Wash. Rev. Code § 87.03.277
Irrigation districts that have designated their own treasurers as provided in RCW 87.03.440 may accept credit cards, charge cards, debit cards, smart cards, stored value cards, federal wire, and automatic clearinghouse system transactions, or other electronic communication, for any payment of any kind including, but not limited to, assessments, fines, interest, penalties, special assessments, fees, rates, tolls and charges, or moneys due irrigation districts. A payer desiring to pay by a credit card, charge card, debit card, smart card, stored value card, federal wire, automatic clearinghouse system, or other electronic communication shall bear the cost of processing the transaction in an amount determined by the treasurer, unless the board of directors finds that it is in the best interests of the district to not charge transaction processing costs for all payment transactions made for a specific category of payments due the district, including, but not limited to, assessments, fines, interest, penalties, special assessments, fees, rates, tolls, and charges. The treasurer's cost determination shall be based upon costs incurred by the treasurer and may not, in any event, exceed the additional direct costs incurred by the district to accept the specific form of payment used by the payer.
RCW 87.03.277