Three linear tectonic dislocation groups of different orientation (and probably also of different age) cut the Estonian oil shale-kukersite deposits. Two younger groups of structures are typical fault zones with N-NE and NW trends, which are expressed topographically as narrow valleys, partly infilled by till, both on land and offshore. The oldest, third group of structures is represented by narrow, somewhat curvilinear, NE-trending folded and fractured zones, associated with extensive dolomitization, hydrothermal mineralization and karst. Oil shale within these structural zones is oxidized and partly replaced by karst clay. All dislocations disrupt and complicate the structure of deposit, which affects mining conditions from the technical point of view and also causes a loss of oil shale resources.

The present paper is based on the results of the research conducted in 2004 by the Department of Mining of the Tallinn University of Technology and Estonian Oil Shale Company. The state of the technogenic water body that has formed in the central part of the oil shale deposit is analysed: the water level in the area of the stopped and closed mines, water amount and movement direction, water quality and its changes. The state of the water is assessed and predicted using modelling of the water tables, statistical analysis of the water quality parameters and the pilot model for describing the migration of water. The results show that the technogenic water body studied is in a relatively stable state, and the quality of the groundwater in that area is fast improving approaching the drinking water standards.

Oil shales used in Estonian power