A recommendation has been made by the Chemical Safety & Hazard Investigation (CSHI) board that aboveground chemical storage tanks be regulated under the Process Safety Management standard overseen by the Occupational Safety and Health Administration (OSHA). The recommendation followed the board's investigation of a July 17, 2001, explosion at a Motiva Enterprise LLC Delaware City, Delaware, refinery. Under federal law, OSHA will have 180 days to consider the recommendation.
Investigators found Motiva did not consider the tank farm to be covered by the requirements of the OSHA Process Safety Management standard, which sets safety standards for various chemical operations.
A contractor employee, Jeffrey Davis, 50, was killed in the explosion. His body was never recovered. Eight other workers were injured when a spark from carbon-arc welding equipment ignited flammable vapors in a 415,000-gallon sulfuric acid storage tank at the refinery. The surrounding sulfuric acid tank farm was heavily damaged in the blast, and an estimated 1.1 million gallons of the corrosive were ultimately released to the environment, including nearly 100,000 gallons that flowed into the nearby Delaware River. A significant fish kill occurred there, according to the information.
According to CSHI board lead investigator David Heller, "Motiva did not act to prevent hot work (high-temperature cutting that could generate molten metal and sparks) from being performed directly above a corroded hazardous storage tank that had holes in its roof and shell, and was known to contain flammable vapors."
The board found that the incident likely would have been prevented if good safety management processes had been adequately implemented at the refinery and cited three root causes for the accident. First, the company did not have an adequate mechanical integrity management system. Second, there was an inadequate system for managing engineering and changes in its equipment and processes. Third, the hot work program was inadequate. The company program permitted work such as welding to be conducted near tanks containing flammable vapors and did not afford workers adequate protection from flammable hazards such as ongoing atmospheric monitoring.
According to the investigation, the refinery's sulfuric acid tanks had a history of leaks, but Motiva took no effective action, even when its own tank inspectors recommended full internal inspections "as soon as possible" in three successive annual reports prior to the explosion. Three weeks before the explosion, an operator submitted a formal unsafe condition report, noting holes in two tanks and pointing out that the hose used to blanket the tank with nonflammable carbon dioxide was improperly installed. The board found Motiva investigated the report but took no action to correct the deficiencies. Interviews with Motiva workers and managers revealed that Motiva did not consider the tank leaks to pose a safety or environmental risk and did not properly engineer an earlier change when the tanks were converted from fresh sulfuric acid storage to used or "spent" acid, which contains flammable hydrocarbons.
The board approved a full suite of preventive measures, including:
#&8226;Recommendations that OSHA expand its Process Safety Management regulatory standard to ensure coverage of similar hazardous storage tanks.
#&8226;The State of Delaware ensure that new regulations under the recent Jeffrey Davis Aboveground Storage Tank Act require prompt action when tank corrosion results in a safety hazard.
#&8226;The Motiva Delaware City Refinery take numerous specific steps to improve chemical process safety, including better mechanical integrity planning, reporting systems, communication with workers, an upgraded hot work program, and improved designs for existing tanks.
The Board also approved a recommendation to the refinery's parent company, Motiva Enterprises LLC, to conduct more stringent safety auditing at all of its US refineries. Motiva Enterprises is a joint venture of Saudi Refining Co. and Shell Oil.
The Board's final report is available from the CSB website, click here: Investigation.