Wash. Rev. Code § 35A.14.320
In the ordinance annexing territory pursuant to a gift, grant, or lease from the government of the United States, a code city may include such tide and shorelands as may be necessary or convenient for the use thereof, and may include in the ordinance an acceptance of the terms and conditions attached to the gift, grant, or lease. A code city may cause territory annexed pursuant to a gift, grant, or lease of the government of the United States to be surveyed, subdivided and platted into lots, blocks, or tracts and lay out, reserve for public use, and improve streets, roads, alleys, slips, and other public places. It may grant or sublet any lot, block, or tract therein for commercial, manufacturing, or industrial purposes and reserve, receive and collect rents therefrom. It may expend the rents received therefrom in making and maintaining public improvements therein, and if any surplus remains at the end of any fiscal year, may transfer it to the city's current expense fund.
RCW 35A.14.320