Wash. Rev. Code § 47.28.260
When the department plans to administer a contract to engineer or construct a project; or oversee or perform work for another public agency, instrumentality, municipal corporation, or political subdivision; and the public agency, instrumentality, municipal corporation, or political subdivision plans to administer a contract to engineer or construct a project; or oversee or perform work, for the department, the department may waive application of its indirect costs by entering into a reciprocal agreement with the public agency, instrumentality, municipal corporation, or political subdivision in which each party agrees to waive indirect costs related to a project or work that will be performed by the party for the other party's benefit. The reciprocal agreement must specify the project or work to be performed by each party and may be for a maximum term of ten years, unless amended by the parties. Each party's obligation for reimbursement of indirect costs under RCW 47.28.140, 39.34.130, and 43.09.210 is deemed to be satisfied by the execution of a reciprocal agreement.
RCW 47.28.260