During filling of the 25,000-litre milk tank on a tanker truck inside a dairy / cheese factory, a glass view lens mounted in series on one of the 3 vehicle outlets broke. The milk spilled onto the retention zone associated with the loading/unloading area, but the liquid flow was too great for the retention capacity and overflow rate. The milk reached the stormwater drainage network, whose outfall into the CAILLY River was closed by activating a manual valve; 4,000 litres of milk nonetheless made their way into the watercourse. According to the operator, the milk would have also reached the wastewater network and the GIE station via a small pipe. The operator requested the milk supplier to repair the defective point in the glass view lens and rectify the modification figures in the loading zone. As a response, the haulier did not anticipate any modifications to the cisterns involved. The Hazardous Installations Inspectorate made a site visit and, as a follow-up, requested that the operator remedy several non-compliance items observed during the visit. The operator proceeded with restoration of the lifting station.