Street Trees

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WHEN ARE STREET TREES REQUIRED?
Street trees are typically required when:

  • Associated with new commercial or industrial development as described in the tables of TMC 13.06.502.E.6;
  • Associated with a site redevelopment that includes a remodel and/or addition within a two-year period whose cumulative value is 50% or greater than the value of the existing development or structure;
  • Associated with a Preliminary Plats or Short Plats of 5 or more lots;
  • Associated with residential small-lot development
  • Constructing new permanent roadways;
  • Alterating the the width of existing permanent roadways;
  • Constructing new sidewalk;
  • Replacing more than 50% of an existing sidewalk along a site’s frontage (when 50 linear feet or more is being constructed)

TREE SELECTION AND INSTALLATION
The Urban Forest Manual (UFM) provides best management practices for plant selection, design, installation, care, and other specifications.

Species shall be selected to avoid or minimize potential conflicts with infrastructure and utilities. Trees under power lines shall have a maximum mature height (at 25 years of age) not greater than 25 feet. This chart includes a reference to maximum mature height of approved street trees.

Street trees shall, when possible, be planted within the right-of-way adjacent to the curb and between the pedestrian lane/sidewalk and curb. When this is not possible or a different location would better achieve the intent, street trees may be located elsewhere within the right-of-way, including behind the sidewalk, in street medians, parking strips or bulbouts. If neither of these preferred locations is possible, such as when existing infrastructure prevents trees from being planted within the right-of-way, trees located within 10 feet of the right-of-way may be counted as street trees.

New tree plantings shall be a minimum of 2 feet from pavement (curb, sidewalk, alley, street), 5 feet from a structure, 5 feet from underground utilities, and 10 feet from light standards. Distances may be reduced, with staff approval, upon a demonstration that the species selected will not cause infrastructure conflicts.

For projects that involve the planting of between four and ten trees, at least two different kinds (Genera) of trees shall be included. For projects involving the planting of more than ten trees, at least three different kinds (Genera) of trees, and a mixture of tree types (evergreen and deciduous) shall be included. For projects that involve planting more than twenty-five trees, no more than 25 percent shall be from one Genera and a minimum of 20 percent must be evergreen.

TREE SIZE
Street trees are categorized as Large, Medium or Small as determined by the Canopy Factor. The Canopy Factor for approved trees within the City is included within this chart, and calculated using the following formula:

(mature height in feet) x (mature crown spread in feet) x (growth rate number) x 0.01 = Canopy Factor

The growth rate number is 1 for slow growing trees, 2 for moderately growing trees, and 3 for fast growing trees.

(A) Large Trees = Canopy Factor greater than 90

(B) Medium Trees = Canopy Factor from 40 to 90

(C) Small Trees = Canopy Factor less than 40

Trees provided to meet the landscaping requirements shall be consistent with the following size requirements at the time of planting:

  • For deciduous trees, at least 50 percent of the trees provided shall be a minimum 2-inch caliper at the time of planting, with the remaining deciduous trees a minimum 1½-inch caliper.
  • For evergreen trees, at least 50 percent of the trees provided shall be a minimum of 6 feet tall, with the remaining evergreen trees a minimum of 5 feet tall at the time of planting. Evergreen trees provided to meet these requirements shall also be species with the ability to develop a minimum branching width of 8 feet within 5 years.

EXISTING TREES
Existing trees which comply with the applicable requirements do count towards the required landscape plantings. Trees also need to be protected during construction work. Before site work begins, guards are required to be placed around trees and shrubs located within the limits of streets and alleys to effectually protect existing trees and shrubs from damage or injury. If retained trees are damaged during or after construction, replacement shall be based upon the same ratios.

The following tree planting credits are available for existing trees, provided a Certified Arborist’s Report determines that the tree(s) is healthy and can be saved through construction activities.

A Certified Arborist’s Report and Tree Protection Plan consistent with the requirements outlined in the UFM showing existing trees, existing and proposed grading, new development on the site (such as buildings, utilities, etc.), measures taken to protect existing trees and any new trees that will be planted on the site shall be submitted if trees are being retained for credit. To be eligible for this credit, trees must be healthy and have minimal serious defects or defects that cannot be mitigated by proper pruning as indicated on the Arborist Report and Tree Protection Plan. Trees shall count according to their species as Small, Medium and Large Trees.

  1. One required tree for every retained tree of at least equal size;
  2. Two required trees for every retained tree that is 8 inches to 20 inches in DBH;
  3. Three required trees, for every retained tree 20 inches to 32 inches in DBH;
  4. Four required trees, for every retained tree over 32 inches in DBH.

PERMITTING
The planting of trees within the City right-of-way requires approval, either through a Street Tree Permit, or a Work Order Permit. The proposed trees may also need to be shown as part of a Site Development and/or Building Permit plan set as a reference to demonstrate that the proposal is meeting the applicable street tree requirements.

Developments with 500 square feet or more of landscaped area, and/or developments that include new permanent roadways that trigger the need for 10 or more street trees are required to submit a Landscape Management Plan, prepared by a Registered Landscape Architect, Certified Landscape Technician, or Certified Professional Horticulturalist, as listed in TMC 13.06.502.C.

RESOURCES