burned everything: wood frames, asphalt shingles, appliances and automobiles. There were shells of cars that contain materials like batteries, oil, operating fluid and tires. Asphalt driveways and roads also burned with tons of hydrocarbons in them," Radoszewski said.
PPI represents mostly polyethylene pipe manufacturers.