The Environmental Protection Division of the Georgia Department of Natural Resources issued an air quality permit, allowing the construction and operation of a power plant, to Duke Energy San-dersville, LLC. The Sierra Club and the Georgia Public Interest Research Group filed an administrative appeal challenging the permit.

Duke then filed a declaratory judgment action in superior court seeking a declaration that a Board of Natural Resources rule which stays permits upon the filing of an administrative appeal does not apply to the construction and operation of its facility. Duke and the Board of Natural Resources each moved for summary judgment. On January 22, 2002, the court granted Duke’s motion and denied the Board’s motion, finding that the stay rule does not apply in this case. The Board has filed the instant appeal from the trial court’s judgment.

In the meantime, Duke, the Environmental Protection Division, the Sierra Club, and the Georgia Public Interest Research Group settled the administrative appeal. Under the settlement, the petition challenging the permit was withdrawn and Duke agreed to modify certain operating conditions contained in the permit. On May 10, 2002, an administrative law judge dismissed that case.

A case is moot if its resolution would amount to a determination of an abstract question that does not arise upon existing facts or *816rights.1 Mootness is a mandatory ground for dismissal of a case.2 In the instant case, the issue of whether Duke’s permit should be stayed by the filing of the administrative appeal is moot because that appeal has been withdrawn and that administrative case has been dismissed. Absent an actual dispute, there is no justiciable controversy for us to review, and we cannot issue a mere advisory opinion.3 Because the question presented by the instant case has become moot, the appeal must be dismissed.4

Appeal dismissed.