Section 11-3403. LANDSCAPE ELEMENT CONDITIONS FOR GREEN AREA RATIO

3403.1 No landscape element may be counted towards a property’s GAR unless it meets the applicable conditions stated in this section.

3403.2 Plantings over the specified soil depths shall meet the required conditions listed in the Table of Landscape Elements and Multipliers in § 3402.9.

3403.3 Bioretention facilities shall be landscaped areas that receive rainwater from surrounding areas and use plants and soils to slow, filter, and infiltrate stormwater runoff.  Bioretention facilities include but are not limited to rain or rainwater gardens, bioretention planters, or linear cells or swales.  These do not include structures made of cement or concrete alone.

3403.4 Trees shall meet the following conditions:

(a) All trees shall be at least two and one-half inches (2.5 in.) in diameter measured at a height four feet, six inches (4 ft. 6 in.) above grade when planted and shall be replaced if damaged or killed by any cause; and

(b) All trees shall meet the American Standard for Nursery stock, as set forth by the American Nursery and Landscape Association.

3403.5Vegetated walls shall meet the following conditions:

(a) The maximum calculated vertical dimension shall not exceed thirty feet (30 ft.) unless the vegetated wall features a built-in growth medium;

(b) The area calculated for the vegetated wall features shall be fully covered within a period of two (2) to five (5) years from planting;

(c) The area calculated is the ground coverage area, not the total plant growth area;

(d) The walls shall be at least five feet (5 ft.) from a side or rear lot line; and

(e) Where stormwater harvesting for irrigation is proposed, vegetated walls shall contain a connection to the proposed irrigation system. 

3403.6Vegetated roofs shall meet the following conditions:

(a) Designs for vegetated roofs must include plans to provide supplemental water;

(b) Where stormwater harvesting for irrigation is proposed, vegetated roofs shall contain a connection to the proposed irrigation system; and

(c) The groundcover vegetation on a vegetated roof is not additionally eligible for groundcover value towards GAR requirements. 

3403.7 Water features shall meet the following conditions:

(a) Water features must use harvested rainwater for at least fifty percent (50%) of the annual flow; and

(b) The water features must be under water for at least six (6) months out of twelve (12).

 3403.8Enhanced tree growth systems shall meet the following conditions:

(a) Be at least twenty-four inches (24 in.) deep, under pavement, and adjacent to planting areas; and

(b) Be composed of soils that are not considered contaminated or compacted according to the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, approved December 11, 1980 (94 Stat. 2767; 42 USC § 9601 et seq.).

3403.9Native plant species shall meet the following conditions:

(a) The plants are listed in the U.S. Fish and Wildlife Service’s Native Plants for Wildlife Conservation Landscaping: Chesapeake Bay Watershed guide; or

(b) The applicant provides two (2) references in current publications showing that the plant is native to the region; and 

(c) The plant is not listed on the U.S. Fish and Wildlife Service’s list of Plant Invaders of Mid-Atlantic Natural Areas.

3403.10Food cultivation shall meet the following conditions:

(a) All food cultivation areas must be easily accessible to at least one occupant of the building;

(b) All food cultivation areas must have a source of water that can reach all portions of the food cultivation area; and 

(c) The cultivation of animals for food is not eligible for GAR credits.

3403.11Harvesting stormwater for irrigation shall meet the following conditions:

(a) If the irrigation type is spray, applicants shall follow treatment standards set forth in the current District Department of Environment’s Stormwater Management Guidebook; and

(b) If the irrigation type is drip, no additional treatment of stormwater is required.

 

 

authority

Section 1 of the Zoning Act of 1938, approved June 20, 1938 (52 Stat. 797; D.C. Official Code § 6-641.01 (2008 Repl.)).

source

Final Rulemaking as published at 60 DCR 10077 (July 12, 2013).