One hybrid aspen plantation in Aidu
was directly planted on levelled quarry spoil (59[degrees]19' N, 27[degrees]03' E) where four sample plots (Al) were established .
Ruskavere, Palamuse, Aidu
, Koksvere, Kingissepa, and Eikla cores), and is the lateral equivalent of the typical red-coloured Jonstorp strata (Kaugatuma and Pamu cores; Figs.
" 1.8 Mine "Estonia" 2.2 Mine "Tammiku" 2.3 Mine "Viru" 2.8 Mine "Ahtme" 3.3 Mine "Sompa" 3.5 Note: Table made from bar graph.
There are five zones for which different proportions were applied: Aidu
and Vanakula opencast with 63%, Kohtla, Mine No 2 and Sompa underground with 41%, Ahtme 40%, Tammiku 44% and Viru 42% [15, 16, 26].
Surface mining technology used in the Aidu
and Narva opencast mines, operated by AS Eesti Polevkivi, developed after World War II when stripping with relatively big bucket (10-35 [m.sup.3]) excavators, mainly draglines, started to be used.
The company Eesti Polevkivi Ltd.--company of oil shale production and distribution owns two operational mines (Estonia and Viru) and two operational opencasts (Narva and Aidu
In 2000 two experimental plantations with hybrid aspen were established in Aidu
oil shale opencast.
The hydrogeological model used was developed by the hydrogeologists Savitski and Savva from the Geological Survey of Estonia for the central part of the Estonian oil shale field and Aidu