CSB Announces Investigation of Industrial Sewer Gas Incident

Yesterday the Chemical Safety Board announced that it was opening an investigation into the fatal chemical release that occurred on January 27, 2026, at the Woodland Pulp, LLC facility in Baileyville, Maine. For news reports about the incident, see here, here, and here. CSB investigators are already on the scene.

Yesterday’s announcement notes that:

“According to initial information submitted by the company to the CSB, the incident may have involved the mixing of concentrated sulfuric acid with sulfurous compounds in an enclosed process sewer, resulting in the generation and release of hydrogen sulfide, a highly toxic gas, in the Bleach Plant area of the facility.”

This incident has not yet been added to the list of CSB’s open investigations. That is not unusual. I would expect to see it added in two to three weeks, after additional internal review of information obtained by investigators. There are nine current investigators listed on the CSB site.

Commentary

Process sewers in chemical manufacturing facilities are a relatively unregulated and often overlooked process safety hot spot. Local permits set limits on what can be sent to local wastewater treatment facilities through these systems and process wastes are typically tested against those standards. EPA regulations about hazardous-waste treatment limit what facilities can do in the way of processing these waste streams without a hazardous waste treatment permit; usually just pH adjustments (often with concentrated sulfuric acid) and solids and oil/grease separations.

While compatibility testing of various waste streams is often not tested, process knowledge should be able to identify potential issues. But, even then, process upsets and on-the-fly processing of those upsets, may produce unexpected waste streams that could pose unanticipated compatibility issues.