Read the full article by Tony Davis
“Tucson Water recently shut down a treatment plant after discovering it was sending water contaminated with chemical compounds to thousands of residents of downtown and the city’s west and north sides.
Shortly after making that discovery, utility officials also learned that they had mistakenly thought for some time that uncontaminated water was coming out of the plant, which has long treated south-side water pollution.
The utility had been sampling the water at a point its officials thought was connected to the south-side treatment plant, but which actually was getting water from other sources, administrators said last week.
It turned out that water coming out of the treatment plant was now tainted with what’s known as perfluorinated chemicals, also known as PFAS compounds. The treatment plant had been built and later upgraded to treat two other pollutants — the solvent trichloroethylene (TCE) and 1,4-dioxane — but not to treat PFAS…
The levels of the chemicals found in the water coming from the treatment plant were lower than the recommended maximum in official EPA health advisories. But they were higher than a recently released federal study says they should be…
Because the utility hadn’t sampled points in the treatment plant’s water-delivery area until this year, Tucson Water officials say they don’t know how long the contaminated water had been served to customers there.
The utility decided to sample that area this year because it was continuing to find these compounds in other locations, forcing it to shut wells, Tucson Water Director Tim Thomure said.
The south-side treatment plant was put back online Sept. 17, after being closed for more than three weeks while the utility took several short-term measures to reduce contamination levels.
Tucson Water has since taken new samples in the area where the treatment plant’s water is delivered and expects they’ll contain significantly lower levels of the contaminants.
But the utility’s reliance on the wrong sampling point drew sharp criticism from City Council members Steve Kozachik and Regina Romero.
The mistake was ‘cavalier,’ given the city’s longstanding history with water pollution and the community’s sensitivity to it, said Kozachik. Last summer, he was the first city official to tell the public about contamination of other city wells by the same compounds…
Romero, whose Ward 1 also is part of the treatment plant’s service area, said she’s ‘very, very disappointed’ and finds it ‘very upsetting’ that Tucson Water was using the wrong sampling point and that she and other council members hadn’t been told of the PFAS contamination in the area until now…
‘We’ve been saying that Tucson Water is transparent, compared to the time of TCE and that we were serving clean water,’ Romero said. ‘Every detail of this bothers me.’ …
The contaminated water had gone through a water-treatment plant, the Tucson Airport Remediation Project, commonly known as the TARP plant.
The plant was first built in 1994 to remove the once-common industrial solvent trichloroethylene from polluted south-side groundwater — a solvent that various aircraft-related industries had dumped into the ground from the late 1940s to the mid-1970s.
In 2014, the plant was upgraded to also remove 1,4-dioxane, an industrial stabilizing agent, from the same groundwater. The dioxane was discovered in the groundwater in 2002.
The plant’s construction was a result of a consent agreement that the city signed with the U.S. Environmental Protection Agency and other parties to start cleaning up the water, long after the TCE was first discovered there in 1981. The plant uses a technology known as advanced oxidation to remove both chemicals…
The TARP plant was not designed to remove perfluorinated compounds, which utility officials had known for some time also have tainted the south-side wells that supply the contaminated water to TARP.
But for a long time, Tucson Water thought it was removing the PFAS anyway. In part, that’s because the treatment plant contains granulated carbon materials that are thought to be good at removing these compounds from water.
That’s also because the utility had repeatedly found none of the compounds when it sampled for them at a water main lying less than 2 miles north of the Santa Cruz Lane Reservoir where the TARP water is stored for delivery. The reservoir, near the Interstate 19/I-10 interchange, lies about four miles north of the TARP treatment plant along Irvington Road near I-19.
But in late August, Tucson Water found levels of the perfluorinated compounds of up to 30 parts per trillion in the area where water from the treatment plant is delivered…
Since 2009, the utility had been sampling its well system and other points in its water-delivery network for the PFAS compounds. It has already shut down three supply wells just north of Davis-Monthan Air Force Base and a half-dozen wells serving customers on the northwest side, including the Continental Ranch area of Marana.
Of the nine south-side wells supplying the TARP system, the three most-contaminated ones ranged from 91 to 190 parts per trillion of the PFAS compounds. At the treatment plant itself, the water averaged about 30 parts per trillion before treatment.
The sampling point north of the Santa Cruz Lane Reservoir was connected to a water main that officials had thought came from the TARP plant, Biggs said. But after PFAS were found throughout the TARP distribution system, ‘We said wait a minute, something’s wrong here,’ he said last week.
Tucson Water immediately started an investigation of the sampling point it had used, Biggs said. The sampling was done through a small spigot, connected to the water main via a steel pipe leading underground in which the spigot was encased. It was most likely installed around February 2000, utility spokesman Molina said.
Looking at old maps of its water system and visiting the area, utility officials discovered that the sampling spigot was actually connected to another main across the street from the water main where most of the TARP water was going, Biggs said. The second main carried water from other sources besides TARP.
Once they realized that, officials for the first time took a sample from the Santa Cruz Lane Reservoir itself. It came out with 30 parts per trillion PFAS. After the samples taken in the TARP delivery area also showed some with levels close to 30, the treatment plant was shut down.
Then, the utility flushed out the water system downstream of the plant by running through it what it said was uncontaminated water from its Central Arizona Project supplies for four or five days. That was to make sure that no contamination was passing through the plant.
Then, it took samples both at the treatment plant and in the distribution system, and found no PFAS compounds. Finally, it shut down the three-most-contaminated south-side wells supplying the TARP plant and started blending the plant water with CAP water coming in at the rate of 2,000 gallons per minute, Biggs said.
These actions were done in consultation with the EPA and the Arizona Department of Environmental Quality, Tucson Water officials said.”