When a complaint is filed with the director of environmental management, he or she shall attempt to secure an explanation or adjustment, and, failing this within ten (10) days, he or she shall cause a copy of the complaint, together with a notice of the time and place for a hearing, to be served personally or by mail upon the applicant or licensee. If served by mail, the complaint and notice shall be directed to the applicant or licensee at his or her place of business, with postage fully prepaid. Service shall be made at least seven (7) days before the hearing. At the time and place appointed for the hearing, the director, or his or her representatives, shall hear the parties to the complaint, shall have power to administer oaths and shall enter in the records of the department of environmental management a decision either dismissing the complaint or specifying the facts which he or she deems established on the hearing.