Wash. Rev. Code § 47.32.160
The department is hereby authorized and empowered at its discretion to adopt reasonable rules governing the issuance of permits under RCW 47.32.150 for the construction of any approach road, facility, thing, or appurtenance, upon state highway rights-of-way. The rules shall be designed to achieve and preserve reasonable standards of highway safety and the operational integrity of the state highway facility. Any permit issued may contain such terms and conditions as may be prescribed. All such construction shall be under the supervision of the department and at the expense of the applicant. After completion of the construction of the particular approach road, facility, thing, or appurtenance, it shall be maintained at the expense of the applicant and in accordance with the directions of the department.
RCW 47.32.160