Wash. Rev. Code § 36.34.180
At the day and hour designated in the notice or at any subsequent time to which the meeting may be adjourned by the board of county commissioners, but not more than thirty days after the day and hour designated for the meeting in the published notice, the board may lease the property in such notice described for a term of years and upon such terms and conditions as to the board may seem just and right in the premises. No lease shall be for a longer term in any one instance than ten years, and no renewal of a lease once executed and delivered shall be had, except by a re-leasing and re-letting of the property according to the terms and conditions of this chapter: PROVIDED, That if a county owns property within or outside the corporate limits of any city or town or anywhere in the county suitable for municipal purposes, or for commercial buildings, or owns property suitable for manufacturing or industrial purposes or sites, or for military purposes, or for temporary or emergency housing, or for any requirement incidental to manufacturing, commercial, agricultural, housing, military, or governmental purposes, the board of county commissioners may lease it for such purposes for any period not to exceed thirty-five years: PROVIDED FURTHER, Where the property involved is or is to be devoted to airport purposes and construction work or the installation of new facilities is contemplated, the board may lease said property for such period as may equal the estimated useful life of such work or facilities but not to exceed seventy-five years.
If property is leased for municipal purposes or for commercial buildings or manufacturing or industrial purposes the lessee shall prior to the execution of the lease file with the board of county commissioners general plans and specifications of the building or buildings to be erected thereon for such purposes. All leases when executed shall provide that they shall be canceled by failure of the lessee to construct such building or buildings or other improvements for such purposes within three years from date of the lease, and in case of failure so to do the lease and all improvements thereon including the rentals paid, shall thereby be forfeited to the county unless otherwise stipulated. No change or modification of the plans shall be made unless first approved by the board of county commissioners. If at any time during the life of the lease the lessee fails to use the property for the purposes leased, without first obtaining permission in writing from the board of county commissioners so to do, the lease shall be forfeited.
Any lease made for a longer period than ten years shall contain provisions requiring the lessee to permit the rentals for every five year period thereafter, or part thereof, at the commencement of such period, to be readjusted and fixed by the board of county commissioners. In the event that the lessee and the board cannot agree upon the rentals for said five year period, the lessee shall submit to have the disputed rentals for the subsequent period adjusted by arbitration. The lessee shall pick one arbitrator and the board one, and the two so chosen shall select a third. No board of arbitrators shall reduce the rentals below the sum fixed or agreed upon for the last preceding period. All buildings, factories, or other improvements made upon property leased shall belong to and become property of such county, unless otherwise stipulated, at the expiration of the lease.
No lease shall be assigned without the assignment being first authorized by resolution of the board of county commissioners and the consent in writing of at least two members of the board endorsed on the lease. All leases when drawn shall contain this provision.
This section shall not be construed to limit the power of the board of county commissioners to sell, lease, or by gift convey any property of the county to the United States or any of its governmental agencies to be used for federal government purposes.
RCW 36.34.180