State Statutes Chapter 293, RSMo requires that each mine be inspected on a regular basis for hazards and unsafe or unhealthy work practices.  Underground mines are inspected on a quarterly basis and surface mines are inspected at least twice a year.  For more information see Chapter 293.020 RSMo, applicability;.  Those mines regulated by the mandates of Chapter 293 shall be assessed an inspection fee based on tonnage of materials produced, sold or shipped per quarter.