Washington County Joint CPO
Tree Group -
Research Committee Report
Urban
Forestry Management Plan
Incentives for Tree Preservation
Responsibility of Property Owners
Help for citizens performing tree maintenance
Methods for Evaluating Tree Ordinances and the Urban
Forest Ecosystem
Performance evaluation of ordinance
Situations which are declared to be public nuisances
Exemption from Oregon Solar Energy Easement/Washington
County Solar Access Standards
References to the Tree Codes for the Cities/Counties
Studied by the Research Committee:
Appendix A – Tree Protection Research Matrix
Appendix B – Economic and Infrastructure Benefits of
Trees
Appendix C – “Elements of an Urban Forestry Program” –
Olympia, WA
Appendix D – Response to Comments to Draft Report and CPO
Presentations.
Introduction
The purpose of this document is to
summarize and detail the Joint CPO Tree Code Group Research Committee's
findings. We will provide a summary of the tree ordinances and policies of the
jurisdictions we have studied along with our group’s analysis and
recommendations for Washington County. It is intended that this proposal shall
be considered by county elected officials and staff who are involved in writing
a comprehensive tree ordinance and policy for Washington County.
We found that there is
consistency among our local neighbor cities of valuing the urban canopy.
The majority of cities within or bordering Washington County already have
significant tree protections in place:
o Banks, Beaverton, Durham, Forest Grove, Hillsboro, Sherwood, Tigard, Tualatin, Lake Oswego, Wilsonville, Portland and North Plains
For detailed research, we selected a number of jurisdictions:
o We
focused on several cities within Washington County because these communities
have needs and issues similar to ours: Beaverton, Hillsboro, Tigard,
Tualatin, and Sherwood.
o For
comparison we included neighboring cities of Portland (Multnomah County)
and Lake Oswego (Clackamas County).
Both have extensive tree protections in place.
We specifically
selected Lake Oswego for its aesthetic
natural beauty due in a large part to a
significant older tree canopy. We would like to note that Lake
Oswego possesses an average home sale price 73% - higher than the Portland
Metropolitan average[1] which is arguably due to in part
to its impressive tree canopy.
o We found that while it is not common for counties to adopt comprehensive tree ordinances, it is not unheard of in urban counties[2]. To cover county-specific issues with tree protections we sought out and included two urban counties with tree protections in our research: Fulton County, GA and Monterey County, CA.
Our research is summarized in this document. In addition, we have provided a matrix detailing the findings broken down by these jurisdictions. (See appendix A)
Scope
For the purposes of our Washington County study and recommendations we will be focusing on the Urban Forest in the unincorporated areas within the UGB (Urban Growth Boundary) of Washington County. While it is conceivable that the Urban Forestry Management Plan could include areas outside of the UGB, our research did not include significant research into state laws regarding trees and Forestry Management (Oregon Forest Practices Act).
We would also like to further limit the scope to include areas within the UGB that are currently developed to an urban standard or are slated for urban development, thus excluding commercial agriculture and forest lands that are within the UGB but still used commercially
There has been discussion and concern among the Joint CPO Tree Code Group about how to protect trees in “reserve lands,” specifically those lands that are designated to be brought in to the UGB at a later date. As they will become urban communities in the future, some consideration should be given to how these lands might be protected so that residents of these future urban areas are able to retain some mature woodland.
Precedence
Although somewhat unusual, there is a precedent for counties to adopt comprehensive urban forest management plans and tree codes. The current circumstances in Washington County lend themselves to adoption of a plan. Even if future annexation brings unincorporated urban areas into cities, it is important not to have a disparate level of tree canopy. We should strive to have a standardized approach for municipal services.
Counties with successful tree codes include Fulton, Monterey, and Sacramento counties. Monterey County has a tiered ecoregional approach with complex protection programs. Sacramento is in the process of expanding their tree code, in existence since 1981, to be more comprehensive and to incorporate important elements of the Sacramento Tree Foundation’s model ordinance program.
The Sacramento Tree Foundation is an organization leading efforts to build an urban forest in the Sacramento region. The foundation is implementing an initiative, with the support of 22 cities and four counties, to expand urban forests and optimize the benefits of tree canopies. This framework includes comprehensive, scalable model ordinances creating an excellent resource for any other jurisdiction seeking to embark on urban forest planning. We strongly recommend that Washington County utilize the excellent materials and training offered by the foundation as guidance in implementing a plan.
Research
Findings
For this report we divided our research findings into six components:
1. Urban Forest Management Plan – lays out the guiding policy document and tree board governance;
2. Preservation - addresses the tools that communities employ to prevent trees from being removed in the first place;
3. Mitigation – outlines rules for replacement and maintenance of trees after development;
4. Protection - specifies how trees that are being retained must be protected during development activities;
5. Public Street Trees/Tree Maintenance - discusses topics for street trees and other public trees including maintenance responsibilities: and
6. Administration - deals with a number of issues we believe are important but which do not fall into one of the other sections.
Urban Forestry Management Plan
The Urban Forestry Management Plan (UFMP) is the "living" policy document that guides planners and policy makers about how to manage the "urban forest."
The Tree Ordinance is not an end in itself. It does not address all the goals. The Forestry Plan supplements ordinances/code and should be revised regularly.
The majority of UFMP documents we reviewed included the
following elements.
Analysis
Most
of the jurisdictions we studied had some sort of stand-alone Urban Forestry
Management plan. The exceptions are
Fulton County, GA and the City of Beaverton, which have a “Tree
Maintenance and Planting” policy document (but it does not appear to be a
comprehensive management policy document.)
Lake Oswego provides an excellent example of a “Comprehensive Tree Management Plan,” which is effectively its Urban Forestry Management Plan. Portland also had a comprehensive set of policy documents. Our analysis of the UFMP topic focuses primarily on Lake Oswego's document, as it is very clear and easy to follow. Most of these same components of Lake Oswego’s policy would be applicable for Washington County’s policy.
The stated goal of the Lake Oswego plan is to create a comprehensive, sustainable, and integrated approach to tree management on both public and private property. The Lake Oswego plan includes governance of both private and public property. The following italicized sections are the key components of the Lake Oswego plan. We recommend these components be included in the Washington County plan. As the Lake Oswego policy is copied below the word “City” could be replaced with “County”.
1. Stewardship and Education: Educate the public about the
importance and value of trees.
o
Promote an urban forestry
stewardship ethic in the community through general education.
o
Foster community support
for the local urban forestry program and encourage good tree management on
privately-owned properties.
o
Develop a NeighborWoods
Program [3]
o
Annually, hold a targeted
education event for builders and landscapers.
o Expand and foster Arbor Week events as an education and
outreach opportunity - This is a requirement to reach Tree City USA status.
o
Increase information
available on stewardship events and general tree care and maintenance through
print publications and City [County] webpage.
o
Produce an annual State
of the Forest report.
o
Identify additional
incentives for homeowners and builders to preserve trees.
o Promote a diversity of large canopy street trees
o
Set and implement goals
for increasing tree canopy in open spaces.
o
Adopt standard for
approval in the development code and administrative policies to foster
increased canopy growth
o
Identify opportunities to
increase canopy cover on public property.
o
Identify opportunities to
increase canopy cover on private property.
Remarks:
The Washington County policy should direct the county planning
departments and Tree Program Manager to work with developers to suggest
alternative placement of structures, roads, and utilities in order to
accommodate existing trees.
A high level goal
of the Joint CPO Tree Code Group's efforts is to restore the
urban forest, whether by a certain percent or by planting a
net number of trees by a future date. The Forest Size component of the UFMP
should state this goal and list measurable actions to be implemented in order
to track progress toward that goal.
American Forests
tree canopy studies sponsored by the USDA Forest Service were cited in a number
of the policy documents we reviewed. American Forests recommends an urban tree cover goal of 50% for
suburban residential areas in the Northwest[4].
Preliminary data
from Metro’s Nature In Neighborhoods biennial study of tree canopy coverage for
the metro region shows that unincorporated Washington County was at 31.5%
canopy coverage at the end of 2007. The full report was due at the end of 2008,
but not ready at the time of this document revision, however Metro provided the
raw canopy coverage data for the Metro area, as we have shown in Figure
1.
Note that highlighted Washington County jurisdictions are at the lower end of
the 3-county metro region.
Figure 1: 2007 tree canopy cover by jurisdiction
(source Metro)
Metro is mandated
to collect this data again at the end of 2009 (reported in 2010) and every 2
years thereafter.17.
One of the
previously mentioned American Forests studies was conducted in the
Willamette/Lower Columbia Region[5]
and found that the average tree canopy cover in this study’s scope has been
reduced nearly in half, from 46% in 1972 to 24% in 2000. The canopy in this
same area’s “urban areas” was down from 21% to only 12% canopy coverage
respectively.
This indicates a
loss of nearly half of the tree canopy in a 28-year period.
A recent and more
detailed study conducted by Portland's Urban Forestry Commission[6]
has shown urban forest canopy growth, not
loss,
in existing East side neighborhoods in the low single digits. They attributed
this growth at least in part to the "Friends of Trees Effect.” Friends of Trees is a non-profit that assists
neighborhoods in planning for and planting street trees. This group is active
in Beaverton as well, and we expect to engage them in future Washington County
restoration efforts.
This data shows that significant canopy loss has occurred, but that also restoration can be achieved, even in dense urban settings. Thus we are recommending adoption of a goal of 40% average canopy tree coverage for unincorporated Washington County. This target would be broken out by type of land use: residential areas = 50% canopy coverage; transit-oriented = 30%; central business districts =15%; industrial = 10% (with percentages to be calculated based on actual zoning breakdown with a 40% average overall).
We recommend using
the percent of tree cover benchmark because 1) it is measurable; 2) it is a
standard often used by other jurisdictions for measuring progress to their
urban forest management plans; and 3) as previously noted, Metro will be
conducting a tree canopy survey every two years at no direct cost to the
County.
Here are a few summary examples of how other jurisdictions have stated their high level tree canopy goals:
o
Fairfax Co. Virginia:
currently at 41% canopy coverage - goal: 45% in 30 years.
o
Portland canopy coverage
goals: residential: 47%, commercial/industrial 12%
o
Annapolis, MD: currently at
41% canopy coverage - goal 50% in 30 years
o
Las Vegas: double the canopy
to 20% in 20 years
A different type of goal may specify a number of trees
planted in a number of year(s). For example:
The Sacramento Tree Foundation plans to plant 5 million trees by 2025 in
the greater Sacramento region in an effort to double the region's urban canopy.
This effort is supported by official resolutions from 22 cities and 4
counties.
Note that this goal is measured by a number of trees planted, which is easier
for people to understand, but the ultimate goal is still to increase the canopy
coverage to a specific value long term. It may perhaps be easier for the public
to rally around shorter term goals that specify a number of trees to plant
("I can do my part by planting 5 trees") vs. a citizen trying to
understand what role they have in helping the county reach some long range goal
based on a measurement like 40% canopy coverage.
o
Clarify responsibilities
for street tree maintenance; identify areas where the City [County] will take
responsibility.
o
Conduct a field inventory
of City [County] maintained tree resources (street and park trees)
o
Conduct a hazardous tree
survey to identify hazardous, dead, or otherwise undesirable street trees along
public trails and in public rights-of-way schedule removal and replacement.
o Develop a tree replacement program for targeted rights-of-way.
Remarks:
The UFMP should provide
guidance for selecting, situating and maintaining street trees appropriately to
maximize benefits and minimize hazard, nuisance, hardscape[7] damage and maintenance
costs.
Representatives
at the Oregon State Department of Forestry[8] have offered to provide professional resources for collecting
a street tree inventory (discussed later in this document) and for assessing
and measuring forest health.
This section of the UFMP should address
establishing and maintaining an optimal level of age and species diversity
(biodiversity), which is a well-established requirement for forest health.
This section should also call for an emphasis
on preservation of trees in clusters as a matter of tree health. Retaining
trees in cluster as opposed to individually, allows the trees to protect each other
during strong winds (public safety issue). It is also beneficial to wildlife.
Encouraging clustered development (homes in clusters) can provide the desired
result.
We suggest that
the policy recommend, where possible and appropriate, leaving the fallen trees to provide natural habitat for
wildlife and returning nutrients to the soils. It may be appropriate to place
removed trees along waterways to help mitigate increased water flows due to
nearby development. Clean Water Services would likely provide these
recommendations on a case-by-case basis based on scientific studies of the
site.
o Develop, adopt, and institutionalize maintenance standards and
practices.
o Create a list of approved [native] street trees of different
planting environments.
o Establish and fund cost effective preventative maintenance
programs to improve the health and safety of City [County] owned or maintained
trees.
o Utilize appropriate technologies, such as structural soil, to
improve growing conditions for trees in urban environments.
Remarks: The International
Society of Arboriculture recommends that the forest policy attempt to solve
conflicts between trees and street improvements by setting priorities. While
trees are often to blame for bulging sidewalks and invading sewer lines
(hardscape), it is also valid to point out that these structures haven’t been
engineered to function in an environment where trees are so prevalent. ISA
recommends that policy establish a priority of trees over hardscape,
acknowledging that individual property owners typically don’t have the
expertise or resources to develop satisfactory solutions to tree-hardscape
conflicts on their own and that the responsibility for correcting these
conflicts should not be assigned to the property owners.
o
Make invasive plant
removal a part of all community outreach efforts.
o
Integrate invasive plant removal
in park management.
Remarks:
Clean
Water Services is involved in efforts to remove invasive species in vegetative
corridors (VC). Development plans that involve VCs are often required to remove
invasive species from those sites.
As Washington County’s park system is small (only Hagg and
Metzger Parks) we think this second bullet could be expanded to include facilities
in addition to park management.
6. Integration: Bring urban forestry concepts/references
into all of the various policy/plans documents, outreach, livability
indicators, etc.
o Integrate urban and community forestry into the Comprehensive
Plan during the next periodic review process.
o Incorporate Park Master Plans and Management Plans into the
Urban and Community Forestry Program as they are developed.
o Include tree conservation and planting in capital improvement
projects and redevelopment plans.
o Include tree canopy measure in the quality of life indicators.
o Link community forestry with the storm water management plan.
o Consistently include Community Forestry in City [County]
sustainability efforts
o Provide information on quantifiable benefits of trees to staff
Remarks: The UFMP should direct the different
agencies to work together and any policy and ordinances should be drafted such
that there are no conflicts between different policies or agencies.
The UFMP should address the concerns we have
heard from the community:
“My worst
fear is if we do nothing…”
”Loss of property values when trees are cut or lost”
”Loss of integrity and the look and feel of established neighborhoods”
”Disconnect from nature; living in an all man-made environment can lead in
part, to social degradation”
”Loss of Oregon’s reputation for its natural beauty and large trees”
The UFMP adopted by Washington County should recognize that the
community has a right to maintain/increase their urban canopy alongside the
rights of landowners to their property.
For the Quality
of Life indicators bullet, we are not aware of any such indicators being
tracked in Washington County. This might be something the county considers
implementing, perhaps in the context of the ongoing Urbanization Forum.
Tree Program Manager
The Tree Program
Manager would be a position on the County staff responsible for:
o
Developing and updating the
Urban Forest Management Plan;
o
Heading the Tree Board or
Commission;
o
Implementing a monitoring
program to evaluate if goals are being met;
o
Directing county tree care
operations, including planting, maintenance, permits, removal, etc.;
o
Evaluating and approving
permits for activities that may affect trees;
o
Seeking funding from State,
Federal or other granting agencies;
o
Conducting community
outreach and education programs;
o
Enforcing Ordinance
provisions;
o
Authorizing stop work orders
and assessing penalties.
Qualifications: The International Society of Arboriculture
defines [9] Certified Arborists and Foresters as:
o
Certified Arborist - An
arborist works with individual trees and knows the essentials for their
surviving and thriving in different environments. The arborist has extensive
knowledge on an individual tree level and is a micro-manipulator of single
trees in a forest or landscape. The arborist practices the science of
arboriculture.
o
Forester - sees trees as a group
and manages from that perspective. Foresters practice the art and science
of silviculture.
Due to the
specialized knowledge required for this position, the Tree Program Manager
should be a Certified Arborist or more preferably a Certified Forester. A
Forester will have the specialized expertise to consider the impacts of the
county’s decisions on a wider basis.
Tree Board or Commission
Another key component of an UFMP is a Tree Board. The Tree Board is responsible for maintaining and updating the policy, advising the Board of Commissioners on changes that need to be made, and producing an annual Urban Forestry Status Report and Budget request. The Tree Board is also charged with educating the public on tree care, the value of trees, and how they can participate in enforcement. The Tree board should establish and administer the Heritage Tree program as well as the “Tree Fund”.
In Tigard and Lake Oswego, this board is
appointed by the commissioners/mayor. The board is made up of arborists,
citizens, developers, and/or green industry professionals on a rotating
appointment schedule.
The Tigard Tree Board's mission is “to
develop and administer a comprehensive tree management program for the
maintenance, removal, replacement and protection of trees on public
property.” The mission of the board was
subsequently expanded to develop a comprehensive tree protection and urban
forest enhancement program throughout the city.
Lake Oswego has at least 2 different
groups to help administer tree protections: They are the:
o
Tree Code Task Force, which
evaluates the Lake Oswego Tree Code and “provides recommendations for potential
amendments. It is the intent of this effort to assess how the current Code is
being interpreted, how the public perceives the Code, and what measures can be
taken to improve the Code.”
o
Natural Resources Advisory
Board (NRAB). Their mission is to
“review trends in air, water, and land quality within the Urban Service
Boundary of the Comprehensive Plan, and to assist in the development and
implementation of plans and policies to protect, restore and enhance the
environmental quality within the Urban Service Boundary of the Comprehensive
Plan. The NRAB shall encourage conservation of natural resources and
preservation and enhancement of the ecosystems, open space, and natural
corridors. Administer the Heritage Tree program.”
Tualatin has a seven-member board and is
directed by the Urban Forestry Manager (who is a Parks and Recreation staff
person and is not an arborist or forester).
Monterey County
does not currently have a Tree Board but they are in the process of
establishing one as well as a Tree Fund for Oak woodlands protection. They do
not have an arborist position on staff, however the planning personnel we
worked with was a certified arborist.
We highly recommend that Washington County establish a Tree Board which includes key stakeholders (industry, community, and builders) who establish future policy and provide the flexibility to keep the UFMP up to date with the latest scientific research, policy directions, and national trends.
Tree Fund
The Tree Board also administers the Tree Fund. The Tree Fund receives fee-in-lieu payments from tree mitigation requirements. The Tree Fund may be used to finance Tree Board activities related to tree canopy increases. When someone opts to pay into the tree fund in-lieu-of performing mitigation/replanting, this money may then be used to fund:
o planting of trees on public property:
parks, schools, street trees, libraries, etc.
o new/replacement or maintenance of existing
street trees for property owners who meet certain financial needs tests.
o stewardship: education programs for the public on the importance of trees.
o other Tree Board programs needing funding
If the board is established as a non-profit organization the tree fund could also potentially accept contributions from the public. The board may solicit tax-deductible contributions from individuals, or partner with businesses who could make a contribution as a marketing strategy (i.e. a car dealership might contribute a fixed dollar amount for each car sold, marketed as a carbon-offset for the vehicle.)
We recommend that
Washington County adopt the following:
o
Create an initial Urban Forestry Management Plan.
o
Measure progress towards the UFMP goals by setting measurable and
actionable targets.
o
Establish a Tree Board or Commission which owns maintenance of the
Urban Forestry Management Plan. The Tree Board or Commission also has
responsibility for tree education and stewardship for the public.
o
Establish a Tree Fund administered by Tree Board.
o
Establish a County Forester/Arborist position on County staff. This role will lead the Tree Board, have
enforcement authority, and have final say in tree-related disputes.
o
Establish a Historic Tree program.
Preservation
A key goal that we are recommending is to establish the Washington County Urban/Community Forest management priorities as follows:
2.
Increase and
Enhance second,
Preserving the urban forest resources that we currently have
to the maximum extent possible is necessary in order to be able to achieve our
goal of restoring the urban forest canopy.
Our region's grand scenery is world-renowned and is a major tourist draw.
People associate Oregon with trees; examples of which are our license plate,
state quarter and state seal. The state's forests are a key street component of
that scenery and we need to do our part to preserve it. This includes our urban
areas, where visitors typically begin exploration of our grand state.
In addition to
trees providing aesthetic beauty, mature trees play a significant and
quantifiable role in reducing storm water runoff, reducing heating and cooling
costs, improving air quality, and increasing property values (which translates
to increased tax revenue).
See Appendix B on Economic and Infrastructure Benefits of Trees.
We recognize that as our county continues to grow and housing and economic requirements increase, some trees will be lost during development. Most of our neighboring communities, including most of the cities within Washington County, are already acting to slow and reverse the impact of growth to their urban forests. It is time for Washington County to take action, to learn from successes and failures of our neighbors, and to keep from falling behind.
Without changes to slow and reverse tree loss, future generations will not benefit from this incredible asset, and “progress” will continue to result in decline in the urban forest canopy. More can certainly be done to encourage smart planning to retain individual or groves of trees during development.
Preservation is generally achieved through two methods: required preservation (permitting) and voluntary preservation through incentives.
This next section will detail tools that may be used to assist the county with tree preservation.
Permits
Our research has shown that currently Washington County has
virtually no regulations regarding tree removal[10]. Washington
County has an existing section on tree preservation and removal permits in its
development code (section 407-3) however it is not clear how or if this section
actually applies to non-development tree removals. We have heard concerns about
implementation and enforcement of this code expressed by county staff.
Most jurisdictions we reviewed dealt with tree preservation, removal and mitigation in their development application process. In these cases a "tree plan" is required to be submitted along with the development application. The Tree Plan specifies the trees to be preserved (and protected during development) and trees that are proposed for removal.
With every development application including the removal of more than three trees, Monterey County requires submittal of a “Forest Management Plan.” Each area differs slightly in the exact requirements; this discussion will focus on the Del Monte Forest region[11].
The plan is developed with the consultation of a certified forester, not an arborist (county maintains list, applicant’s expense). The plan is submitted on a per-parcel basis. It shows proposed and existing roads and structures, grading plans, and contains a list of all existing trees on a parcel above a specified size (varies by species.) It also shows the trees to be removed as well as the details (type and location) of the mitigation trees. They require a narrative describing the reason for each tree removal. The plan also requires long-term and short-term impacts of development of the forest resource, alternatives to minimize development impacts on the resource, and alternatives to tree removal.
The planning personnel that we spoke with[12] indicated that the plans are scrutinized and frequently rejected requiring the applicant to resubmit with changes to minimize the impact or loss of trees further.
All jurisdictions studied require that permits are issued before tree cutting (except for emergency situations where personal safety/property is in danger.)
We are providing a summary of the Lake Oswego tree permits, as they are clear and easy to follow. They are similar in many ways to other jurisdictions studied but probably the most restrictive. We will discuss jurisdictional differences after presenting the Lake Oswego plan:
Summary of Lake Oswego's
Protections/Permitting
There are seven types of tree removal permits:
§
Applicant is required to
demonstrate the tree is dead and warrants removal
§
City may require the tree
retained for wildlife habitat in certain circumstances
§
Clear danger to personal
safety and property
§
Public tree causing damage
to existing public or private facilities or services.
§
Immediate danger of collapse
§
Payment of fee may be waived
§
May be issued retroactively.
§
Only issued where other
pruning practices are impractical
§
Exception for trees in an
open space or undeveloped area to provide a "snag" for wildlife
habitat.
§
A separate approved tree
removal permit does not authorize topping.
o
Type I[13]
§
Residential single family
only
§
Removal of up to two trees
per year, 10" caliper (DBH) or less
§
Not a Heritage Tree or in
some specific areas.
§
These permits are issued
with no further review.
§
All other removals that are
not covered in prior types.
§
Trees to be removed must be
marked in the field and permit application notice posted in the field (viewable
by public)
§
14-day public comment period
o
Verification Permit
§
Required for trees that have
been approved for removal through a separate development application
§
Trees for removal/protection
and proposed buildings identified in the field
§
Verification that trees in
the field match the approved site plan.
Approvals of above Type II and Verification permits are based on
consideration of the following criteria [Lake Oswego code section 55.02.080]
§
Removal will not have
significant negative impact on erosion, soil stability, flow of surface waters,
and protection of adjacent trees or existing windbreaks.
§
Removal of the tree will not
have a significant negative impact on the character, aesthetics, or property
values of the neighborhood.
§
Removal is not for the sole
purpose of providing or enhancing views.
Several jurisdictions require permits to remove trees even without a development application (Beaverton, Lake Oswego, Sherwood, Tualatin, Portland, Monterey County). We expect this to raise concerns from homeowners who would like unlimited control over the trees on their property (i.e. weekend landscaping activities may prevent a homeowner from cutting a tree without planning ahead and first obtaining a permit during business hours.)
The main concern is that without limits for non-development situations, there exists a major loophole allowing a landowner the ability to cut trees prior to submitting a development application (which requires a tree survey). This is the impetus for the Clackamas County Urban Green advocacy group’s current push in Clackamas County for expanded tree protections.
Some jurisdictions get around this concern by allowing a number of trees (per year) to be cut by a homeowner (excludes specially designated trees). In many jurisdictions, this can be done without any permit. It is unclear in these cases how tracking and enforcement is performed.
Beaverton allows removal of up to 4 “Community” trees per year without a permit (community trees are essentially any trees that are not otherwise specially designated.) There is no limit if the property is less than ½ acre. Beaverton has a list of exceptions for situations that don’t require a permit (i.e. minor pruning, nonnative removal, emergency situations, vision clearance, etc). Beaverton’s permit section (Section 40.90.15) provides three tree plan permit levels, with increasing mitigation requirements as increasing percentages of existing trees are removed.
The Type I permit in Lake Oswego allows
for the freedom of a homeowner to remove 2 trees a year without review, but an
administrative permit is still required. This is presumably for tracking and
enforcement.
The Type I permit in Lake Oswego applies
to trees from 0” up to 10”. The Tree Code Group has discussed this particular
point and feels that the 0” minimum would probably not be acceptable with
Washington County residents. We have discussed a range of potential options,
but we feel that more research needs to be done to find an appropriate set of
limits that will be generally accepted by Washington County citizens. The final
decision needs to take into consideration best practices and be aligned
with the goal of increasing forest canopy.
Most jurisdictions established a minimum trunk diameter
(DBH- Diameter Breast Height, trunk diameter measured at 4 and 1/2 feet from
the ground), under which permits are not required to remove a tree. There is a
wide-variation in the minimums: Tigard 12", Beaverton 10” (6” for specific
designated species), Tualatin 8", Sherwood 5". All trees in Lake Oswego are subject to
permit requirements.
While we like the
Lake Oswego plan for its overall clarity and coverage, some surveys with a
wider audience of citizens should be conducted to adjust the numbers and tree
sizes to make it acceptable for the county. The Beaverton plan is quite
difficult to understand. It also seems to allow for a significant degradation of
tree canopy over time (discussed further in the later Mitigation section.)
We would like to see adoption by Washington County of a framework for permitting similar to the Lake Oswego plan.
We also request that removed/preserved trees are shown on all plan overlays so that they can be seen on all the different parts of development (grading, streets, landscaping, etc).
Our
study found some extra protections of specific types of trees in different
jurisdictions. Trees with these classifications should have a higher bar for
removal and mitigation:
Street Trees: Trees in the
right-of-way. They are public property and nearly always called out as having
special protections. (city/county expects homeowner to maintain, permit needed
to remove). These trees are usually excluded from preservation/replacement
calculations
Further discussion in Public
Street Trees section (page 26)
Heritage Tree Programs
-A heritage tree program generally
identifies trees (public and private) that are of special significance to the
community. Trees are nominated for Heritage Tree status designation by citizens
and reviewed by the Tree Board based on some criteria. Trees on private land
may be designated as Historic Trees with the consent of the property owner.
These trees possess special restrictions for removal and sometimes maintenance
(a Heritage Tree Removal permit) and these trees maintain this designation for
life (deed restriction).
Tigard, Tualatin, Lake Oswego, and
Fulton County all have Heritage Tree programs. These programs are independent
of the State of Oregon's Heritage Tree program (which provides no legal
protection of designated trees).
Monterey County does not have a
“Heritage” tree program per se, rather a Landmark Tree program. Landmark trees
are trees greater than 24” diameter, visually significant, historically
significant, and exemplary of its species or more than 1000 years old. These
trees enjoy more stringent protections.
We recommend that Washington County
implement its own Heritage tree program. Washington County should also consider
options for merging with cities within the county that already have adopted a
program and open up the County-wide program to other cities that don't currently
have one.
"Significant
Trees/Groves": Trees in city tree inventory that "have been
determined to possess distinctive or exceptional characteristics, such as
beauty, size, shape, location, natural resource value, etc." (Beaverton
Board of Design Review[14]). This classification allows for a further delineation from
Heritage tree which we believe is important, especially for the option to be
able to declare a “grove” of trees as significant. However a Heritage tree
definition could potentially be expanded to include this definition.
Hazardous/dying/dead trees - Most
jurisdictions allow removal without permit or free permit. One issue with this
type of removal is who/how to make the determination of the status of a
particular tree.
o Beaverton requires City arborist approval for the permit
o These trees are often excluded from preservation/replacement
calculations
Trees Within a
Significant Natural Resource Area (Goal 5): It is our understanding that Washington County
currently does not have protection for trees that exist in a Significant
Natural Resource area, unless they are situated in a Vegetative Corridor (as
defined by Clean Water Services). We request that Washington County establish a
higher bar for removal of trees that
are within a defined Significant Natural Resource Area.
In Tigard, there is a deed restriction for future homeowners on all trees preserved through development process.
Incentives for Tree Preservation
In addition to recommending changes to a development plan,
the development code may offer incentives to preserve trees that otherwise
would not be preserved.
Some options to be considered:
o
Significant and
Historic Resources: Allow for
relaxation of development standards to protect significant natural and historic resources. Such standards may include but are not limited to
minimum setbacks, maximum building height, minimum street
width, location of bicycle, pedestrian and multi-use paths,
etc.
o
Landscaping Requirements: Tigard, Tualatin, Beaverton give landscaping credits in some circumstances
for voluntary tree preservation. [Tigard] "For each 2% of canopy cover
provided by existing trees over 12 inches in caliper that are preserved and
incorporated into a development plan, a 1% reduction in the required amount of
landscaping may be granted. No more than 20% of the required amount of
landscaping may be reduced for any one development."
o
Density bonuses: Portland and Tigard [Tigard] "For
each 2% of canopy cover provided by existing trees over 12 inches in caliper
that are preserved and incorporated into a development plan, a 1% bonus may be
applied to density computations...No more than a 20% bonus may be granted for
any one development" (not applicable to trees preserved in areas that
would otherwise be precluded from development).
o
Lot Size Averaging: [Tigard] "To retain existing trees
over 12 inches in caliper in the development plan for any land division under
Chapter 18.400, lot size may be averaged to allow lots less than the minimum
lot size allowed by the underlying zone as long as the average lot area for all
lots and private open space is not less than that allowed by the underlying
zone. No lot area shall be less than 80% of the minimum lot size allowed in the
zone."
o
Commercial/Industrial/Civic
Use Parking: [Tigard] "For each 2% of canopy cover provided by
existing trees over 12 inches in caliper that are preserved and incorporated
into a development plan for commercial, industrial or civic
uses listed in Section 18.765.080, Minimum and Maximum Off-Street Parking
Requirements, a 1% reduction in the amount of required parking may be granted.
No more than a 20% reduction in the required amount of parking may be granted
for any one development"
o Minimum
setbacks
o
Lot Width and
Depth: [Tigard] "To retain existing trees over 12 inches in caliper in
the development plan for any land division under Chapter 18.400, lot width and
lot depth may be reduced up to 20% of that required by the underlying
zone."
o
Location of
Bicycle, Pedestrian and Multi-use Paths: Allow and suggest paths to meander
among existing trees. Allow some tree preservation requirements exemption for
building these paths under dripline.
o
Bond: Builders
should have a bond to protect the trees during development that could be
reduced or waived if the developer leaves over X% (i.e. 50%) of the existing
trees on the proposed development site.
o
Sliding Scale
Permit Fee: Lower permit cost based on percentage of existing trees
preserved.
o Green Builder: Publicly recognize and acknowledge developers as a "green builders."
Tree Inventory
Most of the jurisdictions studied maintained a tree inventory of some sort. The tree inventory is usually limited to public and street trees.
Tree inventories may be used to manage forest health, diversity and size, determine a dollar value of the urban forest, identify potential planting locations, and baseline and track progress in tree preservation or canopy restoration efforts.
The Tree Inventory can be used to manage forest health by identifying patterns in tree deaths or diseases. If problems can be identified early enough, preventative measures can be instituted to limit the extent of future problems (e.g. expenses).
The non-profit Casey Trees of Washington D.C. provides public access to their tree inventory database[15] where people can identify on an interactive map of their inventory individual trees, their species, size and condition, calculations of the amount and value of air pollutants the tree removes and the value of the tree to a tree appraiser. This inventory of Washington D.C. was catalogued by a team of roughly 500 trained volunteers over the course of a summer.
We recommend that a tree inventory in Washington County also identify possible locations for future tree plantings (street trees, parking lot trees, public services building property, highway medians and cloverleaves, etc). These locations could be used as off-site mitigation planting sites. It would also address a possible developer concern about lack of off-site mitigation options.
A healthy forest requires species and age diversity which minimizes the risk of a disease or infestation devastating the forest (a community asset[16]). If the tree inventory contains information about area tree species and age, it can provide diverse species recommendations for future plantings.
The tree inventory can also be used to identify significant individual trees or groves of trees (e.g. Beaverton). This can include public and private trees. These trees are generally considered separately in the tree removal permitting process.
We recognize collecting and maintaining a tree inventory would likely be a laborious process, especially for an area the size of our county (as compared to a city), however representatives at the Oregon State Department of Forestry have offered to provide professional resources for assessing/measuring forest size and health. They suggested volunteer groups to be trained to perform the legwork (e.g. 4-H GIS-GPS TechWizards collecting street tree inventory in Hillsboro).
In addition, updates to the inventory could be done as part of the development/planning process. When development plans are submitted they include existing trees, planned removed trees, mitigation trees and street trees. An emphasis should be placed on native trees. This submitted information can be standardized so as to easily be incorporated into the tree inventory database.
Monterey County administers this type of tree inventory as every development application involving more than three protected trees is submitted with a Forest Management Plan. Those plans remain on file, and are reviewed when later development applications are filed.
However, a street tree-only inventory would not help much in assessing overall forest size increase goals or identify trees to be protected during private development. To monitor the canopy increase goal, aerial photograph analysis of the forest canopy should be used.
Metro Nature In Neighborhood’s Lori Hennings indicated that starting in 2008, Metro will be reporting detailed canopy coverage measurements broken down by cities/counties, including unincorporated Washington County (within UGB, excluding incorporated areas). They are required to measure and report canopy measurements every 2 years (Title 13, renewal of OR SB100)[17]. We would expect Washington County to take advantage of these reports to assess the canopy increase goals.
The City of Portland had a study performed[18]
to measure their canopy cover at 3 different points in time
based on aerial photographs. This showed tree loss and gain in the Portland
neighborhoods and was even broken down by zoning. Washington County could
conduct a similar study to assess historical loss of canopy to help the tree
board establish and track progress towards canopy restoration goals.
Main
Recommendations for Washington County:
o
Establish a multi-level Tree Plan/Permit
requirement for development applications as well as
individual landowners.
o
Establish Historic and Significant
Individual Tree/Grove Inventory
o
Monitor canopy coverage using Metro’s
biannual canopy reports.
o
Enable protections for trees that are in
Historic, Significant Individual Trees, Significant Groves, Significant Natural
Resource Area (Goal 5).
o
Create incentives for tree preservation
Mitigation
According to our high-level policy goal,
once "preservation" and "enhance and improve" opportunities
have been exhausted, mitigation is the final option.
This section details rules for restoration of trees after development, often
called Mitigation. This section includes quantity, sizes and types of trees for
replacement, locations for replacement, as well as maintenance requirements
after planting. It also includes options for situations where replacement of
trees on-site is not feasible.
Along with preserved trees the mitigation plan is usually listed in a Tree Plan
submitted with a development application.
The quantity of trees which need to be replaced (mitigated) is often based upon
the quantity and size of trees that existed prior to development. As with
preservation, most jurisdictions establish a minimum trunk diameter (DBH). If a
tree is over this minimum size, it shall be considered in the tree plan.
Otherwise it is not a factor in preservation or mitigation. As different trees
grow at different rates, a chart could be included that lists the multiple
minimum DBHs that could be specified depending on the type/species of tree.
An important point is that most jurisdictions exclude trees from their mitigation calculations that would otherwise be required by other development code, such as landscape trees, street trees, and parking lot trees. So a developer does not get to credit street trees towards their mitigation/replacement tree requirements.
Lake Oswego has the most straightforward mitigation requirements: 1 tree removed = 1 tree replaced. The applicant shall plant either a minimum 2-inch caliper deciduous tree or a 6-8 foot tall evergreen tree for each tree removed.
Other jurisdictions such as Beaverton and Tigard are more complex and mitigation requirements are on a sliding scale based on the size and number of trees that will be preserved (above the minimum diameter threshold).
Using this method, the diameter of all trees on site is measured at a specified height from the ground (DBH - Diameter Breast Height, usually 4 .5 feet). If the tree is larger than the thresholds above, that tree is factored into the mitigation calculations.
For Tigard, the calculations are as follows: a) if preserving less than 25% of the existing trees, every removed tree must be replaced for a zero net loss in trees, b) if preserving from 25% to 50% of existing trees, 2/3 of the trees removed must be replaced; c) if preserving 50% - 75% of the existing trees, 50% of the trees removed must be replaced; d) if preserving greater than 75% of the existing trees, no trees need to be replaced.
For Beaverton, the DBH of all* the pre-existing trees on the development lot greater than the above thresholds is summed to get the "Total DBH" for the site. The mitigation requirements are based upon the percentage of that total DBH that is preserved. If greater than 50% of the total DBH is removed, then mitigation is required for the amount beyond 50%, otherwise if less than 50% is removed, then no mitigation is required.
*Note, Beaverton does not require this measurement for all trees. Only trees indicated as Significant Individual Trees/Groves (as indicated in their inventory) or trees within a Significant Natural Resource Area (in Community Plans) need to be mitigated. Beaverton provides incentives for mitigating Community, Historic or Street Tree removal with Landscape credits. Double the credits can be achieved if those trees are preserved in the first place.
Remarks: A significant downside of using this method of mitigation is that it does not include all trees (only Significant Individual Trees and Groves), and up to 50% of these "important" trees can be cleared without any mitigation. This seems a very weak requirement, and as a consequence they will always be losing canopy coverage.
Another negative, especially for those jurisdictions with the larger thresholds (i.e. Tigard 12") is that the end result will not likely have a healthy mix of all ages of trees. There will be a gap in ages between the young replacement trees and the large old preserved trees.
A major concern over the pre-existing tree measurement methods is that if protections for removing trees without a development application are not in place, someone could remove trees prior to submitting a development application and not have to mitigate for them. This was a major issue reported by the Clackamas County Urban Green representatives.
A different method for calculating mitigation requirements is not based on pre-existing numbers of trees, but rather a minimum final overall density. This method is employed by Fulton County, GA (Atlanta resides in this county).
This method appears to have a major benefit in that it could be used to much more effectively achieve one of our main goals of restoring canopy coverage to a prior year level.
Fulton County defines a Tree Unit. For example, for a single-family residential, after development is complete, must have 20 units per acre (30 units for greater than single-family residential and commercial).
First, the Existing Density Factor (EDF) is calculated by summing the trees which will remain on site to be protected during construction. Based on species and size, tables in the ordinance convert existing tree DBH to tree units. Subtracting this EDF from the 20 units per acre density requirement, one is left with the amount of tree units that need to be replanted/mitigated. Another table in the ordinance provides the replacement tree units to DBH conversion.
Generally a 4" replacement tree equals 0.7 tree units. For example, if a 1 acre site single-family residential lot had been cleared before development, mitigation of a minimum of 28 4" trees would need to occur.
For a site that was initially barren of trees, the definition of a tree unit changes to a 4" replacement tree equals 1.4 units, essentially cutting the mitigation requirements in half.
Remarks: Due to the tables which provide mitigation credit for preserved trees as small as 1-4" in diameter, the method allows for a better mix of differently sized trees (forest health). It also allows for a direct connection of mitigation to our 40% canopy coverage goal.
While Fulton County was the only jurisdiction in our study using this method, the Tree code group recommends Washington County adopt this method. Adjustments to specific measurements and tree types will be needed to adapt this method to our specific conditions.
Replanting Location
Nearly all jurisdictions with tree protections studied allowed mitigation to take place on-site, off-site or assess a fee-in-lieu. One notable exception is Monterey County.
To help achieve the goal of maintaining and restoring the urban forest canopy, replacement trees should be placed on the same site from which the associated trees were removed whenever possible.
County Staff or Tree Board should work with the developer to locate replacement trees on-site (parks, greenways, using as a street tree, etc).
The County Staff or Tree Board can also encourage a developer to locate appropriate trees in appropriate buffer locations (adjoining existing development along natural/green spaces).
If all trees cannot be placed on-site due to space constraints and minimum distances between the trees then replacement trees could be planted on a different site owned by the party developer. (Note: currently in Beaverton, placing trees off-site increases the developer’s mitigation requirements. Also Monterey County requires mitigation be performed on-site.)
Another option is that the developer could offer the trees to be planted on adjoining properties (with consent of property owner) to provide extra buffering. There is a question of whether this would be in addition to or credited to the developer's buffering requirements as they are not on the developing property and also if the developer would still be responsible for ongoing maintenance of those mitigated trees.
One option that we did not find offered in the research conducted is that the tree board could maintain a list of property owners that are interested in trees planted on their private property. Mitigation trees will have special protections so the recipient would have to agree to the long-term protections applied to designated mitigation trees.
Another option would be that the tree inventory would maintain a list of potential locations for future tree plantings (including the desired tree types for each location) and the off-site mitigation trees could be planted there.
If there does not exist enough space on the developing site to locate the trees, the developer may choose to pay a fee-in-lieu of planting. This fee-in-lieu will be paid into a newly established "Tree Fund" which would be administered by the newly created Tree Board/Commission. Note: Monterey County also does not allow a fee-in-lieu.
At the discretion of the Tree Board/Commission, these funds may be used for (but not limited to):
o planting of trees on public property:
parks, schools, street trees, libraries, etc.;
o new/replacement street trees for property
owners who meet certain financial needs tests;
o stewardship: education programs for the public
on the importance of trees; and
o other Tree Board programs needing funding.
This fee should be set as to be sufficient to cover the cost of the
tree, cost of planting the tree, maintenance/monitoring of the tree for a
specified number of years after planting, as well as the administrative costs
involved. For example, Beaverton's
Fee-in-lieu charges are: $90 2" conifer, $175 2" deciduous, $200
street tree.
In addition to the site location for replacement trees, the ordinance itself needs to specify requirements on maximum tree planting density to ensure tree health. Beaverton specifies that mitigated trees must be placed at least 10 feet apart.
Tree Selection
All jurisdictions studied maintain an approved tree list. Washington County already has an approved tree list for street trees. Street trees are usually selected for suitability in a location next to impervious surfaces, so they will typically require less water and their root systems will tend not to rise to the surface causing upheaval in sidewalks.
A different tree list will need to be established for general tree replacement. We recommend a certified arborist or Urban Forester familiar with the Pacific Northwest environment be consulted to provide a list of appropriate (non-street tree) replacement trees with a focus on native species. Prohibition of known invasive species is recommended.
The following highlights some specific requirements for tree selection from the jurisdictions studied:
§ Deciduous replacement trees must be native trees 2" or greater caliper (Beaverton, Tigard)
§ Coniferous replacement trees must be native trees between 3 and 4 feet in height (Beaverton)
§ Fulton County requires that at least 4 different varieties of trees must be selected in the mitigation phase. This requirement provides for a diverse forest (forest health).
We recommend that Washington County adopt the Fulton County requirement of species diversity.
Post-Planting Requirements
Most jurisdictions required that the developer maintain (irrigate, monitor for disease/death) mitigated trees and trees that were potentially impacted by development for a period of 2-5 years after the development had been completed. Monterey County has a 7-year monitoring program. They indicated that trees damaged by development activity will often not provide indication for five years.
In addition to general monitoring, some jurisdictions have additional requirements:
§ Beaverton requires that each mitigated tree be insured an appropriate amount.
§ Beaverton, Lake Oswego and Portland, require that all mitigated trees be placed in a conservation easement and as a deed restriction.
§ Beaverton, Lake Oswego, and Sherwood also establish that each mitigated tree inherit the status and protections of the tree(s) they are replacing.
Main
Recommendations for Washington County:
o Adopt a rigorous mitigation policy. Establish a Tree Unit definition appropriate for our environment.
o Allow planting on-site, off-site and a fee-in-lieu.
o Establish a replacement tree list with a focus on native species.
o Diversity: Require a maximum 25% of one type of trees species.
o Establish post-planting maintenance requirements of at least 5 years.
Tree Protection Standards
Trees to be preserved must be provided significant protections while construction activities occur. The development plan should include protections both above and below ground. A change in grade, drainage or soil conditions (compaction, removal of topsoil) around preserved trees is usually the cause for decline and eventual death of a valuable specimen. Large trees adjacent to streets or sidewalks can become especially hazardous, jeopardizing life and property.
Tree
protection standards specified by ISA (International Society of Arboriculture)
have been adopted by essentially all the jurisdictions we have studied. The
following are ISA recommended tree protections:
1.
Fence/Barrier: Install a fence or barrier[19]
at least at the dripline (edge of canopy) of all trees to be preserved (or
twice the dripline for columnar
or fastigiate tree).
There are a few different guidelines about measuring the "Critical Root
Zone" of a tree[20].
The root system of a mature tree can be two to three times the width of the
canopy and protection of as much of the root system is ideal. Monterey County requires the wrapping of
the trunk in some instances.
2.
Most
jurisdictions restrict all construction activity within the protection zone. No
vehicle maneuvering or parking, no construction supplies including
topsoil/dirt, no hazardous materials, no topsoil removal, and no new
construction of structures or impervious surfaces.
3. Retain grade level around any tree so it will not be lowered within the protection zone/drip line.
4.Trenching: Prevent trenching (i.e. for utilities) which could damage protected tree roots. All jurisdictions studied except Tigard and Tualatin specifically prevent utility trenching in a protected tree's dripline. Tigard and Tualatin do not explicitly prevent it but allow it only with a certified arborist's approval. Fulton County prevents trenching but allows/recommends "tunneling" if utilities must be located within a root zone. If trenches must be dug in a root zone, excavate trenches by hand in protection zones.
5.Ensure that preserved trees are not affected by removed trees as they are harvested (directional felling).
6.The builder is responsible for the health of the protected/mitigated trees for 3-5 years after construction:
o Bonds issued to protect the health of the trees in the 3-5 year span. Before a Certificate of Permission for Occupancy, the builder shall provide a Guarantee Bond for the sum value of all the trees on the site.
o If a protected tree dies or is identified by a certified arborist to have been damaged by the construction within the 5 year span, a replacement tree must be planted within three months, a 1 to 1 ratio.
We believe that perhaps developers should sign a statement indicating acknowledgement of understanding and compliance of rules for themselves as well as their subcontractors.
We also believe that protection rules should be posted on site as well at each protection area as people may not always be educated as to the protection rules.
Summary of Recommendations for Washington County:
o
We recommend that Washington County enact strict protections for preserving trees
during construction activity using standards developed by:
o International
Society of Arboriculture
o American
National Standards Institute
o
We recommended that developers sign a statement
acknowledging compliance with the tree protection code, including taking
responsibility for subcontractors and posting on-site tree protection rules.
o
Developers are responsible for health of preserved
trees 5 years after development completion.
Tree Maintenance
The community will not realize the benefits of urban forest if the trees are in poor health. Promoting tree health helps communities to protect their investment in urban forest. Public health and safety also depend on healthy trees. Improperly maintained trees have an increased risk of failure, which can result in personal injury and property damage. Good cultural practices will have major impact on success and longevity of the urban trees.
Responsibility of Property Owners
The purpose of this section is to set forth any responsibilities for maintenance of trees in the public right-of-way (“street trees”). This responsibility should be assigned to property owners regardless of whether or not the property is developed (this is the case currently in Washington County).
Maintenance should include watering, pruning to providing correct clearances for trees around streets and sidewalks, and removal of tree debris. The county should provide education materials (on a website) clearly describing the requirements (i.e. clearances) and proper tree maintenance and pruning methods.
As an alternative, the County may simply require property owners/residents to notify the tree program when problems occurs, and have work done by pre-approved contractors. This allows for greater control over the quality of tree maintenance, but at a significantly higher cost.
This maintenance shall include watering as needed and keeping such strips free from weeds or any obstructions contrary to public safety. Property owners shall be responsible for watering mature city street trees whenever landscaping of the property is changed in such manner as to deprive the tree of its normal source of moisture. Such watering shall be continued during dry weather until the street tree becomes acclimated to the new environment, but need not exceed three years. All watering requirements shall be waived to the extent they are inconsistent with governmental restrictions on water use.
It shall be the duty and responsibility of every person
owning or occupying any real property within the City of Sacramento, to keep
all trees on property trimmed in such a manner that there is a clearance
of at least fourteen feet above any street or alley, and a clearance of at
least seven feet over any sidewalk. It shall also be the duty and
responsibility of every person owning or occupying any real state property
within the City of Sacramento to keep all trees on the public right-of-way
trimmed in such manner that they do not obstruct the view of any traffic sign
or device for vehicle traffic in the direction controlled by a traffic sign or
device [Sacramento, CA: City Code Section 45.5]