(1) Commissioners of public utility districts shall receive salaries as follows:
(a) Each public utility district commissioner of a district operating utility properties shall receive a salary of one thousand eight hundred dollars per month, as adjusted for inflation by the office of financial management in subsection (6) of this section, during a calendar year if the district received total gross revenue of over fifteen million dollars during the fiscal year ending June 30th before the calendar year.
(b) Each public utility district commissioner of a district operating utility properties shall receive a salary of one thousand three hundred dollars per month, as adjusted for inflation by the office of financial management in subsection (6) of this section, during a calendar year if the district received total gross revenue of from two million dollars to fifteen million dollars during the fiscal year ending June 30th before the calendar year.
(c) Commissioners of other districts shall receive a salary of six hundred dollars per month, as adjusted for inflation by the office of financial management in subsection (6) of this section, for each commissioner.
(2) In addition to salary, all districts shall provide for the payment of per diem compensation to each commissioner at a rate of ninety dollars, as adjusted for inflation by the office of financial management in subsection (6) of this section, for each day or portion thereof spent in actual attendance at official meetings of the district commission or in performance of other official services or duties on behalf of the district, to include meetings of the commission of his or her district or meetings attended by one or more commissioners of two or more districts called to consider business common to them, but such compensation paid during any one year to a commissioner shall not exceed twelve thousand six hundred dollars, as adjusted for inflation by the office of financial management in subsection (6) of this section. Per diem compensation shall not be paid for services of a ministerial or professional nature.
(3) Any commissioner may waive all or any portion of his or her compensation payable under this section as to any month or months during his or her term of office, by a written waiver filed with the district as provided in this section. The waiver, to be effective, must be filed any time after the commissioner's election and prior to the date on which the compensation would otherwise be paid. The waiver shall specify the month or period of months for which it is made.
(4) Each district commissioner shall be reimbursed for reasonable expenses actually incurred in connection with such business and meetings, including his or her subsistence and lodging and travel while away from his or her place of residence.
(5) Any district providing group insurance for its employees, covering them, their immediate family, and dependents, may provide insurance for its commissioner with the same coverage.
(6) The dollar thresholds for salaries and per diem compensation established in this section must be adjusted for inflation by the office of financial management every five years, beginning January 1, 2024, based upon changes in the consumer price index during that time period. "Consumer price index" means, for any calendar year, that year's annual average consumer price index, for Washington state, for wage earners and clerical workers, all items, compiled by the bureau of labor and statistics, United States department of labor. If the bureau of labor and statistics develops more than one consumer price index for areas within the state, the index covering the greatest number of people, covering areas exclusively within the boundaries of the state, and including all items shall be used for the adjustments for inflation in this section. The office of financial management must calculate the new dollar threshold and transmit it to the office of the code reviser for publication in the Washington State Register at least one month before the new dollar threshold is to take effect.
(7) A person holding office as commissioner for two or more special purpose districts shall receive only that per diem compensation authorized for one of his or her commissioner positions as compensation for attending an official meeting or conducting official services or duties while representing more than one of his or her districts. However, such commissioner may receive additional per diem compensation if approved by resolution of all boards of the affected commissions.