(1) A chronological index shall be maintained by the public records officer on the following:

(a) All final orders entered after June 30, 1990, issued in adjudicative proceedings;

(b) Declarative orders entered after June 30, 1990, that are issued pursuant to RCW 34.05.240;

(c) Interpretative statements as defined in RCW 34.05.010(8) that were entered after June 30, 1990; and

(d) Policy statements as defined in RCW 34.05.010(14) that were entered after June 30, 1990.

(2) The index shall contain identifying information on each item listed in subsection (1) of this section and shall be maintained in ascending chronological order.