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Oil Tank Safety Study

Overview

CSB study of public safety at oil and gas storage facilities, based on multiple incidents at rural unmanned oil and gas storage sites. The study identified 26 similar incidents from 1983-2010 resulting in 44 fatalities and 25 injuries, and found that public access, insufficient security measures, and lack of uniform guidance contributed to the incidents.

Incident Snapshot

Field Value
Facility / Company
Location Weleetka, OK
Incident Date 2010-04-14
Investigation Status The CSB released its oil tank study at a news conference in Hattiesburg, MS on October 27, 2011.
Accident Type Community Impact Investigation
Final Report Release Date 2011-09

What Happened

On October 31, 2009, two teenagers, aged 16 and 18, were killed when a petroleum storage tank exploded in a rural oil field in Carnes, Mississippi.

Six months later a group of youths were exploring a similar tank site in Weleetka, Oklahoma, when an explosion and fire fatally injured one individual.

Two weeks later, a 25-year-old man and a 24-year-old woman were on top of an oil tank in rural New London, Texas, when the tank exploded, killing the woman and seriously injuring the man.

In April 2010, the U.S. Chemical Safety Board (CSB) initiated an investigation into the root causes of these incidents.

On April 14, 2010, a 210-barrel capacity tank exploded at an oil and gas production site in rural Weleetka, Oklahoma, fatally injuring a 21-year-old male and causing second-degree burns to a 26-year-old male.

Facility and Process Context

  • rural unmanned oil and gas storage sites
  • oil and gas exploration and production facilities
  • storage tanks in tank batteries
  • sites often located in wooded clearings or other isolated locations
  • sites lacking fencing, warning signs, locks on tank hatches, and other security measures

Consequences

  • Fatalities: 44 fatalities
  • Injuries: 25 injuries
  • Environmental release: The exploding tank lost all its contents.
  • Facility damage: The force of the explosion propelled the upper part of the tank approximately 225 feet while the bottom of the tank was thrown about 60 feet in the opposite direction. The tank’s vent pipe and hatch detached from the tank top and landed over 300 feet away.
  • Operational impact: The fire prevented first responders from accessing the sign containing Delphi Oil’s emergency contact information.

Key Findings

Immediate Causes

  • Members of the public, unaware of the explosion and fire hazards associated with the tanks, unintentionally introduce ignition sources for the flammable vapor, leading to explosions.
  • Vapors from the tank ignited and an explosion ensued.
  • The second victim lit the cigarette, an explosion ensued.

Contributing Factors

  • Members of the public, most often children and young adults, commonly visit oil and gas production sites without authorization for recreational purposes.
  • Members of the public gain access to production tanks via attached unsecured ladders and catwalks, and may come into contact with flammable vapors from tank vents or unsecured tank hatches.
  • The three incidents investigated by the CSB in 2009-2010 occurred in isolated, rural wooded areas at production sites that were unfenced, did not have clear or legible warning signs, as required under OSHA’s Hazard Communication Standard, and did not have hatch locks to prevent access to the flammable hydrocarbons inside the tanks.
  • The storage tanks did not include inherently safer design features to prevent tank explosions.
  • E&P storage tanks are exempt from the security requirements of the Clean Water Act and from the risk management requirements of the Clean Air Act.
  • Industry guidance from the American Petroleum Institute recommends specific security measures for storage tanks of refined petroleum products but not for storage tanks at upstream E&P sites, and the National Fire Protection Association standards do not adequately define security expectations where these deadly incidents occurred.
  • The site did not have signage to warn of the hazardous contents of the tanks, hatch locks, perimeter or equipment fencing to deter public access, nor were the tanks designed to avoid an internal vapor explosion.
  • The site lacks a perimeter fence, warning signs identifying hazards of the flammable materials inside the tanks, or hatch locks.
  • The design of the failed tank did not prevent an internal explosion.
  • The site had no fences or hatch locks nor were the tanks designed to reduce the potential of an internal explosion.
  • The site did not have a berm or dike to contain the oil released from the exploding tank when it lost its contents.
  • The dirt road leading to the site is unlit and secured by a typically unlocked iron cattle gate.
  • The gate to the dirt road leading to the oil tank storage site was often left unlocked and on the day of the incident was likely unlocked.
  • The site had one warning sign covered by graffiti; however, its exact location at the time of the incident is unclear.

Organizational and Systemic Factors

  • The CSB analyzed safety and security regulations at the local, state, and federal level as well as relevant industry standards in order to identify systemic gaps and formulate recommendations aimed at preventing future incidents.
  • At the time of the incident, Forrest County had no local zoning ordinances requiring oil and gas facilities to be fenced or marked by warning signs.
  • At the time of the incident, oil field rules promulgated by the MSO&GB did not require fencing, signage, or locks to prevent unauthorized entry to oil and gas sites, apart from those that contain hydrogen sulfide.
  • The MSO&GB does not require inherently safer tank design features be utilized to prevent internal vapor explosions.
  • The OCC oil field rules do not require a perimeter berm or fencing of oil and gas sites, hazard signs, or hatch locks on oil storage tanks not containing hydrogen sulfide.
  • The RRC does not have requirements for using inherently safer tank design to prevent an internal vapor explosion.
  • The CSB found no current federal regulatory standards to protect members of the public, including children and young adults, who enter unattended oil sites without authorization.
  • The OSHA standard has no requirements for security or fencing.
  • The standard also exempts crude oil tanks at E&P facilities from requirements for venting valves and flame arrestors.
  • The CSB determined that there are currently no comprehensive, specific industry standards or guidance addressing the safety of members of the public at oil and gas sites.

Failed Safeguards or Barrier Breakdowns

  • fencing
  • warning signs
  • locks on tank hatches
  • hatch locks
  • perimeter fence
  • equipment fencing
  • locked gate
  • barriers securely attached to tank external ladders or stairways
  • inherently safer tank design features
  • pressure-vacuum devices
  • flame arrestors
  • vapor recovery systems
  • floating roofs
  • berm
  • dike

Recommendations

  1. 2011-H-1-R01 | Recipient: The Environmental Protection Agency | Status: Open | Publish a safety alert directed to owners and operators of exploration and production facilities with flammable storage tanks, advising them of their general duty clause responsibilities for accident prevention under the Clean Air Act.
  2. 2011-H-1-R02 | Recipient: The Mississippi Oil and Gas Board | Status: Open | Amend state oil and gas regulations to require the use of inherently safer tank design features such as flame arrestors, pressure vacuum vents, floating roofs, vapor recovery systems or an equivalent alternative, to prevent the ignition of a flammable atmosphere inside the tank.
  3. 2011-H-1-R03 | Recipient: Oklahoma Corporation Commission | Status: Open | Amend state oil and gas regulations to protect storage tanks at exploration and production sites from public access by requiring sufficient security measures, such as full fencing with a locked gate, hatch locks on tank manways, and barriers securely attached to tank external ladders and stairways; require hazards signs or placards on or near tanks that identify the fire and explosion hazards using words and symbols recognizable by the general public; require the use of inherently safer tank design features such as flame arrestors, pressure vacuum vents, floating roofs, vapor recovery systems or an equivalent alternative, to prevent the ignition of a flammable atmosphere inside the tank.
  4. 2011-H-1-R04 | Recipient: The Texas Railroad Commission (RRC) | Status: Open | Amend state oil and gas regulations to protect storage tanks at exploration and production sites from public access by requiring sufficient security measures, such as full fencing with a locked gate, hatch locks on tank manways, and barriers securely attached to tank external ladders and stairways; require hazards signs or placards on or near tanks that identify the fire and explosion hazards using words and symbols recognizable to the general public; require the use of inherently safer tank design features such as flame arrestors, pressure vacuum vents, floating roofs, vapor recovery systems or an equivalent alternative to prevent the ignition of a flammable atmosphere inside the tank.
  5. 2011-H-1-R05 | Recipient: American Petroleum Institute | Status: Open | Create a new standard or amend existing standards covering exploration and production facilities to warn that storage tanks at unmanned facilities may be subject to tampering or introduction of ignition sources by members of the public, which could result in a tank explosion or other accidental release to the environment; recommend the use inherently safer storage tank design features to reduce the likelihood of explosions, including restrictions on the use of open vents for flammable hydrocarbons, flame arrestors, pressure vacuum vent valves, floating roofs, vapor recovery systems or an equivalent alternative; require security measures at least as protective as API 2610 to prevent non-employee access to flammable storage tanks at upstream E&P sites, including such measures as a full fence surrounding the tank(s) with a locked gate, hatch locks on tank manways, and barriers securely attached to tank external ladders or stairways; require that hazard signs or placards be displayed on or near tanks to identify the fire and explosion hazards using words and symbols recognizable by the general public; recommend that new or revised mineral leasing agreements include security and signage requirements as described above.
  6. 2011-H-1-R06 | Recipient: The National Fire Protection Association | Status: Open | Amend NFPA 30, “Storage of Liquids in Tanks—Requirements for all Storage Tanks” as follows: remove the term “isolated” from the current wording of the standard and replace it with a more descriptive term, such as “normally unoccupied”; remove the words “Where necessary” from Security for Unsupervised Storage Tanks, Chapter 21.7.2.2.; add a reference to a relevant security standard that offers specifications on fencing, locks and other site security measures; add a definition of security encompassing requirements such as fencing, locked gates, hatch locks, and barriers.

Key Engineering Lessons

  • Unmanned upstream oil and gas storage tanks need physical access controls such as full fencing, locked gates, hatch locks, and barriers on ladders or stairways to prevent public access.
  • Warning signs or placards using words and symbols recognizable by the general public are needed to communicate fire and explosion hazards at tank sites.
  • Tank designs should include inherently safer features to reduce the likelihood of internal vapor explosions, such as flame arrestors, pressure vacuum vent valves, floating roofs, vapor recovery systems, or equivalent alternatives.
  • Security expectations for exploration and production tanks should be explicitly defined in standards and regulations rather than left to inconsistent local or industry practice.
  • Sites should not rely on unsecured access points such as unlocked gates, unsecured ladders, or unprotected tank hatches.

Source Notes

  • Priority 1 final report facts were used as the primary authority for incident-level findings and recommendations.
  • The final report is a multi-site study; the incident_date and location fields reflect the Weleetka, Oklahoma event from the provided metadata.
  • Supporting documents and recommendation status pages were used only to supplement or clarify details where consistent with the final report.
  • No external facts were added beyond the provided extracts.

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