(1) As permitted in general terms by the provisions of WAC 197-11-460, the normal sixty-day period for preparation of a final EIS may be extended whenever the proposal is unusually large in scope, or where the environmental impact associated with the proposal is unusually complex. The determination that additional time is required for preparation of the final EIS shall be made in writing by the responsible official or his designee and shall be accompanied by a brief statement explaining the reason that additional time is required.

(2) Availability of the final EIS shall be as stated under WAC 468-12-510.