Wash. Rev. Code § 47.56.040
The department is empowered, in accordance with the provisions of this chapter, to provide for the establishment and construction of toll bridges upon any public highways of this state together with approaches thereto wherever it is considered necessary or advantageous and practicable for crossing any stream, body of water, gulch, navigable water, swamp, or other topographical formation whether that formation is within this state or constitutes a boundary between this state and an adjoining state or country. For the purpose of obtaining information for the consideration of the department upon the construction of any toll bridge or any other matters pertaining thereto, any cognizant officer or employee of the state shall, upon the request of the department, make reasonable examination, investigation, survey, or reconnaissance for the determination of material facts pertaining thereto and report this to the department. The cost of any such examination, investigation, survey, or reconnaissance shall be borne by the department or office conducting these activities from the funds provided for that department or office for its usual functions.
RCW 47.56.040