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11.50.050 On-Site Tree Density Standards.

(Amended by Ordinance Nos. 187675, 188278 and 188959, effective May 24, 2018.)

A.  Where these Regulations Apply. This Section applies to sites within the City of Portland and the County Urban Pocket Areas. Unless exempted in Subsection 11.50.050 B., the following are subject to the On-Site Tree Density Standards:

1.  New Development;

2.  Exterior alterations to existing development with a project valuation that is more than the threshold stated in Subsection 33.258.070 D.2.a.

B.  Exemptions.

1.  The following development activities are exempt from the on-site tree density standards:

a.  A specific condition of land use review approval exempts the site from these density standards;

b.  The site is within the Portland International Airport Plan District or Cascade Station/Portland International Center Plan District and is subject to the Airport Landscape Standards; see Title 33, Planning and Zoning.

c.  On portions of sites located within an IH, IG1, EX, or CX zone.

d.  Work conducted under Demolition, Site Development, Septic, Plumbing or Zoning Permits.

2.  Sites with the following primary uses are exempt from the on-site tree density standards:

a.  Railroad Yards;

b.  Waste Related;

c.  Agriculture;

d.  Aviation and Surface Passenger Terminals;

e.  Detention Facilities;

f.  Mining;

g.  Radio Frequency Transmission Facilities; or

h.  Rail Lines and Utility Corridors;

C.  New development shall meet City specifications and standards in Chapter 11.60 and the on-site tree density requirements in Subsection D., below. Exterior alterations shall meet City specifications and standards in Chapter 11.60 and the on-site tree density requirements in Subsection D., below, but are only required to spend 10 percent of project value on the requirements in Subsection D. and the nonconforming upgrades required by Chapter 33.258, Nonconforming Situations.

D.  On-Site Tree Density Requirements.

1.  Required Tree Area. The required tree area is based on the size of the site and the type and size of proposed and existing development as shown in Table 50-2. Applicants may choose Option A or Option B for calculating required tree area except only Option A may be used to apply standards to a "Development Impact Area".

 Table 50-2

Determining Required Tree Area

Development Type Option A Option B
One and Two Family Residential  40 percent of site or development impact area  Site area minus building coverage of existing and proposed development
Multi Dwelling Residential 20 percent of site or development impact area
Commercial/Office/
Retail/Mixed Use
15 percent of site or development impact area 
Industrial 10 percent of site or development impact area
Institutional 25 percent of site or development impact area 
Other 25 percent of site or development impact area

 2.  Required Tree Density. The required tree area shall be planted with some combination of large, medium or small canopy trees at the following rates:

Table 50-3

Number of Required Trees and Minimum Planting Area

Canopy size category
(at maturity)
Number of trees required
per size of tree area
Min. required planting area per tree
(min. dimension)
Large  1 per 1,000 s.f. 150 s.f. (10’ x 10’)
Medium 1 per 500 s.f. 75 s.f. (5’ x 5’)
Small 1 per 300 s.f.  50 s.f. (3’ x 3’)

Refer to Chapter 11.60, Technical Specifications, to calculate tree canopy size categories. When the canopy size category of the tree species is not or cannot be determined, the tree will be considered a small canopy tree.

3.  Tree Density Credits

a.  Trees planted on site to meet any required stormwater or other landscaping requirement may be counted toward the On-site tree density requirements.

b.  Trees that are retained and protected, including trees preserved per Section 11.50.040, may be credited as follows:

(1)  Trees between 1.5 and less than 6 inches in diameter count as one small canopy size tree.

(2)  Trees 6 or more inches in diameter count as one medium canopy size tree for each full increment of 6 diameter inches.

c.  Payment in lieu of planting. The applicant may pay a fee to the Tree Planting and Preservation Fund per Section 11.15.010 equivalent to the cost of planting and establishing one 1.5-inch caliper tree. The fee per tree shall be credited at a rate of one medium canopy size tree.

d.  On sites less than or equal to 3,000 square feet, healthy non-nuisance species trees planted or retained in the street planting strip may be credited as described in this Subsection.