After the required date for full or provisional certification, you must not operate your municipal waste combustion unit unless one of four employees is on duty:
    
    
        
        (a) 
         A fully certified chief facility operator.
     
    
        
        (b) 
         A provisionally certified chief facility operator who is scheduled to take the full certification exam.
     
    
        
        (c) 
         A fully certified shift supervisor.
     
    
        
        (d) 
         A provisionally certified shift supervisor who is scheduled to take the full certification exam.