If the department has determined that a discharge that may cause or has caused the pollution of state waters has occurred, the department shall conduct an investigation to determine the responsible person. The investigation may include a title search of the affected property and shall attempt to designate as the responsible person the person deemed to be the most responsible for the occurrence of the discharge. If the identity of the person who caused the discharge can be determined, that person shall be designated as the responsible person. If the identity of the person who caused the discharge cannot be determined, the owner of the property or operator of the tank at the time of the discharge shall be designated as the responsible person. If the person deemed responsible for the discharge contests the department's decision, a title search of the affected property shall be done.