(A) Preservation of Existing Vegetation Along Roadways
All uses that require development plan approval shall preserve existing healthy vegetation (as described below) within the streetscape along all existing and proposed streets and thoroughfares.
(1) Residential Development
Natural and dense vegetation along streets is critical to maintain, especially along major collectors and thoroughfares, to mitigate the impact of these roadways. For this reason, existing healthy vegetation shall be supplemented, if necessary, to achieve a Type A (opaque) standard.
(2) Non-Residential Development
(a) Selective thinning of trees less than six (6) inches DBH may occur to improve the viability of trees within the streetscape. An evaluation of the existing vegetation and recommendation for thinning shall be prepared by a certified arborist or by a certified forester and submitted in support of any request involving the removal of trees two (2) inches in DBH or larger. Viable ornamental trees two (2) inches in caliper or larger must be saved.
(b) An applicant may request an exception to remove a portion of existing trees and undergrowth less than two (2) inches DBH to improve the viability of the remaining trees or to allow for greater visibility of the site, unless this vegetation is needed to meet the minimum planting requirements for a streetscape. Viable ornamental trees two (2) inches in caliper or larger must be saved.
(c) All proposals for thinning streetscapes shall be accompanied by a report from a registered landscape architect, certified arborist, or other such specialist justifying the request and containing a more detailed tree survey showing all plant material two (2) inches in caliper or larger that is located within the area of streetscape to be thinned. The Planning Director may require that a portion of existing saplings be left intact to help ensure that the streetscape can function as a natural tree stand.
(d) Non-Residential sites containing existing forest vegetation within an area designated as the streetscape that is subsequently removed due to construction-related activity shall be revegetated to partially re-establish a native forest condition meeting the following criteria:
1. Existing vegetation or planted upper-story deciduous and evergreen trees shall attain a height at maturity of no less than sixty (60) feet.
2. At least fifty (50) percent of the required upper-story trees, and at least seventy-five (75) percent of the required shrubs shall be native, evergreen species locally adapted to the area.
3. The re-established forest shall contain rows of upper-story trees with each row spaced at least fifteen (15) feet apart. Within each row of upper-story trees the trees shall be spaced no wider than twenty (20) feet between tree trunks. The new forest shall also contain native ornamental trees spaced no wider than twenty (20) feet, and one shrub six (6) feet high randomly placed for every ten (10) feet of streetscape length.
4. A re-forested streetscape may include a wall, fence, or landscaped earthen berm, but must also include all required plant material required by this section.
(B) Installation of Planted Vegetation Along Roadways
The Director may allow the installation and maintenance of a planted streetscape in lieu of preservation of the existing vegetation along any streets which are adjacent to the site upon sound justification related to topography, drainage, site configuration, quality and quantity of existing healthy vegetation, the road construction requirements, or other similar issue. If a planted streetscape is permitted, then the following requirements shall apply:
(1) Any required vegetation shall be installed to reforest the buffer in an amount comparable to what existed naturally (given time for maturity at a later date).
(2) Existing healthy vegetation may be removed after review and approval by the Planning Director for the following purposes:
(a) to achieve required automobile sight distance triangles at intersections, driveways, or ingress/egress points;
(b) to provide drive access to the site;
(c) to locate sidewalks, street-side trails and public transit amenities;
(d) to locate residential and non-residential monument signs, provided that no trees greater than six (6) inches dbh are removed for such purpose unless there is no alternative sign location of lesser impact to vegetation outside of the sight distance triangle that would provide adequate visibility for the sign;
(e) to locate stormwater impoundment areas or other BMPs provided that no reasonable alternative location exists.
(3) The applicant may appeal the Director's decision by electing to have the development plan forwarded to Zoning Board of Adjustment for consideration
(C) Required Width of Streetscapes for all Types of Development
(1) The width of the streetscape for non-residential uses shall be a minimum of thirty (30) feet along thoroughfares and collectors designated on the Cary Comprehensive Transportation Plan or otherwise designated by the Town, as measured from the ultimate right-of-way line, except as provided.
(2) For residential developments along thoroughfares, the width of the streetscape shall be a minimum of fifty (50) feet, except as provided; along collectors, a minimum of thirty (30) feet shall be provided, except as provided.
(3) To protect the historic character of the Carpenter community, an historic character preservation streetscape is hereby established. New development (residential and non-residential) located along the following streets shall provide a fifty (50) foot historic character preservation streetscape outside the right-of-way and/or any public access easements:
(a) Both sides of Morrisville Carpenter Road from its intersection with Good Hope Church Road to its intersection with Louis Stephens Drive;
(b) Both sides of existing Good Hope Church Road from its intersection with Morrisville Carpenter Road to a point one thousand one hundred (1,100) feet north;
(c) Both sides of Saunders Grove Lane;
(d) The west side of Louis Stephens Drive from its intersection with Morrisville Carpenter Road to a point nine hundred (900) feet north; and
(e) The west side of Louis Stephens Drive from its intersection with Morrisville Carpenter Road to a point five hundred (500) feet south.
(4) If existing healthy vegetation is located within the streetscape, a ten (10) foot building/five (5) foot vehicular use area setback from the streetscape is required.
(5) According to Section 7.2.10, Allowable Modifications and Reductions, the Planning Director may allow averaging of the width of a residential streetscape to no less than thirty (30) feet only if the remaining streetscape effectively mitigates the impact of the adjacent roadway (i.e., through the use of walls or berms with a substantially more intensive landscape plan). Only the Zoning Board of Adjustment may permit other reductions in buffer or streetscape widths.
(6) Non-residential developments located on local or private streets shall provide a fifteen (15) foot streetscape. In situations where property across the street is zoned or used for residential purposes, the streetscape shall be installed in accordance with the Type A standards.
(7) The Zoning Board of Adjustment may reduce the prescribed width of streetscape to as little as ten (10) feet at the time of
development
plan approval. On redeveloped sites or existing non-conforming sites, the staff may reduce the streetscape to no less than the streetscape shown on a previously approved plan for the site to promote redevelopment and reuse of existing sites where it is impractical to meet current requirements (see Section 7.2.10, Allowable Modifications and Reductions). The applicant shall submit a statement justifying the reduction based on the below criteria:
(a) The relationship of existing topography to the finished street grades.
(b) The type, amount, and location of existing vegetation within thirty (30) feet of the right-of-way line.
(8) All streetscapes are to be made up of existing trees and supplemented if necessary, unless approved by the Planning Director (see subsection 7.2.4(A)).
Streetscape Width based on Use and Roadway Type
(D) Plantings in Streetscape
(1) General Provisions
(a) The property owner or developer shall preserve existing healthy trees.
(b) The calculation of road frontage to meet the spacing requirements for trees shall not include driveway widths measured at the right-of-way line.
(c) In instances where planting requirement calculations produce a fraction, the plants shall be rounded up to the next whole number (e.g. five and one-tenth (5.1) required shrubs shall equal six (6) provided shrubs).
Typical Streetscape Plantings
(2) Upper-story Trees
(a) The property owner or developer shall install three (3) upper-story trees at least two (2) inches in caliper for each one hundred (100) linear feet of streetscape. The maximum spacing between upper-story trees shall be forty (40) feet.
(b) If existing trees that meet the intent of the upper-story tree requirement are preserved, then the requirement shall be reduced proportionally.
(c) Upper-story trees shall be planted at appropriate distances from public rights-of-way, sidewalks, and other utilities as required by the Land Development Ordinance and the Community Appearance Manual.
(d) Within historic character preservation streetscapes, upper-story trees shall be native species, at least fifty percent (50%) of which shall be evergreen. Trees shall be planted at a density of four (4) trees per one hundred (100) linear feet of streetscape, installed in an irregular manner to mimic a natural forest stand.
(3) Understory/Ornamental Trees
(a) Where the required streetscape is thirty (30) feet or less in width, the property owner or developer shall install or preserve five (5) deciduous understory or ornamental trees at least two (2) inches in caliper for each one hundred (100) linear feet of streetscape. The maximum spacing between understory/ornamental trees shall be twenty (20) feet except as noted in Section 7.2.4(D)(3)(c).
(b) Where the required buffer width is greater than thirty (30) feet and less than fifty (50) feet, one (1) additional understory/ornamental tree shall be provided every one hundred (100) linear feet for every four (4) additional feet of buffer width (or portion thereof) beyond thirty (30) feet.
(c) Where the required buffer is fifty (50) feet or greater in width, the property owner or developer shall install or preserve ten (10) deciduous understory/ornamental trees at least two (2) inches in caliper for each one hundred (100) linear feet of streetscape.
(d) Sites with streetscapes that meet all LDO requirements and have a minimum width of at least thirty (30) feet, may cluster understory or ornamental trees in accordance with the following requirements:
(i) Up to twenty percent (20%) of the required understory or ornamental trees (or a minimum of two (2) along a specific frontage) may be relocated elsewhere in the streetscape along the same frontage;
(ii) Gaps that are created between understory or ornamental trees may not exceed eighty (80) feet in length; and there shall be a minimum of two hundred (200) linear feet between gaps.
(iii) When understory or ornamental trees are removed from existing streetscapes, at least an equal number of replacement trees shall be provided and the total diameter of all replacement trees shall be a minimum of fifty percent (50%) of the total tree diameter removed.
(e) Within historic character preservation streetscapes, understory trees shall be native evergreen species and shall be planted behind the required upper-story trees as viewed from the right-of-way or public access easement. Trees shall be planted at a density of fourteen (14) trees per one hundred (100) linear feet of streetscape, in a single row parallel to the right-of-way or public access easement. The intent is for these plantings to mimic a traditional fenceline planting.
(4) Power Line Encroachment
Where overhead power lines encroach into the streetscape or buffer, each required upperstory tree may be replaced with two (2) understory trees. The selected tree type may reach a maximum height of twenty to twenty-five (20-25) feet at maturity.
(E) Tree Placement
Trees shall be installed on the thoroughfare side of any berm or screen planting, and no less than five (5) feet from a sidewalk or trail, or from back of curb where no sidewalk exists or is planned within the thoroughfare right-of-way. Trees should be installed in a staggered fashion, or in clusters or groupings of upper-story and/or understory trees in combination with associated plantings. Trees may be planted in a linear arrangement parallel to the street, depending upon the area (e.g., downtown areas, neotraditional developments, etc.). In order to prevent conflicts and allow for appropriate maintenance, canopy trees shall be placed at least ten (10) feet from electrical transformers and twenty (20) feet from light poles.
Tree Placement
(F) Pervious Area and Soil Volume for New Trees
A minimum of three hundred (300) square feet of pervious ground area and nine hundred (900) cubic feet of total soil volume for roots per upper-story tree shall be provided, unless two (2) or more upper-story trees are sharing one (1) planting bed, in which case at least seven hundred twenty (720) cubic feet of soil must be provided per upper-story tree. Where possible, smaller individual planting areas should be combined to allow for larger planting areas that contribute to healthier trees. Any planting area bounded by an impervious surface should be at least ten (10) feet wide. No upper-story tree should be planted closer than five (5) feet to a sidewalk, paved areas, or other impervious surface. Modifications to soil volume requirements may be granted pursuant to Section 7.2.10(C).
(G) Stabilizing Steep Slopes
All slopes two to one (2:1) and steeper shall be stabilized with permanent slope retention devices or suitable combination of plantings and retention devices. Slopes greater than three to one (3:1) shall not be stabilized with turf grass (e.g., grasses that need to be mowed), but with other permanent ground cover such as those listed in the Standard Specifications and Details Manual, with preference given to native species. No permanent overhead spray-type irrigation is allowed on slopes greater than two to one (2:1).
(H) Planting Criteria for Steep Slopes Adjacent to Rights-of-Way
Where the right-of-way is bounded by slopes steeper than three to one (3:1) or is otherwise not suitable for the planting of upper-story trees, the following standards shall apply:
(1) If natural areas are permitted to be removed and/or graded, the streetscape slope shall be somewhat level (no greater than four to one [4:1]) planting strip for upper-story trees at least ten (10) feet wide, located parallel to both sides of the thoroughfare. The planting strip shall be positively drained throughout. Upper-story trees required by this section may only be located closer than five (5) feet to the curb or sidewalk on certain streets, such as those found in neo-traditional developments, or when trees which do not exceed twenty-five (25) feet in height at maturity are used, but in no case shall they be closer than two and one-half (2 1/2) feet. Plantings may be located in the right-of-way only with the prior approval of the authority or agency that controls the right-of-way (e.g., Town of Cary, Department of Transportation, or other agency).
(2) Existing significant vegetation within thirty (30) feet of and extending to the right-of-way may be used to satisfy the requirements of this section, provided that:
(a) The existing vegetation meets the requirements of this section.
(b) The vertical grade change is less than four (4) feet above or below the existing or proposed permanent features of the thoroughfare.
(I) Ownership of Streetscapes
The ownership of streetscapes shall follow the same requirements as stated in Section 7.2.3(J) Ownership of Buffers.
(Ord. No. 2009-LDO-01, 2-12-09; Ord. No. 2010-LDO-05, 12-16-10)