8.10.020 Definitions | Atherton Municipal Code

8.10.020 Definitions.

As used in this chapter:

A. “Appraised value” means the value of a tree as determined by the town arborist using the most recent edition of the Guide for Plant Appraisal, published by the Council of Tree and Landscape Appraisers for any procedure or requirement as specified in this chapter.

B. “Building official” means the director of building and planning or their designee.

C. “Certified arborist” means an individual possessing a current International Society of Arboriculture arborist certification.

D. “Cutting” means the detaching or separating from a protected tree any substantial limb, branch, or root.

E. “Dead or dangerous” tree means dead or dying trees, dead parts of live trees, or unstable live trees (due to structural defects or other factors) that are within striking distance of people or property, as determined by the town arborist.

F. “Development project” means any construction activity that requires a demolition, grading, drainage, building, or landscape permit.

G. “Diameter at breast height” is the measurement of truck diameter taken at four and one-half feet (or fifty-four inches) above the natural grade. The diameter may be calculated by using the following formula: DBH equals circumference at four and one-half feet divided by 3.142.

H. “Disfavored” tree means any of the following species:

1. Acacia baileyana—Bailey acacia.

2. Acacia decurrens—Green wattle.

3. Acacia melanoxylon—Black acacia.

4. Ailanthus altissima—Tree of heaven.

5. Albizia julibrissin – Mimosa.

6. Any species of eucalyptus.

7. Pinus radiata—Monterey pine.

It is strongly recommended that these trees not be planted in the town of Atherton.

I. “Disturbance or damage to a heritage tree” refers to demolition, construction, subterrain grading activities, landscaping improvements, other development activities and/or any other action, as determined by the building official or town arborist, which may cause damage to the health of a heritage tree, including any heritage tree within fifteen feet of the subject property line. Examples include, but are not limited to, excessive pruning, topping, cutting, girdling, poisoning, over-watering, unauthorized relocation or transportation of a heritage tree, trenching, excavating, altering the grade, compaction or paving near the tree, and screwing anything into the heritage tree (e.g., installing a tree house).

J. “Dripline” means the outermost circumference of the heritage tree’s canopy, from which water drips to the ground. When depicted on a map, the dripline will appear as an irregularly shaped circle that follows the contour of the heritage tree’s branches as seen from overhead.

K. “Excessive pruning” is considered disturbance and/or damage to the heritage tree and is prohibited unless approval is granted by the town arborist prior to initiating the work. The percentage and distribution of foliage to be removed shall be adjusted according to the plant’s species, age, health, and site. Topping and lion’s tailing shall be considered prohibited pruning practices for heritage trees. ANSI A300 (Part 1)-2017 is required to be followed.

1. Lion’s tailing—The removal of interior lateral branches that results in a concentration of growth at the branch ends shall be considered an unacceptable practice.

2. Topping—Is the reduction of tree size by cutting to stubs without regard for long-term tree health or structural integrity.

L. “Heritage tree” means:

1. A tree meeting any of the following conditions:

a. An oak tree (Quercus lobata, Quercus agrifolia or Quercus douglasii) located anywhere on a lot, that has a minimum trunk circumference of forty-eight inches or diameter of fifteen and two-tenths inches, as measured at fifty-four inches above the natural grade.

b. A tree located outside the main buildable area that has a minimum trunk circumference of forty-eight inches or diameter of fifteen and two-tenths inches, as measured at fifty-four inches above the natural grade.

c. A split trunk or low-branching tree located outside the main buildable area that has a minimum trunk circumference of forty-eight inches or diameter of fifteen and two-tenths inches, as measured at fifty-four inches above the natural grade. If the trunk branches or splits below this point, the smallest circumference or diameter below the lowest branch shall be measured.

d. A multi-stemmed tree located outside the main buildable area that has a total trunk circumference of forty-eight inches or total diameter of fifteen and two-tenths inches when calculated as follows: considering all the branches at fifty-four inches above natural grade, add the measurement of the largest branch to one-half the measurement of each additional branch. Reference the Guide for Plant Appraisal authored by representatives to the Council of Tree and Landscape Appraisers.

2. A tree so designated by the city council, based upon findings that the particular tree is unique and of importance to the public due to its unusual age, appearance, location or other factors;

3. A tree that has been removed without a permit that cannot be measured pursuant to subsection (L)(1) of this section will be presumed to have been a heritage tree if it meets any of the following criteria:

a. The tree has a stump of at least seventeen and three-quarters inches in diameter as measured at the natural grade;

b. The tree is a native oak with a minimum of seventy-five years of age;

c. The tree is any other species of tree with a minimum of forty-five years of age, unless otherwise specified in this section;

d. The tree is a redwood with a minimum age of thirty years of age;

e. In the absence of remaining physical evidence, photographs and other circumstantial evidence of characteristics, including but not limited to height, canopy dimensions, and similar trees in the immediate area may be used to create a presumption that the tree was a heritage tree.

Notwithstanding the foregoing, anyone may rebut this presumption by providing substantial evidence to the contrary to the satisfaction of the town arborist.

4. Exemptions. The trees listed below shall not be classified as heritage trees, regardless of their size or age, nor shall they be used for replacement plantings:

a. Acacia baileyana—Bailey acacia.

b. Acacia decurrens—Green wattle.

c. Acacia melanoxylon—Black acacia.

d. Ailanthus altissima—Tree of heaven.

e. Albizia julibrissin—Mimosa.

f. Eucalyptus—Any species.

M. “Injury” means bruising, scarring, tearing or breaking of roots, bark, trunk, branches or foliage, the application of herbicide or poisoning, natural issues such as weather, insects and animals, or any other action that is likely to cause the death of or irreparable damage to a heritage tree.

N. “Irreparable damage” means any action undertaken by a person, as defined in this section, foreseeably leading to the death or permanent injury of the heritage tree, or which places the tree in a hazardous condition or an irreversible state of decline within one year from when action was taken. This includes, but is not limited to, cutting, topping, girdling, poisoning, trenching or excavating within the tree protection zone (TPZ), altering the grade, paving in excess of fifty percent of the dripline, excessive watering of oak trees, and excessive pruning.

O. “Main buildable area” is the area defined by applicable setbacks in which primary development is allowed under the Atherton Municipal Code.

P. ”Natural grade” is the grade, as determined by the town arborist, unaffected by construction techniques such as fill, landscaping, or a berm.

Q. “Person” means anyone having a property interest in a heritage tree. Property owners are liable under this chapter for all violations, whether they were done directly by the property owner or someone acting on their property with or without specific authorization, including but not limited to contractors, gardeners, and maintenance persons; provided, however, it shall not include persons acting under a right of easement without the direction of the property owner (e.g., PG&E).

R. “Project arborist” means a private certified arborist retained by the property owner for the purpose of overseeing on-site activity involving the welfare of the heritage trees to be retained.

S. “Pruning” means the selective removal of plant parts to meet the specific goals and objectives of ANSI A300 (Part 1).

T. “Remove” or “removal” means any act that leaves the tree unviable, removes it from its location, relocates it from its location, or renders it “dead or dangerous” as determined by a certified arborist and approved by the town arborist.

U. “Street heritage tree” means any heritage tree growing within the street right-of-way, outside of private property and adjacent to the applicant’s property.

V. “Town arborist” is an arboricultural professional working for the town of Atherton, and his or her designee.

W. “Tree appraisal” means a method of determining the monetary value of a heritage tree (herein “appraised value”), using its pre-existing condition if it has been removed or damaged. A project arborist shall determine the appraised value as part of the required tree protection and preservation plan.

X. “Tree preservation area” means the area outside the buildable area of the lot, as defined in Section 17.60.020.

Y. “Tree protection zone (TPZ)” is, unless otherwise specified by a project arborist or town arborist, the designated protection area sufficiently large enough to protect a heritage tree and its roots from disturbance and/or damage as defined in subsection I of this section. The TPZ shall be determined and shall meet all provisions as detailed in the town’s current tree preservation standards and specifications document and may extend onto neighboring properties. (Ord. 641 § 1 (Exh. A (part)), 2020; Ord. 533 § 1, 2002; Ord. 462 § 1(B), 1991; Ord. 444 § 2, 1989)