In a special garage for lorries, a 7,000-litre cistern of domestic fuel oil, filled on Thursday 30th September, lost its entire contents. Hydrocarbon polluted the soils and was discharged into the SARTHE River at the level of a stormwater collector pipe subsequent to heavy rains. Iridescence and strong odours were noticed by neighbours on Saturday, 2nd October. Three absorbent dams were set up to contain the pollution, which had spread over 3.5 km.

Prefectural orders were issued prohibiting fishing, nautical activities and water extraction for sprinkling private gardens; a press release was also prepared. The Prefecture, municipality, regional environmental agency, departmental planning unit, regional health office, departmental emergency response unit and operator of the water extraction facility met regularly in order to assess the situation. The dams were cleaned on a regular basis. Dam water releases were scheduled on 4th and 8th October in order to dilute the pollution. The emergency measures were lifted on 12th October at 5:45 pm upon disappearance of the last remaining iridescences.

The investigations enabled localising the origin of this pollution. An inspection of the facility’s fuel oil tanks revealed that their seal had remained intact. The source of the discharge had either been due to a problem encountered during filling (tank error and lack of monitoring) or a problem with a return on the jet. The operator proceeded by cleaning up the site, river and stormwater drainage networks. The contaminated ground and water was discharged by a specialised subcontractor to a certified treatment centre.