In this chapter, the following terms have the meanings indicated. Terms Defined. “Corresponding onshore area (COA)” means, with respect to any existing or proposed OCS source located within 25 miles of a State's seaward boundary, the onshore area that is geographically closest to the source or another onshore area that the Administrator designates as the COA, pursuant to 40 CFR §55.5, as amended. Outer Continental Shelf (OCS) Source. “Outer Continental Shelf (OCS) source” means any equipment, activity, or facility which: Emits or has the potential to emit any air pollutant; Is regulated or authorized under the Outer Continental Shelf Lands Act (OCSLA) (43 U.S.C. §1331 et seq.); and Is located on the OCS or in or on waters above the OCS. “Outer Continental Shelf (OCS) source” includes vessels only when they are: Permanently or temporarily attached to the seabed and erected thereon and used for the purpose of exploring, developing or producing resources therefrom, within the meaning of section 4(a)(1) of OCSLA (43 U.S.C. §1331 et seq.); or Physically attached to an OCS facility, in which case only the stationary sources aspects of the vessels will be regulated.