Pond soils hold contaminants, group asserts | News

Soils at the bottom of an abandoned Oro Valley golf course irrigation pond are contaminated, according to a board-certified environmental scientist.

“This is hazardous waste,” Charles Stack said, gesturing toward the 2.5-acre empty pond within the Vistoso Trails Nature Preserve. “We have a problem here.”

Archaeology Southwest, which oversees the conservation easement on the 202-acre preserve, gathered scientists, media and others on May 4 to share their views of what exists, and what is planned, at the idled depression immediately north of Vistoso Highlands Drive.

Oro Valley has awarded a $1.88 million contract to low bidder KE&G Construction to demolish walls, line the pond, install reclaimed water connections, build a small parking lot and perform other work so the pond can be refilled. It’s part of an overall, $2.3 million investment in and near the pond. 

“The political and aesthetic decision-making has gotten out ahead of the science and engineering,” said John Welch, vice president for collaboration and preservation at Archaeology Southwest.

Both Town Manager Jeff Wilkins and Preserve Vistoso President Gayle Mateer disagree with that assertion (see related stories).

In April, Welch went into the pond site with “distilled water and a clean trowel” to collect samples from the pond’s sediments. “Is it a serious issue?” Welch wondered. “Should we be concerned? We decided to get some solid data.”

Those samples were sent to the Arizona Laboratory for Emerging Contaminants, on the campus of the University of Arizona. A sample, tested twice, showed 47,717 and 49,795 parts per million of “total fluorine,” defined as a measure of combined organic and inorganic fluorine compounds. The so-called “forever” chemicals, per- and polyfluoroalkyl substances or PFAS, fit within that description.

“We got a hit,” Stack said. “That is a very high level of PFAS for an environmental sample.”

 Stack cannot conclude if reclaimed water is the sole source of contaminants in the pond, which was constructed in the mid-1990s as part of the Golf Club at Vistoso, then abandoned after the course was closed in 2018.

“How the sludge in VTNP pond bottom got that high is still a scientific mystery,” Stack said in an email. “The only obvious source is Tucson Water’s reclaimed water, and that the PFAS became concentrated over the years.”  

“There’s something funky about this dirt,” Welch said. “It needs to be cleaned up.”

Welch argues Oro Valley should perform an environmental assessment “before you do anything” at the site, to include spending “$3 million to make another hazardous waste site.”

Likewise, Stack urged analysis of “the muck at the bottom of this pond.”

“We don’t know how deep it is,” Welch said. “We don’t know if it’s consistent top to bottom.” Nor is it known if contaminants have leaked into the aquifer, he said. “We need to find out.”

Given the tainted soils, “you can’t just not do anything,” said Robert Brackenridge, an Oro Valley resident and hydrologist who is also a senior research scientist at the University of Colorado.

Archaeology Southwest argues the proposed use of reclaimed water to fill the pond would “exacerbate and accelerate dangerously high levels of PFAS contamination.”

“I call this the Oro Valley concentrator pond, if this goes forward” without modifications, Brackenridge said. “This is not a golf course pond that’s being planned, it’s completely different, a different animal. … Left without modification, the present design is an entirely predictable environmental train wreck.”

“Ponds don’t belong in the Sonoran Desert,” said Stack, who has consistently spoken against restoring the pond and is a past volunteer representative of Oro Valley to the Pima Association of Governments’ Environmental Planning Advisory Committee.

“The whistle’s been blown,” said Stack, indicating he had a “statutory obligation” to report the issue to county and federal regulators. “I would say this is an environmental liability to the town of Oro Valley.”