105-30 Preservation of Natural Features
The provisions of this Section are applicable to all developments, enlargements and site alterations within the Special Natural Area District, pursuant to Section 105-02 (General Provisions). When pursuant to Sections 105-41 (Certification) or 105-021 (Actions not requiring special review), it is not necessary for an applicant for a development, enlargement or a site alteration to apply for an authorization or special permit, such development, enlargement or site alteration shall nonetheless comply with the natural feature preservation requirements of this Section, inclusive.
To the maximum extent possible, existing trees and vegetation shall be retained. Trees of six-inch caliper or more and vegetation may only be removed or destroyed as a result of a development, enlargement or site alteration, provided that:
(a) such trees or vegetation are located in areas to be occupied by buildings, private roads, driveways, areas for required accessory parking, or within a distance of 15 feet of the exterior walls of such building, provided that it is not possible to avoid such removal by adjustments in the arrangement of such buildings, driveways or required parking areas;
(b) the continued presence of such tree would create special hazards or dangers to persons or property, which would not be possible or practical to eliminate by pruning;
(c) the continued presence of such tree would interfere with the growth or health of another tree of six-inch caliper or more, designated for preservation and belonging to a species listed in Appendix D (Tree Selection List for On-site Trees) of this Chapter; or
(d) an authorization pursuant to Section 105-425 (Modification of botanic environment and tree preservation and planting requirements) has been granted by the City Planning Commission approving the removal of such trees or vegetation.
Any tree of six-inch caliper or more that cannot be preserved as a result of a proposed development, enlargement or site alteration shall be replaced pursuant to the provisions of Section 105-32 (Botanic Environment and Tree Planting Requirements).
Any vegetation that cannot be saved as a result of site alteration, enlargement or development shall be replaced with alternative vegetation to be approved by the City Planning Commission. All developments, enlargements and site alterations shall comply with the tree planting requirements set forth in this Section, whether or not existing trees are removed as a result of such development, enlargement or site alteration.
The replanting of elements of vegetation that are parts of an association or community shall be such as to reestablish, as rapidly as is reasonable, the vigor and character of the association. When necessary to establish ecological balance, the Commission may also require additional vegetation to be planted.
(a) Tree planting
For the purposes of this Section, the following minimum standard shall apply for tree planting:
(1) For any development, enlargement or site alteration within a Special Natural Area District, trees of at least three-inch caliper, pre-existing or newly planted, shall be provided on the zoning lot at the rate of one tree for each 1,000 square feet of lot area or portion thereof or shall equal a total of 51 percent of all tree credits for trees originally on site, whichever is greater.
(2) For any existing tree of at least six-inch caliper that is preserved, credit for one tree shall be given for the first six inches of caliper and, for each additional four inches of caliper, credit for an additional tree shall be given.
Single-trunk trees, newly planted to meet this requirement, shall be of at least three-inch caliper at the time of planting. Multiple-trunk trees and low-branching coniferous evergreens shall be at least 10 feet in height at the time of planting. Trees newly planted to meet this requirement shall be of a species selected from Appendix D of this Chapter, and acceptable from the standpoint of hardiness, appearance and habit of growth suitable to the site.
The Commission may grant a waiver of the tree planting requirements by certification to the Department of Buildings, where the Commission finds that the ecology of the site is such that the substitution of other plant material would be more appropriate than the tree planting requirements and a detailed plan for planting has been filed with the Commission for its approval.
(b) Botanic Environment Planting
For the purposes of this Section, the following minimum standard shall apply for the planting of vegetation.
Any vegetation or topsoil that cannot be preserved as a result of a proposed development, enlargement or site alteration and is not permitted to be removed pursuant to the regulations of Sections 105-31 (Botanic Environment and Tree Preservation Requirements) or 105-425 (Modification of botanic environment and tree preservation and planting requirements), shall be replaced as follows: for every square foot of lot area of removed vegetation or topsoil, plantings shall be provided of the size and number indicated in paragraphs (b)(1), (b)(2), (b)(3) and (b)(4) of this Section. The area of removed vegetation shall be measured so as to include any portions of the zoning lot that were located within the critical root zone of a removed tree of six-inch caliper or more. Species of ground cover and shrubs shall be selected from Appendix C (Selection List for Ground Covers and Shrubs) of this Chapter. Species of on-site trees shall be selected from Appendix D (Tree Selection List for On-site Trees) of this Chapter.
(1) Ground cover shall be planted one at one-foot-on-center and at the rate of one plant for every square foot of lot area of removed vegetation; and
(2) Large trees shall be planted at the rate of one three-inch caliper tree for every 500 square feet of lot area of removed vegetation; or
(3) Small trees shall be planted at a rate of one eight-foot high tree for every 100 square feet of lot area of removed vegetation; or
(4) Shrubs shall be planted at a rate of one gallon container-grown material for every 25 square feet of lot area of removed vegetation.
The planting of species shall not be limited to woody plant materials, but shall include trees, shrubs, vines, ferns, grasses, herbs, annuals, biennials, perennials, mosses and other associated vegetation. All vegetation to be planted shall be either of the species which characterized the area's biological community prior to site alteration, enlargement or development, or of an alternative biologic community found in the area. Species selection shall give particular attention to the relationship of the species to each other and to the surrounding plant community and to the quality of the soil and the vertebrate and invertebrate populations associated with and dependent upon the proposed plants.
or on Sites Granted an Authorization Pursuant to
The maximum permitted percentage of lot coverage for residences on a zoning lot shall be determined by Table I or Table II of this Section, as applicable.
PERMITTED PERCENTAGE OF LOT COVERAGE ON A TIER II ZONING LOT BY ZONING DISTRICT, AVERAGE PERCENT OF SLOPE AND RESIDENCE TYPE
Average Percent of Slope
*or Residence District equivalent when zoning lot is located within a Commercial District
If an authorization is granted for a development, enlargement or site alteration on a zoning lot or portion of a zoning lot having a steep slope or steep slope buffer pursuant to Section 105-422, the maximum permitted percentage of lot coverage for such zoning lot shall not exceed the maximum set forth in Table II of this Section.
PERMITTED PERCENTAGE OF LOT COVERAGE ON ANY ZONING LOT OR PORTION OF ANY ZONING LOT WITH A STEEP SLOPE GRANTED AN AUTHORIZATION PURSUANT TO SECTION 105-422
*or Residence District equivalent when zoning lot is located within a Commercial District
With the exception of private roads and driveways, no grading shall take place beyond 15 feet of the location of a building foundation, measured from the foundation perimeter. The following grading requirements shall apply to all Tier II sites.
(a) Cut slopes shall be no steeper than two horizontal to one vertical; subsurface drainage shall be provided as necessary for stability.
(b) Fill slopes shall be no steeper than two horizontal to one vertical; fill slopes shall not be located on natural slopes 2:1 or steeper, or where fill slope toes out within 12 feet horizontally of the top of an existing or planned cut slope.
(c) Excavating for fill shall be prohibited unless the material is obtained from a cut permitted under an approved grading plan obtained for some purpose other than to produce fill material, or imported from outside the Special Natural Area District.
(d) Fills shall be compacted to at least 95 percent of maximum density, as determined by AASHTO T99 or ASTM D698.
(e) All retaining walls or cuts with a total vertical projection in excess of three feet and associated with cut or fill surfaces shall be designed as structural members keyed into stable foundations and capable of sustaining the design loads.
(f) The top and toe of any cut or fill slope, or where any excavation meets the grade existing on February 2, 2005, should be rounded in a vertical arc with a radius of not less than five feet.
(g) Tops and toes of cut and fill slopes and retaining walls shall be set back from lot lines for a horizontal distance of three feet plus one-fifth the height of the cut or fill but need not exceed a horizontal distance of 10 feet; tops and toes of cut and fill slopes shall be set back from buildings and structures for a horizontal distance of six feet plus one-fifth the height of the cut or fill but need not exceed a horizontal distance of 10 feet.
The provisions set forth in this Section and Section 105-34 (Grading Controls for Tier II Sites) shall apply to driveways and to private roads that provide access to buildings developed after February 2, 2005. The provisions for private roads set forth in Article II, Chapter 6, shall not apply.
(1) The maximum grade of a driveway shall not exceed 10 percent.
(2) The paved width of a driveway shall not exceed 18 feet.
(3) The maximum length of a driveway from a private road or street to an accessory parking space shall not exceed 80 feet.
(b) Private roads
(1) The maximum grade of a private road shall not exceed 10 percent.
(2) The width of the graded section beyond the curb back or edge of pavement of a private road shall extend no more than three feet beyond the curb back or edge of pavement on both the cut and the fill sides of the roadway. If a sidewalk is to be installed parallel to the roadway, the graded section shall be increased by the width of the sidewalk plus no more than one foot beyond the curb back.
(3) The paved width of a private road shall not exceed 34 feet.
(4) Curbs shall be provided along each side of the entire length of a private road and accessory parking spaces may be located between the required roadbed and curb.
(5) A curb cut, excluding splays, from a street to a private road may be as wide as such private road.
(6) Curb cuts providing access from private roads to parking spaces shall not exceed the width of the driveway served and in no event shall exceed a width of 18 feet, including splays.
(7) A minimum distance of 16 feet of uninterrupted curb space shall be maintained between all curb cuts.
(8) Along the entire length of a private road, trees shall be provided and maintained at the rate of one tree for every 25 feet of private road frontage and shall comply with the requirements set forth in Section 105-32 (Botanic Environment and Tree Planting Requirements).
(9) No building permit shall be issued by the Department of Buildings without approval by the Fire Department regarding the adequacy of vehicular access to and within the development for fire safety. Such approval may include the modification of private road width as set forth in paragraph (b)(3) of this Section.
The City Planning Commission may by authorization pursuant to Section 105-434 (Modification of requirements for private roads and driveways), allow modifications to, or waivers of, the requirements of this Section. The prior approval of the Fire Department regarding the adequacy of vehicular access to and within the development for fire safety shall be a condition for any modification or waiver.