Washington Revised Code Title 36. Counties § 36.88.010. Districts authorized--Purposes

All counties have the power to create county road improvement districts for the acquisition of rights-of-way and improvement of county roads, existing private roads that will become county roads as a result of this improvement district process and, with the approval of the state department of transportation, state highways; for the construction or improvement of necessary drainage facilities, bulkheads, retaining walls, and other appurtenances therefor, bridges, culverts, sidewalks, curbs and gutters, escalators, or moving sidewalks; and for the draining or filling of drainage potholes or swamps. Such counties have the power to levy and collect special assessments against the real property specially benefited thereby for the purpose of paying the whole or any part of the cost of such acquisition of rights-of-way, construction, or improvement.