Baia Mare is a small town in the Carpathian Mountains in the north of Romania

There is a seam of gold in the hills, very close to Baia Mare - it has been mined for a very long time and since the resource is around seven kilometres long and up to 450 metres thick there has been a large amount of historic mining and the waste it has produced. For every tonne of rock quarried or mined from the mountain, only around 0.6g of gold can be extracted.

In the gold-extraction process, rock is ground to a fine powder, mixed with aqueous sodium cyanide to "leach" the gold out. Cyanide is an extremely toxic poison which kills rapidly as it interferes with the biological oxidative system. The processing plant is actually within the settlement of Baia Mare, and the waste the cyanide solution is carried by pipe to two above-ground storage lakes, between the villages of Sasar and Bozanta, 12 kilometres south-west of Baia Mare. It was the largest of these lakes (or tailings 'ponds' ) which suffered a structural, on the night of 30 January 2000, and poured 130,000 cubic metres of cyanide-tainted water into the Lupes, Somes, and eventually the Tisza and Danube rivers.