On July 15, 2009, about 8:00 a.m., a cargo transfer hose ruptured shortly after transfer of
anhydrous ammonia began from a Werner Transportation Services, Inc. cargo tank truck to a
storage tank at the Tanner Industries, Inc. facility in Swansea, South Carolina. A white cloud of
anhydrous ammonia, a toxic-by-inhalation gas, moved from the parking lot of the facility across
U.S. Highway 321 to a largely wooded area, where it eventually dissipated. About the same time,
a motorist traveling north on the highway drove into the ammonia cloud, apparently tried to get
away from the cloud, then got out of her car and died of ammonia poisoning. Seven people went
to the Lexington Medical Center emergency department complaining of respiratory problems
and dizziness; all seven patients were treated and released the same day. The anhydrous
ammonia cloud caused temporary discoloration of vegetation in the area, including the leaves on
the trees. Residents in the area sheltered in place, and U.S. Highway 321 was closed until about
2:00 p.m. on the day of the accident. The Lexington County Fire Service arrived on scene about
8:07 a.m. Property damage and losses were limited to the ruptured hose and about 6,895 pounds
of the anhydrous ammonia that was released.
We determined that the probable cause of the accident was Werner Transportation Services, Inc.’s use of a cargo hose assembly that was not chemically compatible with anhydrous ammonia. Contributing to the accident was the lack of explicit requirements by the Pipeline and Hazardous Materials Safety Administration that the motor carrier and the facility carrier verify that the cargo hose assembly is chemically compatible with the product to be transferred before transfer operations begin.
As a result of the investigation, we issued recommendations to the Federal Motor Carrier Safety Administration and the Pipeline and Hazardous Materials Safety Administration.
