Q641. Our utility owns power plants that are subject to Part 98 subpart D and 100-150 substations.  Do we report SF6 and PFC emissions under subpart DD as a separate facility or together?

A641. Subpart D and subpart DD emissions should not be submitted on the same report.  There are different facility definitions for subpart D and subpart DD.  The applicability for each subpart must be separately evaluated according to the appropriate facility definition. The subpart DD definition of facility (see 98.308) applies only to electrical transmission and distribution equipment. Based on that definition, a facility is comprised of all the substations (1) that you own, service, or maintain; (2) that are linked through electric power transmission or distribution lines; and (3) that function as an integrated unit.  All equipment that meets these criteria is part of a single facility that must be registered separately from the power stations.  Your 100-150 substations could be a single facility or multiple facilities depending on how they are configured.  All of the criteria in the definition above must be met for the substations to be considered one facility.  For example, substations and other electric transmission and distribution equipment lines that are linked through separate transmission or distribution or that do not function as an integrated unit would be considered a separate facility (or facilities, as appropriate).  In any scenario, the subpart DD emissions should not be reported at the same facility that subpart D emissions are reported for.