Pollution
Humain
Environnement
Economique

At around 4:45 p.m., a person living along the River LOT reported that the river had a green-white colour. At around 5:10 p.m., a water utility worker saw traces of a recent, heavy flow of whitish slurry downstream of Esclanèdes bridge, more than 1.5 km upstream of the bridge from which the pollution was reported. The pollution was coming from a company that cuts, saws, and planes minerals.

Causes of the pollution

The pollution occurred during the cleaning of a settling tank/receiver used for water laden with limestone fines. Usually, this water is pumped and transferred to a secondary tank by a technician. However, because the surface of water in the tank was frozen, the pumped water slid across the ice and flowed directly into its overflow, filling a safety buffer tank. Once the buffer tank was full, the slurry flowed through a discharge pipe and into a small retention pond along the River LOT. As one of the bunds had been damaged by previous storms, the slurry flowed directly into the river. The operator estimated that the pollution event lasted one hour and released a volume of 8 m³.

Measures taken

The operator repaired the damaged earthen bund and reinforced the retention pond. To avoid any further accidents, it fitted a valve on the secondary basin’s overflow outlet. During cleaning operations, this valve is closed so that any slurry overflowing from the pond does not pass through the overflow and into the buffer tank. A pond cleaning procedure was drafted.