ND-v2009 GIBc7: Minimized site disturbance in design and construction

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  • USGBC

    Excerpted from LEED 2009 for Neighborhood Development

    GIB Credit 7: Minimized site disturbance in design and construction

    Intent

    To preserve existing noninvasive trees, native plants, and pervious surfaces.

    Requirements

    OPTION 1. Development footprint on previously developed land

    Locate 100% of the development footprint on areas that are previously developed and for which 100% of the construction impact zone is previously developed.

    OR

    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 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 (FARFloor-area ratio is the density of nonresidential land use, exclusive of parking, measured as the total nonresidential building floor area divided by the total buildable land area available for nonresidential structures. For example, on a site with 10,000 square feet (930 square meters) of buildable land area, an FAR of 1.0 would be 10,000 square feet (930 square meters) of building floor area. On the same site, an FAR of 1.5 would be 15,000 square feet (1395 square meters), an FAR of 2.0 would be 20,000 square feet (1860 square meters), and an FAR of 0.5 would be 5,000 square feet (465 square meters).) 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 ratioThe density of nonresidential land use, exclusive of parking, measured as the total nonresidential building floor area divided by the total buildable land area available for nonresidential structures. For example, on a site with 10,000 square feet (930 square meters) of buildable land area, an FAR of 1.0 would be 10,000 square feet (930 square meters) of building floor area. On the same site, an FAR of 1.5 would be 15,000 square feet (1395 square meters), an FAR of 2.0 would be 20,000 square feet (1860 square meters), and an FAR of 0.5 would be 5,000 square feet (465 square meters)..



    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.

    AND

    For all projects

    Survey the site to identify the following:

    1. Trees in good or excellent condition, as determined by an arborist certified by the International Society of Arboriculture (ISA).
    2. 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.
    3. All trees larger than 6 inches (150 millimeters) in diameter at breast height (dbh, 4 feet 6 inches [1.4 meters] above ground).
    4. 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:

    1. All heritage or champion trees and trees whose dbh exceeds 50% of the state champion dbh for the species.
    2. A minimum of 75% of all noninvasive trees (including the above) larger than 18 inches (450 millimeters) dbh.
    3. 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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