(1) The board shall, pursuant to RCW 90.58.180, issue a final decision on petitions for review arising out of the granting, denying or rescinding of a permit within one hundred eighty days of the following:

(a) The date the petition for review is filed; or

(b) The date a motion to intervene is filed by the department or the attorney general, whichever is later.

(2) The parties may agree to waive the one hundred eighty-day deadline.

(3) The board may, on its own motion, extend the deadline for thirty days after determining that good cause exists for the extension.