Wash. Rev. Code § 85.28.150
It shall be lawful for any adjacent or abutting owner or owners, to construct a dike, dam, or causeway over or in the waters of the state of Washington described as: That certain body of water lying between Bachelor Island and the mainland, appearing on the state survey map made by Edw. C. Dohm, state field engineer, as Columbia Slough and designated on the map as compiled by the U.S. Coast and Geodetic Survey of September, 1937, Number "U.S.C.&G.S. 6154" as Bachelor Island Slough from its point of confluence with Lake River South to the Columbia River, in sections 13, 23, 24, 26 and 35, township 4 north, range 1 west of the Willamette Meridian, in Clark county, Washington: PROVIDED, That the location and plans thereto are submitted to and approved by the chief of engineers of the United States and the secretary of war of the United States, before construction is commenced subject to the terms of section 9 of the River & Harbor Act, approved March 3, 1899 (30 Stat. 1151; 33 U.S.C. 401 ) and: PROVIDED FURTHER, That all such dikes, dams, causeways, or other structures, shall be constructed at the expense of the owners.
RCW 85.28.150