Q629. To what extent does a subpart DD facility include potential subpart C sources located in the same physical structure?  Would it include sources using natural gas for comfort heating in warehouses and office complexes on the electric power system?

A629. When dealing with subpart C and subpart DD there are two different definitions for facility.  In general, for subpart DD, the facility is comprised of the electric transmission and distribution equipment, and excludes any fuel combustion equipment. Please review the definition of facility for subpart DD found within § 98.308.  The definition of facility that applies to stationary fuel combustion sources (subpart C) is found within Subpart A.  If at some location there is equipment potentially subject to subpart DD and subpart C, then that location contains two facilities; and applicability should be evaluated separately for each facility according to the appropriate facility definition.  For example, if the electrical equipment is part of an electrical power system that is subject to subpart DD, that does not automatically mean that emissions from the fuel combustion equipment must be reported. Applicability to subpart C would be evaluated separately.