Washington Revised Code Title 87. Irrigation § 87.03.139. Lawful disposal of sewage and waste by others--Immunity

No irrigation district, its directors, officers, employees, or agents operating and maintaining irrigation works for any purpose authorized by law, including the production of food for human consumption and other agricultural and domestic purposes, is liable for damages to persons or property arising from the disposal of sewage and waste discharged by others into the irrigation works pursuant to federal or state statutes, rules, or regulations permitting the discharge.