8.3.1 Tree Coverage Standards

The primary purpose of the tree coverage standards is the preservation and maintenance of undisturbed tree cover and the provision of replacement tree cover on development sites in the Urban and Suburban Tiers. Tree coverage serves to reduce glare, noise, air pollution, and soil erosion; to moderate temperatures; to reduce stormwater runoff; to preserve remnants of Durham's native ecology; to provide habitat for native plants and wildlife; to provide a healthy living environment; and to make Durham County a more attractive place to live.

1. Tree coverage standards shall be applied in the Urban and Suburban Tiers, and in the Compact Neighborhood Tier on sites not zoned Design District.

2. Except for trees required on individual lots per paragraphs 8.3.1C.4.c(1)(d) and 8.3.1C.4.d(2) below, developments of less than two acres in size or not utilizing mass grading shall be exempt from tree coverage requirements.

3. Additions to existing residential structures, excluding multiplexes and apartments, are exempt from tree coverage requirements.

1. New development shall include tree coverage areas on a portion of the development tract.

2. Site plans for additions to development shall provide tree coverage as a percentage of the area proposed for disturbance, unless tree coverage in an amount consistent with the required amounts of this Ordinance was provided on the original site plan for the original development.

a. Tree coverage areas in new subdivisions shall be located in common open space or buffers required by other provisions of this Ordinance, except that new subdivisions without buffers that make payment in lieu of required open space under paragraph 7.2.2, Required Open Space, can locate tree coverage areas on private lots or as otherwise specified below.

b. Any forested land in the floodway, non-encroachment area, floodway fringe, non-encroachment area fringe, or Areas of Shallow Flooding (Zone AO) (unless proposed to be filled or developed in accordance with paragraph 8.4.4, Development in Special Flood Hazard Areas and Future Conditions Flood Hazard Areas), preserved wetlands and wetland buffers, steep slope areas, riparian buffers, Durham Natural Inventory sites, major transportation corridor (MTC) buffers, and any portion of the tract left undisturbed that satisfies the minimum size requirements established in paragraph 8.3.1D, Preserved Tree Coverage, below can be used as tree cover.

a. Tree coverage standards can be met either by preserving existing trees on the site, by planting replacement trees, or a combination of both, as required below.

b. The percentage of a tract or phase which shall have tree coverage is as indicated below. The total tree coverage area shown reflects the addition of replacement tree coverage area to the preserved tree coverage area shown. For certain calculation exclusions in paragraph 8.3.1C.5, Tree Coverage Calculation Exclusions, the total required tree coverage may be adjusted.

(a) A minimum of 20% preserved tree coverage shall be required for any phase that does not exceed 35 acres, or if the overall development qualifies as one of the following:

i. An overall development that provides affordable housing utilizing Sec. 6.6, Affordable Housing Bonus, or an approved low-income housing tax credit (LIHTC) development.

ii. An overall development that provides at least 10% of the dwelling units as affordable dwelling units, rental or for sale, at no more than 80% area median income (AMI). All other provisions of an affordable housing dwelling unit, as defined in Sec. 17.3, Defined Terms, shall apply.

iii. An overall development that provides at least three different housing types, with each housing type consisting of at least 20% of the overall number of units of the development. The housing type mix shall be as follows:

a. One of the housing types shall be apartments or multiplex.

b. The other two housing types shall be at the discretion of the applicant.

iv. An overall development site that provides double the minimum riparian buffers (i.e., if the stream requires a 50-foot buffer, then 100 feet is provided; if the stream requires a 150-foot buffer, then 300 feet is provided).

v. In addition to the environmental protections already required elsewhere in this Ordinance: an overall development that provides a minimum 50-foot wide natural, undisturbed wildlife corridor that is maintained through the development site and connects to neighboring, undisturbed natural areas, or tree preservation areas, on adjoining properties. The wildlife corridor shall be protected in accordance with paragraph 7.2.5C.1.

(b) If 20% tree preservation cannot be satisfied with existing on-site vegetation pursuant to paragraphs 8.3.1D, Preserved Tree Coverage, and 8.3.1C.3.b above, then the tree coverage percentages within the table below shall be required:

Preserved Tree Coverage Area (%)	Total Tree Coverage Area Required (%)
At least 15 but less than 20	28
At least 10 but less than 15	29
Less than 10	30

(c) For a phase of a development that exceeds 35 acres and the overall development does not qualify under paragraph 8.3.1C.4.c(1)(a) above, then a minimum of 30% preserved tree coverage shall be required for that phase. If that amount cannot be satisfied with existing on-site vegetation pursuant to paragraphs 8.3.1D, Preserved Tree Coverage, and 8.3.1C.3.b above, then the tree coverage percentages within the table below shall be required:

Preserved Tree Coverage Area (%)	Total Tree Coverage Area Required (%)
At least 25 but less than 30	33
At least 15 but less than 25	34
Less than 15	35

i. In addition to street tree requirements pursuant to Sec. 9.6, Street Trees, an existing tree shall be retained, or a new tree planted, prior to receiving a certificate of compliance for a new primary structure on a single-family or two-family residential lot.

ii. A planted tree shall be an allowable canopy or understory tree pursuant to the Durham Landscape Manual and comply with the minimum planting area.

A minimum of 10% preserved tree coverage shall be required. If that amount cannot be satisfied with existing on-site vegetation pursuant to paragraphs 8.3.1D, Preserved Tree Coverage, and 8.3.1C.3.b above, then the tree coverage percentages within the table below shall be required:

Preserved Tree Coverage Area (%)	Total Tree Coverage Area Required (%)
At least 8 but less than 10	13
At least 6 but less than 8	14
Less than 6	15

(1) Residential developments and development in residential districts shall provide a minimum seven percent preserved tree coverage. If that amount cannot be satisfied pursuant to paragraphs 8.3.1D, Preserved Tree Coverage, and 8.3.1C.3.b above, then the tree coverage percentages within the table below shall be required:

Preserved Tree Coverage Area (%)	Total Tree Coverage Area Required (%)
At least 5 but less than 7	8
At least 3 but less than 5	9
Less than 3	10

(a) In addition to street tree requirements pursuant to Sec. 9.6, Street Trees, an existing tree shall be retained, or a new tree planted, prior to receiving a certificate of compliance for a new primary structure on a single-family or two-family residential lot.

(b) A planted tree shall be an allowable canopy or understory tree pursuant to the Durham Landscape Manual and comply with the minimum planting area.

(3) Single-family and two-family residential developments required to meet standards under Sec. 6.8, Infill Development in Residential Districts, shall meet the standards of that section in lieu of the requirements in paragraphs (1) and (2) above.

(4) All other development shall provide a minimum of three percent tree coverage.

A minimum of three percent tree coverage is required, and can be provided anywhere within the contiguous zoning area.

a. For the purposes of calculating tree coverage requirements, the following shall be excluded from the total area of the development tract:

(1) The water surface area of ponds, lakes and other water bodies (excluding stormwater control structures).

(2) Right-of-way dedication for the widening of existing road right-of-way.

(1) The exclusion shall only apply to single-family and two-family residential development for the area within a utility easement of record (power, gas, water, or sewer) that measures at least 50 feet in width and exists at the time of application submittal.

(2) The exclusion shall only be applied to the area calculation for replacement tree coverage and shall allow for adjustment to the overall tree coverage percentage requirement to accommodate the exclusion.

Example: An application requires tree coverage for a 100-acre development tract, with five acres within a qualifying easement. Per the table in paragraph 8.3.1C.4.a, Suburban Tier, 15% is proposed for tree preservation, therefore requiring eight percent for tree replacement for a total of 23% tree coverage. The exclusion shall be applied as follows:

• 15% of 100 acres = 15 acres for tree preservation

• Eight percent of 95 acres (5 acres removed from the 100 acres) = 7.6 acres

• The total tree coverage required = 22.6 acres, or 22.6% (adjusted from the original 23% requirement to accommodate the exclusion)

6. Tree preservation and tree replacement areas shall be shown on all preliminary plats, final plats, site plans and development plans in order to clearly assign tree replacement responsibility to future owners. Tree preservation and tree replacement areas on any individual lot shall be clearly shown on all plot plans for the lot.

7. Property owners shall be responsible for protecting and preserving tree preservation and tree replacement areas during and after the development process in accordance with standard horticultural practice and paragraph 8.3.2, Protection of Existing Vegetation.

Trees can satisfy both tree coverage requirements, and landscaping and buffering requirements within Article 9, Landscaping and Buffering, as applicable, as along as all applicable standards can be met.

Areas proposed as tree preservation shall meet the following requirements to satisfy the tree coverage standards in paragraph 8.3.1, Tree Coverage and Protection Standards:

1. The provisions of paragraph 8.3.2, Protection of Existing Vegetation, shall be fulfilled.

2. Tree preservation areas shall be located in the areas listed in paragraph 8.3.1, Tree Coverage Standards, above. Additional tree preservation areas can be located outside of these areas, in which case they shall be located in order to preserve major specimen trees and to preserve clusters of trees.

a. The tree coverage area for a cluster of trees shall be determined by the exterior boundary of the total tree protection zones for all of the trees in the cluster.

b. For parcels greater than one acre, no tree preservation area for a cluster of trees shall be counted toward meeting the tree coverage standard unless it includes a minimum of 1,000 square feet (or such smaller area as required by paragraph 8.3.1C.4 above) and has no individual dimension of less than 13 feet. The area protected shall include the entire tree protection zone of the tree cluster, and adequate tree protection measures, as defined in paragraph 8.3.2, Protection of Existing Vegetation, shall be taken during the construction and grading of the project.

c. For parcels one acre or less, no single tree preservation area for a cluster of trees shall be counted toward meeting the tree coverage standard unless it includes a minimum of 500 square feet (or such smaller area as required by paragraph 8.3.1C.4 above) and has no individual dimension less than 13 feet.

d. At least 60% of the tree coverage included within any tree preservation area shall be composed of trees with at least a one inch dbh as determined through use of landscape sampling pursuant to paragraph 9.3.3, Sampling.

e. At least 75% of the tree protection zone for trees within the cluster measuring at least six inches dbh shall remain undisturbed for it to be considered a protected cluster. Root zones extending into rights-of-way shall be considered disturbed areas, unless legally binding protections are placed upon those areas.

a. The tree coverage area for an individual tree shall be determined by the tree’s tree protection zone.

b. At least 75% of the tree protection zone for an individual tree shall remain undisturbed in order for that tree to count as preserved. Root zones extending into rights-of-way shall be considered disturbed areas, unless legally binding protections are placed upon those areas.

c. An individual tree can be counted toward tree coverage credit, provided that its diameter is six inches dbh or greater.

a. Preserved tree coverage areas shall not be disturbed, except the following:

(1) Unpaved walking paths and foot trails constructed with minimal disturbance of tree roots and existing vegetation. No tree six inches dbh or greater shall be removed for the construction of the trail.

(2) Paved trails that are public trails and are shown on the most recent version of the Durham Trails and Greenways Master Plan. In no case shall the clearing of the trail corridor exceed 16 feet in width.

(3) Amenity areas containing such items as picnic tables and benches provided that such areas are unpaved and no larger than 200 square feet or 10% of the tree coverage area, whichever is smaller. No tree six inches dbh or greater shall be removed for the construction of an amenity area.

b. All buildings, utilities, and stormwater facilities shall be set back at least 10 feet from the edge of any preserved tree coverage area. No easements, except conservation, greenway, and landscape easements, shall be included within a tree coverage area.

Areas proposed as tree replacement shall meet the following requirements to satisfy the standards found in paragraph 8.3.1C, Tree Coverage:

1. For parcels greater than one acre, no tree replacement area shall be counted toward meeting the tree coverage standard unless it includes a minimum of 1,000 square feet (or such smaller area as required by paragraph 8.3.1C.4 above) and has no individual dimension of less than 25 feet.

2. For parcels one acre or less, no tree replacement area shall be counted toward meeting the tree coverage standard unless it includes a minimum of 500 square feet (or such smaller area as required by paragraph 8.3.1C.4 above) and has no individual dimension less than 15 feet.

3. When replacement trees are provided in order to satisfy the requirements of paragraph 8.3.1C, Tree Coverage, coverage credit shall be accrued in accordance with the following table with credit calculated based on the required planting area for the proposed trees.

Hardwood Caliper (inches)	Non-Hardwood Height (feet)	Credit (square feet)
4	18 or over	275
3½	16 to 18	250
3	14 to 16	225
2½	12 to14	200
2	10 to12	175
1½	8 to 10	150
1	7 to 8	100
0.75	5 to 7	75
Less than 0.75	Less than 5	No credit

Example: Ten trees at 2½-inch caliper require 2,000 square feet of planting area (10 X 200 = 2,000), and provide 2,000 square feet of replacement tree credits.

4. At least 50% of replacement trees shall be one inch caliper or greater.

5. All tree species shall be native to the North Carolina Piedmont region. A minimum of 50% of replacement trees shall be hardwood canopy species. The remainder of the replacement trees shall be a mix of understory hardwood and non-hardwood species, as long as no more than 50% of this remainder is pines.

6. Replacement trees shall be provided as a mix of species, in accordance with the standards set in paragraph 9.2.3B.6, Mixing of Tree Species, and shall consist of species allowed for “Tree Coverage” in tables 1A through 1H within the Landscape Manual for Durham, North Carolina.

7. One hundred percent of the replacement trees planted to augment preserved tree coverage clusters pursuant to paragraph 8.3.1D.3, Clusters of Trees, shall be native understory hardwoods of one-inch caliper or greater.

8. Areas designated as replacement tree coverage shall be subject to the use limitations imposed on preserved tree coverage in paragraph 8.3.1D.5, Construction in Preserved Tree Coverage Areas, except that stormwater control measures designed as bioretention facilities shall be allowed.

9. Replacement trees shall be planted before any Certificate of Compliance is issued, unless the planting has been deferred to an appropriate season in accordance with the requirements of paragraph 9.11.2, Extensions for All Other Development.