To authorize a variance for a particular use of a parcel of land or for an existing building thereon after public hearing for which notice has been given by publication and posting as provided in Article XII, § 175-82E of this bylaw and by mailing to all interested parties. To grant upon appeal or upon petition with respect to particular land or structures a variance from the terms of this bylaw where the Board specifically finds that owing to circumstances relating to soil conditions, shape, or topography of such land or structures and especially affecting such land or structures but not affecting generally the zoning district in which it is located, a literal enforcement of the provisions of the bylaw would involve substantial hardship, financial or otherwise, to the petitioner or appellant, and the desirable relief may be granted without substantial detriment to the public good and without nullifying or substantially deviating from the intent of this bylaw. The Board may impose conditions, safeguards, and limitations both of time and for use, including the continued existence of any particular structures but excluding any condition, safeguards or limitation based upon the continued ownership of the land or structures to which the variance pertains by the applicant, petitioner or any owner. If rights authorized by a variance are not exercised within one year of the date of grant of such variance, they shall lapse and may be reestablished only after new notice and public hearing.