What is a complex?
Some facilities must meet the requirements of two or more federal agencies, because they engage in activities that fall under the jurisdiction of those agencies. These agencies include the U.S. Coast Guard, the Department of Transportation's (DOT) Office of Pipeline Safety, and EPA.
A 1971 Memorandum of Understanding (MOU) between EPA and the DOT defines which types of activities are regulated by each agency. You can find the definitions from this MOU in Appendix A to 40 CFR Part 112. According to the MOU, the DOT regulates transportation-related activities, while EPA regulates non-transportation-related activities. The activities at many facilities may be entirely non-transportation-related, and therefore only regulated by EPA. A facility with both transportation-related and non-transportation-related activities is regulated by both agencies, and as such, it is a complex and must comply with all the regulatory requirements of both agencies. For example, a complex may have a transportation-related transfer area regulated by the U.S. Coast Guard (USCG) or a pipeline regulated by the Office of Pipeline Safety under DOT and a non-transportation-related oil storage area regulated by EPA. The owner or operator must compare calculated discharge volumes for the two agencies and plan for whichever quantity is greater.