Benzene found in the water supply of fire-ravaged Paradise, California

After the October 2017 Tubbs wildfire, the northern California town of Santa Rosa was blindsided when it discovered that some of its fire-damaged water systems were contaminated with the carcinogen benzene. This phenomenon, never before reported, threatened to add millions and months to recovery cost and time. Little more than a year later, it happened again.

In November 2018, the Camp Fire—California’s most destructive wildfire in history—leveled the town of Paradise. Water officials there now report they have discovered the same problem with benzene and other volatile organic compounds (VOCs) that plagued Santa Rosa, but on an exponentially greater scale.

Whereas Santa Rosa will be replacing up to 500 service lines at a cost of several million dollars, Paradise has 10,500 affected lines—roughly 280 km of pipe. Paradise estimates replacing the pipes could cost as much as $300 million, and it may be 2 years before the city can provide safe drinking water to its residents. The legal limit in California for benzene in drinking water is 1 part per billion, while average levels in benzene-positive samples in Paradise have been 31 ppb.

The contamination in Santa Rosa and Paradise paints a grim picture for wildfire-vulnerable towns in the western US as climate change increases fire frequency and intensity. When only Santa Rosa was affected, people might have thought it was extra-bad luck. Now that it’s happened in Paradise also, “I have a feeling people are paying attention to this now,” says Jackson Webster, a water quality engineer at California State University, Chico. The need for water scientists and engineers to pay attention is great: there is no standard protocol to test water after a wildfire, let alone courses of action to prevent water system contamination.

The California towns are leading the way out of necessity. Santa Rosa established a protocol of letting water sit inside a pipe for 72 hours before testing, to allow contaminants to collect. Though it takes two weeks for contents in a pipe to reach equilibrium, 72 hours has appeared to work well, water officials say.

Paradise is stepping up from Santa Rosa and is now undertaking an arduous testing program. On the advice of Andrew Whelton, an environmental engineer at Purdue University, Paradise has decided to test not only for benzene, but 65 other VOCs, setting a bar for rigorous contaminant detection.

As for prevention strategies, those may hinge on pinpointing the mechanism of contamination. One likely source is fires causing plastic pipes—a necessity in earthquake country for their flexibility—to melt or combust. Then the extreme amounts of water needed to fight these enormous blazes could create a pressure drop that allows vapors or particulates to be sucked into the water system. But these are still theories, Whelton says.

Further complicating the picture is that not all recently fire-ravaged northern California towns suffered the fate of Santa Rosa and Paradise. Redding, which was devastated by the Carr fire in August 2018, did not report benzene or other contamination in its water system. Whelton cautions, however, that without standardized water testing, it’s hard to know what really happened in Redding.

Meanwhile, Paradise residents desperate for drinking water may be taking risks. Some whose houses are still standing are spending thousands of dollars on large temporary water filtration systems. Others are simply using refrigerator or pitcher filters. The efficacy of such filtration for the extreme conditions in Paradise hasn’t been established, Whelton says. The Paradise school district is installing “industrial strength activated carbon systems” in two schools it hopes to reopen in August, according to an April 11 facilities update sent to families.

And after a winter of average or greater precipitation, much of the Western US is carpeted in greenery that will soon dry into fuel for the next fire season.