20.25A.120 Green and sustainability factor.
A. General. All new development shall provide landscaping and other elements that meet a minimum Green and Sustainability Factor score. All required landscaping shall meet standards promulgated by the Director to provide for the long-term health, viability, and coverage of plantings. These standards may include, but are not limited to, the type and size of plants, spacing of plants, depth of soil, and the use of drought-tolerant plants. The Green and Sustainability Factor score shall be calculated as follows:
1. Identify all proposed elements, presented in Figure 20.25A.120.A.5.
2. Multiply the square feet, or equivalent unit of measurement where applicable, of each landscape element by the multiplier provided for that element in Figure 20.25A.120.A.5 according to the following provisions:
a. If multiple elements listed in Figure 20.25A.120.A.5 occupy the same physical area, they may all be counted. For example, groundcover and trees occupying the same physical space may be counted under the ground cover element and the tree element.
b. Landscaping elements and other frontage improvements in the right-of-way between the lot line and the roadway may be counted.
c. Elements listed in Figure 20.25A.120.A.5 that are provided to satisfy any other requirements of Part 20.25A LUC may be counted.
d. Unless otherwise noted, elements shall be measured in square feet.
e. For trees, large shrubs and large perennials, use the equivalent square footage of each tree or shrub provided in Figure 20.25A.120.A.5. Tree sizing shall be determined by the Green and Sustainability Factor Tree List maintained by the Director in the Development Services Department. If a tree species is not included on the list, the Director shall determine the size of the proposed tree species.
f. For green wall systems, use the square footage of the portion of the wall that will be covered by vegetation at three years. Green wall systems shall include year-round irrigation and a submitted maintenance plan shall be included as an element in the calculation for a project’s Green and Sustainability Factor Score.
g. All vegetated structures, including fences counted as vegetated walls shall be constructed of durable materials, provide adequate planting area for plant health, and provide appropriate surfaces or structures that enable plant coverage. Vegetated walls shall include year-round irrigation and a submitted maintenance plan shall be included as an element in the calculation for a project’s Green and Sustainability Factor Score.
h. For all elements other than trees, large shrubs, large perennials, green walls, structural soil systems and soil cell system volume; square footage is determined by the area of the portion of the horizontal plane that lies over or under the element.
i. All permeable paving and structural soil credits may not count for more than one-third of a project’s Green and Sustainability Factor Score.
3. Add together all the products calculated in Figure 20.25A.120.A.5 to determine the Green and Sustainability Factor numerator.
4. Divide the Green and Sustainability Factor numerator by the lot area to determine the Green and Sustainability Factor score. A development shall achieve a minimum score of 0.3. On DT-Small Sites, a development shall achieve a minimum score of 0.25.
5. The Director has the final authority in determining the accuracy of the calculation of the Green and Sustainability Factor score.
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A. Landscape Elements |
Multiplier |
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1. Bioretention Facilities and Soil Cells. Bioretention facilities and soil cells shall comply with Bellevue’s Storm and Surface Water Engineering Standards. Bioretention facilities shall be calculated in horizontal square feet. The soil cell systems shall be calculated in cubic feet. The volume of the facility shall be calculated using three feet of depth or the depth of the facility, whichever is less. |
1.2 |
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2. Structural Soil Systems. The volume of structural soil systems can be calculated up to three feet in depth. The volume of structural soil systems shall be calculated in cubic feet. The volume of the facility shall be calculated using three feet of depth or the depth of the facility, whichever is less. |
0.2 |
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3. Landscaped Areas with Soil Depth Less than 24 Inches. |
0.1 |
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4. Landscaped Areas with Soil Depth of 24 Inches or More. |
0.6 |
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5. Preservation of Existing Trees. Existing trees – proposed for preservation shall be calculated at 20 square feet per inch d.b.h. Trees shall have a minimum diameter of six inches at d.b.h. Existing street trees proposed for preservation shall be approved by the Director. |
1.0 |
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6. Preservation of Existing Evergreen Trees Bonus. Existing evergreen trees proposed for this bonus shall be calculated at 20 square feet per inch d.b.h. and shall have a minimum diameter of six inches at d.b.h. |
0.1 |
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7. Shrubs or Large Perennials. Shrubs or large perennials that are taller than two feet at maturity shall be calculated at 12 square feet per plant. |
0.4 |
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8. Small Trees. Small trees shall be calculated at 90 square feet per tree. Consult the Green and Sustainability Factor Tree List for size classification of trees. |
0.3 |
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9. Medium Trees. Medium trees shall be calculated at 230 square feet per tree. Consult the Green and Sustainability Factor Tree List for size classification of trees. |
0.3 |
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10. Large Trees. Large trees shall be calculated at 360 square feet per tree. Consult with the Green and Sustainability Factor Tree List for size classification of trees. |
0.4 |
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B. Green Roofs |
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1. Green Roof, Two to Four Inches of Growth Medium. Roof area planted with at least two inches of growth medium, but less than four inches of growth medium. |
0.4 |
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2. Green Roof, at Least Four Inches of Growth Medium. Roof area planted with at least four inches of growth medium. |
0.7 |
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C. Green Walls |
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1. Vegetated Wall. Façade or structural surface obscured by vines. Vine coverage shall be calculated with an estimate of three years’ growth. A year-round irrigation and maintenance plan shall be provided. |
0.2 |
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2. Green Wall System. Façade or structural surface planted with a green wall system. A year-round irrigation and maintenance plan shall be provided. |
0.7 |
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D. Landscape Bonuses |
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1. Food Cultivation. Landscaped areas for food cultivation. |
0.2 |
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2. Native or Drought-Tolerant Landscaping. Landscaped areas planted with native or drought-tolerant plants. |
0.1 |
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3. Landscape Areas at Sidewalk Grade. |
0.1 |
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4. Rainwater Harvesting. Rainwater harvesting for landscape irrigation shall be calculated as a percentage of total water budget times total landscape area. |
0.2 |
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E. Permeable Paving |
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1. Permeable Paving, Six to 24 Inches of Soil or Gravel. Permeable paving over a minimum of six inches and less than 24 inches of soil or gravel. |
0.2 |
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2. Permeable paving over at least 24 inches of soil or gravel. |
0.5 |
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F. Publicly Accessible Bicycle Parking |
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1. Bicycle Racks. Bicycle racks in publicly accessible locations shall be calculated at nine square feet per bike locking space and shall be visible from sidewalk or public area. |
1.0 |
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2. Bicycle Lockers. Bicycle lockers in publicly accessible locations shall be calculated at 12 square feet per locker, and shall be visible from public areas and open for public use. |
1.0 |
(Ord. 6377, 10-16-17, § 2)