Each employee who has a non-paid lunch period shall have an uninterrupted, duty free lunch at or near the mid-point of the work shift. Length of lunch period shall not be changed except in an emergency. The department manager shall schedule lunch periods based on the customary practices of the department. If an emergency arises, employees may be assigned to work during their lunch period. Employees unable to take lunch due to assigned work shall be compensated at the appropriate overtime rate. Customary and reasonable delays in lunch periods shall not cause the application of overtime.