Upon receiving an application for a permit, the Department shall make such investigation as may be necessary to process the application properly under this Act. Such investigation shall be conducted so as to determine, in the opinion of the Department, a location and height for a structure for the particular purpose proposed in the location proposed as will best serve the safety, health and welfare of persons and property in the area and on the ground and other technical and economical factors involved; provided, however, when the facilities or structures proposed are those of a public utility, no determination, ruling or order of the Department shall be valid or binding on such public utility without, in each such case, the concurrence of the Illinois Commerce Commission.
     If, upon such investigation, the Department determines that a permit should not issue or that the height or location should be other than as applied for, the Department shall thereupon notify the applicant in writing of its determination. Such notification may be served by delivering it personally to the applicant or by sending it by first class mail to the applicant at the address specified in the application. Such determination shall become final 20 days after notification thereof is served unless the applicant, within such 20-day period, requests in writing that a hearing be held before the Department with reference to the application. All such hearings shall be open to the public. Any person interested may appear and be heard either in person or by counsel and may present such evidence and testimony as may be pertinent.