Where, by reason of topographical conditions, district borderline situations or because of other unusual circumstances solely with respect to a certain parcel of land and not affecting generally the district in which it is situated, the strict application of any provision of this part would result in exceptional practical difficulty or undue hardship upon the owner of any specific property, the commission in passing upon applications shall have power to vary or modify strict adherence to said sections or to interpret the meaning of said sections so as to relieve such difficulty or hardship; provided such variance, modification or interpretation shall remain in harmony with the general purpose and intent of said sections so that the general character of the district shall be conserved and substantial justice done. In granting variations, the commission may impose such reasonable and additional stipulations and conditions as will, in its judgment, better fulfill the purposes of said sections. In addition to the filing required by subsection (b) of section 7-147e, the commission shall, for each variation granted, place upon its records and in the notice to the applicant the reasons for its determinations.