The solution presents additional walls preventing storage petrol tanks from leaking petroleum products into the ground and the surface water. The additional walls consist of a two-layer coating made of a double fleece material that is stiffened by the hardening resins and outer laminate layer made of the resin reinforced by the glass fibre. The leakage monitoring takes place in the coating by using permanent monitoring and leakage signalling installation by both dry and wet systems. The above-presented solution can be widely used in military units - especially in tanks installed earlier in former fuel stations.