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For the purposes of this chapter, the words and phrases below shall be defined as set forth herein. If not defined in this chapter, the definitions provided in Chapter 18.20 CMC shall be applicable. In the event of a conflict between the definitions set forth in this chapter and the definitions set forth in Chapter 18.20 CMC, the definitions in this chapter shall govern. Words used in the singular include the plural, and words used in the plural include the singular. Words used in the masculine gender include the feminine gender and vice versa.

“At-risk tree” means any significant tree determined by a qualified arborist through a tree risk assessment as a likely source of imminent danger to life or property, or determined to have a structural defect, combination of defects, or disease, resulting in the loss of a major structural component of that tree in a manner that is likely to:

(1) Damage a residential or accessory structure, place of employment or public assembly, or approved parking for a residential structure or accessory structure or place of employment or public assembly;

(2) Damage an approved road or utility facility; or

(3) Prevent emergency access by first responders.

“Best management practices (BMPs)” means adherence to tree health care standards detailed in the current edition of the American National Standards Institute (ANSI) A300 and the current edition of the International Society of Arboriculture (ISA) BMPs including the special companion publication to the ANSI A300, Best Management Practices for Utility Pruning of Trees.

“Brushing” means an allowed practice of removing ground cover, shrubs and vegetation not defined as a tree to create better visibility on a site for purposes of public safety, surveying or marketing.

“Caliper” means the diameter of a tree trunk, applied only to new or replacement nursery-grown trees, which shall be measured six inches above the ground for trees with a caliper up to and including four inches. For trees with a caliper greater than four inches, measured six inches above the ground, the caliper shall be measured at 12 inches above the ground.

“Canopy” means the part of the tree crown composed of leaves and small twigs or the collective branches and foliage of a group of trees’ crowns.

“City” means the City of Covington, King County, Washington.

“Clearing” or “land clearing” for purposes of this chapter means the direct and indirect removal of trees, including topping and limbing, from any public or private undeveloped, partially developed, or developed lot, public lands, public right-of-way, or utility easement. This shall also include any destructive or inappropriate activity applied to a tree that will result in its death or effectively destroy the functionality. “Clearing” shall not include landscape maintenance, brushing, or pruning consistent with accepted horticultural practices which does not impair the health, survival, or function of trees.

“Critical root zone (CRZ)” means the International Society of Arboriculture (ISA) definition of CRZ, which is an area equal to a one-foot radius from the base of the tree trunk for each one inch of the tree diameter at four and one-half feet above grade (referred to as diameter at breast height). Example: A 24-inch-diameter tree at four and one-half feet above grade would have a critical root zone radius (CRZ) of 24 feet. In this example, the total protection zone, including trunk, would be 50 feet in diameter.

“Crown” means that portion of the tree stem that is occupied by branches with live foliage.

“Development” is the division of a parcel of land into two or more parcels; the construction, reconstruction, conversion, structural alteration, relocation, or enlargements of any structure; any mining, excavation, landfill, stockpiling, clearing or land disturbance; and any use or extension of use of the land.

“Diameter breast height (DBH)” is a tree’s diameter in inches at four and one-half feet above the ground at the lowest point surrounding the trunk, and is used to measure existing trees on a site. Where a tree splits into several trunks below DBH, the DBH for the tree is the square root of the sum of the DBH for each individual trunk squared (example with three trunks: DBH = square root of [(stem 1)2 + (stem 2)2 + (stem 3)2]).

“Dripline” of a tree is the outermost circumference of the tree canopy, from which water drips onto the ground. The “dripline area” is taken to include the soil and roots that lie within that circumference.

“Excessive canopy raising” means the excessive removal of lower canopy limbs (especially on conifers), by reducing the live crown ratio (the ratio of live crown to total tree height) lower than 60 percent of the original crown. Excessive canopy raising can pose a high risk. A tree’s hinge point changes under wind load forces. Articulation occurs significantly higher on the upper stem not accustomed to these load forces, which significantly increases chances of upper stem failure.

“Ground cover” means any living plant material that is normally terrestrial and grows low to the ground, as well as other small trees less than four inches in DBH and not defined as a tree. Ground covers are intended to stabilize soils and protect erosion.

“Heritage tree(s)” means a significant tree that is equal to or greater than 32 inches DBH.

“Imminent danger” means a condition which could cause serious or life-threatening injury or death at any time.

“Invasive tree” is a species that was introduced by humans to locations outside of the tree’s native range that spread and persist over large areas. Invasive species negatively impact natural ecosystems by displacing native species, reducing biological diversity, and interfering with natural succession. Tree species known to be invasive in the Pacific Northwest are listed below. The City may determine that additional tree species should be classified as invasive if the species clearly exhibits the detrimental characteristics of invasive species.

Common Name

Species Name

Norway maple

Acer platanoides

Sycamore maple

Acer pseudoplatanus

Horse chestnut

Aesculus hippocastanum


Ailanthus altissima

European white birch

Betula pendula

English/European hawthorn

Crataegus monogyna

English holly

Ilex aquifolium

Princess tree

Paulownia tomentosa

White poplar

Populus alba

Sweet cherry

Prunus avium

Cherry laurel

Prunus laurocerasus

Portugal laurel

Prunus lusitanica

Black locust

Robinia pseudoacacia

European mountain ash

Sorbus aucuparia

Siberian elm

Ulmus pumila

“ISA” means International Society of Arboriculture.

“ISA TRAQ,” tree risk assessment qualified, is a designation administered by the International Society of Arboriculture.

“Landmark tree” means a significant tree that is equal to or greater than 22 inches DBH and less than 32 inches DBH.

“Landscape architect” means an individual currently licensed by the State of Washington as a landscape architect.

“Land use application” means an application, supplied by the Department, which must be completed and accompany any submittal packet for the desired development permit.

“Limits of disturbance” means the boundary between the area of minimum protection around a tree and the allowable site disturbance as determined by a qualified arborist.

“Multi-stemmed tree” means a tree that has one trunk at ground level but that splits into two or more trunks above ground level. Trees whose trunks diverge below ground level are considered separate trees.

“Normal and routine maintenance” means the standard practice and care of trees and vegetation normally required to maintain life, including watering, feeding or fertilizing, spraying, pruning and trimming according to best management practices, and removing of dead or unhealthy branches.

“Nuisance tree” is a species that is known to be weak-wooded and unstable, or one that exhibits other traits that render it prone to creating nuisance conditions for persons and property located in close proximity to such trees. Tree species categorized as nuisance trees in the City are listed below. The City may determine that additional tree species should be classified as nuisance trees if the species clearly exhibits the detrimental characteristics of nuisance species.

Common Name

Species Name

Red alder

Alnus rubra

Black cottonwood

Populus trichocarpa

“Protected tree” means a tree and associated understory vegetation that are identified for retention and protection on an approved tree protection and replacement plan and/or permanently protected by easement, tract, or covenant restriction.

“Pruning” means cutting back of limbs larger than one and one-half inches in diameter.

“Qualified arborist” is an individual who is a certified professional with academic and field experience that makes them a recognized expert in urban forestry and tree protection during development. A qualified arborist shall be a member of the International Society of Arboriculture (ISA) and/or the Association of Consulting Arborists and shall have specific experience with urban tree management in the State of Washington. Additionally, the qualified arborist shall be a certified arborist or board-certified master arborist, as certified by the ISA, and be ISA tree risk assessment qualified and have the necessary training and experience to use and apply the appraisal methodology prescribed in the current edition of the ISA Plant Appraisal Guide.

“Remove” or “removal” is the act of removing a tree by digging up, cutting down, or any act which causes the tree to die within a period of three years, including, but not limited to: damage inflicted on the root system by machinery, storage of materials, or soil compacting, or changing the ground level in the area of the tree root system; damage inflicted on the tree permitting infections or infestation; excessive pruning; topping; paving with concrete, asphalt, or other impervious material within the dripline; or any other action which is deemed harmful to the tree.

“Risk” in the context of trees is the likelihood of a tree failure occurring combined with the severity of the associated consequences of such failure to a target.

“Significant tree,” for purposes of this chapter, means a tree that is in a healthy condition, not a nuisance tree, and is a noninvasive species, which is:

(1) Any deciduous tree that is 12 inches or more in diameter at DBH;

(2) Any coniferous tree that is six inches or more in diameter at DBH;

(3) A required replacement tree of any size;

(4) Any tree that is six inches or more at DBH that is located within critical areas or the shoreline jurisdiction unless the tree is determined to be an at-risk tree;

(5) Any landmark trees; or

(6) Any heritage trees.

“Target” or “risk target” means people, property, or activities that could be injured, damaged, or disrupted by a tree.

“Tree” means any woody plant characterized by one main stem or trunk and many branches, or multi-stemmed trunks, which have a diameter individually or cumulatively of four inches DBH or larger.

“Tree appraisal” is a method of calculating the value of a tree, which shall be based on the “trunk formula method” as set forth in “The Guide for Plant Appraisal” authored by the Council of Tree and Landscape Appraisers.

“Tree enhancement plan” means a plan prepared by a qualified arborist and required of all commercial or industrial properties when any tree removal or tree clearing takes place. The tree enhancement plan shall combine tree retention and preservation of existing trees pursuant to CMC 18.45.080(1) with the tree replacement and replanting requirements of CMC 18.45.080(2). The tree enhancement plan shall incorporate trees in as many areas as feasible such as tree tracts, boundary trees, perimeter landscaping, parking lot landscaping, street and driveway trees, facade landscaping, or other viable stands of trees, considering the type of commercial or industrial development.

“Tree harvesting” means tree logging, felling, cutting, or taking of trees, standing or down, on privately or publicly owned land for sale or for commercial, industrial, or other use, governed under RCW 76.09.470.

“Tree inventory” means a detailed list of all trees of four inches DBH or larger, located on a site for which a tree permit is required, and which is prepared by a qualified arborist. A tree inventory shall be included on a site plan drawn to scale, and provide the number, size, approximate height, specific location, and tree species of all trees of four inches DBH or larger, with a summary of all significant trees in sufficient detail for the City to review.

“Tree owner” means the owner of the real property where 51 percent or more of the diameter of the trunk of the tree at ground level is located.

“Tree risk assessment” means the systematic process conducted by a qualified arborist or tree risk assessor to identify, analyze, and evaluate tree risk. Tree risk assessment shall be conducted in accordance with the American National Standards Institute (ANSI) A300 and the current edition of the International Society of Arboriculture (ISA) BMPs: Tree Assessment.

“Tree risk management” means the application of policies, procedures and practices used to identify, evaluate, mitigate, monitor, and communicate tree risk.

“Tree topping” is an extreme form of crown reduction that removes whole tops of trees or large branches and/or trunks from the tops of trees, leaving stubs or lateral branches that are too small to assume the role of a terminal leader, which is the vertical stem at the top of the trunk. Tree topping severely cuts back large trees to a predetermined size in a manner that:

(1) Leaves large exposed wounds that can become infested;

(2) Ruins tree structure;

(3) Removes too much foliage, disrupting the tree energy storage;

(4) Stimulates vigorous new growth, which is prone to breakage;

(5) Increases tree maintenance costs; or

(6) Destroys a tree’s appearance and value.

“Tree tract” is a separate portion of land, specifically set aside for the preservation, retention or protection of existing trees or the planting of new trees to maintain a beneficial tree canopy in a subdivision or on a development site and that meets minimum tree preservation requirements of this code. The tree tract shall be a separate designated lot(s) or tract(s) shown on the subdivision plat map, site development plan, or binding site plan and shall be recorded on the property title with the King County Recorder’s Office with appropriate description of purposes and restrictions. Restrictions applied to the tree tract will reserve the tract for the protection and preservation of trees in perpetuity. Tree tracts can be used for other open space uses when such use is compatible with trees and will not impact tree health. The tract shall be dedicated to, and owned and maintained by, the home owner(s), property owners association, or comparable entity.

“Understory vegetation” means small trees, shrubs, and ground cover plants growing within the dripline or critical root zone (CRZ) of a significant tree.

“Viable (tree)” means a significant tree that a qualified arborist has determined to be in good health with a low risk of failure, is relatively windfirm if isolated or exposed, is a species that is suitable for its location, and is therefore worthy of long-term retention. (Ord. 02-21 § 2 (Exh. A); Ord. 05-20 § 2 (Exh. A); Amended at request of department 2/08; Ord. 04-08 § 2)