A second grove of lush riparian habitat could soon be in the making on the Santa Cruz River on Tucson’s south side, thanks to a new city effort to discharge up to 2 million gallons of treated groundwater a day into the river.
But at the same time, some people are concerned about the prospect the treated groundwater could be carrying low levels of the “forever chemicals” known as PFAS compounds, although city officials say they would be lower concentrations than exist in the river’s underlying aquifer today.
Since Tuesday, Tucson Water has been discharging something less than 1,500 gallons a minute of treated groundwater, with no detected PFAS, into the usually dry riverbed just north of Irvington Road.
Since the utility first rolled out its Santa Cruz River Heritage Project in June 2019, it has been releasing treated sewage effluent into the river just north of 29th Street, and that water has at times flowed as far north as the downtown Tucson stretch.
The new discharge, at what the utility calls its Heritage Project Irvington Outfall Site, has stirred hopes in a prominent naturalist that it will create a cluster of riparian habitat as rich as at the original Heritage Project.
University of Arizona ecologist Michael Bogan and his students have documented the presence at the original site of more than 300 species of dragonflies, damselflies, other insects, birds, native amphibians and a native gartersnake.
That’s along with at least 20 species of wetland plants including cattails and rushes.
PFAS in low concentrations
The Irvington site’s water may at times be carrying low levels of PFAS compounds, because it will come from the city’s Tucson Airport Remediation Project at Irvington just west of Interstate 19.
The plant had been removing PFAS and two organic solvents from contaminated south-side groundwater for years so it could be served to residents. The city shut it down in June because the PFAS levels in groundwater were quickly rising, for unknown reasons, raising concerns the plant might eventually fail.
It’s now been reopened, and the water is instead being discharged into the river, with a permit from state environmental regulators, as city officials say they will no longer serve this treated water to residents.
It’s not clear how much or how often PFAS will be in the water over time. Tucson Water spokesman James MacAdam said that overall, the concentrations will be less than 18 parts per trillion. That’s the maximum level the utility allows in drinking water served to homes and businesses.
It’s also significantly below the Environmental Protection Agency’s Health Advisory Level of a 70 parts per trillion limit for people to avoid exceeding in drinking water over a lifetime.
The Tucson Airport Remediation Project treatment plant (background) on the east bank of the Santa Cruz River has been removing PFAS from contaminated south-side water for years. The treated water will no longer be served to residents but instead is being released into the Santa Cruz River, with a permit from state environmental regulators.
City officials say that at times, at least, the treated water will carry no PFAS, since the treatment plant had, before the groundwater contaminants rose, reduced PFAS concentrations in the water served to people to levels its equipment couldn’t detect.
City Councilman Steve Kozachik said his understanding is the utility will try to keep discharges to zero PFAS at first. On Friday, Tucson Water said two samples it collected from the TARP plant on Tuesday when the discharges began showed no detectable PFAS.
A permit the Arizona Department of Environmental Quality issued to Tucson Water on Monday authorizes up to 70 parts per trillion PFAS in the discharged water. Utility officials have said they have no intention of putting that high a concentration into the river.
‘Personally very, very excited’
Even if they do carry PFAS, the discharges should improve water quality in the Santa Cruz’s aquifer, officials say. It now contains much greater PFAS concentrations — 85 parts per trillion at a nearby well, and 30 to 70 elsewhere, Mayor Regina Romero and Tucson Water officials say.
“I just want to emphasize ... that we will be remediating groundwater there. It will actually be better, as we recharge the Santa Cruz, in terms of the quality of the water,” Romero said at an Oct. 19 City Council session. “I am personally very, very excited about creating another riparian area on the south side.”
Interim Tucson Water Director John Kmiec told the council that day, “We’ll actually be remediating PFAS, and putting very clean water on top of already impacted groundwater.”
Kozachik said he’s not comfortable with having pollutants such as PFAS discharged into the Santa Cruz.
“They say the levels that are already there are more polluted than what’s being put in. I understand the arithmetic but not the rationale. We’re still putting something in that’s not so good,” when and if PFAS gets put into the river, he said.
Pima County and the Pima Association of Governments had urged ADEQ to limit discharges into the river to 18 parts per trillion PFAS.
Replying, ADEQ said it doesn’t have legal authority to limit discharges to that level because there’s no federal standards limiting discharges of PFAS in effluent into surface water.
Kozachik also said the city hasn’t addressed the PFAS concentrations in the groundwater coming into the treatment plant. “We still haven’t addressed the issue of the PFAS levels incoming to the TARP plant,” he said. “If the PFAS concentrations were so significant we had to shut it down, they still are. Why is this a solution?” There’s still a risk to the plant, he said.
Tucson Water couldn’t immediately reply to Kozachik’s comments, but promised to do so in the future.
Longtime south-side activist Yolanda Herrera said she’d rather see the city reuse the TARP water by sending it to car washes or ice rinks or other such facilities.
“Instead of using drinking water to wash someone’s car why don’t we divert that and save the groundwater?” said Herrera, president of the Sunnyside Neighborhood Association.
Such a step would require construction of expensive infrastructure to transport the TARP water to relevant businesses throughout the city, officials have said. The water would have to be trucked or piped somewhere. Even if you give it to car washes, it still goes into the environment, to be discharged into the sewer system and ultimately the river, officials say.
To get the groundwater cleaned up, there’s money available in the $1 trillion infrastructure package passed by Congress and the Build Back Better bill pending there.
Where utility officials, Kozachik and the mayor agree is that to permanently fix this problem, the federal government needs to step in and pay for the cleanup, since the likely source for the south side’s PFAS pollution is the Morris Air National Guard Base, an Air Force facility. Firefighting foam previously used by many military bases around the U.S. contained PFAS compounds.
Dragonflies, toads attracted
Sitting by the Santa Cruz’s west bank near Irvington on Thursday afternoon, ecologist Bogan was in an upbeat mood about the discharges.
“We’re making lemonade out of lemons,” he said, referring to the once-heavily contaminated TARP water now treated and spilling into the river.
As he talked, rivulets of water poured into the river through a series of small, vertical concrete structures at the city’s round discharge outfall just across the stream.
The river was flowing about 10 to 15 feet wide, with a wide band of dirt and rock separating him from the water.
Bogan had been at the river three straight days after the discharge began, to examine the water’s effects. Thursday morning, he brought his stream ecology class there for four hours.
In 2019, on the first day of the original Santa Cruz Heritage Project releases a couple of miles farther north, he saw seven species of dragonflies near the water.
He saw none at the new site Tuesday, the day discharges began there. But on Wednesday, he saw six species of dragonflies perched on rocks along or sticking out of the water in a mile-long stretch of river north to Ajo Way.
“We also saw two species of toads in the last three days, Tuesday, Wednesday and Thursday,” Bogan said.
Asked about birds — at least 100 species of which have been documented at the original Heritage site since 2019 — he said, “Until there is stuff to eat in the river, other things like birds won’t be that attracted to it, because there’s not a lot of insects in the water, not a lot of extra food.
“My guess is, it will take a couple of weeks before things really start to pick up,” he said.
Water has already traveled further downriver than he thought it would, said Bogan, adding he’s heard secondhand reports it’s reached as far north as Julian Wash, just south of 29th Street, and about 1.75 river miles north of the discharge point.
“What we don’t know is how the infiltration dynamic will change” over time, he said. When water first flows over soil, the soil tends to be a little hydrophobic, a little water repellent, because it hasn’t had water on it for a long time. That allows water to travel farther, at first.
“But eventually, all the sands and gravel you see here become saturated, so the infiltration rate could increase, so the water wouldn’t travel as far,” he said.
Still, “Maybe the water here could get all the way to the other one,” he said, referring to the original Heritage Project where water dumped into the river at about 25th Street.
He thinks the Irvington area has the potential to match the richness of wildlife and habitat at 25th because of the channel’s relatively untouched nature at Irvington, he said. Its west bank is packed with desert shrubs and the sediment remains in place, he said.
“Ecology is always weird. You never know what something is going to do,” Bogan said. “You create an identical habitat and animals never show up sometimes. There’s a lot about the lives of animals that we do not understand.”
The annual event to honor lost loved ones returned Nov. 7, 2021 as costumed participants walked the two-mile procession route on Tucson's west side.
This marks the All Souls Procession's 32nd year after it was started in 1990 by local artist Susan Johnson.
