Marengo explosion and fire ruled accidental

A December explosion and fire that injured a dozen people and caused a small-scale evacuation in Marengo was caused when an “unknown mechanical failure” ignited flammable air vapor, the State Fire Marshal reported.

C6-Zero, a company founded by Howard Brand III, was attempting to dissolve used roofing shingles into Marine-grade diesel fuel, fiberglass and sand. The chemical process created flammable vapors that permeated the plant at 810 E. South St., according to a two-page summary of the State Fire Marshal’s final report.

The Gazette asked for the full report, but the Fire Marshal provided only the summary.

“The structure had been in its respective location for many years and never had any significant events like what happened on Dec. 8, 2022,” the summary states.

But around 11 a.m. Dec. 8, near a conveyor belt that carried the shingles into a chemical bath, a mechanical failure sparked the blast.

“This caused a vapor air explosion and fire that damaged the facility and injuries to employees and people on a tour inside the plant,” the report states.

Between 10 and 15 people were taken to area hospitals, and neighbors around the plant were evacuated as black smoke was visible for miles. Firefighters from up to 20 agencies battled the blaze for 18 hours. Water used to extinguish the fire carried diesel fuel and other unknown contaminants into a nearby stormwater basin.

“Based on the totality of circumstances and a joint investigation by the State Fire Marshal Division, Division of Criminal Investigation, Iowa State Patrol, ATF (Bureau of Alcohol Tobacco, Firearms and Explosives) and Marengo Police Department, the fire does not meet the SFM criteria of an intentionally set fire,” the report states. “This fire has been determined to be ‘accidental.’”

The Fire Marshal said the fire investigation will be considered closed unless new information comes to light.

The report said Nationwide Insurance had coverage of the building and operations.

After the Iowa Attorney General sued C6-Zero to force the company to comply with a Dec. 15 emergency order to clean up the site, the company agreed to pay $333,580 to EcoSource, a Des Moines-based company, to clean up contaminated soil and water at the site. C6-Zero also committed to put $75,000 in a trust account to fund assessment and remediation work.

The state is paying TetraSolv Filtration, an Indiana company, up to $834,000 to remove perfluoroalkyl and polyfluoroalkyl substances (PFAS) from the retention basin holding runoff from the fire. The PFAS, known as forever chemicals because they do not dissipate with time, came from firefighting foam used to battle the blaze.

Another company, Rain for Rent, has created a ditch to divert new rain and water from melting snow away from the retention basin during PFAS removal.

Iowa Homeland Security will pay more than $600,000 to replace firefighting clothing and equipment damaged in the explosion and fire after C6-Zero refused to pay.

C6-Zero Fire Marshal Summary by Gazetteonline on Scribd

Comments: (319) 339-3157; erin.jordan@thegazette.com