A motion for leave to intervene in proceedings pursuant to this chapter shall be filed, in writing, with the Commission, stating the grounds upon which an interest in the proceeding is claimed and stating the extent to which intervention is sought. An original and one copy of such motion shall be filed, together with proof of service of a copy of such motion upon the parties. The Chair, or such other Commission designee, in his or her discretion, may permit intervention to such extent and upon such terms as may be deemed just.
N.J. Admin. Code § 19:18-3.1