In a chemical plant, a leak of effluents containing acetonitrile (a harmful and flammable solvent) from the process wastewater system lead to groundwater contamination. As the network was used only sporadically, the duration of the leak could not be accurately determined. A maximal estimate gave 557 days. The potential loss is estimated to be 61 t of acetonitrile.

Wells were established to try to recover the pollutant through pumping and to sample the groundwater. Three tonnes of acetonitrile were recovered by pumping operations over a period of 3 months.

The cause of the pollution was attributed to corrosion of the wastewater system by chemical effluents. The concrete wastewater channel, coated with lead and tiled with ceramic, had cracked. Over time, the ceramic tiles became porous, and the frequent fluctuation of the effluent’s pH caused the lead oxide layer on the surface and the lead covering to dissolve. The seals between the ceramic tiles are probable starting points for corrosion.

The organisational cause of this pollution goes back 12 years. The plant changed owners in 2003. The latter did not retain the masonry personnel as they were no longer required to maintain the process equipment. Moreover, the ceramic surfaces of the wastewater network were no longer maintained. Shortcomings in the change management processes indicate the importance of maintaining masonry skills to guarantee the tightness of the wastewater network.

Finally, regular third-party inspections of the plant did not identify the downgraded condition of the channel due to poor coordination between the operator and the third-party inspection body. The inspection by a third-party body is a valuable tool for checking integrity and safe operating conditions. The operator considered that the channel had already been inspected, but the third-party inspection body had not understood that the channel was part of its inspection perimeter. The results of the third-party inspections did not therefore make the operator aware of the downgraded condition of the channel.

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