Hazardous Waste Tank Explosions — Reactive Chemical Mixing
Midland Resource Recovery Tank Explosions
Midland Resource Recovery
📍 Philippi (Barbour County), WV
Incident: May 24, 2017  •  CSB Report: December 17, 2019
3
Fatalities
Hazardous Waste Oils / Flammable Vapors
Chemical Involved
0
CSB Recommendations
📋 Incident Summary

Two explosions at the Midland Resource Recovery hazardous waste oil recycling facility in Philippi, West Virginia, killed three people: two workers in the first explosion on May 24, 2017, and one contractor in a second explosion on June 20, 2017 — while the CSB was still actively investigating the first event. The facility received and processed various hazardous waste oils for recycling and resale.

The CSB investigation examined whether incompatible hazardous waste materials were mixed in storage tanks, generating flammable gases in tank headspaces that ignited. The facility's waste acceptance practices, chemical compatibility controls, and tank management procedures were central to the investigation. The second explosion — occurring during an active investigation — highlighted the facility's failure to implement corrective actions after the initial fatalities.

The CSB December 2019 report focused on findings and analysis — the lack of a formal chemical compatibility program and inadequate controls for waste oil receipt and storage were identified as critical deficiencies.

🔎 Key Findings
Finding 01
Second Explosion Occurred During Active CSB Investigation
The second explosion on June 20, 2017, occurred while the CSB was actively investigating the first on May 24, 2017 — the facility did not implement adequate immediate corrective actions following the first fatal event to prevent a second.
Finding 02
Incompatible Waste Oil Mixing Likely Generated Flammable Vapors
CSB investigation found evidence suggesting incompatible hazardous waste materials may have been mixed in storage tanks, generating flammable gases in the tank headspace that accumulated and ignited.
Finding 03
No Formal Chemical Compatibility Program for Waste Receipt
The facility lacked a formal chemical compatibility assessment process for the hazardous waste oils it received and stored — no systematic evaluation of whether incoming waste streams were compatible with materials already in storage tanks.
Finding 04
Waste Acceptance Practices Did Not Control Reactive Hazard
Waste oil acceptance procedures did not require adequate characterization of incoming waste streams or verification of chemical compatibility before commingling wastes in storage tanks.
Finding 05
Tank Headspace Flammable Vapor Hazard Not Managed
The potential for flammable vapor accumulation in hazardous waste oil storage tank headspaces was not systematically managed — no monitoring, inerting, or ignition source control program was in place.
🔍 Root Causes
1
No Chemical Compatibility Management System for Waste Receipt
Midland Resource Recovery had no systematic process for evaluating chemical compatibility of incoming hazardous waste streams with materials already stored — allowing potentially incompatible materials to be combined without hazard assessment.
2
Absence of Reactive Hazard Controls for Tank Storage
Operations lacked engineering and administrative controls appropriate for hazardous waste oil storage, including waste characterization requirements, tank monitoring, and ignition source management for flammable vapor hazards.
3
Failure to Implement Corrective Actions After First Explosion
The second explosion, occurring during investigation of the first, represents a failure to take immediate and effective corrective action — the most basic post-incident safety obligation was not fulfilled.
☑ CSB Recommendations
→ Midland Resource Recovery (Findings-Based)
Implement a formal chemical compatibility evaluation procedure requiring waste characterization data for all incoming hazardous waste streams before acceptance, and compatibility verification before commingling in storage tanks.
→ Midland Resource Recovery
Develop and implement a tank management program addressing flammable vapor hazard in hazardous waste oil storage tanks, including headspace monitoring, ignition source control, and emergency response procedures.
→ Midland Resource Recovery
Immediately suspend receipt of new hazardous waste streams following any explosion event until a formal investigation and root cause analysis is complete and corrective actions are implemented and verified.
→ Regulatory Authorities
Review requirements for chemical compatibility management and reactive hazard controls at hazardous waste oil recycling facilities to ensure adequate process safety requirements apply to operations handling diverse, potentially incompatible waste streams.
💡 Lessons Learned
Hazardous waste recycling facilities that combine multiple unknown or poorly characterized waste streams are reactive chemical reactors in disguise. Chemical compatibility assessment for incoming waste streams is essential, not optional.
The second explosion at Midland — occurring during the CSB investigation of the first — is a stark lesson in the obligation to stop and fix after a fatal incident. Continuing normal operations without implementing immediate corrective actions is both a moral and operational failure.
Flammable vapors accumulate in tank headspaces — especially when waste oils of unknown composition are stored together. Tank storage of hazardous materials requires a management program addressing the vapor hazard, not just the liquid.
Waste characterization is a safety function, not just a regulatory compliance exercise. Knowing what is in an incoming waste stream before it enters your tank is the foundation of chemical compatibility management.
Incidents that happen twice at the same facility share a common root cause: the failure to learn and act. Every post-incident corrective action program should include a verification step confirming changes were made before operations resume.
PSI: Process Safety InformationPHA: Process Hazard AnalysisSOP: Operating ProceduresHWP: Hot Work Permit
🔨 Safety Meeting Toolbox Talk
►Does your facility receive materials from multiple sources that could be incompatible? How do you verify compatibility before combining or storing them together?
►If an explosion or major incident happened at your facility today, what is the protocol for deciding whether and when to resume normal operations? Who makes that call?
►What do you know about the composition of the materials you store in tanks — and is there a hazard assessment evaluating flammable vapor generation in tank headspaces?
►How does your waste acceptance or raw material receiving process verify chemical compatibility of incoming materials before they are introduced to storage or process equipment?
►Have you ever received a material that turned out to be different from what was described on the documentation? What happened, and how was it handled?
Immediate Action Items
✓Review your incoming material acceptance procedure to confirm it requires chemical compatibility verification before any new material is combined with existing inventory in storage tanks or vessels.
✓Identify all storage tanks containing mixtures of materials from multiple sources and confirm that a chemical compatibility assessment has been documented for those combinations.
✓Verify that your tank management program addresses flammable vapor hazards in storage tank headspaces — including monitoring, inerting, and ignition source control requirements.
✓Review your post-incident protocol to confirm that a clear authority exists to suspend operations following a fatality or major incident.
✓Brief your operations and maintenance team on the Midland Resource Recovery incident and ask them to identify any areas where materials of unknown or variable composition are combined without a formal compatibility check.
🔗 PSM Failures Behind This Incident

This incident traced to breakdowns across 4 PSM elements (PSI · PHA · SOP · HOW). Each represents a documented gap that process safety documentation and consulting can close before a similar event occurs at your facility.

Process Safety Information (PSI)
Accurate, complete Process Safety Information is the foundation every other PSM element depends on. When PSI is missing or wrong — chemistry data, equipment specs, P&IDs — the entire hazard analysis is built on a flawed base.
Supporting documents in our library →
Process Hazard Analysis (PHA)
A structured PHA or HAZOP study exists to identify exactly these scenarios before they occur. When PHA is absent, superficial, or overdue for revalidation, hazards operate unseen until they kill someone.
Supporting documents in our library →
Operating Procedures (SOPs)
Operators cannot reliably hold safe operating limits without clear, current, enforced procedures. Deviation from acceptable operating conditions — a root cause here — is a direct consequence of SOP failure.
Supporting documents in our library →
Hot Work Permits
Unauthorized or poorly controlled ignition sources near flammable atmospheres are entirely preventable. A rigorous hot work permit system with pre-job atmospheric testing closes this pathway.
Supporting documents in our library →
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