Systems and/or methods of waste disposal use human-made caverns that are constructed within deep geological formations. A given human-made cavern may be constructed by first drilling out a vertical wellbore to a deep geological formation. Then a bottom portion of the vertical wellbore is jet drilled using an abrasive jetting fluid to form a launch chamber of void volume, that is sized to fit a reaming tool in its deployed open configuration. A reaming tool, in a closed configuration, is then inserted into the vertical wellbore for landing in the launch chamber. The reaming tool is then deployed into its open configuration while in the launch chamber. Reaming operations then occur from the launch chamber directed downwards within the deep geological formation, forming a given human-made cavern. The newly formed human-made cavern may be conditioned and/or configured for receiving amounts of the waste for long-term disposal and/or storage.