Abstract <p>The article presents the results of the study of the actual state of the reservoir no. 5 of the emergency diesel fuel storage at Thermal Power Plant no. 3 in Norilsk and its supporting structures using seismic exploration methods of the CMRW, inspection of the reservoir structures using the standing wave method, ground penetrating radar profiling and seismological observations. The velocity structure of the average under the reservoir to depths of ~30 m was determined. Based on the reduced values of P- and S-wave velocities, it was established that the foundation soils are in a plastic–frozen state. A surface of dense rocks was constructed at depths of 11.5–13 m, to which, presumably, the piles under the reservoir were driven; in the northwestern part of the site, its depth increases to 17–23 m. The reservoir structure was examined using the standing wave method. The full lengths of piles and the depths of piles underground (~10–12 m) were determined; the western, northwestern and southwestern parts of the pile field are noted for their lower pile depth and higher pile resonance frequency. Based on the results of the examination of the foundation slab, 7 modes of natural horizontal oscillations were identified and the absence of its natural bending oscillations was established, which indicates good stability of the slab. An increase in the amplitudes of standing waves and peak accelerations of ground displacements was detected in the western part of the reservoir no. 5, which indicates strong rocking of the foundation slab here, which could lead to fluctuations of the fuel in the reservoir and weakening of the strength of the reservoir and piles. Based on the detailed geophysical information obtained, a conclusion was drawn about the influence of the heterogeneous structure of the environment under the reservoir on the occurrence of accidents.</p>