A commissioner of any port district may waive all or any portion of his or her compensation payable under RCW 53.12.260 as to any month or months during his or her term of office, by a written waiver filed with the secretary of the commission. The waiver, to be effective, must be filed any time after the commissioner's election and prior to the date on which said compensation would otherwise be paid. The waiver shall specify the month or period of months for which it is made.