Iowa officials sue Sioux City, alleging secret sewage dumping from overburdened treatment plant

State officials announced Friday that they are suing Sioux City for allegedly dumping partially untreated sewage into the Missouri River while covering up the environmental violation for more than three years.

“The city potentially endangered human lives and wildlife by violating water-quality rules and perpetrating a fraud to conceal its employees’ actions,” Iowa Attorney General Tom Miller said in a statement.

Miller's lawsuit alleges that the city's wastewater treatment plant "did not work properly and could not consistently disinfect the millions of gallons of wastewater." It says city officials began hiding its deficiencies in 2012 or earlier to avoid the obstacle a deficient plant would pose to potential business growth.

According to the suit, workers at the plant, in advance of state water quality tests, dramatically increased the amount of microbe-killing chlorine the plant used. A federal investigation found they would briefly raise it to as much as 120 gallons per hour on testing days from 2.5 gallons per hour at other times.

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That drove down, for short periods, the levels of waste-related bacteria those tests would show, the suit says. However, it alleges, the plant could not sustain those chlorine levels and that doing so would have released dangerous amounts of the chemical — toxic to fish, wildlife and recreational users — into the river.

City leaders said through their attorney that they were unaware of any fraudulent activity until receiving an anonymous tip in 2015, and they then acted quickly to notify authorities.

The lawsuit claims the alleged cover-up was motivated by city officials' desire to keep the plant running, even though it was over capacity, as they sought to have the plant's licensed capacity increased.

According to the suit, an engineering firm working for the city determined it was wastewater from industrial users similar to those the city hoped to attract that was preventing the plant from performing at its licensed capacity.

The civil suit over the alleged cover-up follows federal convictions of two city workers who pleaded guilty to criminal charges under the Clean Water Act.

Miller and the Iowa Department of Natural Resources placed the state's civil case on hold in 2016 to allow the federal cases to proceed first, said Lynn Hicks, Miller's chief of staff.

Jay Niday, wastewater operator-in-charge at the plant, and Pat Schwarte, a shift supervisor, pleaded guilty to conspiracy and knowingly falsifying, tampering with, and rendering inaccurate a monitoring device or method required to be maintained under the Clean Water Act.

Niday was assessed a $6,000 fine and sentenced to three months in prison in 2021, federal prosecutors said in a statement. Sentenced in 2019, Schwarte was ordered to pay a $5,000 fine and serve two years of probation, a separate statement by the prosecutors said.

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Sioux City officials maintain through their attorney that senior city leaders were unaware of the employees' falsifications before reporting them in June 2015 — a few months after an employee sent an anonymous tip to state regulators, according to the state. They also dispute the claim that the plant was unable to function at capacity at the time.

The two workers chose to engage in the fraud "for their own reasons," said the attorney, Guy Cook.

"The point is this that since this rogue conduct came to light the city took immediate action to dismiss these persons and began a mission to improve wastewater treatment," he said.

Federal prosecutors said that the plant employees had been hiding information from DNR since at least 2011 — the year the city took over day-to-day operation of the plant from longtime contractor American Water, where both men had worked.

That was also the year during which U.S Environmental Protection Agency and Iowa Department of Natural Resources officials had mandated the city to come into compliance with up-to-date environmental standards and complete planned improvements.

The city has stopped the fraudulent tests but repeatedly has released excessive levels of toxic chlorine and ammonia into the Missouri, state officials said.

Cook said the city has spent millions of dollars to improve the wastewater treatment facility since 2015.

Neither the civil suit nor the criminal cases specifically identify whether city officials were involved, but the civil suit cites communications between unspecified city officials and an engineering firm working on the plant.

According to the suit, the city officials asked the firm to cancel a draft planning report that "concluded the current process could not provide adequate disinfection" and contracted with a new firm to create a new report instead.

Daniel Lathrop is a staff writer on the Register's investigative team. Reach him at (319) 244-8873 or dlathrop@dmreg.com. Follow him at @lathropd on Twitter and at facebook.com/IowaGadfly.

This article originally appeared on Des Moines Register: Iowa suit claims Sioux City secretly dumped sewage into Missouri River