Wash. Rev. Code § 67.30.010
The participation of counties and cities in multipurpose sports stadia which may be used for football, baseball, soccer, conventions, home shows or any and all similar activities; the purchase, lease, condemnation, or other acquisition of necessary real property therefor; the acquisition by condemnation or otherwise, lease, construction, improvement, maintenance, and equipping of buildings or other structures upon such real property or other real property; the operation and maintenance necessary for such participation, and the exercise of any other powers herein granted to counties and cities, are hereby declared to be public, governmental, and municipal functions, exercised for a public purpose, and matters of public necessity, and such real property and other property acquired, constructed, improved, maintained, equipped, and used by counties and cities in the manner and for the purposes enumerated in this chapter shall and are hereby declared to be acquired, constructed, improved, maintained, equipped and used for public, governmental, and municipal purposes and as a matter of public necessity.
RCW 67.30.010