Solid waste heaps

On the flat landscape of Northeast Estonia, several kinds of man-made land forms occur: cone-shaped solid waste dumps and plateaus, ash plateaus and black semi-coke heaps (reaching 110 m at Kiviõli).

The solid waste heaps contain the residues of oil shale benefication. After oil shale is extracted from limestone, the limestone residue still yields some oil shale. The oxidation of pyrite ignited fires in all these waste heaps in the 1960s, causing the natural coking process to begin inside the heaps, which released toxic waste into ground water

The burned heaps are located near Kukruse, Jõhvi and Rutiku. Later, the benefication residues were formed into low plateaus. This has helped to avoid the self-ignition of solid waste heaps.

The ash plateaus are formed of the ash washed away from the oil shale power plants at Narva and Ahtme. Oil shale burnt in power plants is composed of about 50% mineral content, half of which is alkaline caustic lime (CaO). Using special closed water pipe systems, the ash is directed to ash plateaus. Eventual breakthrough of this highly alkaline water, caused by high precipitation, may endanger nearby natural water bodies.

The black semi-coke heaps are the residues of the process of coking oil shale for oil in the chemical factories at Kiviõli and Kohtla-Järve.

Organic waste leaking from black semi-coke heaps includes oil, phenols, ketones and other toxic liquids. This toxic waste has been carried to the Gulf of Finland by the Purtse and Kohtla Rivers. The toxic waters of the Erra River, running through the Uhaku karst field, have left a solid bituminous layer in the karst field and in the river bed.

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