RCW 36.88.350

After the completion of any construction or improvement under this chapter, all maintenance thereof shall be performed by the county at the expense of the county road fund, excepting furnishing electric energy for and operating and maintaining street and road lighting systems: PROVIDED, That maintenance of canal protection improvements may, at the option of the board of commissioners of the county, be required of the irrigation, drainage, flood control, or other district, agency, person, corporation, or association maintaining the canal or ditch. If such option is exercised reimbursement must be made by the county for all actual costs of such maintenance.