Above Ground Storage Tanks (AST) and underground tanks differ in many characteristics from structural engineering to access entry points. For access, AST’s most often have at least one top hatch on the roof panels, and some even have a secondary access point on the sidewall of the tank called a manway. Either of these and often both are required in project specifications from the engineer, architect, and designer. These access point have been through the years debated on size and locations on tanks, but the minimum that you usually specify is a 24″ to 30″, and its always a good note to point out that depending on the tanks end usage, there may be additional requirements so check first. Additionally refer to officials in your local and state agencies for guidance and direction on the use of confined space requirements and practices.