The Selectmen shall have the following powers and duties to be exercised only upon written appeal by a party aggrieved by a decision of the Director of Public Works, Plumbing Inspector and/or Town Health Officer, insofar as such decision arises from requirements of this chapter:
A.
To determine whether the decisions of these authorities are in conformity with the provisions of this chapter, and to interpret the meaning of this chapter in a case of uncertainty.
B.
To grant variances from the terms of this chapter where there is no substantial departure from the intent of this chapter and where necessary to avoid undue hardship. A projected expenditure of an amount exceeding 15% of the assessed value of the buildings on the land to be served by the public sewer shall be considered as prima facie evidence of undue hardship.
C.
To permit an exception to this chapter only when the terms of the exception have been specifically set forth in this chapter.