On Monday, May 4, 2009, about 5:10 a.m. eastern daylight time, Florida Gas Transmission Company’s (FGT) line 100, an 18-inch-diameter natural gas transmission pipeline, ruptured about 6 miles south of Palm City, Florida. The rupture occurred in a sparsely populated rural area of Martin County and displaced about 106 feet of buried pipe onto the right-of-way between Interstate 95 (I-95) and the Florida Turnpike (SR-91). An estimated 36 million cubic feet of natural gas was released during the accident without ignition. Two parallel FGT natural gas transmission pipelines in the same right-of-way were undamaged. Three minor injuries were attributed to the rupture: two people were injured escaping from a vehicle that lost control and ran off the turnpike, and one member of the Palm Beach County Sheriff’s department walked through a dense cloud and inhaled natural gas. The rupture occurred between two automatic shutoff valves (ASV), but only one valve shut in response to the pressure drop on the pipeline.
Emergency responders rerouted traffic on both SR-91 and I-95 and evacuated a high school and a residential subdivision that were nearby. The FGT control center did not receive any Supervisory Control and Data Acquisition (SCADA) alarms or recognize the rupture from SCADA data. However, emergency response personnel began notifying the FGT control center at 5:49 a.m., after which the control center dispatched three field operators to the scene. By 7:30 a.m., the field operators had stopped the flow of natural gas. Local authorities reopened I-95 by 8:00 a.m. and SR-91 by 11:15 a.m. About 2 hours 20 minutes had elapsed from the time of the rupture to the complete isolation of the flow of gas
We determined that the probable cause of the accident was environmentally assisted cracking under a disbonded polyethylene coating that remained undetected by the integrity management program.
Contributing to the accident was Florida Gas Transmission Company’s failure to include the pipe section that ruptured in the integrity management program. Contributing to the prolonged gas release was the pipeline controller’s inability to detect the rupture because of SCADA system limitations and the configuration of the pipeline.
