Accidents that took place in the past at the Bor tailings pond have deposited tailings at the rivcrbanks. An accidental pollution incident resulted in severe contamination of over 40 km2 of the most fertile agricultural land along the banks of Borska and Timok Rivers in Serbia and in Bulgaria (4.5 km3) by heavy metals and other toxic substances. Old plans for the re-cultivation of the contaminated soils have not yet been realized due to financial constraints.