Wash. Rev. Code § 70.44.240
Any public hospital district may contract or join with any other public hospital district, publicly owned hospital, nonprofit hospital, legal entity, or individual to acquire, own, operate, manage, or provide any hospital or other health care facilities or hospital services or other health care services to be used by individuals, districts, hospitals, or others, including providing health maintenance services. If a public hospital district chooses to contract or join with another party or parties pursuant to the provisions of this chapter, it may do so through establishing a nonprofit corporation, partnership, limited liability company, or other legal entity of its choosing in which the public hospital district and the other party or parties participate. The governing body of such legal entity shall include representatives of the public hospital district, which representatives may include members of the public hospital district's board of commissioners. A public hospital district contracting or joining with another party pursuant to the provisions of this chapter may appropriate funds and may sell, lease, or otherwise provide property, personnel, and services to the legal entity established to carry out the contract or joint activity.
RCW 70.44.240