A 20-m³ spill of acrylic resin was noticed at 8 am in a varnish factory’s storage retention basin. The personnel were able to recover 18 m³ through pumping into containers. The remaining resin was sprinkled throughout the night to prevent drying. The next day, a specialist firm pumped the residual quantity. This pumping step caused foam to form in the cistern, which wound up spilling over due to a lack of monitoring, given that the cistern’s high-level alarm did not respond to foam. Since the lorry was not parked in a zone equipped with a retention facility, 20 l of a water-resin mix flowed onto the street and into the storm drain network, both of which needed to be rinsed. The factory operator blocked the storm drains and pumped this mix into a retention basin closed by 2 valves. These valves however were not sealed due to poor system design and the presence of sand. The rinsing water then flowed into a pit leading to a brook. The municipality and owner of the parcel crossed by the pit were informed. An earthen dam was built upstream of the brook and inflatable plugs installed at the retention basin outlet in order to limit flow. The pit was pumped and then cleaned. The operator notified the inspection authorities for classified facilities.
On the morning of the accident, the resin storage unit had been closed and pipes disassembled for cleaning subsequent to resin drying out inside the pipes. This shutdown in turn cut off the air intake to the tank outlet’s pneumatic valve, which remained in the open position, yet no plug was installed upstream of the valve: resin leaked into the retention basin until the spill could be visually detected. The operator proceeded by: verifying the cut-off valve seal on the retention, modified manholes adjacent to the valves to avoid sand accumulation, and revised subcontractors’ procedures to better handle possible product flows (cleaning, maintenance, loading, transfer).