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Preservation
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EDMOND
Tree Preservation Guide
Version 1
Introduction / Overview
2
Benefits to Saving Trees
4
Hiring a Professional
6
Surveying the Site
7
The Remnant Forest
11
Tree Protection Zones
12
Plan Drawings
14
Written Portion of Preservation Plan
16
Submittal & Approval Process
17
Preservation Techniques
18
Resourcs
24
Tree Preser vation Guide
1
INTRODUCTION
Tree Preservation
Let Us Help You
For assistance regarding any
Saving trees during construc-
process to provide you with
information in this guide, please
tion doesn’t have to be hard.
incentives to facilitate this
The basic concept is the ability
idea. Always contact the city
to avoid changing or damaging
forester’s office when you are
a tree’s critical root system. The
in doubt. Walking through the
Urban Forester
real key to success is good plan-
site initially with the forester
City of Edmond
ning. Complications arise when
and spotting possible tree is-
proper consideration is not
sues can save you a great deal
made for tree protection prior
of time and money. Keep in
to submitting a site plan. As a
mind also that it is not always
result, poor compromises are
possible to save all trees dur-
made and the trees die after a
ing construction, some trees
few years. It is absolutely critical
just shouldn’t be saved due
that you evaluate your site first
to their condition, species,
for the trees that you want to
or location. The community
save, before starting the engi-
of Edmond loves their trees
neering process. It is difficult,
and would like to see as many
if not impossible, to change an
saved as possible. This means
engineering plan after it’s been
evaluating the site, designing
drawn. We want to help you
to accommodate the trees,
as much as possible with this
and following through with
change and have designed a
good construction practices.
contact the following urban
foresters for the City of Edmond.
359- 4799
Assistant Urban Forester
City of Edmond
359- 4759
Tree Preser vation Guide
2
Here’s What You Need To Know
Basic Steps To A Successful Plan
a.
Hire a professional forester or certified arborists to help compile the tree preservation plan.
b.
Do a site survey and tree inventory.
c.
Determine if you have remnant forest near your site.
d.
Determine tree(s) to be preserved on site and their required tree protection zone.
e.
Develop plan drawings.
f.
Develop written portion of plan.
g.
Acquire approval of plan through the site plan review process.
h.
Once approved, place all tree protection devices on site before any site clearing, grading,
or construction begins. Notify urban forester for approval.
i.
Benefits to Preservation- There are considerable monetary benefits to saving trees.
Tree Preser vation Guide
3
BENEFITS TO SAVING TREES
Why Do All Of This?
Landscaping is an expensive investment. Tree preservation can save you money in design costs,
material costs, installation costs, and eventually maintenance costs. The citizens of Edmond hold
a high standard for the look and quality of development in their community. By incorporating
tree preservation, you can save a great deal of money and at the same time reap the benefits of
mature landscaping that projects an immediate sense of class and style into your project.
Example: A site with a requirement of 1000 plant units (PU)
Landscaping Only / No Preservation
Tree Preservation with some Landscaping
GENERAL COSTS
Landscape Design
$1,500
Landscape Design
$ 500
Forester Review
$1,500
Maintenance first year
$2,500
Maintenance
$250
Irrigation
$ 6,000
Irrigation
$ 600
LANDSCAPING COSTS
40 trees (3”)
600 PU
$14,000
4 trees (3”)
60 PU
$1,400
150 shrubs (5 gal)
300 PU
$ 6,500
15 shrubs (5 gal)
30 PU
$ 650
300 ground covers
150 PU
$2,400
30 ground covers
15 PU
$240
Preservation
900 PU
PRESERVATION COSTS
No preservation
Total
Tree Preser vation Guide
1050 PU
4
$ 32,900
Cost of fencing and signage
$1,000
Cost of root pruning
$2,000
1050 PU
$ 8,140
Tax Benefits
If you are able to retain a significant amount of land in preservation area, it is possible
that you could qualify for a conservation easement. The Edmond Land Conservancy (ELC)
is a land trust agency in Edmond that holds title to conservation easements in an effort to
keep natural areas intact. Conservation easements can provide you with tax benefits as
well as fulfill your landscape requirements if your preservation area qualifies.
ELC
Edmond Land Conservancy
Post Office Box 3301
Edmond, OK 73083-3301
405.285.8352
www.elc-ok.com
Tree Preser vation Guide
5
HIRING A PROFESSIONAL
According to
Title 22, Chapter 6, Section 22.6.1, (D), (4), (d), iii
The tree preservation plan shall include “A letter of review and
support from an ISA Certified Arborist, SAF Certified Forester,
or a degreed urban forester (other qualifications may be
What is a certified
arborist?
substituted if approved by the urban forester).”
An arborist is a specialist in the
For a list of certified arborist
develop a forest management
art and science of planting, car-
in Oklahoma see list at www.
plan that starts with your goals
ing for, and maintaining individ-
isa-arbor.com/findArborist/
and objectives, incorporates
ual trees. Arborist can provide
locateresultCity.asp or consult
regulatory requirements, and
professional service in the
your local phone book.
provides management alterna-
areas of pruning, tree removal,
emergency tree care, planting,
tives and timeframes. A listing
What is a forester?
fertilization, cabling and brac-
of consulting foresters is kept
by the Oklahoma Department of
ing, aeration to improve root
A professional forester is
Agriculture Food and Forestry.
growth, installation of lighting
someone with at least a bach-
Copies are available from the
protection systems, and spray-
elor’s degree in forestry. A
City Forester’s office.
ing or injecting to control insect
forester learns the art and
and disease problems.
practice of forestry through
The Certified Forester program
comprehensive scientific and
is a national program spon-
technical coursework and prac-
sored by the Society of Ameri-
tical field experience.
can Foresters. The program is
The certified arborist program
is sponsored by the International Society of Arboriculture
voluntary and recognizes excel-
(ISA). To become a certified
A forester can help you as-
lence in professional forestry
arborists a person must have a
sess the value of your trees,
and assures the public of a
minimum of three years experi-
increase wildlife habitat, re-
commitment to provide quality
ence in arboriculture, pass a
duce tax liabilities, improve
resource stewardship. For more
certification exam, and com-
protection from fire, and pre-
information on Certified Forest-
plete 30 hours in continuing
vent or control harmful insects
ers see www.safnet.org/certi-
education every three years.
and diseases. They can help
fiedforester/directory.cfm
Tree Preser vation Guide
6
SURVEYING THE SITE
According to
Title 22, Chapter 6, Section 22.6.1, (D), (4), (a),
In order for plant unit credits to be awarded for preserved
trees, a survey of the site has to be conducted first.
Do I have to count every single tree I want to save?
You do not have to count every tree on sites larger
Individual trees located on site less than 3 acres.
than three acres. Sites larger than three acres use
29
measurements called “stands”. Sites smaller than
three acres must have each tree diagramed and mea-
Fo
f
t Bu
re s
sured on the preservation plan. Once measured, the
fe r
32
trees are assigned plant units based on their diameters (see diagram).
33
48
A stand is a term in forestry used to describe a group-
36
42
ing of trees with similar ages, species, and site characteristics. Foresters are trained to delineate stands and
32
30
35
45
are the preferred professionals to use on large acreage
tree preservation plans. See the section titled “Hiring
a Professional” to find a forester in our area.
each cirle = 1 tree
Area of forest stand in acres
Number of fixed plots
Less than 3 acres stands
Count every tree
2” DBH or greater
3
1
4
2
5
2
You use a sampling method called fixed
6
2
plot sampling. Random points are cho-
7
2
sen and located within each stand. The
8
2
9
3
10
3
For larger than
10 acres stands
(# of acres) / 3 Round
to the nearest number
How do you count the trees
in a stand?
For sites larger than 3 acres.
number of points located is based on the
size of the stand. See the table below.
Tree Preser vation Guide
7
SURVEYING THE SITE
Sampling Procedure
1
diameter within the 37.24 radius
(see illustration above). Partial
You will need two people.
diameters are not counted.
Have one person stand in the
middle of your plot holding a
Fixed plot locations should be
measuring tape set at 37.24 ft.
2
selected on a map or aerial
Have the second person hold
Using a diameter tape or tree
photo before traveling to the
the other end of the measur-
caliper, measure all of the trees
site or measuring the plot to
ing tape and walk around the
within the circle of flagged
ensure unbiased selection of
edge of your plot dodging
trees at DBH (Diameter at
trees for the sample. One fixed
trees and extending the tape
Breast Height, 4.5 ft off the
plot (1/10th acre size) should
out to see how many trees are
ground). Record their species
be put in for every 3 acres
actually in the plot. A good
and DBH on a table.
stand of trees. For areas less
idea would be to use flag-
than 10 acres, see table on pre-
ging to mark those trees that
vious page.
represent the outside edge
of your plot. Count all of the
trees with at least half of their
3
This is your representative
sample data for the entire stand
of trees. To extrapolate this
data out you will need to multiply your results on a per acre
basis times the number of acres
you have. For multiple samples
you will need to combine your
FTRADIUS
totals, multiply on a per acre
basis, and then divide by the
each cirle = 1 tree
/54
number of samples taken. Then
use the plant unit table for preserved trees times the number
).
Use the diagram as a guide for the instructions above.
This is the method of sampling referred to in Title 22.
Tree Preser vation Guide
8
of trees for each diameter class
found to find base point totals
per preserved stand.
4
5
Results should include a map
Mark your sample plots with
of your sample points, totals
flagging so they can be veri-
of plant units per stand, a ta-
fied by the urban forester.
ble of diameter distributions
and species for each stand,
Point sampling on a site larger than 3 acres.
and an overall map of total
forested areas for review. Remember, your samples must
be representative for the
Plot 1
areas so the more points you
use, the more accurate your
Plot 2
results. The table representing sample size shown previously is the minimum allow-
Plot 3
able. Results will be checked.
Inaccurate results will not be
used and the urban forester
Plot 4
will consult with the applicant
to correct the problem.
each cirle = 1 tree
Example of diameter distribution table for one sample plot.
Post Oak
Blackjack Oak
Diam. (in.) Quantity
Diam. (in.) Quantity
Elm
E. Red Cedar
Diam. (in.) Quantity
2
15
2
1
2
2
3
15
3
5
3
1
4
10
4
5
5
1
5
18
5
2
6
7
11
1
8
1
16
1
Diam. (in.) Quantity
12
1
Tree Preser vation Guide
9
SURVEYING THE SITE
Analyzing the Data
Table for tree preservation plant units
The following table should be used to find the plant unit totals for existing trees. These values are
also used to find plant unit totals for preserved stands by multiplying the numbers of trees per
diameter class by their plant unit value. When measuring trees, always round down from the halfinch mark. Example: 3.5 inch tree should be in the 2-3 inch classification. A 3.6 inch tree should be
in the 4-5 inch classification. No points will be given for cottonwoods or for eastern red cedar less
than 12 inches in DBH.
DBH (inches)
Plant Units
2-3
7.5
Preservation can only be
4-5
15
successful if proper tech-
6-7
30
niques are combined with
8-9
40
10-11
45
12-14
50
15-18
55
Bonus plant units
the right trees to save. The
Urban Forester has the ability to assign bonus plant
19-21
60
units to preservation plans
22-24
65
that demonstrate the best
25-27
70
preservation standards. The
28-30
75
bonus will range from an
31-33
80
additional 10% to 50% plant
34-35
85
36-37
90
38-39
95
40
100
unit credits per stand depending on site factors that
influence the overall health,
41
105
structure, viability, function,
42
110
and value of the stand.
43
115
44
120
Tree Preser vation Guide
10
REMNANT FOREST
What is the remnant forest?
The remnant forest is a term used in Edmond
community both historically and ecologically. All
to describe forested areas that have existed
site plans will be reviewed with consideration to
since before settlement of Oklahoma in 1889.
proximity of remnant forests. Applicants are encour-
These areas of forest were found during a
aged to consider preserving as much of this area
2003 GIS study of Edmond, where layers of
as possible. The following map shows locations (in
historical data were used to track the changes
green) in Edmond where remnant forests exist. For
in forest canopy over the last 100 years. This
more information contact the City Forester’s office
forest is considered highly valuable to our
for a copy of the complete remnant forest study.
Map of Remnant Forest
Tree Preser vation Guide
11
TREE PROTECTION ZONES
Determining the Tree Protection zone (TPZ)
The TPZ is a relatively straightforward concept. It is the area
of undisturbed space that is needed for the trees to retain
good health and vigor during and after construction.
The standard for determining the TPZ for the City of Edmond
will be the dripline method. The use of an alternative method
will be evaluated on a case-by-case basis and will need the
approval of the Urban Forester.
Dripline method – This is the area directly below the branches
or canopy of the tree.
Tree Protection Zone (TPZ)
8.5x11-inch warning signs
one each side
Tree Preser vation Guide
12
4-foot high o
range c
o
nstru
ctio
n
fen
cin
g
Installing the Tree Protection zone (TPZ)
Tree Protection Sign
•
As a minimum, install bright orange poly-
•
Stipulate that the surface drainage not be
propylene fencing. The best option is to
altered so as to direct water into or out of
install a chain link fence. The fencing is to
the TPZ.
be installed before any site clearing, grading, or construction begins.
•
Require that site drainage improvements
be designed to maintain the natural water
•
Post “Off limits” signs. Specify that no
table levels within tree preservation areas,
storage, dumping of materials, parking,
and that such improvements be designed
placement of construction trailers, under-
to maintain the natural volume and season-
ground utilities, irrigation lines, fires, etc.
al distribution of water in those areas. If
be allowed within the TPZ.
water must be diverted, permanent irrigation systems should be provided to replace
•
Stipulate that no hazardous materials or
natural water sources for the trees.
liquid construction wastes (i.e. washing of
concrete trucks) are to be stored or oc-
•
If any tree branches extending outside the
cur within 100 feet of the TPZ. The fenc-
TPZ will be damaged by machinery, they
ing must be maintained upright during the
should be pruned before construction
entire construction process.
starts by an ISA certified arborist.
Tree Preser vation Guide
13
TREE PRESERVATION PLAN
Diagram / Drawings
Key elements:
1
It should show the delineation (outlines) of
Details for Tree Preservation Plan
the original stand(s) or individual trees on
the site. This can be on an aerial photo or
located on another drawing that is to scale.
The locations of sample points should also
be included.
2
It should show the actual tree protection
zones along with the placement of all utility lines (above and below ground) and
easements (utility, drainage, etc.). PLEASE
NOTE THAT TREES IN UTILITY EASEMENTS
OR RIGHTS-OF-WAY CANNOT BE COUNTED
TOWARDS PRESERVATION PLANT UNITS
3
It should show all of the built elements,
including parking lots, drainage structures,
and the footprint of the building being proposed on the overall site plan.
4
ll drawings should be to scale and have
a north arrow. It is sometimes easier to
combine the tree preservation plan with the
landscape plan to encompass all of these
elements.
Tree Preser vation Guide
14
Samples of Tree Preservation Diagram
Diameter of Tree Crown
Retain Existing Earth
Root Prune Trench
Cut All Around Tree
Diameter of Tree Crown
Within Crown Spread Area
Retain Existing Vegetation
or Apply 2” to 3” Mulch
Plastic Construction
Barrier Fence on
Steel Posts
Silt Fence
Old Grade
New Grade
Root Prune
Trench Cut
All Around
Tree
Retain Existing Earth
Mulch Over
Silt Cloth
Old Grade
New Grade
Tree Preser vation Guide
15
TREE PRESERVATION PLAN
Written Portion
Tree Protection Specifications
1.
The General Contractor shall utilize ISA (International Society of Arboriculture) certified arborists in
implementing the specifications listed in this plan.
Key elements :
2.
1
certified arborists: www.treesaregood.com
Basic description of preservation
areas and numbers of plant units
3.
No work shall begin prior to the installation of tree
protection as specified in this plan.
found for stands or individual trees.
2
Consult the following website to search for local ISA
4.
Any damage to the preservation trees that occurs
during site work including violation of the preserva-
A diameter distribution list that
tion area or damaging protected trees shall be the
shows the species and the sizes of
responsibility of the general contractor to repair. Re-
trees found in the samples taken.
pairs may include whole tree replacements, apprais-
3
als of tree damage and incurred liquidated damages,
A letter of review and support
or treatments supplied by the urban forester.
by an ISA Certified Arborist, or
5.
a Degreed Forester.
Root pruning shall be done at the edge of all tree
preservation areas prior to site clearing or grading.
4
6.
Tree protection fencing shall be installed after root
The written portion of the
pruning and shall consist of a combination of silt
plan should also describe the
fence reinforced with t-posts with barbed wire and
construction techniques and
flagging or orange construction fence with a single
prescriptive treatments that
strand of wire ran at the top of the fence.
will be done to the tree to help
minimize stress during and after
7.
All pruning will be done by an ISA certified arborist
and shall be done in accordance with ANSI Z133.1-
construction.
See page 18 for examples.
2000 standards
8.
Liquid root stimulator shall be applied every 2-3 ft
along the entire length of tree preservation area.
Tree Preser vation Guide
16
SUBMITTAL & APPROVAL
Submitting Your Plan
The tree preservation plan can be submitted separately or in combination with your landscape plan. This is part of your site plan packet that
you turn into the Edmond City Planning Department. After receiving
your complete packet, the Planning Department will distribute your
information to the urban forestry staff to be reviewed. The review process may involve consultations or on-site inspections with the Forester
or Assistant Forester.
Checklist of requirements
The Basics—
1.
2.
3.
Did you talk with the urban forester prior to designing your plan?
Did you identify whether you have remnant forest on your property?
Did you hire an ISA certified arborist or a forester to assist you in putting your tree
protection plan together and include a letter of support from them with your packet?
4.
Does your plan show the following?
a.
All of the trees identified either individually or by stands?
b.
All of the proposed and existing utilities, topography, drainage structures,
lighting structures, proposed building footprints drives, and parking areas,
a scale, and a north arrow?
c.
5.
Remnant forest identified?
Does your plan include a verbal description of methods that you will use pre, post, and during
construction? (Example: Will identify preservation areas with signage on fencing every 150 ft.)
6.
Did you include the tree preservation language on all of your construction documents to
ensure contractors will not disturb these areas?
Tree Preser vation Guide
17
Preservation Techniques
Ways To Minimize Construction Impacts To Trees
The following is a list of treatments that can be included in
the written portion:
You have your preliminary plan. However, upon inspection of the
plan the consultant forester has concerns with how the design will
affect the trees to be preserved. In most cases, the conflicts identified can be resolved in a number of different ways with the three
main ways being to modify the design, modify the construction procedures, or to perform preconstruction treatments.
Modify the Design
W hen evaluating impacts to trees,
Footing &
Foundation Design
design alternatives should be selected
to reduce overall effects whenever
possible. The options selected should
minimize injury to the trees while still
allowing the required construction.
The degree of impact to a tree varies
greatly by the amount of soil excavation and compaction that is needed
per the design of the footings and
foundations. When structures must
Grade Changes &
Transitions
be placed close to trees, there are
alternatives. However, your engineer
and forester should be consulted to
Tree Preser vation Guide
18
If a grade change is unavoidable
help determine which would pro-
within the root zone of existing trees,
vide fewer impacts to trees while
there are a number of techniques that
still maintaining structural integrity.
can be used to minimize the impacts
Some alternatives to consider are to
on the trees. One alternative is to
use custom footings in the vicinity of
construct retaining walls to reduce
the tree that bridges over the roots, to
the horizontal distance needed for the
cantilever the structure so the building
grade change. Keep in mind retain-
extends outwards from the footing,
ing walls are not the “cure all” due to
and/or install a raised foundation with
concerns with how much excavation
discontinuous footings. When con-
is needed to construct the wall and
sidering alternatives always keep in
necessary footings. Another method
mind the diameter, depth, and spacing
of retaining a cut is by “soil nailing”
of footings; the size and weight of the
walls. This is where the wall is built
equipment needed to drill holes; and
from the top down without disrupting
the excavation needed at the base of
the vegetation or soil behind it.
each footing.
Utility & Services
Pavement
With utility lines the shortest,
The main concern with pavement near
straightest line possible is usu-
trees is how the impervious surface and
ally used for installation. If a line
compaction of the subsoil damage roots
is suppose to run through a tree
and restrict the movement of air and
protection area you must re-route
water to the roots. If installing pavement
the line around the area. If re-rout-
near a tree is unavoidable, the most
ing is not possible, tunnel under the
important impacts to minimize are root
Porous pavements are most com-
area instead of trenching to minimize
removal and soil compaction. How-
monly used in parking lots, low
damage to the tree root system.
ever, new technologies such as porous
traffi c areas, and pedestrian walk-
pavements, structured soils, and root
ways. Their porous nature captures
Water, storm, and sewer lines are
barriers are helping to eliminate conflicts
rainwater, recharging ground water
usually not as fl exible requiring spe-
between trees, roots and pavement (See
and increasing the amount of rain
cifi c amounts of separation and must
below for more information on each of
available to trees without reducing
tie into existing systems. If trees are
these techniques). Adjust finish grades
usable area, reduces storm water
along the street edge, consider plac-
so that the pavement is built on top
runoff and helps owners comply with
ing the lines on the opposite side of
of the natural grade (using a “no-dig”
EPA regulations. Porous pavements
the road. Manholes in addition to
design), increasing the strength of the
do not cost more than conventional
utility junction and splice boxes re-
paving material so that it does not rely
pavement because of the reduced
quire extensive excavation and large
on a compacted subbase for strength,
cost of being able to eliminate
equipment to install. Therefore, they
and reduce subbase compaction require-
stormwater pipes, inlets, and deten-
should be placed outside of the TPZ.
ments by placing a geotextile fabric at
tion basins. There are many types
the bottom of the pavement section.
of porous pavements, with the most
Porous Pavements
common being porous concrete
and asphalt and the use of pavers.
Another name for porous concrete
and asphalt is “no-fines” concrete
and asphalt. By not using fines in
the mixture, interconnected voids on
the order of 15% to 35% are created.
These voids allow water to infiltrated
to the ground below at the rate of 2
to 18 gallons per minute per square
foot for porous concrete. Most common type of pavers is either plastic
or concrete interlocking units with
cellular voids that can be filled with
grass or gravel. They can withstand
heavy loads while still maintaining
Tree Preser vation Guide
19
Root Barriers
common root barriers either defl ect or
Tree roots can be very aggressive,
be solid plastic, metal, or wood. These
growing near the soil’s surface in
barriers attempt to change the normal
search of water, nutrients, and oxygen.
root orientation to keep the roots from
They can extend underground, spread-
growing in a certain area, or to repo-
optimum drainage capability. See
ing outward, two to three times the
sition roots in order to generate less
http://cfpub2.epa.gov/npdes/storm-
diameter of the tree canopy. As the
damage. Inhibitors use chemical con-
water/menuofbmps/post_21.cfm,
tree grows, the roots grow, becoming
trol agents or toxins to constrain root
http://www.greenworks.tv/storm-
larger and larger, exerting tremendous
growth. These agents control or inhibit
water/porouspavement.htm, and
pressure on concrete and asphalt. It is
the growth of root tips. In addition
http://www.grasscrete.com/ for
these surface roots that produce the
to keeping roots out of certain areas,
additional information or contact your
damage to streets and sidewalks. The
they can also be used to keep roots out
local engineer, architect, or landscape
severe problems of tree root damage,
of sewer pipe gaskets and plastic drip
architect.
tree loss, and our ability to manage the
irrigation emitters. Their length of vi-
living root system has led to the inven-
ability is dependent on the agent used,
tion of tree root barriers. The most
and soil moisture conditions.
Structured Soils
A soil mix developed that provides
both the structural or load-bearing
capacity needed to support pavements, and the root growth/penetration, aeration, drainage needed by
trees. Structured soil provides a
continuous subbase layer under pavements while providing a material for
tree root growth. This shifts designs
away from individual tree pits to an
interconnected tree pit with stable
pavement system above. The longterm benefi ts include signifi cantly
improved tree growth, health, and life
expectancy along with reduced movement, failures, and maintenance costs
for adjacent pavements.
Tree Preser vation Guide
20
inhibit the tree roots. Defl ectors can
Modif y
Construction
Procedures
help reduce the soil compaction by
The closer the encroachment is to
paction. It has been found to reduce
the trees, the more care should be
compaction to depths of 4-inches,
taken with the work around the trees.
6-inches of wood chips or 4-inches of
Therefore, a number of different con-
¾ inch crushed gravel should be place
struction work procedures exist that
over the soil surface. It only take one
can help to protect the trees depend-
pass of a vehicle on unprotected soil
ing on the type or method of construc-
to cause compaction.
tion and distance from the tree.
the equipment. Applying a surface
mulch can help distribute the weight
of the load and minimize the soil com-
Root pruning is most effi ciently done
with equipment designed for that purpose. Large circular saws used to cut
concrete, and rocks are also effective.
The saws must be able to cut through
Root Pruning
roots to the same depth as excava-
Site Clearing
Soil excavation near trees causes un-
very close to a tree, it may be neces-
Damage to trees often occurs during
necessary damage for some distance
sary to dig the soil away with a shovel,
this process. Because the machines
towards the tree by pulling, ripping,
then cut the exposed roots with a saw.
are often large and require a lot of
and shattering roots. When soil ex-
When any root pruning needs to be
space for movement, the TPZ’s need to
cavation must be done near trees, the
done consult a professional forester
be in place before any clearing is made
roots should be pruned first to sever
or arborist.
and verified that the machine has
them cleanly.
enough clearance for safe movement.
If not, then the next smallest machine
tion. When excavation must occur
Don’t clear sites without first putting up tree protection.
should be used. Who should clear
unwanted vegetation around trees that
will remain? It is recommended that
the clearing is done by or the work
supervised by a professional forester
or arborist. Methods used should not
damage trees or the ground around
them (this includes the soil and leaf
litter). This usually means use of hand
tools only and no vehicles in the TPZ.
Soil Protection
& Damage
When movement of equipment across
root areas is unavoidable the number
of passes should be kept at a minimum and preventative steps taken to
Tree Preser vation Guide
21
Preconstruction
Treatments
Trenching & Tunneling
Irrigation
Before construction starts, a number
The single most important treatment
of activities may be implemented to
is to provide supplemental irrigation
invigorate trees and thereby increase
for trees under water stress. Irriga-
their tolerance of construction im-
tions should be designed to wet the
pacts. The applicability of each tech-
soil within the TPZ to the depth of the
Trenches should be routed outside the
nique to a given situation depends
root system and to replace that water
TPZ. Soil removed from the trench
on the amount of time available for
once it is depleted. Light, frequent irri-
should be placed on the side away
treatment before construction begins,
gations should be avoided. Irrigations
from trees and replaced as soon as
as well as the potential of the tree to
should wet the top 2 to 3 feet of soil.
possible. Utility trenches should be
respond to the treatment. The goal is
backfilled with good quality soil within
to maximize stored carbohydrates and
Early in the project, there may be no
the rooting area of trees that lies out-
the effectiveness of growth regula-
ready access to water on site. One
side of the TPZ. It is recommended
tors in the tree to quickly produce new
way to irrigate in that situation is to
that the trench is not backfi lled with
root, shoot, and adaptive growth and
create a 6-inch-high berm around
concrete, slurry, gravel, stone, or
to compartmentalize wounds. Appro-
trees, at the edge of the TPZ, and fill
other such materials especially in the
priate treatments should be applied
the basin from a water truck.
tree lawn between the curb and side-
as early as possible because mature
walk/property line.
trees take time to respond.
The way in which trenches are dug
and routed can greatly infl uence the
root systems of trees. To help reduce
the width of deep trenches, the walls
of the trench could be shored instead
of sloped. If lines need to be placed
across root systems, an alternative
to trenching is tunneling. Tunneling
under root systems can greatly reduce
both damage to the tree and the cost
to repair landscape and other features
destroyed in the trenching process. It
is typically recommended that trenching should be replaced with tunneling
when roots 1 inch or greater in diameter are encountered. For trees less
than 7 inches in diameter, no trenching should occur under the dripline.
Tree Preser vation Guide
22
Fertilization
Pest Control
The need for supplemental fertiliza-
Pests that signifi cantly affect tree
tion depends on the history of care
health should be controlled both
of the tree. In general, fertilizing is
before and during construction. For
recommended if the tree has been
example, diseases or insects that
growing slowly, has poor color, or if
would defoliate the tree and stimulate
the leaf litter has been removed. In
production of new leaves at the ex-
most cases nitrogen is the only ele-
pense of stored carbohydrates should
ation is the time of year of the pruning
ment required. It can be applied to
be controlled.
and the tree’s susceptibility to insect
and diseases. A qualifi ed arborist
the soil surface and irrigated in, or
injected into the soil as a liquid.
Pruning
should perform all pruning.
Fertilization may be benefi cial if
Pruning should be performed to clean
Brush can be chipped and spread un-
done the season before construction.
the crown of dead, diseased, crossing,
der the tree for mulch to help protect
Fertilization of trees during, and for at
weak, and dead wood, and to provide
against surface compaction, to stabi-
least one year following, construction
adequate clearance for equipment
lize soil temperatures, and to conserve
is not advised. Consult a professional
and construction. In general, no more
soil moisture. Toxicities have been re-
forester or arborist on the individual
than 20% of the live foliage should be
ported with cedar sawdust and do not
needs of your trees.
removed. A very important consider-
chip herbicide killed plant material.
Tree Preser vation Guide
23
Resources
Helpful Links
International Society of Arboriculture website
• www.treesaregood.com
The Oklahoma Urban and Community Forestry Council website
• www.okplanttrees.org
the USFS Urban Forestry website
• www.treelink.org
the National Arbor Day Foundation website
• www.arborday.org
The USFS Southern region Urban Forestry website
• www.urbanforestrysouth.org
The International Society of Arboriculture Southern Chapter
• www.isasouthern.org
The Oklahoma County Assessor’s property search page
• www.oklahomacounty.org/assessor/Searches/DefaultSearch.asp
Oklahoma State University Extension Fact Sheet search page
• pods.dasnr.okstate.edu
The Society of Municipal Arborists Page
• www.urban-forestry.com/mc/page.do
The Society of American Foresters website
• www.safnet.org
Urban Forestry Library
• forestry.lib.umn.edu/bib/urban.phtml
Tree Preser vation Guide
24
treee
Preservation
Guide
A
G R E A T
P L A C E
T O
G R O W
©2005 by City of Edmond, Oklahoma
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