To preserve existing noninvasive trees, native plants, and pervious surfaces.
OPTION 1. Development footprint on previously developed land
OPTION 2. Undeveloped portion of project left undisturbed
Depending on the density of the project, do not develop or disturb a portion of the land that has not been previously developed on the site, exclusive of any land preserved by codified law or a prerequisite of LEED for Neighborhood Development; or exempt areas designated as nonbuildable in land-use comprehensive plans and stipulate in covenants, conditions, and restrictions (CC&R) or other binding documents that the undisturbed area will be protected from development in perpetuity. Densities and minimum percentages are as follows (mixed-use projects must use the lowest applicable density or calculate a weighted average per the methodology in NPD Credit 2, Compact Development):
Table 1. Minimum undeveloped area, by project density
|Residential density (DU/acre)||Residential density (DU/hectare)||Nonresidential density (FAR)||Minimum area left undisturbed|
|< 15||< 37||< .50||20%|
|15 – 21||37 – 52||.50 – 1.0||15%|
|> 21||> 52||> 1.0||10%|
|DU = dwelling unit; FAR = floor-area ratio.|
For portions of the site that are not previously developed, identify construction impact zones that limit disturbance to a minimum of 40 feet (12 meters) beyond the building perimeter; 10 feet (3 meters) beyond surface walkways, patios, surface parking and utilities less than 12 inches (300 millimeters) in diameter; 15 feet (4.5 meters) beyond street curbs and main utility branch trenches; and 25 feet (8 meters) beyond constructed areas with permeable surfaces (such as pervious paving areas, stormwater retention facilities, and playing fields) that require additional staging areas to limit compaction in the constructed zone.
For all projects
Survey the site to identify the following:
- Trees in good or excellent condition, as determined by an arborist certified by the International Society of Arboriculture (ISA).
- Any heritage or champion trees of special importance to the community because of their age, size, type, historical association, or horticultural value, as defined by a government forester.
- All trees larger than 6 inches (150 millimeters) in diameter at breast height (dbh, 4 feet 6 inches [1.4 meters] above ground).
- Any invasive tree species present on the site, and whether those trees threaten the health of other trees to be preserved on the site, as determined by an ISA-certified arborist.
Preserve the following trees that are also identified as in good or excellent condition:
- All heritage or champion trees and trees whose dbh exceeds 50% of the state champion dbh for the species.
- A minimum of 75% of all noninvasive trees (including the above) larger than 18 inches (450 millimeters) dbh.
- A minimum of 25% of all noninvasive trees (including the above) larger than 12 inches (300 millimeters) dbh if deciduous, and 6 inches (150 millimeters) dbh if coniferous.
Tree condition ratings must be based on assessment by an ISA-certified arborist using ISA approved assessment measures.
Develop a plan, in consultation with and approved by an ISA-certified arborist, for the health of the trees, including fertilization and pruning, and for their protection during construction. The plan must include protective fencing located 1 foot for (300 millimeters) each 1-inch (25 millimeter) caliper from the trunk
or at the tree drip line, whichever is larger, and specify that if trenching or other disturbance is necessary within the protected zone, this work must be done by hand. If disturbance includes a permanent excavation of 3 feet (900 millimeters) or deeper, the excavation must start from a point not closer than 15 feet (4.5 meters) from the tree’s drip line. If an ISA-certified arborist has determined that any trees to be preserved are threatened by invasive vegetation, develop a plan to reduce the invasive vegetation to the maximum extent possible. Stipulate in CC&R or other binding documents that the undisturbed area of the preserved trees will be protected from development in perpetuity.
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