Wash. Rev. Code § 85.06.010
Any portion of a county, requiring drainage, which contains five or more inhabitants and freeholders therein may be organized into a drainage district, and when so organized such district and the board of commissioners hereinafter provided for shall have and possess the power herein conferred or that may hereafter be conferred by law upon such district and board of commissioners, and said district shall be known and designated as drainage district No. . . . . (here insert number), of the county of . . . . . . (here insert the name of the county), of the state of Washington, and shall have the right to sue and be sued by and in the name of its board of commissioners hereinafter provided for, and shall have perpetual succession, and shall adopt and use a seal. The commissioners hereinafter provided for and their successors in office shall, from the time of the organization of such drainage district, have the power, and it shall be their duty, to manage and conduct the business and affairs of the district, make and execute all necessary contracts, employ and appoint such agents, officers and employees as may be required, and prescribe their duties, and perform such other acts as hereinafter provided, or that may hereafter be provided by law.
RCW 85.06.010