Londonderry Port and Harbour Commissioners have been fined £3,000 for unlawfully having a scrapped car metal shearing operation at Lisahally Port.
The firm which ran the operation, Foyle Recycling Company, was fined £10,000.
Its director, Sinead O'Hara from County Leitrim, was fined £1,000.
All three pleaded guilty to breaking environmental laws following an investigation by the Northern Ireland Environment Agency in 2007.
The judge said had there been any evidence of pollution, the fines would have been a lot heavier.
He also said he accepted that the case involved a complex planning issue, but all three defendants should have obeyed the law when they were warned about the illegal nature of their activities.