Section 10A. Notwithstanding the provisions of section ten, not less than ten persons may intervene in any adjudicatory proceeding as defined in section one, in which damage to the environment as defined in section seven A of chapter two hundred and fourteen, is or might be at issue; provided, however, that such intervention shall be limited to the issue of damage to the environment and the elimination or reduction thereof in order that any decision in such proceeding shall include the disposition of such issue. In any proceeding pursuant to chapter 91, at least 5 of the 10 persons shall reside in the municipality in which the license or permitted activity is located. The intervention shall clearly and specifically state the facts and grounds for intervening and the relief sought, and each intervening person shall file an affidavit stating the intent to be part of the group and to be represented by its authorized representative. Notwithstanding any other provision of this chapter, any intervener under this section may introduce evidence, present witnesses and make written or oral argument, except that the agency may exclude repetitive or irrelevant material. Any such intervener shall be considered a party to the original proceeding for the purposes of notice and any other procedural rights applicable to such proceeding under the provisions of this chapter, including specifically the right of appeal.