The Board of Adjustment shall have the following powers and it shall be its duty:
1. To hear and decide appeals where it is alleged there is an error in any order, requirement, decision or determination made by the Zoning Administrator in the enforcement of the Zoning Ordinance or of any supplement or amendment.
2. To hear and permit special exceptions to the terms of the Zoning Ordinance upon which the Board of Adjustment is required to pass under the Zoning Ordinance.
3. To authorize, upon appeal, in specific cases, such variance from the terms of the Zoning Ordinance as will not be contrary to the public interest, where owing to special conditions a literal enforcement of the provisions of the Zoning Ordinance will result in unnecessary hardship, and so that the spirit of the Zoning Ordinance shall be observed and substantial justice done.