For every mining company a correct model of the deposit is most important. During mining activities in the oil shale open pit a discrepancy between deposit model and reality was found. Therefore, the aim of this work is to check the current model and revise it on basis of the geological exploration. Based on this new model the mining strategy was changed and the minable ore masses were recalculated. The recultivation planning was adjusted to the new situation. Finally, it was checked whether the proposed changes of mine planning, strategy and recultivation consitute an essential change of the existent mining permission.