A below-grade, modular cast concrete containment vault which contains one or more primary liquid storage tanks. Dispensing pumps and sundry conduits and support equipment are attached to or supported within a cast cover. The cover is secured to the tanks. The pumps can be coupled to a remote control and communications kiosk. A manhole permits access to a ventilated secondary containment and inspection space within a base unit. Spill and overflow containment assemblies surround fill and vent pipes in the cover and direct spillage to the secondary storage space. Tertiary and auxiliary containment is also provided for spillage from the dispensing pumps and backup storage for the overflow containment assemblies. Additional standpipes communicate with the base and support additional monitoring and inspection equipment.