A leak on a 212 t tank at an oil plant, resulted in 40 t of pure vegetable oil being spilled into the municipal sewer system. The company director had the tank drained into two 21 t mobile tanks; the residue was then pumped out and stored in an effluent pre-treatment buffer tank inside the plant. The oil refinery’s operations were expected to resume on Sunday at 3 pm instead of the Monday morning. The incident was caused by corrosion of the bottom of the 25 year old tank, the absence of a retention tank, a leak detection alarm fault and the malfunction of 2 sump pumps, which should have sent the oil-containing effluents into a buffer tank. The consequences for the environment were limited to a surplus of pollution to be treated (grease and COD) at the entrance of the urban water treatment plant. Production losses were estimated at €63,000.