The Board shall have the following powers and duties:

1.   To hear and decide appeals where it is alleged there is error in any order, requirement, decision or determination made by an administrative official in the enforcement of this chapter.

2.   To hear and decide special exceptions to the terms of this chapter.

3.   To authorize upon appeal in specific cases such variance from the terms of this chapter as will not be contrary to the public interest, where owing to special conditions a literal enforcement of this chapter will result in unnecessary hardship, and so that the spirit of this chapter shall be observed and substantial justice done.