(1) Each permit shall contain terms and conditions that assure compliance with all applicable requirements at the time of permit issuance. Every requirement in an operating permit shall be based upon the most stringent of the following requirements:

(a) The FCAA and rules implementing that act, including provisions of the approved state implementation plan;

(b) Chapter 70.94 RCW and rules implementing that chapter. This includes requirements in regulatory orders issued by the permitting authority;

(c) In permits issued by a local air pollution control authority, the requirements of any order or regulation adopted by that authority;

(d) Chapter 70.98 RCW and rules adopted thereunder; and

(e) Chapter 80.50 RCW and rules adopted thereunder.

(2) Legal authority. The permit shall specify and reference the origin of and authority for each term or condition, and identify any difference in form as compared to the applicable requirement upon which the term or condition is based.

(3) Acid rain. Where an applicable requirement of the FCAA is more stringent than an applicable requirement of regulations promulgated under Title IV of the FCAA, both provisions shall be incorporated into the permit and shall be enforceable by the administrator.

(4) Where an applicable requirement based on the FCAA and rules implementing that act (including the approved state implementation plan) is less stringent than an applicable requirement promulgated under state or local legal authority, both provisions shall be incorporated into the permit in accordance with WAC 173-401-625.