What is a vaulted AST?
A. A vaulted tank is the term that was originally used to describe any tank that was surrounded in concrete and/or offered fire resistance beyond that of a bare steel tank. However, with advancements in the design and manufacturing of AST’s in recent years, the term vaulted has taken on a different meaning. The industry now reserves the term vaulted for a tank that is installed in a below-grade concrete enclosure. Such tanks are classified as aboveground tanks by nationally recognized codes, and by the Illinois OSFM, despite the fact that they are actually installed below-grade. The enclosure containing the tanks, being the equivalent of a large concrete bathtub without a drain, allows visual inspection of the tanks, and does not allow leaking product to contact the surrounding earth. These vaults are not backfilled. (Backfilling the vault will essentially classify the installation as an underground tank site). There are strict rules within NFPA standards for such vaulted installations
