Abstract: A full double wall tank, primarily for underground fluid storage, which is simpler and more economical to construct than conventional full double wall tanks. An inner tank shell, preferably of steel, provides primary fluid containment and is the principal structural basis of the tank. An intermediate barrier layer is applied over the inner shell to define secondary containment space, and provides a base for application of a resin outer secondary containment tank shell which is preferably fiber-reinforced. Monitor sensor means is provided having access to the secondary containment space, preferably proximate the bottom of the tank. The barrier layer is preferably such as to provide a minimum of fluid-receiving secondary containment space for rapid and highly sensitive monitoring, and to provide cathodic protection for a steel inner tank shell.

Abstract: Tank secondary containment system, principally for underground fluid storage tanks such as for fuel storage, which is applicable to both single wall tanks and double wall tanks for providing secondary, double wall fluid containment in the regions of access pipe fittings and pipe connections, which are the places most prone to failure. For double wall tanks, the invention completes the secondary containment which is conventionally only partially afforded by double wall tank construction. Access fittings at the top of the tank and at least lower portions of their respective function pipes which extend to surface equipment are surrounded by tubular secondary containment covering, the lower portion of which is preferably a riser, which is bonded and sealed to the outside of the tank for either a single or double wall tank, and for a double wall tank may extend through an aperture in the outer wall down to the inner wall.

Abstract: Tank secondary containment system, principally for underground fluid storage tanks such as for fuel storage, which is applicable to both single wall tanks and double wall tanks for providing secondary, double wall fluid containment in the regions of access pipe fittings and pipe connections, which are the places most prone to failure. For double wall tanks, the invention completes the secondary containment which is conventionally only partially afforded by double wall tank construction. Access fittings at the top of the tank and at least lower portions of their respective function pipes which extend to surface equipment are surrounded by tubular secondary containment covering, the lower portion of which is preferably a riser, which is bonded and sealed to the outside of the tank for either a single or double wall tank, and for a double wall tank may extend through an aperture in the outer wall down to the inner wall.

Abstract: A double wall manway assembly for double wall tanks intended primarily for underground use, wherein an inner wall provides primary fluid containment and an outer wall provides secondary fluid containment, and a monitor between the walls can detect leakage past the inner wall into the space between the walls. The double wall manway assemby of the invention includes a riser conduit extending through apertures in the two tank walls and having an in-turned inner flange and an out-turned outer flange, with inner and outer cover members removably sealingly engaged over the respective inner and outer flanges. The space within the riser between the two covers communicates with the space between the two tank walls through one or more vent holes through the wall of the riser, for conducting any fluid leakage through the inner cover flange seal to the monitor between the tank walls. In some forms of the invention, a plurality of pipe fittings are embodied in the double wall manway as structural parts thereof.