In M1-1D, M1-2D, M1-3D, M1-4D and M1-5D Districts, new residences or enlargements of existing residences may be permitted by authorization of the City Planning Commission provided the zoning lot existing on June 20, 1988, meets the criteria of paragraphs (a), (b) or (c) of this Section.

(a)        On zoning lots containing residential or community facility uses, new residences or enlargements of existing residences may be authorized, provided:

(1)        the zoning lot contains a building that has one or more stories of lawful residential or community facility uses and no more than one story of commercial or manufacturing uses therein;

(2)        the zoning lot contains no other commercial or manufacturing uses; and

(3)        25 percent or more of the aggregate length of the block fronts on both sides of the street facing each other is occupied by zoning lots containing residential or community facility uses.

(b)        On vacant zoning lots, new residences may be authorized, provided:

(1)        the zoning lot has been vacant continuously since June 20, l988, or has been vacant continuously for five years prior to the date of application for such authorization;

(2)        a zoning lot abutting on one side lot line and fronting on the same street is occupied by a community facility building or a building containing residences; and

(3)        either of the following conditions exist:

(i)        such vacant zoning lot and any contiguous vacant zoning lots and land with minor improvements fronting on the same street aggregate no more than 10,000 square feet of lot area, and 50 percent or more of the aggregate length of the block fronts on both sides of the street facing each other is occupied by zoning lots containing residential or community facility uses; or

(ii)        such vacant zoning lot and any contiguous vacant zoning lots and land with minor improvements fronting on the same street aggregate no more than 5,000 square feet of lot area, and 25 percent or more of the aggregate length of the block fronts on both sides of the street facing each other is occupied by zoning lots containing residential or community facility uses.

(c)        On land with minor improvements, new residences may be authorized provided such land with minor improvements otherwise meets all the criteria for vacant zoning lots listed in paragraph (b) of this Section, except that new residential use shall not be authorized on land with minor improvements that:

(1)        is used for parking, storage or processing in connection with a conforming, enclosed commercial or manufacturing use within the district; or

(2)        has been so used within five years prior to the date of application, unless such land has not been so used since June 20, 1988.

(d)        In determining eligibility for residential use, pursuant to paragraphs (a), (b) or (c) of this Section, the following regulations shall be applicable:

(1)        In order to determine whether a corner lot meets the criteria of paragraph (a), (b) or (c) above, the aggregate length of the block fronts occupied by zoning lots that contain residential or community facility uses may be measured along any block front upon which such corner lot has frontage.

(2)        In determining the percent of the aggregate length of the block fronts occupied by zoning lots that contain residential or community facility uses, the length along the block front of every zoning lot, whether occupied or not, shall be measured and aggregated, and this total shall be divided by the aggregate length of the block fronts occupied by zoning lots containing lawful residential or community facility uses. Vacant zoning lots and land with minor improvements shall not be counted as residential or community facility frontage.

For the purpose of this Section, the length along the block front of any zoning lot occupied by a building that contains one or more stories of residential or community facility use and no more than one story of commercial or manufacturing use shall be considered as a frontage of residential or community facility uses, and the length along the block front of any zoning lot occupied by a building that contains one or more stories of residential or community facility use and more than one story of commercial or manufacturing uses shall be considered as a frontage of commercial or manufacturing uses.

(3)        New residential use shall not be authorized on any floor area that is vacant or that is occupied by a commercial or manufacturing use, except that in a building designed for residential use where at least 50 percent of the floor area is occupied by residential use, the residential use may be extended.

(4)        In any building, no residential use may be located on or below a story occupied by a commercial or manufacturing use.

(5)        For the purposes of this Section, a through lot fronting on no more than two streets shall be treated as if it consisted of two separate zoning lots with abutting rear lot lines at a line midway between the two street lines upon which such through lot fronts. In the case of a through lot that fronts on more than two streets, the through lot portion shall first be considered as if it were so divided, and then any remaining portion shall be considered as if it were a separate zoning lot. Notwithstanding, in no event shall contiguous portions of a through lot that front on the same street be treated as if they were separate zoning lots.

Each resulting portion of such through lot on each street frontage shall be considered separately to determine whether it meets the criteria for new residences set forth in paragraphs (a), (b) or (c) of this Section, and only on such portion may new residences or enlargements of existing residences be authorized. Only the lot area of such portion shall be calculated in determining the permitted amount of floor area to be authorized pursuant to this Section.

(6)        A zoning lot or contiguous zoning lots existing on June 20, 1988, that have been vacant continuously since June 20, 1988, or have been vacant continuously for five years prior to the date of application for such authorization, that are contiguous to and front on the same street as a vacant zoning lot or land with minor improvements that meets all the requirements of paragraph (b) or (c) of this Section, may be combined with such eligible zoning lot in its application to authorize residential use. The aggregate lot area of all such contiguous vacant zoning lots or land with minor improvements shall be limited by the requirements of paragraph (b)(3).

(e)        In authorizing such residential uses, the Commission shall find that:

(1)        the residential uses will not be exposed to excessive noise, smoke, dust, noxious odor, toxic materials, safety hazards or other adverse impacts from current or previous commercial or manufacturing uses;

(2)        there are no open uses listed in Use Group 18 within 400 feet of the zoning lot;

(3)        the residential uses will not adversely affect commercial or manufacturing uses in the district; and

(4)        the authorization will not alter the essential character of the neighborhood or district in which the use is located, nor impair the future use or development of commercial and manufacturing zoning lots.

In granting such authorization, the Commission may prescribe additional conditions and safeguards as the Commission deems necessary.

Residential uses authorized pursuant to this Section shall be subject to the regulations of Sections 43-61 (Bulk Regulations for Residential Uses in M1-1D Through M1-5D Districts) and 44-28 (Parking Regulations for Residential Uses in M1-1D through M1-5D Districts).

Regulations governing other residential uses in M1-D Districts are set forth in Article V, Chapter 2 (Non-conforming Uses).

Residential uses in M1-D Districts may enlarge pursuant to the regulations of Section 52-46 (Conforming and Non-conforming Residential Uses in M1-1D through M1-5D Districts) or of this Section.