Annotation

The monitoring of hydrogeological conditions on the territory of Stebnyk potash ore deposit in Drohobych district of Lviv region was carried out in 2018–2020 within the framework of ecological researches. The long-term operation of the potassium mine by the Stebnyk State Mining and Chemical Enterprise «Polymineral» has resulted in formation in the depth of ground (due to surface water impregnation) and accumulation on the surface (due to their annual pumping) of the large amount of brine (3 million m3) containing K, Na, Mg and trace elements. The highly concentrated brines are constantly pumped out into the tailings pond. There is a risk of brine licking into surface waters.

According to the results of the chemical analysis of brines, which took place before as well as after contact with sandstones of the productive horizon, the weak chemical interaction between brine and rock was concluded. A certain increase of chloride concentration occurs due to residual salts of formation waters, which are included in the core samples. Such situation evidences the absence of chemical clogging processes.

It was demonstrated that a large amount of brine causes activation of karst-suffusion processes and subsidence phenomena in the mine area. As a result of the permeation of fresh surface water into underground cavities, the depressurization of the earth's surface above the mine fields takes place. Such hydrological conditions cause the dissolution of the rock and create a potential technogenic risk of chasms formation.

The development of karsts affects the zonal water conductivity of the aquifer complex. Near the feeding area, gypsum anhydrites are completely dissolved and above located poorly permeable clays and sandstones are brought down to the surface of the limestones, partially clogging the cracks.