In reaching a decision official notice may be taken, either before or after submission of the case for decision, of a generally accepted technical or scientific matter within the agency's special field, and of a fact that is judicially noticed by the courts of the state. Parties present at the hearing shall be informed of the matters to be noticed, and those matters shall be noted in the record, referred to in the record, or appended to it. A party present at the hearing shall, upon request, be given a reasonable opportunity to refute the officially noticed matters by evidence or by written or oral presentation of authority. The agency shall determine the manner of this refutation.