Abstract: A side loading system and method for the underground disposal of radioactive waste is disclosed herein. The vault system is formed from at least one vault cell that comprises a floor slab disposed within a recess in the earth, a ceiling slab disposed over the floor slab, an earth cap disposed over the ceiling slab and an elongated wall assembly disposed around the periphery of the floor slab for supporting the ceiling slab and earth cap. The elongated wall assembly is preferably four times as long as it is wide, and includes a back wall and a front wall, the front wall having an accessway for the side loading of radioactive waste. Radioactive waste is loaded in sequential rows starting from the back wall of the vault cell.