The Planning Board, when acting upon applications for preliminary or minor subdivision approval or preliminary site plan approval, shall have the power to grant such exceptions from the requirements for subdivision or site plan approval as may be reasonable and within the general purpose and intent of the provisions for subdivision or site plan review and approval of this chapter, if the literal enforcement of one or more provisions of these ordinances are impractical or will exact undue hardship because of peculiar conditions pertaining to the land in question.