Vale Newfoundland and Labrador pleaded not guilty to three charges under the Fisheries Act in court on Thursday.
The company is accused of dumping a 'lethal effluent' into Edwards Cove, Anaktalak Bay in Labrador. The area is near the Voisey's Bay nickel mine site.
The offence period is from Oct. 4 to 31, 2011.
Vale is also accused of not taking adequate steps to prevent it, and with failing to report the incident.
The matter is back in court on March 18.