CSB recommendations to Didion Milling left unanswered

The U.S. Chemical Safety and Hazard Investigation Board (CSB) recently stated Didion Milling, Inc. has so far failed to implement nine safety recommendations.

The recommendations were issued following the agency’s investigation of combustible dust explosions at the company's Cambria, Wisconsin dry corn mill in May 2017 that killed five employees and seriously injured 14 others.

The CSB made the safety recommendations to Didion Milling in December 2023, as part of the agency’s final report on the fatal incident. To date, however, Didion Milling has not implemented any of the safety recommendations, and the CSB said it has not received an adequate response from the company about the status of the safety recommendations, despite multiple outreach efforts to the company by the CSB.

Attorneys claim safety gaps addressed by OSHA citations

The CSB said it formally transmitted the safety recommendations to Didion Milling in a letter dated December 11, 2023 from Charles Barbee, CSB director of recommendations, to Riley Didion, the company’s president.

Didion Milling has never responded to the CSB’s letter. Instead, the CSB received a letter on July 9, 2024 from the company’s attorneys that did not substantively address the CSB’s safety recommendations. Didion Milling’s attorneys claimed the company's steps to address a settlement agreement with OSHA also addressed the CSB recommendations.

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While OSHA’s agreement addressed 14 willful citations and five serious citations resulting in more than $1.8 million in civil penalties, in addition to subsequent criminal penalties, the OSHA citations solely addressed violations of OSHA’s regulations.

In contrast, the CSB recommendations addressed various other identified gaps in Didion Milling’s inadequate safety management system as well as the company’s failure to properly implement other safety standards and guidance, regardless of whether they violated existing statutes or regulations.

Engagement attempts unanswered, final opportunity to respond

After receiving the attorneys’ letter, Barbee sent another letter on September 11, 2024, to Riley Didion, outlining the information and documentation necessary for the CSB to evaluate Didion Milling’s progress in addressing the CSB’s safety recommendations.

To date, Didion Milling has never responded to that letter and has not provided any of the information or documentation requested by the CSB. In addition to the letters, the CSB has made several other attempts to engage with the company’s leadership about the safety recommendations, including phone calls and emails, that also have gone unanswered.

On August 5, 2025, the CSB’s Executive Director of Investigations and Recommendations, Stephen Klejst, sent a letter to Riley Didion again requesting a response to the nine safety recommendations and offering Didion Milling a final opportunity to respond. If the company fails to respond again and takes no action to implement any of the safety recommendations, the CSB Board may decide to close the recommendations with a formal designation “Closed - Unacceptable Response/No Response Received”.

“Most companies willingly implement the safety recommendations that they receive as a result of the CSB’s investigations,” said Steve Owens, CSB chairperson. “Because the CSB is a nonregulatory agency that does not issue fines or citations, safety recommendations are the primary tool that the agency has to help prevent future horrific incidents that kill and seriously injure people like the massive explosions that occurred at Didion’s facility. We urge Didion to respond constructively and take action toward implementing these recommendations.”