An improved storage reservoir assembly has increased resistance to leakage of fluid from the assembly into the ground. The assembly comprises a storage reservoir suitable for being buried beneath ground level and suitable for containing a fluid and at least one support unit attached to or disposed adjacent to the reservoir and suitable for attachment to an above-ground canopy. The assembly also provides for substantially surrounding the reservoir with a hydrostatic head of a second fluid for detecting reservoir leaks by infiltration of the second fluid within the reservoir. This may be accomplished through an enclosure suitable for substantially surrounding the reservoir or through the use of a double-walled reservoir, with the second fluid contained within the enclosure or between the walls of a double-walled reservoir. In addition, the assembly provides for a piping network of the distribution system for supplying remote service islands to be located within a primary above-ground canopy.