Wash. Rev. Code § 54.04.055
Any public utility district which provides for the coverage of any of its employees under any plan for individual annuity contracts, retirement income policies, group annuity contracts, group insurance for the benefit of its employees, or any other contract for the benefit of its employees, and pays all or any part of the premiums or other payments required therefor, is hereby authorized to continue to make such payments for such employees after their retirement from employment. Such payments agreed to by the public utility district shall be considered as deferred compensation. Such payments shall not be retroactive but shall only be available for those employees employed on or after August 6, 1965 provided that such payments for retired employees shall not exceed those being paid for regular employees.
RCW 54.04.055