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Marengo cleanup underway, but when will it be done and who’s paying?
Treated water from the C6-Zero explosion site now being released into Iowa River

Mar. 10, 2023 8:55 am, Updated: Mar. 10, 2023 8:14 pm
MARENGO — The cleanup of Marengo is underway, as private contractors — some paid for by taxpayers — treat water and remove soil contaminated in a December explosion and fire at C6-Zero.
Runoff from the fire has been filtered to remove toxic “forever chemicals” and already is being released into the Iowa River, officials said.
Meanwhile, the Iowa Department of Natural Resources won’t say whether C6-Zero has met court-ordered deadlines and the court’s mail to CEO Howard Brand III has been returned “unknown, unable to forward,” court records show.
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But the U.S. Environmental Protection Agency says it is monitoring C6-Zero and communicating with officials in other states about the company.
“EPA regional offices and program offices at EPA headquarters communicate regularly on issues of national significance — including issues surrounding companies with repeat noncompliance,” Kellen Ashford, a spokesman for the EPA’s Region 7, said in an email to The Gazette. “Likewise, EPA coordinates with state partners to protect human health and the environment by ensuring compliance and compliance issues are prioritized. EPA Region 7 has shared information about the C6-Zero incident in Marengo with EPA headquarters and other regional offices.”
C6-Zero, which was trying to dissolve used roofing shingles into sellable components, did not have a permit to operate at the Marengo plant, yet had already processed 1,700 tons of shingles before the Dec. 8 explosion, the company told the EPA in new records released to The Gazette.
Hundreds of thousands of gallons of hazardous chemicals, including diesel fuel, soybean oil and a mysterious solvent called Kaniksu were on site when an “unknown mechanical failure” ignited flammable air vapor.
The blast injured about a dozen people and forced evacuation of nearby houses. Firefighters from several counties fought the blaze for 18 hours. Water used to extinguish the fire dispersed hazardous liquids into water and soil around the site.
The environmental cleanup around C6-Zero is happening on two fronts.
- EcoSource, a Des Moines-area contractor, is removing water and soil contaminated with petroleum products and other chemicals stored at the manufacturing site. A judge ordered C6-Zero to pay EcoSource $330,000 and put $75,000 in trust for further cleanup.
- The state is paying Indiana firm Tetrasolv up to $834,000 to remove toxic “forever chemicals” from water in a 12-million-gallon basin holding runoff from the fire. The perfluoroalkyl and polyfluoroalkyl substances (PFAS) in the basin came from firefighting foam used to fight the fire.
In EcoSource’s March 4 update to the DNR, company officials said they were done vacuuming up water standing at the site and had filled four tanks with a total 70,000 gallons. Early tests of the water indicate it’s not hazardous, EcoSource said in the report. If the DNR confirms the assessment, the Metro Waste Authority may take the water, EcoSource said.
C6 Zero Weekly Status Report March 4, 2023 by Gazetteonline on Scribd
EcoSource says it will be done implementing the site assessment plan by March 31, but this was a task that was supposed to be done by Feb. 17, according to the Feb. 6 deal between C6-Zero and the Iowa Attorney General.
The DNR did not respond to The Gazette’s questions about whether C6-Zero has met other deadlines, including a March 3 deadline to submit a remedial action plan. It’s also unclear whether the company will be able to repay the state more than $1.4 million for cleaning up the PFAS and replacing firefighter gear contaminated during the fire.
Tetrasolv and subcontractor Rain for Rent have treated 2.6 million gallons of water from the stormwater retention basin for PFAS as of March 3, the DNR said in an email Tuesday. Samples of the treated water have been tested at the State Hygienic Laboratory in Coralville.
“The results demonstrated that the treatment is working and that the PFAS results were under the minimum reporting level of 2 parts per trillion,” DNR Spokeswoman Tammie Krausman said.
The treated water was scheduled to be released into the Iowa River Friday, Iowa County Emergency Management Agency Coordinator Josh Humphrey said Thursday.
David Cwiertny, a University of Iowa engineering professor and director of the Center for Health Effects of Environmental Contamination, said the report is encouraging.
“It seems the activated carbon is working well at removing the PFAS. That is good and largely expected,” he said. “With no detections in the treated water, discharge to the river is as safe as it is going to get.”
DNR Director Kayla Lyon said Feb. 20 her agency had not yet received an inventory of hazardous materials stored at C6-Zero, despite a court-ordered deadline of Feb. 17.
Krausman said the DNR now has received that list, but she didn’t say when C6-Zero provided it. C6-Zero asked that the information be kept confidential — Brand says the Kaniksu recipe is proprietary — and the court allowed that.
“That being said, EPA and DNR can disclose that the hazard characterization of chemicals stored at the facility and involved in the Dec. 8, 2022, fire are flammability and moderate toxicity,” Krausman said in an email.
Heartland Coop, which operated a soybean processing facility in the Marengo plant before C6-Zero rented the space, has filed two new lawsuits in Iowa County against Brand and Dylan Brand, Howard’s son.
The lawsuits, filed Feb. 28, allege Heartland supplied C6-Zero last fall with more than $130,000 worth of diesel fuel for C6-Zero’s operations, but C6-Zero never paid for the fuel. A judge in January ordered C6-Zero to pay Heartland $137,000 for the fuel, but the new lawsuits also ask for “punitive damages in an amount sufficient to deter similar future conduct.”
Comments: (319) 339-3157; erin.jordan@thegazette.com
The damaged C6-Zero facility is seen in the background as a pipe travels over an embankment of a holding basin to water filtration equipment of Tetrasolv set up in a nearby field closer to the Iowa River in Marengo, Iowa, on Friday, Feb. 24, 2023. An explosion and fire at the shingle recycling business Dec. 8, 2022, injured 15 people and required the evacuation of nearby neighborhoods until it was safe for residents to return. Water from the area surrounding the facility is being treated for PFAS chemicals before being released into the Iowa River. (Jim Slosiarek/The Gazette)
Workers with Rain for Rent work on piping from a storage basin to Tetrasolv water filtration equipment near the C6-Zero facility in Marengo, Iowa, on Friday, Feb. 24, 2023. An explosion and fire at the shingle recycling business Dec. 8, 2022, injured 15 people and required the evacuation of nearby neighborhoods until it was safe for residents to return. Water from the area surrounding the facility is being treated for PFAS chemicals before being released into the Iowa River. (Jim Slosiarek/The Gazette)