Wash. Rev. Code § 35.56.240
While acquiring the rights-of-way for such canals or waterways or at any time thereafter such city may acquire for its own use and public use by purchase, gift, condemnation or otherwise, and pay therefor by any lawful means including but not restricted to payment out of the current expense fund of such city or by bonding the city or by pledging revenues to be derived from rents and issues therefrom, lands abutting upon the shore lines or right-of-way of such canals or waterways to a distance, depth or width of not more than three hundred feet back from the banks or shore lines of such canals or waterways on either side or both sides thereof, or not more than three hundred lineal feet back from and abutting on the outer lines of such rights-of-way on either side or both sides of such rights-of-way, and such area of such abutting lands as the council or commission may deem necessary for its use for public docks, bridges, wharves, streets and other conveniences of navigation and commerce and for its own use and benefit generally.
RCW 35.56.240