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Soaring contamination causes shutdown of Tucson water treatment plant
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Soaring contamination causes shutdown of Tucson water treatment plant

Tucson Water has been removing PFAS-contaminated water at the TARP treatment plant but says that as levels of the chemical compounds soar, it can no longer confidently remove enough to make the water safe for drinking.

The groundwater on Tucson’s south side has become so contaminated that Tucson Water will soon shut down the plant that’s been treating it for 27 years.

Although city officials say the plant has always delivered water that’s safe to drink, they can’t guarantee that any longer because of rising levels of chemical compounds known as PFAS in groundwater the plant is supposed to clean up.

“Unfortunately, we have hit a critical moment where we can no longer confidently deliver safe drinking water” from the Tucson Airport Remediation Project, Mayor Regina Romero said at a news conference Tuesday.

“When it comes to our drinking water — our most precious resource here in the Sonoran Desert — quality and safety come first, which is why we are taking this proactive step out of an abundance of precaution,” Romero said.

Once the plant is shut down, homes and businesses getting its water can access another supply from the Central Arizona Project, which brings Colorado River water via canal, or from other wells, city officials say.

But in the long term, the shutdown deprives the city of an alternative drinking supply if CAP deliveries are cut back to Tucson.

When and if the plant is reopened, it will no longer serve drinking water to people. Its treated water will be discharged into Tucson’s reclaimed water system, the Santa Cruz River or both, according to city officials.

Fragility of drinking supply

The plant will be indefinitely shut down June 21 because it’s getting too difficult to remove the PFAS chemicals, officials say.

The plant’s closure underscores the continued fragility of the city’s drinking water supply. Tucson already has shut off wells in large parts of the central city and the south side due to contamination.

And its current main drinking supply, the CAP water from the Colorado River, faces long-term threats due to continued hot and dry weather across the West, triggered in part by climate change.

The plant, known as TARP, has served 60,000 customers in downtown Tucson and other parts of the city’s urban core with water that’s been treated to remove PFAS and two other contaminants, trichloroethylene (TCE) and 1,4-dioxane.

It’s operated under a consent order with the U.S. Environmental Protection Agency, which requires the city to serve the plant’s treated water to individuals and businesses.

In 2020, the treatment plant sent 6,120 acre-feet of treated water to customers in an area bounded by River Road and El Camino del Cerro on the north, nearly the Tucson Mountains on the west, the Campbell Avenue area on the east and almost to 29th Street on the south.

Although “we’re not at that level” at which the plant can’t clean up the water, that point is imminent, said Tucson Interim Assistant City Manager Tim Thomure at the news conference. “Once you get to that point, there’s no going back.”

PFAS compounds, also known as perfluorinated compounds, are considered “forever chemicals” by many pollution experts. They don’t break down easily in water. The EPA considers several chemicals in the PFAS family potentially cancer-causing.

The city sets 18 parts per trillion as a limit for drinking water, or 70 parts per trillion in reclaimed water. The level coming out of the TARP plant is below the level that the city’s equipment has the ability to detect.

The water flowing into the TARP plant is now at 95 parts per trillion.

It reached about 125 parts per trillion in April, and city officials do not want it exceeding 140 parts per trillion. The levels fluctuate as the city turns on and off wells that deliver water to the plant, Thomure said.

The EPA sets no mandatory limit for drinking water, although it advises, for health reasons, a limit of 70 parts per trillion for lifetime exposure.

The federal government says that when consumed at high enough levels over a lifetime, PFAS can cause a long list of ailments, led by kidney and testicular cancer. Others include developmental delays in fetuses and children, decreased fertility, changes to the immune system and increased asthma risks.

PFAS levels soar

The city uses what’s known as a granular activated carbon process to remove the PFAS.

But in the past four years, levels of the compound, once commonly used by the military in firefighting foam, have soared up to 300% and 400% in the plant’s feeder wells.

To keep the plant running properly, the utility has replaced tanks containing granulated activated carbon, where the cleanup occurs, four times. While that has cost the city $1.8 million, cost is not driving the plant closure, Thomure said.

It’s that the city has no backup plan in case the rising PFAS levels ultimately overwhelm the plant’s ability to clean the water, he said.

The carbon filter system “is our spare tire,” Thomure said. “The spare tire works and it has limitations. We’ve been able to drive a spare tire at 30 mph for a certain distance, but road conditions are changing. We’re about to move from smooth pavement onto a gravel road, using a spare tire. It’s not about not having enough money to buy spare tires.”

Residents’ concerns

Speaking at the news conference, south-side activist Yolanda Herrerra said she is concerned about potential effects of the plant shutdown on whether the EPA will continue to be OK with the pace of the broader pollution cleanup.

After dozens of south-side residents sued the city and various polluters in the 1990s over TCE contamination there, the EPA signed off on the use of the TARP plant as part of the settlement of the lawsuit, she said.

“The city has to keep that plant running to remove all the TCE. They are sanctioned to do that as a result of the lawsuit,” said Herrera, who chairs an advisory board overseeing the overall south-side water cleanup. “You say it’s temporarily but indefinitely shut down. What does it mean?”

She expects a grandchild to be born into her family next month and wants to insure the child has a good quality of life, Herrera said at the news conference.

South-side resident Robert Jaramillo told the news conference that the plant shutdown is long overdue.

“I want to thank the mayor and City Council for stepping up to the plate and saying enough is enough. Please reach out to responsible party to take care of our community,” he said. “This is nothing new to us, the contamination. We’ve lived it, we’ve breathed it and a lot of us have eaten it. We all had classmates, siblings, parents and children who suffered the consequences.

“They’ve tested the heck out of the water. I’d like to know when they’re going to test the community,” Jaramillo said.

Federal funding sought

The plant will stay closed until either whoever contaminated the area’s aquifer with PFAS cleans it up or the city finds another use for its treated water, utility officials said.

But Tucson Water officials are concerned the plant’s continued closure will let aquifer contamination migrate downstream, untreated, fouling more of the groundwater supply.

That illustrates why it’s important to get federal funding for cleaning up the PFAS from the aquifer, said Romero and City Councilman Steve Kozachik.

Since TCE was discovered, city taxpayers stepped in and supported cleanup, not knowing whether they’d be reimbursed by the feds, Romero said at the news conference.

“Decades later, we have stepped up the treatment of PFAS contamination, because our top priority is insuring residents and customers have access to safe, clean drinking water. However, city taxpayers and ratepayers are not responsible and should not be left holding the tab,” Romero said.

People must recognize contamination and climate change “are a one-two punch at our water supply,” Romero said. “It is unfortunate that we are forced to increase our reliance on CAP water from the Colorado River at a time when the climate is getting hotter and the desert is getting drier.”

No federal cleanup money has been forthcoming despite numerous efforts to obtain it by city officials and now, most recently, in an April 2021 letter to Defense Secretary Lloyd Austin from Gov. Doug Ducey.

Never again, utility says

Tucson Water doesn’t intend to ever again serve TARP-treated water to customers because of the risks that something could go wrong with the plant’s treatment that would allow unsafe levels to be served to customers, said utility spokesman James MacAdam.

“It may take years to clean up and also, quite frankly, it’s industrially contaminated water,” MacAdam said. “As science evolves, look what happened with 1,4-dioxane. People were drinking untreated dioxane in the water until we learned it was there.”

The south-side aquifer served thousands of residents with drinking water for decades until TCE was discovered in it in 1981.

Citywide, Tucson Water has closed 18 wells because of PFAS contamination.

The south-side PFAS contamination was publicly disclosed in spring 2019, when authorities released an internal Air National Guard report showing widespread contamination underneath the guard’s base adjoining Tucson International Airport.

The Air National Guard Base lies just across East Valencia Road from a residential area. It plays host to the 162nd Air National Guard Wing.

That fall, test results showed five monitoring wells outside the air base had PFAS levels of up to 13,850 parts per trillion. A couple of private drinking wells in the area also had PFAS levels above the EPA’s recommended level, with one at 2,300 parts per trillion.

In the past few years, PFAS levels have soared in all but one of nine south-side wells that the city taps to produce water to deliver to the TARP treatment plant, city statistics show.

In four wells, PFAS concentrations have since 2017 risen from a range of virtually nothing to less than 200 parts per trillion to a range of 400 to 800.

In four other wells, PFAS concentrations rose from very little to a range of 100 to nearly 200 parts per trillion.


That triangle of arrows indicates the item is recyclable, but not necessarily here in Tucson or Pima County. The little number in the middle is important. Video courtesy of Tucson Environmental Services.

Contact reporter Tony Davis at 520-349-0350 or tdavis@tucson.com. Follow Davis on Twitter@tonydavis987.


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Marana will have two treatment plants online to remove contamination from PFAS and another chemical from its drinking water by early February at the latest. The Arizona Department of Environmental Quality expects to have a pilot treatment plant in operation by summer 2021 to start cleaning up PFAS-tainted groundwater in Tucson Water's central wellfield, just north of Davis Monthan Air Force Base.

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