A 1-litre leak of dielectric fluid occurred on an “A” high-voltage/”A” low-voltage transformer placed at the pavement edge (2 m from the road). Its support was positioned at the base of an active ditch and against a slope overlooking beef cattle pastureland. Oil temporarily seeped around the instrumentation terminals and a few droplets spread at the foot of the column over a 4-m² ground area, extending between the hedge and the road berm.

The polluted zone was demarcated. The transformer dated from 1976 and contained a dielectric fluid with trace amounts of PCB (83 ppm according to analyses); it had been exposed to an overcurrent (and short-circuited) due to conductors jumbled into the downstream low-voltage network.

The inspection authorities for classified facilities requested the operator to conduct several measures:

• fence off the affected zone and decontamination worksite to block public access
• cover the accident zone to protect it from foul weather
• remove polluted lands and objects for discharge to an installation authorised for this purpose
• perform analyses at the ditch bottom and along the excavation contours.

This undeclared transformer had in fact been installed improperly.