(a) Definition. Underground space is hereby defined as the entire cavern resulting from the extraction of subsurface-located material in such a manner that the surface area of the property is not disturbed except in the vicinity of the entrances and easements servicing the development.

    (b) Purpose. District M-U is established for the following purposes:

    (1)    To accommodate and permit the use of underground space; and

    (2)    To protect any other properties and persons from adverse effects caused by activities in underground space; and

    (3)    To protect the health, safety and welfare of persons in or around underground facilities.

    (c) Conditions for Establishing District M-U.

    (1)    District M-U shall be permitted only where the primary entrance is located in district M-1 or M-C, and:

        a.    Where usable underground space exists; or

        b.    Where material intended to be extracted exists adjoining an existing district M-U, M-1 or M-C.

    (2)    Any application for a change in zoning to district M-U shall include a certified survey map showing the extent of existing underground mining and all points of access to the surface whether they be vehicle entrances or other entrances for ventilation or utility purposes.

    (d) Permitted Uses. In district M-U, no building, land or premises shall be used and no building or structure shall hereafter be erected, constructed or altered except for one or more of the following uses:

    (1)    All permitted uses in the zoning district controlling the surface property at the primary entrance to district M-U. The primary entrance is determined to be that having the most intensive traffic.

    (2)    Extraction of limestone or other subsurface materials.

    (e) Standards and Requirements. Underground space in district M-U is authorized to develop in accordance with the provisions herein, subject to the following standards and requirements:

    (1)     Location. Underground development districts shall apply only to the subsurface of property under the same ownership as the surface property, and will not affect the zoning district or districts designated for the surface above district M-U.

    (2)     Access. The access to all districts M-U shall be through property owned or controlled by the owners or operators of the underground space.

    (3)     Building permits. Where applicable, underground space must have a building permit to develop a habitable underground building and to qualify for a certificate of occupancy.

    (4)     Safety. The owners or operators of underground space shall file with the department of public works a certificate by a registered professional engineer as to the structural integrity of the underground space. Such certificate may provide for exceptions or conditions which must be adhered to as a condition of building permit approval. Such certificate shall be valid for newly added, or mined-out areas, if it is so described in the certificate. Such certificate must have been dated within the past ten (10) years to be valid for its application to new areas.

    (5)     Surface zoning exclusion. With the exceptions as noted herein, all districts M-U as they are created are separated from the provisions of the surface zoning districts, even though they may underlie them.

    (6)     Surface and special easements. Penetrations from district M-U to the surface property above it shall be permitted without regard to the provisions of the surface zoning district, provided that such penetrations are for the purpose of connecting utilities or to contain safety, relief or life-support systems to the underground. All penetrations must be contained within a public easement to assure perpetuity and continued service to the underground development.

(Ord. No. 10847, § 1, 1-6-86)