After wildfires, a risk to drinking water
Experts focusing on effects of toxic chemicals caused by fires flooding into plumbing systems
Two months after a wildfire burned through Paradise, Calif., in 2018, Kevin Phillips, then a manager for the town’s irrigation district, walked from one destroyed home to another. Burned out cars, the occasional chimney and the melted skeletons of washers and dryers were the only recognizable shapes.
“You started to actually be shocked when you saw a standing structure,” he said.
Phillips, now Paradise’s town manager, was following the team taking samples from intact water meters connected to homes that were now reduced to gray ash. He knew from the Tubbs Fire in 2017 that toxic chemicals were very likely to be in the water distribution system: Rapid action would be needed to protect people returning to the community from the dangers of substances like benzene, which can cause nausea and vomiting in the short term, or even cancer over time.
Wildfires, which turned skies a dim orange over cities from Seattle to Santa Cruz, Calif., this year, are increasingly engulfing people’s homes, continuing to rage in California, Colorado, Oregon and Washington state in recent weeks. But even when homes don’t burn, other dangers arise in the aftermath, and experts are focusing more attention on what happens to municipal water systems after a fire, when released toxic chemicals can get pulled into plumbing systems, and other damage can linger in pipes for years.
After the fire that destroyed Paradise, for example, tests reported in a new study showed benzene levels in drinking water at 2,217 parts per billion. The Tubbs Fire led to levels as high as 40,000 parts per billion. California health authorities say 1 part per billion is dangerous over the long term, and 26 parts per billion is dangerous for short-term exposure. And many other compounds that end up in water after a fire can also create health risks.
“It’s hard enough having the pandemic restrictions,” said Angela Aurelia, a resident of Boulder Creek in Santa Cruz County, whose home was partly damaged in August. “And then you have a wildfire, and you lose access to your home and then we can’t even go back home because the water isn’t likely safe to use.”
Phillips and some others who work to ensure that the water flowing into homes is safe say they are following guidelines that are not devised for this kind of disaster.
After a fire, water in houses and in the underlying pipes “can become contaminated with an array of volatile organic compounds and semivolatile organic compounds” at levels that exceed the regulatory limits set by the state of California as well as the federal Environmental Protection Agency, said Amisha Shah, a water quality engineer at Purdue University. “It’s very clear it needs to be addressed.”
Volatile organic compounds, such as benzene, naphthalene and methylene chloride, have a low boiling point and can be dispersed into the air easily. Semivolatiles, including chrysene and benzo(b)fluoranthene, have a higher boiling point but can be dispersed during, for example, a warm shower. Although not all of these compounds are harmful, some have been found to cause cancer in the long term.
Shah was a co-author of the study published in July by AWWA Water Science that summarized the lessons from the past few years. Analyzing sample data from the Tubbs Fire as well as the Camp Fire that destroyed Paradise, the researchers found some of those harmful chemicals caused by wildfires throughout the distribution system. Earlier concern had focused on ash runoff making its way into water sources, like reservoirs.
The researchers’ observations lined up with Phillips’ experience in Paradise two years ago.
“Over 50 percent of those service lines from burned structures had some detection of contamination,” he said.
But he noticed there was a randomness to it. Water in one house would be contaminated, while the neighboring system would be clear.
The state’s regulations appeared inadequate to deal with a post-wildfire situation, forcing Phillips and his team to effectively improvise their own standards. “We did go over and above what maybe the water board would’ve required us to do,” he said.
Had they not, he said, it might have taken years, if not decades, to have clean drinking water again in the town.
How water moves through distribution systems, especially during a wildfire, is complex and needs more study. But Shah and the other researchers say that a loss in pressure, which occurs when fires damage pipes, turns the plumbing into a vacuum that sucks smoke and other toxic chemicals out of burning homes. Those substances then get circulated throughout a community’s water distribution system. It can even become worse, for example, when firefighters use a nearby hydrant, a necessary step that effectively encourages circulation.
In addition to toxic substances becoming more widely dispersed from those charred buildings, plastic piping common in California’s mountainous areas releases chemicals when heated, melted or burned. The study’s authors said such piping, even if it was not damaged, could absorb harmful chemicals passing through them that would leach into the water over a long period of time.
In San Lorenzo Valley, for example, 7.5 miles of high-density polyethylene pipes burned and were destroyed on Aug. 21. The aboveground pipes, which wound through a steep, heavily wooded mountain in Santa Cruz County, supplied water to more than 21,000 residents.
During the chaotic aftermath of a wildfire, members of water districts can feel overwhelmed and confused about the best course toward ruling a system safe to use again. While many local water districts and other water utilities test for volatiles, most are not looking for semivolatiles.
In the case of the San Lorenzo Valley pipes, regulators have been told to test only for the 80 or so compounds in the EPA’s volatile organic compounds screening, despite evidence that burning plastic pipes release some semivolatiles, too.
Advice for residents has also been inconsistent. While the state recommends “do not use” orders when there is “an unknown contaminant,” most utilities are being told to issue “do not drink, do not boil” orders to prevent ingestion. But scientists worry that even taking a shower or washing may not be safe if the water has high levels of the compounds.