Safe storage of waste, including the residues of the underground coal gasification process, is a serious problem from a technical point of view and requires knowledge regarding not only the chemical composition of the pollutants themselves but also the extent of their elution. Because geo-reactors are situated in the vicinity of natural geological formations of varying structure and properties, there is always a risk that, despite proper prior hydrogeological examination, the thermal and mechanical factors accompanying the process of UCG significantly alter rock mass parameters and thus enable the BI-D1870 of eluted substances into the environment (for example, with newly formed cracks, crevices or sinks). Because each waste remaining in the environment represents a potential threat, the possibility of quantifying the waste is pistil even more important.
During UCG risk of water pollution in the vicinity of the site of operation is negligible, because the pressure of the process is lower than the pressure in the overburden and contaminants are retained inside the cavern. After completion of the process, groundwater may flow into the post-UCG area and have contact with the post-process residues, eluting impurities from waste and carrying them into the surrounding aquifers (on the principle of circulation of groundwater).