(a) Following the admission in evidence of the materials described in § 104.9(b), the Agency shall have the right at the commencement of the hearing to supplement that evidence or to introduce additional relevant evidence. Thereafter the evidence of each objector shall be presented in support of its objection and any proposed modification. The Agency staff shall then be given an opportunity to rebut or respond to the objectors' presentation, including at its option the introduction of evidence which tends to support a standard or standards other than as set forth in the Agency's own initially proposed standards. In the event that evidence which tends to support such other standard or standards is offered and received in evidence, then the objectors may thereafter rebut or respond to any such new evidence.

(b) The burden of proof as to any modification of any standard proposed by the Agency shall be upon the party who advocates such modification to show that the proposed modification is justified based upon a preponderance of the evidence.

(c) Where necessary in order to prevent undue prolongation of the hearing, or to comply with time limitations set forth in the Act, the Presiding Officer may limit the number of witnesses who may testify, and the scope and extent of cross-examination.

(d) A verbatim transcript of the hearing shall be maintained and shall constitute a part of the record.

(e) If a party objects to the admission or rejection of any evidence or to any other ruling of the Presiding Officer during the hearing, he shall state briefly the grounds of such objection. With respect to any ruling on evidence, it shall not be necessary for any party to claim an exception in order to preserve any right of subsequent review.

(f) Any party may at any time withdraw his objection to a proposed effluent standard.