The principle of the method proposed is to assess blast vibration impact on the environment for the cases when the blasting in an opencast mine had been performed long time ago. Restoration of the blasting situation and establishment of the method used studying the properties of vibration medium of the blasting site allow determining vibration intensity at the time and site we are interested in. The method is applicable to assess blast vibration impact in the case of both closed oil shale opencasts and working ones. In the case of working opencast it is necessary when blasting parameters, situation or local regulations have been changed.