Water from six wells in Tulare flunked a new test when a cancer-causing chemical came in above state standards, the city said in a letter to customers.
But the water is still safe to drink, the city said, because the presence of the chemical is not an emergency.
There is no need for Tulare residents to buy bottled water, the letter to 17,000 customers said.
The chemical is 1, 2, 3-Trichloropropane, or TCP, a waste product from making plastic. For years, it was added to fumigants that farmers put in the soil to kill tiny worms called nematodes.
To solve the problem, the city will install water treatment tanks containing granulated activated carbon that strip away the TCP.
"It's like a massive Brita filter," said utility manager Tim Doyle. The first tanks will be in place by mid-2019.
Until last year, there was no state standard for the amount of TCP in drinking water and there is no federal standard. But last year the state said public water systems could have no more than 5 parts per trillion of TCP. The Tulare wells tested at 8 parts per trillion.
The standard assumes if someone consumed two liters of water with too much TCP in it for 70 years, there would be a 1-in-100,000 chance of getting cancer, Doyle said.
The water treatment tanks will be be funded by the $23.8 million paid to the city by Dow and Shell, the two companies that from the 1940s to the 1980s manufactured the chemical and added it to fumigants.
Two new wells will also be built using the money.
Some experts call TCP a "garbage" chemical that didn't have to be added to fumigants in the first place, but to get rid of it and avoid the costs of disposal the companies added it to fumigants.
The solution caused problems for the natural environment because fumigants decay into harmless compounds but the TCP remains in the soil and travels to groundwater.
Several cities in California including Tulare have sued the two companies. The law firm of Robins Borghei LLC in San Francisco represented several of them and got multi-million dollar settlements.
In addition to Tulare, Clovis reached a settlement of $22 million in 2016, and Parlier, Reedley, Kingsburg and some small southeast Fresno water systems also reached settlements, said lawyer Todd Robins.
"This really gets the cities out of the dilemma of safe water or affordable water," Robins said. "It shifts the costs in the right direction."
Fresno, meanwhile, has three wells that have too much TCP. The wells have treatment systems already in place. It is likely that more city wells will test too high, said Mike Carbajal, assistant director of the Department of Public Utilities.
Litigation against Dow and Shell is ongoing, but the city expects to also reach a multimillion dollar settlement, he said. The money would be used to add water treatment tanks, Carbajal said.
Lewis Griswold: 559-441-6104, @fb_LewGriswold: https://twitter.com/fb_LewGriswold