Wash. Rev. Code § 87.03.695
In case of the exclusion of any lands under the provisions of this act, the board of directors shall determine what refund, if any, shall be made to any person or persons who have paid any assessments to such district on any lands so excluded, but such refund, if any, shall be on a basis equitable alike to lands remaining in the district and lands excluded therefrom. Such payment shall be made in the manner as other claims against the district, and from such fund or funds as the board of directors may designate, and which may be legally applied to such payments. The board may, in its discretion, determine what portion, if any, of the assessments remaining unpaid shall be canceled. Said cancellation, if any, shall be accomplished by an order entered upon the minutes of the board and certified to the office of the county treasurer. Upon the filing of such certified order, said assessments, or any portion thereof, canceled by said order shall be marked "Canceled" upon the treasurer's records. The lien of such portion of said assessments, if any, as the board shall refuse to cancel, shall continue against the lands excluded, and the district shall retain all of its rights to such assessments or portions thereof as if said lands had not been excluded.
RCW 87.03.695