After wildfire tore through Paradise, Calif., tests found high level of benzene in pipes to the structures that remained.

Recovery teams work in the damaged region around Paradise, Calif.

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.

The Camp Fire destroyed nearly 90 percent of the homes and other structures around Paradise, Calif., and was so hot it melted plastic auto parts.

A year earlier, the Tubbs fire scorched 36,807 acres, destroyed 5,643 structures and killed 22. It had been California's most destructive wildfire until the Camp Fire.

In Santa Rosa, benzene was discovered in the water when residents started moving back in early November 2017. Someone called to complain about the taste and smell of the water.

The staff of the local utility, Santa Rosa Water, took water samples and found contaminants including benzene, which had never before been detected in the water system, at levels above the allowable regulatory limit. The utility issued an advisory about water quality in the contaminated area.

The area of concern for benzene was limited, however, to 5 miles of drinking water pipes in a neighborhood called Fountaingrove, where about 13 of 352 houses were left standing. It was not as widespread as Paradise, and it could be isolated.

Santa Rosa Water fixed the problem for about $8 million by replacing the 352 service lines, eight hydrants and 1,300 feet of water main. The city went with poly-coated copper tubing as the replacement material for the service lines.

The polymer used to coat the copper is polyethylene, Joe Schiavone, Santa Rosa's deputy director of Water and Sewer Operations, told Plastics News in an email.

"The benefit of the poly coating is that it protects the copper from corrosion caused by the soil it's buried in," Schiavone said.

The Paradise utility is facing a longer time frame and a much steeper tab of $53.3 million to fix its damaged water system. The recovery plan calls for sampling 20,000 service lines and water mains for VOCs in addition to replacing and flushing pipes to restore drinking water by early 2021.

The city will use HDPE to replace all damaged service lines, noting in public documents that it is simple to install and is the most cost effective material. To replace mains, the PID will go with PVC or ductile iron for shallow-trenched mains and fusible HDPE for deeper mains.

"The fact that Paradise will still be using PVC water pipe going forward is a testament to PVC's reliability, durability and safety," Uni-Bell's Hollands said.

PPI members are seeing a lot of success with PE pipe in California because it can be fused, which stops costly and wasteful leaks, and it is flexible to withstand earthquakes.

"It is the best product in seismic areas whether its gas or water," Radoszewski said.

While the recovery plan awaits implementation and funding, Paradise residents are setting up giant water tanks that hold 330-2,500 gallons of water and paying about $250 to fill them for three or four weeks for bathing and cooking.

Pipe that had been stored outside during a wildfire shows damage from the heat.

In Santa Rosa, the city and utility worked with state and federal agencies, toxicologists, forensic chemists and national water quality experts to understand the causes and extent of the contamination, Jennifer Burke, interim director of Santa Rosa Water, told Plastics News.

"The good news is, based on the methodical and data-driven investigation, that we were able to determine that melted plastics, smoke, soot and ash entering the water system during the fires was the source of the contamination," Burke said.

The city also found the highest levels of contamination were occurring in service lines, she added.

A five-page technical memorandum issued in March 2018 by Santa Rosa Water says benzene and other contaminants entered the water system by three "circumstances." First, water infrastructure was exposed to extremely high temperatures, which can cause pyrolysis, or thermal decomposition.

The memo says during the peak of the Tubbs fire, temperatures reached sufficient levels to cause pyrolysis, and studies show pyrolysis of HDPE can produce benzene and other contaminants. PE pipe experts strongly disagree with that point.

Second, the loss of water pressure created a vacuum that pulled contaminants into the system. The memo says contaminants from pyrolyzed pipes and appurtenances, along with contaminated hot air, ash, char, and other debris, were back-siphoned into service lines and distribution main lines when the water system lost pressure.

Third, the drinking water picked up contaminants from water distribution infrastructure. The memo says clean water stored in or traveling through contaminated portions of the water system can absorb benzene and other contaminants.

"The contamination either adhered to copper water service lines or absorbed into plastic water service lines," Burke said in an email. "By replacing contaminated components of the system, we have been able to resolve the issue and restored water quality to that area in October 2018."

Damage left behind from the Camp Fire.

PPI raises several issues related to the Santa Rosa findings. Although the plastic pipe in the system may have burned or melted, Radoszewski said the trade group doesn't believe that the specific contaminants that have been detected in the water system originated from the burning or melting of PE pipe.

"Where is this stuff coming from in the quantities they are talking about? Is plastic pipe just an easy foil?" Radoszewski asked. "The city water department indicated that their water system used polyethylene only in service lines, which constitute a minor component of water distribution systems. This is small service tubing about an inch in diameter. It's a fraction of the mass of a house, but some want to blame that for benzene."

In a typical dwelling fire — with conditions of 1,000° F and the presence of oxygen — pyrolysis wouldn't occur, according to PPI. Instead, combustion of polyethylene would occur, forming significantly different contaminants, such as carbon dioxide and water. That would be the case for all PE piping products, PPI says, including service lines, cross-linked PE plumbing, telecommunications conduit and corrugated drainage pipe.

The technical director at the Vinyl Institute, another trade group, said there is some evidence that PVC can produce benzene by pyrolysis, but only in highly controlled environments without any air. Wildfires occur above ground in the open air.

"Since PVC does not produce benzene in open-air combustion, PVC pipes could not have emitted the benzene found in the cities' water," Domenic DeCaria, a chemical engineer at the Vinyl Institute, said in a recent blog.

PPI also points to a 1996 study by the Society of the Plastics Industry Inc. — now the Plastics Industry Association — that evaluated the substances released when PE was in a molten state. The study demonstrated that no aromatic substances, such as benzene, are generated when PE melts, PPI says.

"We recognize that introduction of ash, soot and other wildfire combustion byproducts certainly could have been back-siphoned into the water system service lines and mains from severed dwelling connections during the fire," Radoszewski said. "In our view, the introduction of these combustion byproducts into the water system is the likely source of the contamination and not burning or melting of the polyethylene pipe. This phenomenon would likely have occurred for any water system that experienced the significant damage as that was observed in Santa Rosa."

The cause and extent of the benzene-tainted water system in Paradise and other communities in Butte County, Calif., still isn't fully known.

"It wasn't just Paradise. About 2,400 private wells and a number of smaller public water systems that serve 25-200 people each also were impacted," Andrew Whelton, an associate professor of civil and environmental engineering at Purdue University, said in a phone interview.

After the county health department warned residents not to use home filtration systems, because they may not provide adequate protection, Whelton recommended Paradise home and business owners go with temporary water tanks until the damaged system is repaired.

Paradise officials initially contacted him with questions about water testing, he said, then he participated in weekly conference calls about the Camp Fire response and recovery.

"A community of scientists, engineers and public health officials are struggling to understand where the contaminants are coming from. Are they being generated or are they migrating into the system? That's our main interest," Whelton said.

He traveled to Paradise, where he said he heard a handful of theories suggesting the problem could be related to depressurization of the water system, toxins created by burning plastic water system materials, or leaching or leaking underground storage tanks.

"The fact of the matter is there's no conclusive evidence yet of where the sources are for these contaminants and if there are different sources for the same water system," said Whelton, who continues to be involved with helping residents understand lab results on a voluntary basis.

Because water distribution systems involve a variety of different materials and appurtenances, Radoszewski said a comprehensive study of how to design systems to address problems would be best conducted with either the American Water Works Association or the Water Research Foundation.

"We encourage the entire water industry to study this issue," he said.

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