A leak detected late on a pipeline (10”, 2 bar) serving a port petrochemical site along the Juliana canal was the caused 3 000 m³ (2500 tonnes) of methyl tertiary butyl ether (MTBE) to be released thus polluting soil and underground water. The MEUSE river flowing nearby was also polluted. The pumping of the river waters meant for human consumption (300 000 persons) had to be stopped.

The leak was detected in October 2004 after a detailed inspection of the pipeline further to problems in the material balance. The leak in all probability lasted long and went undetected during the yearly inspections. The accident occurred due to faulty construction of the pipeline in 1976. The pipeline was built simultaneously from both ends to save time and required the assembly of an S-shaped threaded fastener due to a 70 cm difference in height between the two sections. The welding of the poorly cut component (1.5 cm gap filled in by welding) was apparently not in line with the best practices in the industry and was not inspected. The crack probably grew in size with time and under the effect of ground movements.

Several measures to clean up the site were deployed: excavation of polluted soil, pumping of MTBE, blowing air through the water table and subsequent treatment of the return air, etc. Moreover, a 15 m deep dike separating the Juliana canal was reinforced by a 15 m steel wall (below the ground water level).

In April 2005, 6 months later, the pumping station located 30 km downstream the Meuse river detected a significant hydrocarbon pollution which was later on identified as MTBE. After investigation, it was found that the point of origin of the pollution was at the petrochemical port: an 800 m x 200 m pollution zone of 300 mg/L of MTBE was detected between the accident site and the Meuse river, polluting the river at a rate of 50 to 100 kg / day.

A treatment device covering a wider area was put in place in the beginning of 2006.

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