The structure involved in this accident is an underground gas pipeline buried 1.10 m below the ground surface; it connects the port city of Zeebrugge (North Sea) with France. At the accident site, 2 gas pipes were operating at a distance of 7 m apart. One had a diameter of 90 cm and was built in 1982,while the other (which broke and ignited) was 1 m in diameter and installed in 1991. Natural gas flowed at a pressure of 80 bar, for a flow rate of 1.6 million m3/hr.