Members of the board of diking commissioners of any diking district in this state may receive as compensation the sum of up to ninety dollars for actual attendance at official meetings of the district and for each day or part thereof, or in performance of other official services or duties on behalf of the district and shall receive the same compensation as other labor of a like character for all other necessary work or services performed in connection with their duties: PROVIDED, That such compensation shall not exceed eight thousand six hundred forty dollars in one calendar year, except when the commissioners declare an emergency. Allowance of such compensation shall be established and approved at regular meetings of the board, and when a copy of the extracts of minutes of the board meeting relative thereto showing such approval is certified by the secretary of such board and filed with the county auditor, the allowance made shall be paid as are other claims against the district.

Each commissioner is entitled to reimbursement for reasonable expenses actually incurred in connection with such business, including subsistence and lodging, while away from the commissioner's place of residence, and mileage for use of a privately owned vehicle in accordance with chapter 42.24 RCW.

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 secretary 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.

The dollar thresholds 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.

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.