Section 11-C602. CALCULATION OF GREEN AREA RATIO

602.1 The GAR shall be calculated using the following formula:

 

    (area of landscape element 1 x multiplier)+

  GAR =  (area of landscape element 2 x multiplier)+…

    Lot Area

602.2 For the purposes of the above formula and the remainder of this chapter:

(a) The term “landscape element” refers to one (1) of the elements listed in the table in Subtitle C § 602.9, and will be hereafter referred to as “landscape element” or “element”;

(b) The term “multiplier” refers the number listed Table C § 602.9 that corresponds to a “landscape element”; and

(c) The “area of landscape element” shall be the square feet of a landscape element, unless the element is a tree or large shrub, in which case “area of landscape element” refers to the element’s equivalent square footage as indicated in Subtitle C § 602.7.

602.3 The process for calculating a property’s GAR under the formula is as follows:

(a) The area of each landscape element is multiplied by its corresponding multiplier;

(b) The resulting numbers for all landscape elements are added together;

(c) The resulting point total is then divided by the total land area of the lot; and

(d) The product of the equation equals the property’s GAR.

602.4 The total points for all permeable paving and enhanced tree growth credits may not count for more than one-third (1/3) of the GAR score for a lot.

602.5 If multiple landscape elements occupy the same area, for example groundcover under a tree or trees and shrubs on an intensive green roof, the full square footage or equivalent square footage of each element may be counted.

602.6 A landscape element must meet the eligibility conditions of Subtitle C § 603.

602.7 Equivalent square feet of tree canopy and large shrubs are identified in the table below:

 

TABLE C § 602.7:  GAR Equivalent square feet of tree canopy and large shrubs

 

GAR LANDSCAPE ELEMENTS	EQUIVALENT SQ. FT.
Plants, not including grasses, at least 2 feet tall at maturity	9 sq. ft. per plant
Tree canopy for trees 2.5 inches to 6 inches in diameter	50 sq. ft. per tree
Tree canopy for trees 6 inches to 12 inches in diameter	250 sq. ft. per tree
Tree canopy for trees 12 inches to 18 inches in diameter	600 sq. ft. per tree
Tree canopy for trees 18 inches to 24 inches in diameter	1,300 sq. ft. per tree
Tree canopy for trees larger than 24 inches in diameter	2,000 sq. ft. per tree

602.8 Landscape elements of the GAR shall be measured in the following ways:

(a) All trees shall be measured for diameter at a height four feet, six inches (4 ft. 6 in.) above grade when planted and the square footage equivalent based on diameter shall be as established in the table in Subtitle C § 602.7;

(b) For vegetated walls, the area calculated is the height times the width of the area to be covered by vegetation; and

(c) For all other elements other than trees, large shrubs, perennials, and vegetated walls, square footage is determined by the area of a horizontal plane that is over the landscape element.

602.9 Eligible landscape elements are identified in the table below:

 

TABLE C § 602.9:  GAR Landscape Elements and Multipliers

 

GAR LANDSCAPE ELEMENTS	MULTIPLIER
Landscaped area (select 1 of the following for each area)
Landscaped areas with a soil depth of less than 24 inches	0.3
Landscaped areas with a soil depth of 24 inches or more	0.6
Bioretention facilities	0.4
Plantings
Ground covers, or other plants less than 2 feet tall at maturity	0.2
Plants, not including grasses, at least 2 feet tall at maturity	0.3
Tree canopy for all new trees with mature canopy spread of 40 ft. or less calculated at 50 sq. ft. per tree	0.5
Tree canopy for all new trees with mature canopy spread of greater than 40 ft. calculated at 250 sq. ft. per tree	0.6
Tree canopy for preservation of existing trees 6 inches to 24 inches in diameter	0.7
Tree canopy for preservation of existing trees 24 inches in diameter or larger	0.8
Vegetated wall, plantings on a vertical surface	0.6
Vegetated roofs
Extensive vegetated roof over at least 2 inches but less than 8 inches of growth medium	0.6
Intensive vegetated roof over at least 8 inches of growth medium	0.8
Permeable paving
Permeable paving over at least 6 inches and less than 2 feet of soil or gravel	0.4
Permeable paving over at least 2 feet of soil or gravel	0.5
Other
Enhanced tree growth systems	0.4
Renewable energy generation (area of)	0.5
Water features (using at least 50% recycled water)	0.2
Bonuses
Native plant species listed in Subtitle C § 603.9	0.1
Landscaping in food cultivation	0.1
Harvested stormwater irrigation	0.1

 

 

 

authority

§ 1 of the Zoning Act of 1938, approved June 20, 1938 (52 Stat. 797, as amended; D.C. Official Code § 6-641.01 (2012 Repl.)).

source

Final Rulemaking published at 63 DCR 2447, 2712 (March 4, 2016 – Part 2).