May be extended up to but shall not exceed an increase of 50% in floor area with no height increase, nor increase in amount of units, of the square footage that existed as of December 31, 2007. Such expansion is subject to site plan approval by the Planning Board, which shall be conditioned on the owner of the nonconforming commercial or multi-family/residential use demonstrating that the structure meets, or will meet in the permitted construction process, all New York State Building and Fire Code provisions and bringing the entire building to modern construction standards and demonstrating that proper sewer and water capacity exist, if applicable, for the increase in floor area. The 50% addition shall be wholly in the Planning Board's discretion, based on the health, safety and welfare of the neighborhood and Town as a whole. The expanded nonconforming commercial or multi-family structure shall comply with the area, yard, height and other bulk and density regulations of the district in which the use is located. The Planning Board, in carrying out the provisions of this article, may impose reasonable conditions set forth in writing, to gradually bring preexisting nonconforming development for which expansion is proposed into closer conformance with the community character and with the use standards of the district in which the use is located as is necessary to protect the public health, safety and general welfare and, more specifically, the safety of access, the location of refuse containers, appearance and size of signs, lights, number and arrangement of parking spaces, and dissemination of noxious odors, dust or other hazardous pollutants; and