Temporary construction trailers and one sign not exceeding 100 square feet, advertising the prime contractor, subcontractor, architect, financing institution and similar data for the period of construction, beginning with the issuance of a construction permit and concluding with the issuance of a certificate of occupancy for one year, whichever is less, provided the trailer and sign are on the site where construction is taking place and are set back at least 15 feet from all street and lot lines;