Any county may establish a system of emergency medical service as defined by RCW 18.73.030(11). The county legislative authority may adopt by resolution procedures to collect reasonable fees in order to reimburse the county in whole or in part for its costs of providing such service: PROVIDED, That any county which provides emergency medical services supported by an excess levy may waive such charges for service: PROVIDED FURTHER, That whenever the county legislative authority determines that the county or a substantial portion of the county is not adequately served by existing private ambulance service, and existing private ambulance service cannot be encouraged to expand service on a contract basis, the emergency medical service that is established by the county shall not be deemed to compete with any existing private ambulance service as provided for in RCW 36.01.100.