(1) Petition to intervene.

(a) Who may petition; when petitions must be filed. The commission strongly prefers written petitions to intervene from any person who seeks to appear and participate as a party in a proceeding before the commission other than the original parties, commission staff, and public counsel. Written petitions to intervene should be filed at least three business days before the initial hearing date or prehearing conference date, whichever occurs first. A person may petition orally for leave to intervene at the time of the initial hearing or prehearing conference, whichever occurs first, unless the commission requires written petitions to intervene in a notice prior to the first hearing or prehearing date.

(b) Late-filed petition to intervene. The commission may grant a petition to intervene made after the initial hearing or prehearing conference, whichever occurs first, only on a showing of good cause, including a satisfactory explanation of why the person did not timely file a petition to intervene.

(c) Contents of petition. Any petition to intervene must disclose:

(i) The petitioner's name and contact information as specified in WAC 480-07-360(3);

(ii) The petitioner's interest in the proceeding;

(iii) The petitioner's position with respect to the matters in controversy;

(iv) Whether the petitioner proposes to broaden the issues in the proceeding and, if so, a statement of the proposed issues that clearly and concisely sets forth the basis for the petitioner's proposal to broaden the issues; and

(v) The name and contact information as specified in WAC 480-07-360(3) of the persons the petitioner has authorized to act as the petitioner's representatives, including attorneys, if any.

(2) Response. Parties may respond to any petition to intervene. Responses may be written or may be heard orally at the prehearing conference or hearing at which the commission considers the petition. A party's written response to a timely filed written petition to intervene should be filed and served at least two business days before the prehearing conference or hearing at which the commission will consider the petition, or at such other time as the commission may establish by notice.

(3) Disposition of petitions to intervene. The commission generally will consider petitions to intervene at the prehearing conference or at the initial hearing if the commission does not conduct a prehearing conference. The presiding officer may grant a petition to intervene if the petitioner has a substantial interest in the subject matter of the hearing or if the petitioner's participation is in the public interest. If the commission grants intervention, the petitioner becomes a party to the proceeding as an intervenor. The presiding officer may impose limits on an intervenor's participation in accordance with RCW 34.05.443(2).

(4) Dismissal of intervenor. The commission may dismiss an intervenor from a proceeding at any time after notice and a reasonable opportunity to be heard if the commission determines that the intervenor has no substantial interest in the proceeding and the public interest will not be served by the intervenor's continued participation.

(5) Interlocutory review by commission. The commission may review a decision regarding a petition to intervene or dismissal of an intervenor pursuant to WAC 480-07-810.