During a weekend, 300 m³ of leachate derived from a class 2 landfill was released into the SEILLETTE basin via the storm drain. On Monday morning, the technicians isolated the basin responsible for the accident to stop the release by closing the manual valves. The chances of a retention wells located 5 km downstream being polluted were not excluded. Water samples were taken both upstream and downstream the accident site. The accident occurred due to a power supply failure following an intervention on Friday afternoon by technicians from the electricity department who failed to restore the power supply before leaving. Due to lack of power, the valve system controlling the leachate storage abruptly opened allowing the waste water to be released into the basin directly connected to the storm drain network. This network ended in a single rejection point in the middle of the natural environment fitted with a automatic closure valve coupled with a pH and resistivity analyser and an alarm. This valve did not function. The inspection authorities for classified facilities noted the facts and ordered the operator to secure the site and submit a report on the causes, circumstances and consequences of the accident, as well as the measures taken to reduce the chances of reoccurrence of such accidents.