Wash. Rev. Code § 86.13.040
When such a contract shall have been entered into the power of eminent domain is hereby vested in each of such counties, to acquire any lands necessary to straighten, widen, deepen, dike or otherwise improve any such river, its tributaries or outlet or to strengthen the banks thereof, or to acquire any land adjacent to such river, or its tributaries, or the right to cut and remove timber upon the same for the purpose of preventing or lessening the falling of timber or brush into the waters of such river or tributaries, or to acquire any rock quarry, gravel deposit or timber for material for the prosecution of such improvement, together with the necessary rights-of-way for the same, or to acquire any dam site or other property necessary for flood control purposes. Any such land, property or rights may be acquired by purchase instead of by condemnation proceedings. Said right of eminent domain shall extend to lands or other property owned by the state or any municipality thereof. The title to any such lands, property or rights so acquired shall vest in the county in which situate for the benefit of such enterprise and said fund, but when said contract shall have terminated by lapse of time or for any other reason, then such title shall be held by such county independent of any claims whatsoever of the other county, but any material, equipment or other chattel property on hand shall be converted into money and the money divided between the two counties in the ratio of their respective contributions to the fund. The exercise of such rights of eminent domain or purchase shall rest in the joint control of the two boards of county commissioners. Such eminent domain proceedings shall be in the name of and had in the county where the property to be acquired is situate: PROVIDED, If either county shall fail or refuse to institute and prosecute any condemnation proceedings when directed so to do by any legal meeting provided for in RCW 86.13.050, such proceeding may be instituted and prosecuted by and in the name of the other county. The proceedings may conform to the provisions of *sections 921 to 926, inclusive, of Remington & Ballinger's Annotated Codes and Statutes of Washington, or to any general law now or hereafter enacted governing eminent domain proceedings by counties. The awards in and costs of such proceedings shall be payable out of such funds. The purposes in this act specified are hereby declared to be county purposes of each and both of such counties.
RCW 86.13.040
*Reviser's note: "Sections 921 to 926, inclusive, of Remington & Ballinger's Annotated Codes and Statutes" (except for section 923) are codified as RCW 8.20.010 through 8.20.080. Section 923 was repealed by 1935 c 115 s 1 but compare the first paragraph of RCW 8.28.010 relating to the same subject matter as the repealed section.