A gasoline pipeline (diameter: 10″ or 254 mm; year of service start-up: 1953; grade “C” type steel; 7-mm nominal thickness) broke around 9:45 am subsequent to transient pressure surges caused by closure of a safety valve. The pressure value recorded at the time of the tear equalled 82 bar. This pressure was considerably less than the tube design pressure.
Around 1:30 pm, residents notified fire-fighters of the lingering smell of hydrocarbons. First responders installed a 400-m safety perimeter and placed absorbent sandbags in the adjacent watercourse. Students, as well as employees at a nearby factory and neighbours, were confined indoors for an hour. Hydrocarbon discharges into the river were also observed. At 2:53 pm, explosion meter readings indicated the absence of an explosion risk.
The leak source was pinpointed at about 4 pm by the pipeline operator 300 m west of the river. A 3-m diameter crater was also found at the discharge site. The Regional Health Agency asked the operators of water intake facilities in the area to perform analyses; these revealed no presence of contamination. The site was monitored throughout the night. The pipeline was drained and then repaired.
The quantity of gasoline lost was estimated at 182 m³. To clean up the site, the pipeline operator undertook the following actions:
- pumping of all residual gasoline remaining in the pipeline (20 m³ recovered);
- mapping of the soil pollution, and release of a pollution clean-up management plan (this action step began on 28 september by installing 4 piezometers);
- storage of polluted land (400 m³), in conjunction with a planned bioventing treatment.
The residual volume of hydrocarbons present in the ground was assessed at 100 m³.
The pipeline had been damaged at the leak site (perforation, pitch lining not present, scratch marks, etc.). The inspection authorities for classified facilities asked the operator to deliver a report on the accident causes, along with proof of the facility’s maximum service pressure (on the order of 80 bar) relative to its state of repair.
The pipeline company conducted other facility inspections, namely: pipe lining by determining the direct current voltage gradient (DCVG), launch of a leak detector scraper, missing metal and geometric defects including penetrations, hydraulic strength test before pipeline restart at a lower allowable service pressure and safety sensor settings (64 bar). A scraper for detecting cracks was also part of these control measures.
