Flooding the residual gaps of former lignite open pits is often applied worldwide, offering opportunities for the use of the lake and the reclaimed land, as well as many benefits, ranging from the restoration of ecosystems to the development of the local economy. The flooding process is conditioned by the available quantities of water from natural and/or artificial sources. Flooding can be done either by natural methods (underground water inflow plus intake of water from rainfall and superficial drainage), or by natural and artificial methods (water adductions from superficial collectors). Unlike artificial flooding, natural flooding has the advantage of reduced costs, but it is a long-lasting process. Depending on the flooding speed, as a result of rising water level and saturation of rocks from the final slopes, geotechnical phenomena such as landslides may occur. The paper aims at establishing the dependence between the rhythm of raising the water level in the lake and the geotechnical behavior of the rock in the internal dump. Depending on this, there is a need to accelerate the flooding process through adductions, as the hydrostatic pressure manifested on the final slopes determines the increase of their stability reserve.

Controlled flooding of the remaining gaps of former quarries (especially lignite quarries) and the formation of lakes that can take different uses is one of the ways of recovering and rehabilitating degraded mining lands which offer opportunities for sustainable development of a mining region. The advantages of such a solution are multiple, starting from the restoration of biodiversity, to economic and social benefits. Basically, several flooding techniques are known, but depending on the geological, geotechnical, hydrological and hydrogeological conditions characteristic for a particular region, these techniques must be adapted to the risks that may arise before, during and after flooding the remaining gap. Most of the times, the risks are of geotechnical nature and arise as a result of the interaction between the rocks and the mixture of loose rocks that form the final slopes and the dump with water. The paper is part of an extensive research, which is carried out under the concrete conditions of the remaining gaps in the Rovinari mining basin, and essentially aims at: identifying the main categories of geotechnical risks that can occur under the given conditions, determining the triggering factors, to produce negative geotechnical phenomena and their effects, as well as to identify the main measures to avoid them.