A fatal natural gas rig blowout that killed five people last year in Oklahoma was called out by the U.S. Chemical Safety Board (CSB) on Wednesday, which said operators, regulators, industry groups and the state need to rectify the dearth of regulations governing onshore drilling safety.

The final investigation report details the deadly blowout at the Pryor Trust gas well in early 2018 at a rig operated by Patterson-UTI Energy Inc.

CSB determined that the explosion in Pittsburgh County resulted from a lack of regulations and “shortcomings in safety management systems and industry standards utilized by the industry.”

“Our investigation found significant lapses in good safety practices at this site,” interim CSB executive Kristen Kulinowski said. “For over 14 hours, there was a dangerous condition building at this well. The lack of effective safety management at this well resulted in a needless catastrophe.”

Two preventive barriers failed, according to CSB, each intended to prevent blowouts. Failures were found in the primary barrier, which is hydrostatic pressure in the well produced by drilling mud, and in the secondary barrier, which is human detection of gas flowing into/expanding in the well that would activate the blowout preventer.

The report detailed that “unplanned underbalanced drilling and tripping operations allowed a large quantity of gas to enter the well,” while safety-critical operations, i.e. flow checks used to determine if gas is in the well, were not performed.

“Industry best practices recommend always having two protective barriers in place during drilling operations. Our investigation found that both of those barriers failed.”

The final report outlines several factors that contributed to the loss of barriers “including a lack of planning, training, equipment, skills and procedures,” investigators noted.

“The investigation revealed that there are no regulations specifically developed for onshore oil and gas well drilling.”

Oil and gas well drilling is exempted from the Occupational Safety and Health Administration (OSHA) Process Safety Management standard, which governs safety for chemical processing facilities. OSHA has been using the general duty clause, which “protects workers from serious and recognized workplace hazards,” but the clause “fails to address the unique safety hazards associated with drilling for oil and gas.”

The CSB urged OSHA to develop effective oversight that addresses the hazards unique to the onshore drilling industry.

CSB also determined that the drilling contractor failed to maintain an effective alarm system. “Likely due to excessive ‘nuisance’ or unnecessary alarms, the entire alarm system was disabled by rig personnel,” investigators said. “Ultimately, the lack of critical alarms contributed to workers being unaware that flammable gas was entering the well during operations before the incident.”

CSB investigator Lauren Grim said an effective alarm system can ensure workers are “aware of hazardous conditions, like gas entering the well. With the alarm system off, the safety of the operation solely relied on workers to either visually identify signs of the gas influx or calculate volume differences that could indicate gas influx -- and in this case, neither method was effective, and workers were unaware of the very large gas influx into the well before the incident. As a result, the workers had little knowledge of the impending disaster.”

At the time of the explosion, three employees were determined to be in the driller’s cabin. Two other employees “who were on the rig floor ran into the driller’s cabin during the blowout and fire. All five of these workers were killed.”

“When the blowout mud and gas ignited, it created a massive fire on the rig floor,” Grim said. “All five of the workers inside the driller’s cabin were effectively trapped because fire blocked the driller’s cabin’s two exit doors. Our investigation found that there is no guidance to ensure that an emergency evacuation option is present onboard these rigs or can protect workers in the driller’s cabin from fire hazards.”

CSB called on the American Petroleum Institute (API) to address design improvements to protect driller’s cabin occupants from blowout and fire hazards. The report also recommended API create guidance on alarm management for the drilling industry to help ensure systems are effective in alerting drilling crews to unsafe conditions.

“As onshore oil and gas extraction grows, it is imperative that the industry is using proven and reliable safety standards and practices,” Kulinowski said. “If some of these safety practices had been in place, this tragedy could have been averted. Our report lays out a strong case for recognizing the hazards in this industry and ensuring the safety of its workers.”

The independent federal agency, which does not issue or implement regulations, is directed to “drive chemical safety change through independent investigations to protect people and the environment.” Board members are appointed by the president and confirmed by the Senate.