Toxic compounds that have commonly turned up in groundwater near military bases around the country have been found in two city wells just north of Davis-Monthan Air Force Base.

Tucson Water officials shut the wells off when the pollution was discovered. They say these wells were only rarely used before, and that it’s unlikely people were exposed to enough contamination from them to be harmed.

Officials are concerned about the contamination, however, because the pollution levels have risen since they were discovered in 2016 and 2017, respectively.

That raises the possibility the pollution could ultimately spread farther north and west toward numerous other city wells in the midtown area’s central well field.

Tucson has drastically reduced use of the central well field since Colorado River water started being used here for drinking in 2001. But city officials want to ensure the wells stay in good shape in case they’re needed during a future cutback in river water deliveries via the Central Arizona Project…

Tucson Water officials say they’re encouraged because they’re collaborating closely with the Air Force to try to pin down the contamination’s source so it can be cleaned from the groundwater…

Samples of four other city wells near the two contaminated wells haven’t detected the compounds at all, utility officials noted.

‘This is a story about us trying to maintain a reliable resilient supply and being proactive on water quality,’ Elder said. ‘I think it’s a good story. We’re on the leading edge of some sort of PFOS-PFOA contamination plume.’

Two samples taken last October and in March 2018 of the most contaminated well near the base contained more than 3,300 and more than 2,900 parts per trillion of the two compounds, respectively. The U.S. Environmental Protection Agency sets a health advisory of 70 parts per trillion for the compounds. The second well had 133 and 97 parts per trillion of the compounds in samples taken at about the same times.

Though the concentrations of PFOA and PFOS dropped during this period, they are still higher than when the wells were discovered in 2016 and 2017…

City officials also shut down six city wells on the northwest side near the Santa Cruz River in 2016 that were found contaminated with PFOS and PFOA. Four of the wells had levels above the EPA advisory level, while the other two had contamination levels at or below that.

Tucson Water samples taken in February 2018 also found the compounds in eight south-side wells at levels above and below the EPA advisory level. Those wells aren’t used for drinking either, Tucson Water says. Their water is taken to a south-side treatment plant, whose February 2018, post-treatment sample showed the compounds at 41 parts per trillion. That plant’s treated water is delivered to a large area from about 29th Street on the city’s south side to the north and northwest sides, up to River and Sunset roads, respectively.”

Read the full article by Tony Davis