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An ordinance to amend Title 17 of the Metropolitan Code of Laws, the Zoning Ordinance of the Metropolitan Government of Nashville and Davidson County, to amend Chapters 17.04 and 17.28.065, Pertaining to Trees, all of which is described herein (Proposal No. 2024Z-019TX-001).
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WHEREAS, tree protection during construction prevents soil compaction, that causes loss of air and water availability to roots, and reduces tree mortality; and
WHEREAS, NashvilleNext encourages the retention and expansion of the existing urban tree canopy cover; and
WHEREAS, current industry standard related toward protection of trees during construction utilizes critical root zone rather than dripline; and
WHEREAS, other local governments within Tennessee including Chattanooga, Franklin, Knoxville, Murfreesboro, and Williamson County require a critical root zone to determine the area required for tree protection during construction; and
WHEREAS, peer cities such as Denver, CO, Atlanta, GA, and Charlotte, NC require critical root zone to determine the area required for tree protection during construction; and
WHEREAS, established trees provide benefits to native wildlife, reduction in stormwater runoff, reduce the urban heat island effect, and aid in air purification.
NOW, THEREFORE, BE IT ENACTED BY THE COUNCIL OF THE METROPOLITAN GOVERNMENT OF NASHVILLE AND DAVIDSON COUNTY:
Section 1. That Section 17.04.060 of the Metropolitan Code of Laws is amended by adding the following definitions in alphabetical order:
“Critical root zone” (CRZ) means the area of soil around a tree where the minimum area of roots considered critical to the structural stability and health of the tree are located. The CRZ is to be determined by measuring one foot per each inch of tree diameter at breast height, with a minimum of ten feet.
“Structural root zone” (SRZ) means the area of soil around a tree where the minimum area of roots required to maintain the structural stability of the tree are located. The SRZ is to be determined by measuring one-half foot per each inch of tree diameter at breast heigh, with a minimum of six feet.
Section 2. That Section 17.28.065.D of the Metropolitan Code is deleted in its entirety and replaced with the following:
D. Protection of trees during development activities.
1. General. To assure the health and survival of retained trees, the following kinds of tree injuries shall be prohibited during all development activities:
a. Mechanical injuries to roots, trunk and branches;
b. Injuries by chemical poisoning or soil flooding;
c. Injuries by grade changes;
d. Injuries by excavations, trenching, or soil compaction; and
e. Injuries by paving or other soil covering or material storage.
2. Tree Protection Zone. A tree protection zone shall be established around each retained tree, tree preservation area, and natural area, as required, as shown in Figures 17.28.065.D. The tree protection zone shall be comprised of two distinct areas.
a. The Structural Root Zone (SRZ) is to be determined by measuring one-half foot per each inch of tree diameter at breast height. If the SRZ is less than six feet, then the SRZ shall be a minimum of six feet.
1. No area within the SRZ shall be disturbed or modified.
b. The Critical Root Zone (CRZ) shall be directly adjacent to the SRZ and is to be determined by measuring one foot per each inch of tree diameter at breast height. If the CRZ is less than ten feet, the protection zone shall be a minimum of ten feet.
1. The configuration of the CRZ may be adjusted up to 20% upon approval of Planning or Codes Staff, as applicable. This may include pre-existing site conditions such as structures, foundations, or utilities. It may also include tree characteristics such as species and tolerance to stress and construction activities.
Figure 17.28.065.D
3. Development Prohibited within the Tree Protection Zone. All development activities shall be prohibited within the tree protection zone provided for any protected trees, including any construction of buildings, structures, paving surfaces, and storm-water retention/detention ponds. All temporary construction activities shall also be prohibited within tree protection areas, including all digging, concrete washing, storage of construction material, and parking of construction vehicles.
4. Development Prohibited within the Natural Areas. All development activities shall be prohibited within any tree protection zone established for a natural area preserved in open space pursuant to Section 17.12.090 Conservation Development.
5. Fencing of Tree Protection Zone or Natural Area Open Space. Prior to the commencement of grading or construction, the developer shall enclose the entire tree protection zone or natural area open space within a fence as follows:
a. Chain link fencing at least four feet in height and secured using appropriate posts spaced not more than ten feet apart.
b. During construction, each tree protection zone shall be identified with temporary signs to clearly demarcate the extent of the zone. Signs shall be made of a recyclable material and installed on the tree protection fence, visible on all sides of the fenced-in area at a rate of at least one sign for every 100 linear feet. The size of each sign must be a minimum of two feet by two feet and shall contain the following language in English and Spanish: “TREE PROTECTION ZONE: KEEP OUT. ZONA DE LA PROTECCION DEL ARBOL. NO SE PERMITE ENTRAR". The owner shall maintain the protective barrier during the entire construction process and shall make certain that it is observed by the contractor.
c. The location of tree fence shall be coordinated with any required silt fence. Tree fence shall be located toward the tree with the silt fence outside to prevent erosion inside a tree preservation area.
d. Tree fence shall be maintained until applicable Staff has completed a final inspection and released the project.
6. Tree Protection Zone Encroachment.
a. Utility Excavation. Excavating or trenching shall not be permitted within the tree protection zone. Utilities shall be located away from the tree protection zone. If trees are damaged or destroyed during excavation or trenching, the damaged or destroyed trees shall be replaced in accordance with section 17.28.065. Placing of utilities through the use of tunnelling may be permitted with approval from Planning or Codes Staff, as applicable. Applicable Staff may propose rules and regulations governing and/or limiting utilities in the tree protection zone.
b. Sodding and Groundcover. Placement of sod or other groundcovers and the preparation of the ground surface for such covers shall be permitted within the tree protection zone, so long as tree roots in the area are not damaged by the method of preparation.
c. Tree Care. Pruning of branches or roots or removal of dead limbs on a tree/s located within the tree protection zone shall be permitted. An ISA certified arborist shall be required to supervise all operations related towards tree care. All tree care activities shall be done without the use of heavy machinery or vehicles within the tree protection zone. Prior to tree care activities, Planning or Codes Staff, as applicable, shall be informed in writing.
7. Inspections.
a. All retained trees, pursuant to a tree survey, shall be inspected by applicable Staff one year following completion of the project to ensure that they are surviving in a healthy condition.
b. Retained trees which require replacement shall be determined by Planning or Codes Staff, as applicable.
c. Any retained tree which is damaged during construction, or with damage occurring as a result of construction, shall be replaced as provided in Section 17.28.065. Trees planted to replace damaged or removed protected trees shall not be counted toward the site TDU.
d. The owner shall be notified in writing of Staff’s determinations.
8. Tree Protection Violations.
a. Civil penalties shall be assessed in the event of injury, damage, or removal of trees within the tree protection zone. Penalties shall be assessed at $50 per violation, per day. Each tree, in which a violation occurred, shall be considered an individual violation. No notice of violation shall be required prior to the assessment of civil penalty pursuant to this subsection.
b. In the event disturbance occurs, all trees within the Tree Protection Zone shall no longer be counted for TDU requirements unless an assessment has been provided by an ISA Certified Arborist and approved by Applicable Staff.
c. Any injury, damage, or removal of tree shall be determined as removal without a permit and shall be replanted in accordance with 17.28.065.
d. A site shall be considered in compliance with the submittal of a revised landscape plan and planting deadline approved by Planning or Codes Staff, as applicable. In the event that replacement trees are not planted by the agreed-upon deadline, civil penalties previously assessed shall resume until final inspection of replacement trees.
Section 2. The Metropolitan Clerk is directed to publish a notice announcing such change in a newspaper of general circulation within five days following final passage.
Section 3. This Ordinance shall take effect upon publication of above said notice announcing such change in a newspaper of general circulation, the welfare of The Metropolitan Government of Nashville and Davidson County requiring it.
Agenda Analysis
Analysis
This ordinance amends Sections 17.04.060 and 17.28.065 of the Metropolitan Code to add definitions for ‘Critical root zone’ and ‘Structural root zone’ and to modify the standards for the protection of trees during development activities.
The ordinance proposes to define ‘Critical root zone’ as “the area of soil around a tree where the minimum area of roots considered critical to the structural stability and health of the tree are located. The CRZ is to be determined by measuring one foot per each inch of tree diameter at breast height, with a minimum of ten feet.” ‘Structural root zone’ would be defined as “the area of soil around a tree where the minimum area of roots required to maintain the structural stability of the tree are located. The SRZ is to be determined by measuring one-half foot per each inch of tree diameter at breast heigh, with a minimum of six feet.” Currently, there are no definitions for ‘Critical root zone’ or ‘Structural root zone’ in Title 17.
The ordinance also proposes to modify the standards for the protection of trees during development activities by changing the measurement of determining the tree protection zone from the drip line, which is based on the tree canopy, to the critical root zone and structural root zone, which are based on measurements of the tree trunk diameter at breast height, as well as prohibiting trenching within the tree protection zone. Additionally, the ordinance would clarify that there are civil penalties for violations of tree protection standards during development activities. The penalties include a $50 fine per violation, per day, with each damaged tree being considered a separate violation, and a required replanting of any damaged or removed tree.
The Planning Commission recommended approval of this item (7-0) at its October 24, 2024, meeting.
The Council adjourned pursuant to Robert’s Rules of Order Rule 21 prior to consideration of this legislation at the February 18, 2025 Council meeting. Pursuant to Robert’s Rules of Order Rule 21, remaining business is immediately resumed at the next meeting at the point it left off.