The Board, or the hearing officer, shall not communicate, directly or indirectly, with any party or his representatives in connection with any issue involved except upon notice and opportunity for all parties to participate, shall not take notice of any communication, reports, staff memoranda, or other materials, except advice from its solicitor, unless the parties are afforded an opportunity to contest the material so noticed, and shall not inspect the site or its surroundings after the commencement of hearings with any party or his representative unless all parties are given an opportunity to be present.