Wash. Rev. Code § 35.56.250
If the city is not using the abutting lands so acquired it may lease any parcels thereof as may be deemed for the best interest and convenience of navigation, commerce and the public interest and welfare to private individuals or concerns for terms not exceeding thirty years each at such annual rate or rental as the city council or commission of such city may deem just, proper and fair, for the purpose of erecting wharves for wholesale and retail warehouses and for general commercial purposes and manufacturing sites, but the said city shall never convey or part with title to the abutting lands above mentioned and so acquired nor with the control other than in the manner herein specified. Any lease or leases granted by the city on such abutting lands shall never be transferred or assigned without the consent of the city council or commission having been first obtained.
A city shall never lease to any individual or concern more than four hundred lineal feet of canal or waterway frontage of said land and no individual or concern shall ever hold or occupy by lease, sublease, or otherwise more than the said four hundred lineal feet of said frontage: PROVIDED, That any individual or concern may acquire by lease or sublease whatever additional frontage of such abutting land may be in the judgment of the city council or commission necessary for the use of such individual or concern, upon petition presented to the city council or commission therefor signed by not less than five hundred resident freeholders of such city.
RCW 35.56.250