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Chapter 11.60 Technical Specifications


11.60.010 Where These Regulations Apply.

A.  City of Portland. This Chapter applies to all regulated trees within the City of Portland.

B.  County Urban Pocket Areas. Trees in the County Urban Pocket Areas are subject to all regulations of this Chapter except Section 11.60.060, Tree Maintenance Specifications.


11.60.020 Tree Planting Specifications.

The following specifications apply to trees planted to meet a requirement of this Title. These specifications may be combined with other requirements as necessary to ensure trees are properly selected, spaced, and sized.

A.  Prohibited Locations.

1.  In the South Waterfront Plan district area, planting trees is not allowed between the riverfront trail and the river at major or minor viewpoints as designated in Title 33 Planning and Zoning.

2.  In the Columbia South Shore Well Field Wellhead Protection Area as designated in Title 21, planting trees over the top of polyethylene geomembrane liners installed to meet the requirements of the Columbia South Shore Well Field Wellhead Protection Manual is prohibited.

3.  Trees may not be planted on or within 25 feet south of the toe of the Marine Drive levee slope.

B.  Planting size. In general, the following represent the minimum tree planting size standard; however, the City Forester may allow smaller or require larger trees to suit the site conditions.

1.  Broadleaf trees. Broadleaf trees shall meet the minimum caliper size as determined by the development type listed in Table 60-1:

Table 60-1 Broadleaf Tree Size Requirements

Development
Type

Tree Size

On Site

Street

One and Two Family Residential

1.5”

1.5”

Multi Dwelling Residential

1.5”

2”

All others

1.5”

2.5”

2.  Coniferous trees. Conifer trees shall be a minimum of 5 feet in height.

3.  Native tree exception. The minimum planting size for native broadleaf trees may be reduced to ½" caliper on sites when planted in an environmental (c, p), greenway (n, q, or greenway setback and riverward portion of g, i, and r overlay zones), or Pleasant Valley Natural Resource (v) overlay zone. When planting Garry Oak, Pacific Madrone, or native conifers in these areas, the minimum planting size may be reduced to a 3 to 5-gallon container size. For Street Trees in these areas, the City Forester may approve a smaller planting size for native species.

C.  Canopy size category. Tree canopy types are categorized as small, medium, or large based on the estimated canopy size at maturity. The "Portland Tree and Landscaping Manual" suggested plant lists include the size categories recognized for many trees. To determine the size category of a tree not listed in the "Portland Tree and Landscaping Manual", the applicant shall provide an objective source of information about the tree’s mature height, crown spread, and growth rate. This information can come from published sources, internet sources, or nursery information such as cut sheets.  The canopy size category is calculated according to the following formulas, which incorporate the estimated height and crown spread of a mature specimen and the tree species’ growth rate:

1.  Small trees have a canopy factor of less than 40, Medium trees have a canopy factor from 40 to 90, and Large trees have a canopy factor greater than 90;

2.  Canopy factor = (Mature height of tree) x (Mature canopy spread) x (Growth rate factor) x 0.01;

3.  The growth rate factor is 3 for fast-growing trees, 2 for medium-growing trees, and 1 for slow-growing trees.

D.  Species requirements.

1.  Species diversity. If there are fewer than 8 required trees, they may all be the same species. If there are between 8 and 24 required trees, no more than 40 percent can be of one species. If there are more than 24 required trees, no more than 24 percent can be of one species. This standard applies only to the trees being planted, not to existing trees.  For Street Trees, the City Forester may make an exception to this requirement in order to fulfill or complement an adopted street or landscape plan.

2.  Nuisance species. Trees listed in the "Nuisance Plants List" are prohibited for proposed planting or required replacement.

3.  Native species. Any trees required to be planted in environmental (c, p), greenway (n, q, or greenway setback and riverward portion of g, i, and r overlay zones), scenic corridors (s), or Pleasant Valley Natural Resource (v) overlay zones shall be native species. Refer to the "Portland Plant List" for information on appropriate native species for the specific site conditions. Planting activities shall be conducted with hand tools, and may not disturb other native vegetation.  In streets, the City Forester may make an exception to allow planting of non-native Street Trees in these areas when the proposed species of tree will not likely displace native species, and the soil conditions, available growing space, or other site constraints make planting a native tree species infeasible.

4.  Adopted guidelines. The City Forester will require species that do not conflict with the requirements of this Section and, to the extent practical, are consistent with characteristics set forth in applicable historic design or other adopted guidelines.

5.  Street Tree species. Street Tree species shall conform to the City Forester’s "Recommended List of Street Trees". The City Forester may approve or require an alternate or unlisted species when the alternate species is an appropriate and viable selection and is consistent with applicable objectives of an adopted area-specific tree plan or guidelines.

E.  Installation and establishment.

1.  Installation. All required trees shall be planted in-ground, except when in raised planters that are used to meet Bureau of Environmental Services stormwater management requirements. Plant materials shall be installed to current nursery industry standards and proper arboricultural practices. Plant materials shall be properly supported to ensure survival. Support devices such as guy wires or stakes shall not interfere with vehicular or pedestrian movement.

2.  Timing. All trees required or approved to be planted by this Title shall be planted or payment in lieu of planting made prior to the expiration of the permit or City’s final acceptance of the project, as applicable. However, it is encouraged that planting occur during the wet months or as per City Forester recommendations. Planting of trees may be deferred between May 1 and September 30 upon filing a performance guarantee as provided in Section 11.10.060 or other assurance deemed acceptable by the City Forester or BDS Director as applicable.

3.  Maintenance. Maintenance of required trees including meeting the maintenance specifications in this Chapter is the ongoing responsibility of the property owner. Trees that die shall be replaced in kind. The cost of the tree and maintenance is the responsibility of the property owner.


11.60.030 Tree Protection Specifications.

A.  Intent. Tree protection during development helps to reduce the negative impacts of construction. The tree protection regulations keep the foliage crown, branch structure and trunk clear from direct contact and injury by equipment, materials or disturbances; preserve roots and soil in an intact and non-compacted state; and visibly identify the root protection zone in which no soil disturbance is permitted and other activities are restricted. Maintaining these protections through development will lessen undesirable consequences that may result from uninformed or careless acts, preserve both trees and property values, and reduce risks associated with damaged or destabilized trees.

B.  Applicability. These standards apply to any tree that is required to be retained on site or in the street during a development activity. Proposed tree protection shall meet the requirements of Subsection C., below, except that the City Forester may approve or require alternate protection methods for Street or City Trees.

C.  Protection methods. The Tree Plan shall show that trees retained are adequately protected during construction using one of the methods described below:

1.  Prescriptive Path.

a.  A root protection zone is established as follows:

(1)  For trees on the development site - a minimum of 1 foot radius (measured horizontally away from the face of the tree trunk) for each inch of tree diameter (see Subsection 11.80.020 C., Measurements):

(2)  Street Trees – the City Forester may prescribe greater or lesser protection than required for on-site trees.

(3)  Encroachments into the root protection zone are allowed provided:

(a)  the area of all encroachments is less than 25 percent of the total root protection zone area; and

(b)  no encroachment is closer than 1/2 the required radius distance (see Figure 60-1);

Figure 60-1 Permissible RPZ Encroachments

 

b.  Protection fencing consisting of a minimum 6-foot high metal chain link construction fence, secured with 8-foot metal posts shall be established at the edge of the root protection zone and permissible encroachment area;

c.  Signage designating the protection zone and penalties for violations shall be secured in a prominent location on each protection fence;

d.  The following is prohibited within the root protection zone of each tree or outside the limits of the development impact area: ground disturbance or construction activity including vehicle or equipment access (but excluding access on existing streets or driveways), storage of equipment or materials including soil, temporary or permanent stockpiling, proposed buildings, impervious surfaces, underground utilities, excavation or fill, trenching or other work activities; and

e.  The fence shall be installed before any ground disturbing activities including clearing and grading, or construction starts; and shall remain in place until final inspection.

2.  Performance Path. When the prescriptive path is not practicable, the applicant may propose alternative measures to modify the prescriptive root protection zone, provided the following standards are met:

a.  The alternative root protection zone is prepared by an arborist who has visited the site and examined the specific tree’s size, location, and extent of root cover, evaluated the tree’s tolerance to construction impact based on its species and health, and identified any past impacts that have occurred within the root zone;

b.  The arborist has prepared a plan providing the rationale used to demonstrate that the alternate method provides an adequate level of protection based on the findings from the site visit described above;

c.  The protection zone shall be marked with signage, stating that penalties will apply for violations, and providing contact information for the arborist;

d.  If the alternative methods require the arborist be on site during construction activity, the applicant shall submit a copy of the contract for those services prior to permit issuance and a final report from the arborist documenting the inspections and verifying the viability of the trees prior to the City’s final inspection;

e.  If the alternative tree protection method involves alternative construction techniques, an explanation of the techniques and materials used shall be submitted;

f.  The arborist shall sign the tree preservation and protection plan and include contact information.

The BDS Director may require the proposed tree protection method to be peer reviewed for adequacy; reject the proposal if deemed insufficient to meet Subsection C.2.b, above; or require a performance guarantee per Section 11.10.060 in order to ensure the protection methods are properly implemented.

3.  Additional information. The City may request additional information regarding the proposed development, including construction management approaches, if the proposed development and tree protection appear to conflict. The purpose of this provision is to ensure that logistical considerations are adequately addressed in order to prevent the need for changes to the tree protection measures during the construction process.

D.  Changes to tree protection. Changes to the tree protection measures during the course of the development may be approved as a revision to a permit provided that the change is not the result of an unauthorized encroachment into a root protection zone, and the applicant demonstrates that the tree protection standards of this Section continue to be met. When an unauthorized encroachment has occurred, the city may pursue an enforcement action or other remedy per Chapter 11.70.

E.  Tree protection inspections. The City Forester or BDS Director may conduct inspections during the course of project activity to determine compliance with this Title and confirm that tree protection zones are being maintained and root protection methods are effective. No person may refuse entry or access to a permitted development site to any authorized representative of the City who provides proper credentials and requests entry for the purpose of conducting a Tree Protection inspection. In addition, no person may obstruct, hamper or interfere with any such representative while in the process of carrying out their official duties.


11.60.040 Tree Pruning and Root Cutting Specifications.

Pruning or root cutting shall be in accord with proper arboricultural practices, using clean and sharp tools. No tree may be excessively pruned or topped as defined in this Title.


11.60.050 Tree Removal Specifications.

Trees shall be removed in a manner that will not jeopardize the public safety or damage structures including utility lines or services, or adjacent trees. In most cases, trees shall be entirely removed. Where appropriate, standing dead trees, or snags, may be left by cutting them to a height that will not threaten a target such as people or structures. Fire safety and preventing harmful pests should also be considered. However, well situated snags can function as important wildlife habitat providing nesting sites and a food source for foraging birds.

A.  Completion. To prevent the creation of hazards from partially removed trees, once work has commenced to remove a tree, this work shall be completed in a timely manner. A tree will be considered completely removed when reduced to a stump no taller than 4.5 feet. The City Forester may grant an exception to this specification to allow snag creation. For Street Tree removals, the City Forester may direct that the stump be ground out up to 18 inches below grade.

B.  Disposal of wood and woody debris.

1.  City and Street Trees. Disposal, use, or reuse of wood and woody debris from City or Street Trees is at the sole discretion of the City Forester including specific disposal methods for infected wood. Cost for disposal is the responsibility of the property owner (or adjoining property owner for Street Trees). If the City Forester determines that the cost of storage or sale of the wood is not commercially feasible, the City Forester may give such surplus wood to the adjoining property owner or other group as the City Forester may so designate. Unless the City Forester has given the wood to a group, organization, or individual, it is unlawful for any person to possess or dispose of any wood from any City or Street Tree.

2.  Private Trees. Disposal, use, or reuse of wood and woody debris from Private Trees is at the property owner’s discretion, provided storage of wood does not constitute a public health or safety nuisance. In environmental (c, p), or Pleasant Valley Natural Resource (v) overlay zone, large woody debris may be required to remain or portions of trees left standing as snags. If the City Forester has determined that the tree is affected by a pathogen or insect infestation that will likely adversely impact surrounding trees, all portions of the tree shall be removed from the site and properly disposed at the property owner’s expense.


11.60.060 Tree Maintenance Specifications and Responsibilities.

The following specifications apply to all trees in the city. The purpose of these provisions is to protect the health, safety and welfare of the public, safeguard public infrastructure assets, and ensure the continued health of the urban forest.

A.  General.

1.  Permits required. Any person pruning, removing, or conducting any other work on any Street Tree or City Tree and any person removing any regulated Private Tree in order to comply with the requirements of this Section, shall first obtain a Type A tree permit in accordance with the provisions of Chapter 11.30. The application fee may be waived when the City forester has directed the work to be done.

2.  Responsibilities.

a.  Property owner. It is the duty of every owner of property to maintain trees located on the property or on the adjacent street planting area in accordance with this Section. Further, the owner shall be responsible for all costs associated with such maintenance, removal and any tree replacement, if required.

b.  Bureau of Transportation. For trees located in center medians, the Bureau of Transportation is responsible for the requirements of this Section.

c.  Bureau of Environmental Services. For trees located in green street facilities as described in Title 17, the Bureau of Environmental Services is responsible for the requirements in this Section.

3.  City Forester authority for tree maintenance. The City Forester may or may direct others to prune, remove or treat to control insects and disease for any trees in the streets, parks, other City owned or managed properties, or private properties if the City Forester determines that controlling insect infestations, disease or dangerous conditions is needed to maintain the public health, safety or health of the urban forest.

4.  Available remedies. In addition to specific remedies cited in this Section, any infractions or violations of these requirements may additionally be corrected or enforced per the provisions in Chapter 11.70.

B.  Dead, Dying and Dangerous Trees.

1.  All trees which are determined by the City Forester or a private arborist to be dead, dying, or dangerous as defined in this Title are required to be removed to safeguard people or property. The City may require a replacement tree at the property owner’s expense.

2.  Conflicting determinations. In the case where there are conflicts in the determinations from a private arborist or arborists, the City Forester shall make the final determination.

3.  Exceptions. A dead or dying tree that is being maintained as a snag, or does not otherwise result in a public nuisance as described in this Section or Chapter 29.20, Property Nuisances, may remain provided it is not deemed dangerous.

C.  Dutch Elm Disease prevention and eradication.

1.  Infected elms and elmwood. All species and varieties of elm trees (genus Ulmus) infected with the fungus known as Dutch elm disease (Ophiostoma ulmi or Ophiostoma novo-ulmi) as determined by laboratory analysis are declared to be a public nuisance. It is the duty of any owner of a lot or parcel where infected elmwood is present to promptly remove any such elm tree or dead elmwood under the supervision and direction of the City Forester.

2.  Pruning restrictions. Pruning any species or varieties of elm trees between April 15 and October 15 is prohibited. This prohibition may be waived by the City Forester when such pruning is necessary to remove hazard limbs, provide the clearances otherwise required by this Section or for other causes as deemed necessary by the City Forester. In cases where the City Forester has allowed pruning to occur during the pruning prohibition period, the responsible party shall properly dispose of removed elm wood within 24 hours.

3.  Authority to inspect. The City Forester is hereby authorized to enter upon any lot or parcel during business hours for the purposes of inspecting any elm tree or dead elmwood situated thereon, obtaining specimens for the purpose of laboratory analysis or to determine whether such tree because it is dead or substantially dead may serve as a breeding place for the European or native elm bark beetle (genus Scolytus). If the City Forester determines that the tree serves such purpose, the City Forester may declare the elm tree or dead elmwood a public nuisance.

4.  Determination and action. If, based on analysis of specimens removed from any elm tree, it is determined that such tree is infected, or the City Forester determines that any dead or substantially dead elm trees or dead elmwood may harbor the elm bark beetle, the City Forester will serve a written notice requiring the property owner or responsible party to remove, destroy and properly dispose of such trees or dead Elmwood located on the property or on the adjacent street planting area. If the property owner or responsible party fails, neglects or refuses to remove and destroy, or properly dispose of, such elm tree or dead elmwood within 15 days after service of such notice, the City Forester may abate the nuisance as provided in Chapter 11.70.

D.  Clearances. The property owner or responsible party is required to prune or remove, if necessary, any tree located on the property or on the abutting street planting area when said trees are not maintained to meet the branch clearances as set forth below:

1.  Sidewalk clearance. Branches of trees extending over sidewalks may not be less than 7½ feet above the sidewalk.

2.  Roadway clearance. Branches of trees extending into any public or private roadway may not be less than 11 feet above the pavement. Moreover, on any street designated as a Regional Trafficway, Major City Traffic Street, District Collector, or a one-way street where parking has been prohibited, branches shall be trimmed to a height of 14 feet above the crown of the street.

3.  Overhead powerline clearance. Branches of any tree may not interfere with any light, pole, or overhead powerline used in connection with or as a part of the City or Public Utility system. In addition to the authority granted to the City to prune or direct property owners to prune trees in violation of this Section, a Public Utility operating pursuant to an approved Programmatic Permit may also prune any tree which interferes with the safe operation of the utility system.

E.  Visibility. The owner or responsible party shall keep trees located on the property or on the adjacent street planting area from completely or partially obstructing visibility as follows:

1.  Visibility of traffic control devices such as directional and informational signs as defined by the Manual of Uniform Traffic Control Devices;

2.  Visibility for drivers, bicyclists, or pedestrians; or

3.  In any way that presents an unreasonable hazard to the travelling public.

F.  Sidewalks and curbs.

1.  Obstructions. The owner or responsible party shall keep the sidewalk adjacent to the owner’s property clear of branches, leaves, flowers, fruit or other organic matter that may obstruct or render the passage of persons unsafe.

2.  Repairs. When the curb or sidewalk, or both, abutting any property become damaged or in a state of disrepair because of a tree maintained by the property owner, the repair of the curb or sidewalk, or both, will be treated as other curb or sidewalk repairs in accordance with the provisions of Title 17. The removal of any tree or portion thereof, as the Responsible Engineer in consultation with the City Forester may determine necessary, will be granted through the appropriate tree permit. The City may require alternative construction methods be used in order to retain the tree. If the tree is removed, the City Forester may require that the removed tree be replaced in accordance with the required permit.

G.  Public waterlines, storm sewers and sanitary sewers.

1.  Damage from Roots. Whenever the Responsible Engineer finds that roots of any tree have entered any sewer, drain or waterline in the street or City-owned easement, and are stopping, restricting, retarding the flow of sewage or drainage, or causing waterline leakage or believes that removal of the tree is necessary to reasonably prevent future root entry into the sewage, drainage, or water facility, the Responsible Engineer may refer the condition to the City Forester.

2.  Remedies. In addition to the remedies described in Chapter 11.70, the City Forester may remedy the violation by directing the property owner or responsible party to prune the roots or remove the tree. If the City Forester believes that the required amount of root pruning will irreparably damage or destroy the tree, the City Forester will notify the owner and require removal and replacement of the tree. Nothing in this Subsection will be construed to limit the Responsible Engineer’s authority to separately invoke abatement proceedings.