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Tesoro Martinez Sulfuric Acid Spill

Overview

The CSB investigated two sulfuric acid releases at the Tesoro Martinez refinery in Martinez, California, on February 12, 2014 and March 10, 2014. The investigation found that a weak process safety culture created conditions conducive to the recurrence of sulfuric acid incidents that caused worker injuries over several years.

Incident Snapshot

Field Value
Facility / Company Tesoro Martinez refinery
Location Martinez, CA
Incident Date 02/12/2014
Investigation Status The CSB's investigation was released at a news conference in Emeryville, CA, on 8.2.2016. A sulfuric acid spill on February 12, 2014, burned two workers in the refinery’s alkylation unit, who were transported to the nearest hospital burn unit by life flight. The incident occurred when the operators opened a block valve to return an acid sampling system back to service. Very shortly after this block valve had been fully opened, the tubing directly downstream of the valve came apart, spraying two operators with acid.
Accident Type Release Investigation Status: The CSB's investigation was released at a news conference in Emeryville, CA, on 8.2.2016 A sulfuric acid spill on February 12, 2014, burned two workers in the refinery’s alkylation unit, who were transported to the nearest hospital burn unit by life flight. The incident occurred when the operators opened a block valve to return an acid sampling system back to service. Very shortly after this block valve had been fully opened, the tubing directly downstream of the valve came apart, spraying two operators with acid.
Final Report Release Date 08/02/2016

What Happened

  • On February 12, 2014, a mechanical integrity failure released sulfuric acid in the alkylation unit, which burned two Tesoro Martinez refinery employees.
  • Approximately 84,000 pounds of sulfuric acid were released during the incident.
  • On March 10, 2014, sulfuric acid sprayed and burned two contract workers while they removed piping in the same alkylation unit.
  • The February 12, 2014 sample system was out of service for maintenance beginning November 26, 2013 due to leaking tubing and an improperly manufactured sample container.
  • Tesoro performed maintenance on the sample system on February 10 and 11, 2014, which included replacing the container.
  • On February 12, 2014, operators opened a valve to return an acid sampling system back to service and the tubing directly downstream of the valve came apart at the connector.
  • Acid continued to spray out of the failed tubing for over two hours until responders isolated the system.
  • On March 10, 2014, contract workers cut into approximately 40 feet of 1-inch piping using a portable band saw and sulfuric acid sprayed from the piping.
  • The piping had been placed out of service in December 2013 with a single isolation valve and was not adequately drained of process chemicals.
  • Two days after the March 2014 incident, Tesoro modified the isolation for the liquid butane piping from using single valve isolation to blinding.

Facility and Process Context

  • Tesoro Martinez refinery in Martinez, California
  • The Martinez refinery has been in operation for more than 80 years.
  • Its main products are motor fuels such as gasoline and diesel.
  • The alkylation process takes place in the alkylation unit of a refinery and occurs when isobutane combines with light olefins in the presence of sulfuric acid.
  • The alkylation unit’s spent sulfuric acid is highly corrosive, reactive, and can be flammable.
  • To ensure the alkylation unit is operating within its safe operating limit the sulfuric acid concentration must be controlled, which requires frequent sampling and testing.
  • The refinery had a history of sulfuric acid worker injuries during the five-year period of 2010 to 2014.
  • The refinery had previous major process safety incidents in 1997 and 1999.
  • The 1999 refinery was then called the Avon refinery, owned by the Tosco Corporation.

Consequences

  • Fatalities: 0
  • Injuries: 4 workers injured in the February and March 2014 incidents; two workers burned on February 12, 2014 and two contract workers burned on March 10, 2014; two of these workers each missed over 150 days of work
  • Environmental release: Approximately 84,000 pounds of sulfuric acid were released during the February 12, 2014 incident; Tesoro records indicate 84,346 pounds of sulfuric acid and 26 pounds of sulfur dioxide were released
  • Facility damage: The concrete containment area had badly deteriorated from routine exposure to sulfuric acid; the February 12, 2014 incident involved a loss of primary containment
  • Operational impact: Cal/OSHA required the process to remain shut down from February 18, 2014 until February 28, 2014; the alkylation unit was shut down during the March 10, 2014 incident response

Key Findings

Immediate Causes

  • the failure of a ¾-inch diameter stainless steel tubing connector that came apart due to insufficient tightening between a tube and a compression joint at the sulfuric acid sampling station
  • the piping was not adequately drained of process chemicals and remained under pressure
  • Tesoro used a single isolation valve to isolate the butane piping
  • the drain piping was internally plugged, preventing the residual sulfuric acid inside the pipe from draining through the open valves

Contributing Factors

  • Due to maintenance program deficiencies including gaps in planning, documentation, and communication, Tesoro did not effectively repair or leak-test the tubing prior to placing it back in service.
  • The Tesoro Martinez refinery did not require workers to leak-test tubing of this type following repairs.
  • The sample system was out of service for maintenance beginning November 26, 2013 due to leaking tubing and an improperly manufactured sample container.
  • Tesoro ceased efforts to make the upgraded sample systems functional and took them out of service.
  • The upgraded sample systems had reliability problems including plugging, foaming of the collected sample, and problems with the nitrogen purge supply.
  • Tesoro relied on the old sample systems, the use of which resulted in the February 2014 sulfuric acid release incident that injured two workers.
  • The sampling process generated a hazardous white vapor cloud likely consisting of acid gas and hydrocarbon vapor when the material drained from the acid settler to the process chemical sewer.
  • The acid sampling procedure required operators to evacuate nearby workers from the area prior to initiating the sampling procedure.
  • The procedure did not recommend or require any respiratory protection to be worn.
  • Workers only wore the goggles and chemical gloves; the acid suit jacket was not available and the face shield was never worn because it interfered with the goggles and hard hats.
  • The PHA Team identified the sampling hazard to have a potential severity of a lost workday injury, which they anticipated to be likely to occur within 20 years.
  • The PHA team listed PPE as the only safeguard necessary to mitigate the worker injury hazard despite the fact that not all of the PPE required by the procedure was available.
  • In its 2013 PHA, Tesoro did not specifically evaluate the hazards of the sulfuric acid sample stations.
  • The checklist questions did not evaluate sampling system hazards and were limited to evaluating issues involving accessibility.
  • The refinery used a single isolation valve rather than disconnecting and/or blinding, contrary to corporate standards.
  • The site policy allowed single valve isolation for short duration high risk work and greatly expanded upon the situations allowing single isolation valves.
  • The refinery policy allowed single isolation valves, and workers were unable to identify the plugged drain valve.
  • The pressure indicator on this piping system was not available because it had been previously removed and replaced with a plug.
  • Tesoro supervisors conducted routine investigations to determine why jobs took longer for the operators to prepare than the supervisors initially believed they should have taken.
  • Workers perceived intense pressure to avoid delaying maintenance work.
  • The operator had no indication of the dangerous condition that a pressurized inventory of concentrated sulfuric acid remained in the piping.
  • The operator and contractors did not take any extra steps to ascertain whether the piping was properly drained and depressurized.
  • The job the workers were performing at the time was not on the permit readiness sheet as requiring a hot work permit.
  • The permit readiness program only informed night shift operators about 25 percent of permits requiring safe equipment preparation.
  • Tesoro did not effectively prepare the butane piping prior to issuing the hot work permit for maintenance, as required by the Tesoro corporate blinding and isolation standard.
  • The safety culture at the Tesoro Martinez refinery’s alkylation unit did not support the safer course of action, involving additional steps such as blinding the piping on the butane side, verifying drain valves were open and free of plugging material, and flushing the line to ensure it was free of residual hazardous chemicals.

Organizational and Systemic Factors

  • weak process safety culture
  • Minimization of the seriousness of the February 12, 2014 process safety incident involving chemical burns to workers and a loss of primary containment
  • Routine alkylation unit worker exposure to hazardous vapors, acids, and caustic
  • Taking inherently safer acid sample systems out of service
  • Reliance on inadequate temporary alkylation unit equipment or other workarounds
  • Failure to provide alkylation unit workers with necessary and functional personal protective equipment (PPE)
  • Establishment of site-specific safety policies that were less protective than corporate standards and established industry good practice
  • Permit readiness program deficiencies resulting in perceived pressure on alkylation unit workers to expedite work
  • Failure to take corrective actions to address findings from refinery safety culture assessments
  • Ineffective incorporation and communication of lessons learned from previous safety incidents
  • Withdrawal from safety programs that workers believed were effective
  • Reports of pressure on alkylation unit workers to reduce cost by running at lower acid concentrations, but without adequate technical controls and infrastructure needed to operate safely at the desired conditions
  • Staffing resource limitations due to numerous worker injuries and workforce reductions
  • Reports of increased management pressure on alkylation unit workers to expedite training and qualifications in order to fill gaps in staffing
  • Tesoro did not follow through on its commitment to develop an action plan to strengthen areas of perceived weaknesses identified in the 2007 survey.
  • Tesoro ended the Martinez refinery’s participation in the United Steelworkers Triangle of Prevention Program and the California Voluntary Prevention Program in 2012.
  • Some workers believed dropping these programs demonstrated further deterioration in Tesoro’s commitment to process safety.
  • Some alkylation unit workers said there is a constant battle with management wanting to cut acid feed to the alkylation reactors.
  • Tesoro management had been trying to achieve more economical operation and was routinely pushing operators to run near these limits.
  • At the time of the March 10, 2014 incident only six of the 12 operator positions were filled.
  • In 2013 workers in the alkylation unit averaged nearly 800 hours of overtime, more than any of the other 15 units within the refinery and 180 percent above the refinery average.
  • Tesoro attempted to reduce the required staffing to do some jobs, which would then increase the operator workload.
  • Some operators perceived tremendous pressure to expedite training to get qualified for the alkylation operator position.
  • Tesoro more recently pressured operators to qualify in as little as 44 days.
  • Alkylation unit operators expressed concern that Tesoro’s inspection department does not inform them of significant mechanical integrity issues.
  • Some workers believe the health and safety department positions were cut and many shifts now operate without health and safety coverage.
  • Tesoro only informed night shift operators about 25 percent of permits requiring safe equipment preparation.
  • Management critically assessed operators for holding up maintenance work.

Failed Safeguards or Barrier Breakdowns

  • failure to preserve key evidence
  • did not obtain a sample of the sulfuric acid in the settler as requested by the CSB
  • replaced the agitator coupling for the alkylation reactor without providing CSB investigators the opportunity to inspect and document its condition
  • did not effectively repair or leak-test the tubing prior to placing it back in service
  • did not require workers to leak-test tubing of this type following repairs
  • the acid suit jacket required by the procedure was not available in Tesoro’s PPE inventory
  • the face shield attachment interfered with how the goggles attached to the operators’ hard hats
  • the upgraded sample systems were taken out of service
  • the PHA did not adequately evaluate the hazards associated with the acid sample stations
  • the 2013 PHA did not specifically evaluate the hazards of the sulfuric acid sample stations
  • the checklist questions did not evaluate sampling system hazards
  • the refinery used a single isolation valve rather than blinding and flushing the piping before conducting hot work
  • the pressure indicator had been removed and replaced with a plug
  • the drain piping was internally plugged
  • the permit readiness program was a failed system
  • the job was not on the permit readiness sheet as requiring a hot work permit
  • Tesoro did not effectively prepare the butane piping prior to issuing the hot work permit
  • Tesoro did not effectively continue to implement or communicate important safety lessons from the 1999 Tosco incident
  • Tesoro’s investigation of the January 2012 incident did not trigger a thorough hazard review of the temporary equipment
  • Tesoro did not take corrective actions to address findings from refinery safety culture assessments

Recommendations

  1. Recommendation ID: Not provided
    Recipient: Not provided
    Status: Not provided
    Summary: No recommendation entry was provided in the source extract. The schema placeholder was preserved with empty fields.

Key Engineering Lessons

  • Sampling systems handling concentrated sulfuric acid should be designed and maintained so that repairs are verified before return to service, including leak testing where required by the investigation findings.
  • Single isolation valve arrangements were less protective than disconnecting and/or blinding, and the investigation identified blinding and flushing as the safer course of action for the butane piping work.
  • Pressure indication and drain path integrity are critical safeguards; removing a pressure indicator and leaving plugged drain piping can prevent operators from recognizing and removing a pressurized hazardous inventory.
  • Hazard reviews must specifically evaluate sulfuric acid sample station hazards rather than relying on general checklist items about accessibility.
  • Personal protective equipment must be both specified and actually available/usable; the investigation found gaps between procedure requirements and the PPE inventory and compatibility of components.
  • Temporary or upgraded sample systems with reliability problems should not be relied upon as substitutes for inherently safer designs when they are not functioning as intended.

Source Notes

  • All fields were consolidated from the provided final report extract, which has source_priority 1 and overrides lower-priority material.
  • No external facts were added.
  • The recommendations list in the source extract was empty, so the schema recommendation entry is preserved with empty fields.

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