applicable SIP
Applicable implementation plan or applicable SIP means the portion (or portions) of the SIP or most recent revision thereof, which has been approved under section 110(k) of the Act, a Federal implementation plan promulgated under section 110(c) of the Act, or a plan promulgated or approved pursuant to section 301 (d) of the Act (Tribal implementation plan or TIP) and which implements the relevant requirements of the Act.