Smoke ashes from the Tadeusz Kościuszko electric power plant in Polaniec might have an application in the filling of post-exploitation cavities in the sulphur mine "Osiek". Such a possibility is primarily the result of an investigation of the sub-surface space created by the underground melting of sulphur, as well as from an analysis of the state of the ore. Simulations performed on a hydrogeological model of a section of the ore itself, from the standpoint of experimental trials, indicates the feasibility of such an undertaking. The results of the study provide a basis for defining the increase in aquifer pressure and also allow the area of influence of the tamponage holes to be determined. The results also indicate that favourable conditions for the backfilling of post-exploitation cavities of the sulphur deposit with ash occur, if use is made of recirculation holes. The removal of water from these holes in amounts necessary to facilitate the continuous preparation of hydromixture, decidedly limits the zone of dynamics change within the ore series. The supply of hydromixture with the required flow intensity requires that there be suitably lower pressures. Experimental trials of the injection of water-ash mictures will allow for an accurate estimation of the quantity of ash waste that can be located within the post-exploitation cavities of the deposit. These results can be used to evaluate the feasibility of work of such kind on an industrially viable scale. In the case of positive wxperimental results, it will be necessary to modify the technological methods for the underground melting of sulphur, by considering the planned element of using industrial ash waste to tamponage the exploited part of the deposit.