Petition to intervene: Filing; response; delay in filing.

1. A petition for leave to intervene and proof of service of a copy of the petition on each party of record must be filed with the Board at least 30 days before the time set for the hearing. A response to the petition may be made by any party not later than 7 days after receipt of the petition. 2. If a petition for leave to intervene is filed after the applicable period, the petition must state to the satisfaction of the Board a substantial reason for the delay. If a reason is not stated, the petition may be summarily denied by the Board.