Soil and Planting Area Requirements

SEC. 51A-10.104. SOIL AND PLANTING AREA REQUIREMENTS.

(a) In general.

Planting areas dedicated to the growth of roots may include open soil areas, covered soil areas, root paths, and drainage.

(b) Soil areas.

Except as provided in this section, required landscape areas must include the following:


(1) Soil resource plan. A soil resource plan is required with the submission of a landscape plan or tree protection plan. A soil resource plan is used to distinguish landscaping zones from construction zones on the building site and to determine soil protection or soil modification for vegetation, if applicable. Zones that are required to be shown include:

(A) protected zones where existing soil and vegetation will not be disturbed;

(B) zones for soil amendment or treatment with minimal disturbance;

(C) zones where construction traffic and staging will be allowed; and

(D) zones for stockpiling topsoil and imported soil amendments.


(2) Soil resource assessment. A soil resource assessment is only required in conjunction with sustainable development incentive requirements and installation of legacy trees.

(A) A soil resource assessment must be provided before submittal of a building permit.

(B) A soil resource assessment may be included in other engineering site assessments for the property.

(C) A soil resource assessment must include information on all proposed landscape planting areas that delineates, quantifies, and characterizes the topsoils and subsoils of a site before these materials are excavated for reuse on site.

(D) The ranges for physical, chemical, and biological indicators of soil quality for urban trees is determined from the ISA Best Management Practices for Soil Management for Urban Trees, or in another publication approved by the building official.


(3) Additional minimum soil quality requirements. Soils used in landscape areas for tree planting must be shown on a landscape plan or a tree protection plan in protected zones where existing soil and vegetation is not disturbed, or in zones modified to correct limiting factors for tree establishment and longevity.


(c) Planting area requirements.

Except as provided in this section, planting areas must meet the following requirements:

(1) For each small tree installation, a minimum of 24 inches of soil depth and 25 square feet of open soil area (total of 50 cubic feet) must be provided.

(2) For each large or medium tree installation, a minimum of 36 inches of soil depth and 160 square feet of open soil area (total of 480 cubic feet) must be provided.

(3) Except as provided in this section, trees may share open soil areas.

(4) Except as provided in this section, large trees and medium trees must be planted a minimum of four feet from pavement.

(5) The planting areas must have native soils, prepared soils, or structural soils, and may include permeable pavement, sidewalk support, and soil cells.

(6) Required areas for plant materials must be protected from vehicular traffic through the use of concrete curbs, wheel stops, or other permanent barriers.

(7) Planters may be used to satisfy the requirements of this article provided that the soil requirements in Section 51A-10.104(b) are met.


(d) Legacy tree soil and planting area requirements.

(Refer to 10.135 for alternative methods of replacement)

(1) Except as provided in this paragraph, large legacy trees must be planted in a minimum 500 square foot open soil area with a minimum average soil depth of 36 inches (1500 cubic feet) per tree. For locations with shallow soils of less than 36 inches in average depth, the open soil area must be a minimum 750 square feet.

(2) Except as provided in this paragraph, medium legacy trees must be planted in a minimum 400 square foot open soil area with a minimum average soil depth of 36 inches (1200 cubic feet) per tree. For locations with shallow soils of less than 36 inches in average depth, the open soil area must be a minimum 750 square feet.

(3) Legacy trees must be a minimum of 30 feet measured horizontally from the closest point of a building or other structure on the property or an adjacent property at the time of installation.

(4) Legacy trees may not share required minimum open soil areas with large or medium trees.


(e) Alternative planting area requirements.

(1) Planting areas in an urban streetscape or located above underground buildings or structures must have the following open soil area depths and dimensions:

(A) For each small tree installation, a minimum of 30 inches of soil depth and 25 square feet of open soil area (total of 62.5 cubic feet)

(B) For each large or medium tree installation, a minimum of 36 inches of soil depth and 25 square feet of open soil area and a combination of open soil area, covered soil area, and root paths for a minimum of 240 cubic feet of soil volume. Large or medium trees planted in less than 480 cubic feet of soil volume do not count as replacement trees for purposes of Division 51A-10.1300

(2) Trees may share open soil areas.


(f) Waiver.

The building official may waive the minimum open soil and planting area requirements if a landscape architect certifies that

(1) the proposed alternative soil depths and dimensions are sufficient to support the healthy and vigorous growth of the plant materials affected;

(2) the depth to impermeable subsurface prohibits minimum soil depth requirements; or

(3) that the proposed structural soils or suspended paving system are sufficient to support the healthy and vigorous growth of the plant materials.


(g) Adequate space.

All required trees must be planted in adequate space to allow unobstructed growth to maturity.


(h) Tree locations.

(1) In general.

All required trees must be located a minimum distance of:

(A) two feet from side yard and rear yard property boundaries;

(B) 20 feet from traffic signs and light poles;

(C) two-and-one-half feet from pavement; and

(D) five feet from electrical transmission boxes, fire hydrants, in-ground or above-ground utility access, underground local utility lines, and water meters.


(2) Small trees.

Small trees must be located a minimum distance of:

(A) five feet from buildings; and

(B) 10 feet from all other trees.


(3) Medium trees.

Medium trees must be located a minimum distance of:

(A) 12 feet from buildings;

(B) 10 feet from small trees;

(C) 20 feet from other medium trees;

(D) 20 feet from large trees; and

(E) 15 feet from the closest point of an overhead electric line.


(4) Large trees.

Large trees must be located a minimum distance of:

(A) 15 feet from buildings;

(B) 10 feet from small trees;

(C) 20 feet from medium trees;

(D) 25 feet from other large trees; and

(E) 20 feet from the closest point of an overhead electric line.


(5) Legacy trees.

Legacy trees must be located a minimum distance of 30 feet from the closest point of an overhead electric line.


(6) Measurement.

For purposes of this subsection, all distances are measured horizontally from the center of the tree trunk.

PLANT SMART - ONCOR - Information on recommended planting distances for small, medium, and large trees. The regulations in this ordinance provide a separate minimum distance standard.