Each port district, which has not previously done so, shall within thirty days of June 8, 1955, submit for approval by the governor a plan for extending the benefits of Title II of the federal social security act, as amended, in conformity with applicable provisions of said act as set forth in chapter 41.48 RCW, to employees of such port district who are employed in positions not covered by the employees' retirement system of the state of Washington. The plan required to be submitted by this section shall be as set forth in RCW 41.48.050 and shall be in conformance therewith.