Wash. Rev. Code § 36.89.050
A county may finance, acquire, construct, develop, improve, maintain and operate any open space, park, recreation and community facilities, public health and safety facilities, stormwater control facilities and highways authorized by this chapter either solely or in conjunction with one or more governmental agencies. Any governmental agency is authorized to participate in such financing, acquisition, construction, development, improvement, use, maintenance and operation and to convey, dedicate or lease any lands, properties or facilities to any county for the purposes provided in this chapter and RCW 86.12.020, on such terms as may be fixed by agreement between the respective governing commissions or legislative bodies without submitting the matter to a vote of the electors unless the provisions of general law applicable to the incurring of public indebtedness shall require such submission.
No county shall proceed under the authority of this chapter to construct or improve any stormwater control facility or highway or part thereof lying within the limits of a city or town except with the prior consent of such city or town. By agreement between their respective legislative bodies, cities, towns and counties may provide that upon completion of any stormwater control facility or highway or portion thereof constructed pursuant to this chapter within any city or town, the city or town shall accept the same for maintenance and operation and that such stormwater control facility or highway or portion thereof shall thereupon become a part of the respective stormwater control facility or highway system of the city or town.
A county may transfer to any other governmental agency the ownership, operation and maintenance of any open space, park, recreation and community facility acquired by the county pursuant to this chapter, which lies wholly or partly within such governmental agency, pursuant to an agreement entered into between the legislative bodies of the county and such governmental agency: PROVIDED, That such transfer shall be subject to the condition that either such facility shall continue to be used for the same purposes or that other equivalent facilities within the county shall be conveyed to the county in exchange therefor.
RCW 36.89.050