“An impounding area surrounding containers, used in areas with potential for large discharges, such as single or multiple above ground storage tanks and certain piping. The purpose of dikes is to minimize the potential of accidental discharges from containers, equipment or pipelines such that a discharge does not endanger adjoining property or important process equipment and/or structures.”

Reference: Assessment of Tankfield Dike Lining Materials and Methods (API PUBL 315).  Standard by American Petroleum Institute.

Standard for the production, storage, and handling of liquefied natural gas LNG (NFPA 59 A).Standard by American Petroleum Institute 2013.

Various regulations may specify volume of tankage that should be contained in diked area.