City officials tested some 2,000 water samples after the fire, and have now concluded the contamination came from plastic water supply pipes that melted in the fire.
Santa Rosa’s problem, however, is the first known case of plastic pipes causing widespread water contamination after a fire.
“We now know that the combustion, the burning, the melting of various plastic components in our distribution system gave off constituents that got into the water system,” said Bennett Horenstein, Santa Rosa’s director of water.
Thirteen Fountaingrove homes survived the fire and remain exposed to the contamination.
The long-term solution, said Horenstein, involves replacing the entire water supply system in the affected Fountaingrove neighborhood, including underground water mains that did not melt.
Some samples taken from the Fountaingrove neighborhood after the Tubbs Fire detected benzene at 80 times that limit.
Horenstein said there’s nothing unique about Santa Rosa’s water system or the materials used in its plumbing.
First, plastic water system components in homes – faucets, water lines in walls and crawl spaces – burned and melted in the fire.
The chemicals generally like to be in the plastic and not so much in the water.” Plastic pipes, in other words, are permeable.
He defended the organization’s testing protocol, and said it is willing to consider new testing methods.