The channel was used during the heavy rain at two occasions, once February 17 and periodically between February 20-25.

The controlled release of treated rainwater through this channel was done to relieve the water treatment plant, which was under heavy pressure because of the rain. The discharges of treated rainwater on February 17 and periodically between February 20-25 are not covered under the current license. Alunorte notified local environmental authorities SEMAS about the use of the channel.

The water was pH-treated at the inlet to the channel, before it was released and then mixed with water treated in the water treatment plant. Rainwater in the refinery area may contain bauxite dust and residues of caustic soda.

Hydro has detected some spillover from a neighboring channel into Canal Velho, containing the same, pH-treated rainwater.

Hydro has no indications that the controlled release from Canal Velho during the heavy rain in February has had a negative environmental impact. The use of the channel and notifications are part of the ongoing internal investigations and the independent external review.