Wash. Rev. Code § 78.16.010
Whenever it shall appear to the board of county commissioners of any county in this state that it is for the best interests of said county and the taxing districts and the people thereof, that any mining claims, reserved mineral rights, or any other county owned or tax acquired property owned by the county, either absolutely or as trustee, should be leased for the purpose of exploration, development, and removal of any minerals, oil, gas and other petroleum products therefrom, said board of county commissioners is hereby authorized to enter into written leases, under the terms of which any county owned lands or county owned mineral rights, or reserved mineral rights, are leased for the aforementioned purpose, with or without an option to purchase. Any such lease shall be upon terms and conditions as said county commissioners may deem for the best interests of said county and the taxing districts, and as in this chapter provided, and may be for such primary term as said board may determine and as long thereafter as minerals, including oil, and/or gas, may be produced therefrom.
RCW 78.16.010
Construction-1945 c 93: "Chapter 38, Laws of 1907, is amended by adding a new section to be designated as section 8, to read as follows:
Section 8. Nothing herein contained is intended to or shall be construed as affecting any existing rights granted under chapter 38, Laws of 1907." [ 1945 c 93 s 6.]