According to a 1971 Memorandum of Understanding between the Department of Transportation (DOT) and the Environmental Protection Agency, EPA regulates non-transportation-related facilities and DOT regulates transportation-related facilities:

• Mobile refuelers that operate solely within the confines of a non-transportation-related facility subject to the SPCC rule must comply with the general secondary containment requirements during all periods of operation.
• Other mobile refuelers (i.e., transportation-related) involved in a transfer operation at an SPCC-regulated facility would be subject to the loading/unloading rack requirements when the transfer occurs at a rack or the general secondary containment requirements for all other transfers.

For more information on EPA's jurisdiction, please see Appendix A to 40 CFR Part 112