HomeMy WebLinkAbout08022007 BSC Agenda Item 5 • S •
CRITERIA MANUAL
FOR THE URBAN FOREST
of the
CITY of WEST UNIVERSITY PLACE, TEX A S
February 1994
CRITERIA MANUAL (February 28, 1994) Page CM--1
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TABLE OF CONTENTS
INTRODUCTION: PHILOSOPHY AND GENERAL RULE 4
1.TREE SURVEY STANDARDS 4
1.1 REQUIRED FIELD DATA 4
1.1.1 Location 4
1.1.2 Circumference 4
1.1.3 Type (Species) 4
1.1.4 Critical Root Zone; Crown 5
1.2 RECOMMENDED ADDITIONAL FIELD DATA 5
1.2.1 Crown Clearance 5
1.2.2 Condition 5
1.2.3 Spot Elevation 5
1.3 PLAN GRAPHICS 5
1.3.1 Trunk Location 5
1.3.2 critical Root Zone (CRZ); Crown; Retained Trees 5
1.33 Sizes and Types 6
2. TREE EVALUATION AND SITE PLANNING 6
2.1 TREE EVALUATION 7
2.1.1 Tree Evaluation Method 7
2.1.2 Condition 7
2.1.3 Type 7
2.1.4 Size 8
2.1.5 Screening; Aesthetics 8
2.1.6 Energy Conservation and Heat Abatement 8
2.1.7 Safety 8
2.1.8 Adjacent Trees 9
2.1.9 Water Quality Protection and Soil Conservation 9
2.1.10 Wildlife Habitat 9
2.1.11 Historical significance 10
2.2 TREE PRESERVATION CRITERIA 10
2.2.1 Root Zone Impacts 10
2.2.2 Crown Impacts 11
2.2.3 Deviations from Criteria 11
2.3 DESIGN CONSTRAINTS AND ALTERNATIVES 11
2.3.1 Permeable Paving 11
2.3.2 Building Alternatives 12
2.3.3 Sidewalks 12
2.3.4 Grading 12
2.3.5 Utilities 13
3. MITIGATIVE MEASURES AND REPLACEMENT TREES 13
3.1 MITIGATIVE MEASURES 13
3.1.1 Tree Maintenance 13
3.1.2 Special Construction Techniques 13
3.2 REPLACEMENT TREES 14
3.2.1 Quantities of Replacement Trees 14
3.2.2 Available Planting Area: On-site and off-site Replacement 15
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3.2.3 Survival Potential; Irrigation and Maintenance 15
3.2.4 Types of Replacement Trees 15
3.2.5 Minimum Standards For Total Number of Trees 15
3.2.6 Enforcement Criteria; Delayed Planting 16
4. TREE PHYSIOLOGY 16
APPENDIX A: CLASSES OF TREES 19
APPENDIX B. WARNING SIGN REQUIRED FOR TREE PROTECTION FENCES 23
LIST OF FIGURES
Figure 1. Measurement of various tree configurations
Figure 1.b Example of crown area measurement
Figure 2. Example of typical plan graphics
Figure 3. Aeration systems for trees in fill areas
Figure 4. Retaining walls to mitigate cuts and fills
Figure 5. Minimizing root impact by boring
Figure 6. Tree Structure And Physiology
IMPORTANT NOTE
This manual is to be used and interpreted in accordance with the City's ordinances on urban forest
preservation and enhancement, codified as Article XIV of Chapter 6 of the City's Code of Ordinances.
Unless the context indicates that another meaning is intended, terms used in this manual have the same
meanings as in Article XIV.
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INTRODUCTION: PHILOSOPHY AND GENERAL RULE
It is the intent of thc City to preserve thc Urban Forest as a whole through two approaches:
■ Preservation or replacement of existing trees. The City seeks to: (i) avoid tree damage wherever
feasible; (ii) mitigate damage when it occurs; (iii) require on-site replacement of trees that must be
removed, and (iv) require off-site replacement of trees that cannot be replaced on-site, either by
direct planting or through a Tree Trust.
■ Require sites where major development takes place to attain a Minimum Planting Standard for
trees, regardless of the number of pre-existing trees.
1. TREE SURVEY STANDARDS
1.1 REQUIRED FIELD DATA
Tree data submitted for a Tree Survey or Tree Disposition Conditions must be obtained from a ground
survey. The data that must be obtained in the field arc Tree locations, circumferences, types (species),and
crown areas (the driplinc).
1.1.1 Location
Tree Surveys must be as accurate as possible, but need not be certified_ Levels of inaccuracy that will
result in a failure to comply with the City ordinance and construction specifications may necessitate new
surveys and plan adjustments prior to permit approval.
Trees on City easements adjoining the site must be surveyed.
Trees with 30% or more of their Critical Root Zones extending onto an affected Subject Site or project
casement must be surveyed. Trunk locations of off-site Trees may be estimated to avoid trespass problems.
Methods for locating Trees may vary depending on the size of the project and number of Trees. In most
cases, taping the distance to the center of the trunk from two (2) known points is a viable option.
1.1.2 Citcumference
The circumference of a Tree trunk is measured 4.5 feet above the ground using an ordinary tape measure or
diameter tape. (A Tree on a slope shall be measured from the high side.) Measurement is taken just above
or just below any unusual swells in the trunk, as closely as possible to the 4 and one-half foot level (see
Figure 6-502(1)). For Multiple-Trunk Trees, the trunk Circumference is deemed to equal the Circumference
of the largest trunk plus half the Circumference of each additional trunk. Measurements should be accurate
to the nearest 112 inch.
1.1.3 Type (Species)
Tree types should be accurate to the species level and may be listed by common names or botanical names
(e.g. Post Oak or Qucrcus stellata).
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Good field references for Houston arc: Texas Trees, a Friendly Guide, by Paul W. Cox and Patty Leslie
(available from Chickadee Nature Store, 713-956-2670); the Trees For Texas Resource Guide, available
from the Texas
Department of Agriculture, 512-463-7504; Field Guide to Texas Trees, by Benny J. Simpson; and Trees,
Shrubs and Woody Vines of East Texas, by Elray Nixon.
1.1.4 Critical Root Zone; Crown.
The Critical Root Zone (or 'CRZ') means, for any given Tree, the area within a circle centered on the
trunk location. The circle's diameter is one-half the sum of the broadest and the narrowest dripline
diameters. See Figure lb,attached.
The dripline and crown information will also be useful in assessing the impact of projected construction.
1.2 RECOMMENDED ADDITIONAL FIELD DATA
1.2.1 Crown Clearance
This information is often critical in determining whether a given structure of vehicular use area can
practically be placed within the dripline of a Tree. If this information is recorded, the surveyor should
consider the vertical distance to any major branches.
1.2.2 Condition
This is one of the principal factors in determining whether a Tree should or should not be preserved.
Surveyors should not speculate about the condition of Trees unless they have the necessary credentials;
however, if a Tree is obviously in poor condition, it should be noted.
1.2.3 Spot Elevation
Taking an elevation reading near the trunks of some Trees will provide valuable information for project
designers. Since grade changes have a very destructive impact on Trees, it is important to get the most
accurate information possible.
1.3 PLAN GRAPHICS
The standard Tree graphics discussed below are important to provide consistent information in the most
useful format for efficient plan review. Sec Figure 2 for examples of Tree graphics.
1.3.1 Tnink Location
The trunk location on the plan must represent the center of the trunk at ground level. If the Trcc leans
substantially above that point, show the direction of the lean with an arrow.
1.3.2 Critical Root Zone (CRZ); Cmwn; Retained Trees
The Critical Root Zone should be indicated by a circle centered on the trunk. If the crown is significantly
skewed or irregular, show also a circle with a radius in feet equal to the diameter of the Tree in inches or
CRITERIA MANUAL (February 28, 1994) Page CM--S
per measurement of crown area whichever is greater. The actual crown may also be shown if it is skewed
and will have a significant impact on construction. Note that the actual amount of critical roots for any tree
will depend upon many factors (see Section 2.2.1 Root Zone Impacts).
Trees proposed to be retained are to be represented by circles drawn with a solid line, while Trees proposed
to be removed arc to be represented by dashed lines. Proposed replacement Trees should be graphically
differentiated, as shown in Figure 2.
1.3.3 Sizes and Types
Tree circumferences and types must also be shown on the plan. This information should be shown adjacent
to each trunk location. For sites with a large number of Tr ee s, this data should be shown in legend form
referenced by a Tree number adjacent to each trunk location. Legends can be useful because they allow for
the presentation of other data such as crown configuration, height, condition, etc.
1.4 SMALL-SCALE PROJECTS
The Urban Forester may prescribe the contents for a simple, low-cost Tree Survey for small-scale projects.
For these projects, the Urban Forester may allow the deletion of some data and details otherwise required
and may make provisions to assist lay persons preparing their own surveys.
2. TREE EVALUATION AND SITE PLANNING
The Urban Forester shall use the following criteria to evaluate Trees shown in Tree Surveys and, working
with the applicant and City building officials, the Urban Forester shall prepare or approve Tree Disposition
Conditions complying with: Chapter 6 of the Code of Ordinances, this Chapter 2, the provisions of Chapter
3 (relating to mitigation, if applicable) and the other applicable provisions of this manual.
The Urban Forester may prescribe simple, low-cost Tree Disposition Conditions for small-scale projects.
For such projects, the Urban Forester may allow the deletion of some data and details otherwise required
and may make provisions to assist lay persons preparing their own plans.
While the guidelines set forth here are intended to be as comprehensive as possible, no printed document
can substitute for the knowledge and experience of a qualified urban forester. The recommendations of the
City Urban Forester may differ from a simple 'face value' interpretation of these guidelines;however,the
Forester should work cooperatively with the applicant and with City building officials to reach a mutually
agreeable solution. The Forester should also be prepared to justify 'non-standard' decisions by presenting
the special circumstances that apply.
The process of Tree evaluation and site planning will include:
o The identification of valuable Trees;
o An assessment of minimum standards for Tree preservation;
o An analysis of design constraints and alternatives; and
o The negotiation of mitigative measures when necessary.
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2.1 TREE EVALUATION
The City's ordinances address the preservation of Large Trees. Ilowcvcr, not all Largc Trccs have the same
value, duc to such factors as type (species) or condition. Conversely, some smaller trees may have greater
value duc to their rarity, screening potential or other factors.
2.1.1 Tree Evaluation Method
The following factors must all be considered in determining the value of any tree. Weighing factors are
included to aid in this determination.
Using these criteria, a designer can walk the project area and perform a rough analysis of the tree situation
before starting the design of the project. The Urban Forester should use these same factors in approving the
Tree Disposition Conditions.
Ten factors are included: condition, type, size, aesthetics, energy conservation and heat abatement, safety,
adjacent Trees, water quality protection and soil conservation, wildlife habitat and historic significance.
The sum of scores for all ten factors determines the relative value of a Tree. In general,highly valued
Trees (total rating of 30 or more out of a possible 40) should be preserved if at all possible. In all cases,
the initial calculation of replacement inches required will depend on the valuation and size of the Tree being
removed.
2.1.2 Condition
In assessing a Tree's condition, the forester considers trunk condition, growth rate, tree structure, insect and
disease problems,crown development and life expectancy. A score is assigned as follows:
I = Poor
2 = Fair
3 = Good
4 = Excellent
2.1.3 Type
The species of Trees found in the City have been divided into four classes based on overall quality. The
chart in Appendix A indicates how each species fits in this general classification. A score is assigned as
follows:
1 = Class IV
2 = Class III
3 = Class II
4 = Class I
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2.1.4 Size
Tree sizes arc divided into four categories. A score is assigned for cach size category as follows:
1 = Less than 25 inchcs circumference (8 inches diameter)
2 = Between 25 inches cf. and SO inchcs cf. (16 inches diameter)
3 = Between 50 inches cf. and 75 inches cf. (25 inchcs diameter)
4 = More than 75 inchcs cf.
2.1.5 ScrecninE; Aesthetics
Trees may score high in this area if they provide screening and privacy to the property or if they arc in
good condition and have exemplary form. A score is assigned as follows:
1 = Poor
2 = Fair
3 = Good
4 = Excellent
2.1.6 Encrpy Conservation and Heat Abatement
If a Tree is shading a building or pedestrian use area in its existing situation, it receives a high score under
this category. The energy conservation and heat abatement potential is also considered even if there are not
obvious benefits, since trees in general cool the air. For example, large Trees west of a buildable area will
score high. A score is assigned as follows:
1 = Poor
2 = Fair
3 = Good
4 =Excellent
2.1.7 Safety
If a Tree is in a hazardous situation due to external factors related to man-made features (not inherent in the
condition of the Tree), for example, its location relative to a road intersection, etc., it receives a low score.
Scores reflect the feasibility of mitigating the safety problems and are assigned as follows:
1 = Hazardous; low mitigation potential
2 = Hazardous; medium mitigation potential
3 =Hazardous; high mitigation potential
4 = Not hazardous
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2.1.8 Adjacent Tires
The proximity of other Trees has a bearing on a Trcc's value. Everything else being equal, a lone Tree has
greater value than one Tree of many. The fate of other Trccs in the vicinity also affects this rating factor.
A score is assigned as follows:
1 = Many Trees; high retention potential of adjaccnt Trees
2 = Many Trees; low retention potential of adjacent Trees
3 = Few adjacent Trees
4 = Lone Tree
2.1.9 Water Quality Protection and Soil Conservation
Trees help reduce storm water runoff and enhance ground water recharge by breaking the impact of
raindrops and improving soil structure. A Tree's effectiveness in this capacity is correlated with the size of
the crown and root area. Large Trees with full crowns and unrestricted root areas score highest in this
category. A score is assigned as follows:
1 = Poor
2 = Fair
3 =Good
4 = Excellent
2.1.10 Wildlife Habitat
This factor is rated on the basis of the intrinsic value of the type of Tree as a provider of food and forage
and general wildlife cover characteristics, or on the basis of field observations of a particular Tree.
Regarding field observations, an individual Tree may rate higher than the assigned intrinsic value of the
genus due to such things as the presence of food-bearing parasites or epiphytes or due to the potential for or
actual presence of wildlife nesting cavities. A score is assigned as follows:
1 = Poor
2 = Fair
3 =Good
4 = Excellent
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2.1.11 Historical significance
The highcst rating in this category is reserved for Trees that fit one of the following criteria:
o The Tree is on a registry of historic or especially important Trees.
o The Tree has been documented as historically significant.
o The Tree is rare in the Houston area.
o Due to its location and size, the Tree serves as a significant landmark on the landscape.
Since historical significance is largely a function of age, the Urban Forester's estimate of the age of the Tree
also has a bearing on this value. A score is assigned as follows:
1 = Less than 20 years old.
2 = Between 20 and 40 years old.
3 = Greater than 40 years old.
4 = Registered, rare or landmark tree.
2.2 TREE PRESERVATION CRITERIA
2.2.1 Root Zone Impacts
Although a Tree's root system ranges well beyond the dripline, for the practical purposes of this Criteria
Manual and the ordinances, the Critical Root Zone (CRZ) has been established.
As more completely described in Chapter 4, most of the important roots are shallower than three feet,so the
Urban Forester will normally require much less protection (or no protection) for subsurface areas deeper
than three feet, even if they are nominally within a CRZ. Boring of utility lines, for example, might have
very little or no impact on tree roots if carried out deeper than three feet.
Because existing development on a site may affect the actual distribution of tree roots,the Urban Forester
may require protection of areas outside the CRZ and may determine that it is not necessary to protect areas
within the CRZ where there may be few, if any, significant roots. For example, a Tree growing next to a
house on a slab will not normally have as many significant roots beneath the slab as the side of the root
system growing without the covering of a non-porous surface. This will allow new buildings to be erected
on the site of the old slab near a Tree to be preserved.
Design constraints often dictate that Trees slated for preservation have
some encroachment on their CRZ. Weighing this fact with what appears to be an acceptable degree of risk
to most Trees, the following maximum allowable impacts have been established for Trees with normal
CRTs:
o A minimum of 75% of the CRZ must be preserved at natural grade,with natural ground cover.
o No cut or fill greater than two (2) inches will be located within
the inner 3/4 of the CRZ.
In order to ensure that root zones are adequately preserved, protective fencing should be erected to enclose
areas with significant roots. Root areas that will be covered with permeable paving must be protected by
fencing until the immediate time for construction of the permeable paving. If this is not possible (due to
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limited access to the site), mitigative measures must be taken to protect the roots as much as possible (sec
Section 3.1.2).
2.2.2 Crown Impacts
The following is thc maximum allowable impact for Trce crowns:
o A maximum of 30% of thc viable portion of a Tree's crown may be removed.
Construction methods must also be considered. For example, a building wall may only require the removal
of 30% of the crown, but the scaffolding necessary to construct the building may require the removal of
another 20% of the crown.
2.2.3 Deviations from Criteria
These criteria represent minimum standards for determining whether or not a Tree is 'preserved." Grcatcr
impacts may be allowed, provided that all design alternatives have been proven unfeasible and that some
acceptable form of mitigation such as a remedial care program is negotiated (see Section 3.1.1).
Conversely,some cases may require that a larger area of root area be preserved to increase the survival
potential of particularly valuable Trees.
These design criteria are enforced in the field as well as on the plan. Plan adjustments made during
construction must be reviewed and approved by the City Urban Forester prior to the adjustments being
made.
2.3 DESIGN CONSTRAINTS AND ALTERNATIVES
In addition to the preservation of valuable Trees, many other factors can affect site planning: reasonable and
lawful use of the property,cut and fill limitations,access and egress restrictions, parking and driveway
requirements, and impervious cover limitations. Tree preservation is intrinsically less definitive than most
of these restrictions, and all factors must be considered together to arrive at a reasonable solution. In some
cases it may be desirable or necessary to remove Trees and replace them with newly planted Trees.
In order to best provide for the preservation of Trees, the project designer should carefully consider different
design alternatives in the initial planning of the project. Meeting with the City Urban Forester in a
preliminary consultation prior to submitting plans for review is advised when there appear to be conflicts.
In the review of a proposed project, the first indicator of how well Trees have been incorporated in the
design process is the impact on Large Trees. These Trees are considered on an individual basis, and a
proposal to remove any of them is carefully scrutinized.
Another indicator is how the proposal will impact smaller, valuable Trees. These Trees are typically
considered in mass as they relate to the overall preservation of the character of the site.
The following sections describe some design alternatives that can be used to preserve Trees.
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2.3.1 Permeable Paving
This alternative is less preferable than leaving 75% of the root area natural. The qualities that make a good
paving surface are in direct conflict with the qualities necessary to save tree roots. Permeable paving is
permitted,however, provided the installation meets City specifications and the following criteria:
o Finished grade of the permeable paving surface may be required to be set above existing grade, if
necessary to provide room for base and paving material without unreasonable cutting,and if
elevating the paving would not cause significant problems not related to trees.
o A minimum of 60% of the CRZ must remain at natural grade with a natural ground cover.
o The combined area of permeable paving and natural cover around a Tree must be at least 80% of
the CRZ.
o Permeable paving is only permitted in parking spaces and low traffic drives.
2.3.2 Building Alternatives
In many cases Buildings have been erected very close to the Tree with little adverse effect on the Tree.
Construction methods that make this possible include:
o Pier and beam foundations, with sufficient air space to allow oxygen to penetrate into the soil for
the roots.
o Finished floor elevations that minimize cut and fill.
o Buildings notched around significant trees.
o Buildings designed to fit under crowns of adjacent Trees.
To comply with the design criteria requiring retention of 70% of a Tree's crown, consideration must be
given to the following:
o Providing adequate work space during construction;
o Providing a safe distance between limbs and walls, caves, roofs, etc.; and
o Applying proper pruning techniques.
2.3.3 Sidewalks
Sidewalks appear innocuous on plans, but can be very detrimental to Trees because of grading requirements.
Some design alternatives that should be considered arc:
o Move sidewalk as far from Tree trunks as possible.
o Construct sidewalk on grade in the location of the original sidewalk.
o Provide a finished grade above existing grade for sidewalks required in close proximity to a Tree
trunk.
o Route drainage under sidewalks where elevated grade is required.
o Reduce width of sidewalk.
2.3.4 Grading
A grade change of a few inches can be extremely detrimental to a Tree.
Some design alternatives that can be used to preserve Trees arc as follows:
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o Provide Tree well and/or aeration systems for Trees in fill areas. (Sec Figure 3.)
o Provide retaining walls to mitigate cuts and fills. (Sec Figure 4.)
2.3.5 Utilities
Underground water and sewer lines, storm sewers, lawn irrigation systems have significant impact on Trees,
as do overhead electric and telephone utilities. Some typical design alternatives that should be considered
arc as follows:
o Establish the trenches for underground utilities where they will have the least impact on Trees.
o Stack underground utility lines to reduce the number of trenches required.
o Bore or tunnel under Trees to minimize root impacts (See Figure 5).
o Hand-dig trenches to avoid cutting any roots larger than one (I) inch diameter.
o When planting Trees, plant low-growing Trees under power lines.
3. MITIGATIVE MEASURES AND REPLACEMENT TREES
Many of the existing trees in the City grow very slowly,making preservation very critical to avoid long-
term impacts. At the same time, land is at a premium, and there is considerable pressure to build on as
&much land as possible. In many cases, it will be difficult to meet the above minimum standards, in which
cast, the Urban Forester may specify that Replacement Trees be planted or that special mitigative measures
be taken to protect existing Trees.
3.1 MITIGATIVE MEASURES
To protect Large Trees in cases in which it is not possible to meet the minimum design criteria, the Urban
Forester may stipulate mitigative measures. Some of these mitigative measures include:
3.1.1 Tree Maintenance
A remedial cart program can increase the survival potential to an acceptable level in many cases. The City
urban forester must review the remedial care program to estimate whether it will accomplish what is
necessary to maintain the viability of affected Trees. Such a program might include schedules for watering,
feeding, soil aeration, spraying, etc.
To ensure compliance, the program must be documented by a plan note at the time of plan approval. In
addition, prior to issuance of a certificate of occupancy,a permittee may be required to submit, in especially
critical cases, the following:
o A signed service contract for review and approval by the City; and
o Fiscal security in an amount equal to the going rate for the approved service plus 15% to cover
administrative costs.
These measures are necessary because the remedial care program must typically extend over a minimum 12-
month period after completion of the project.
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3.1.2 Special Construction Techniques
In conjunction with remedial care, mitigation may include special construction techniques not normally
required in standard specifications. Some of these techniques include the following:
o Leaving existing sidewalks and driveways in place for storage of materials and vehicular access,
until construction of the Building is complete.
o Prior to excavation within Tree driplines or the removal of Trees adjacent to other trees that are to
remain, make a clean cut between the disturbed and undisturbed root zones with a rock saw or
similar equipment to minimize root damage.
o In significant root areas that cannot be protected during construction with fencing and where
vehicular traffic is anticipated,cover those areas with four (4) inches of organic mulch or gravel
topped by two-inch road boards to minimize soil compaction and root damage.
o Perform all grading within significant root areas by hand or with small equipment to minimize root
damage.
o Water all Trees most heavily impacted by construction activities deeply once a week during periods
of hot,dry weather. Spray Tree crowns with water periodically to reduce dust accumulation on the
leaves.
o When installing concrete adjacent to significant roots of a Tree,use a plastic vapor barrier behind
the concrete to prohibit leaching of lime into the soil.
3.2 REPLACEMENT TREES
The most common measure used to mitigate Tree removals in the planting of Replacement Trees. The
following factors affect tree replacement:
o The uantit of Replacement q y o p ment Trees; ,.
o The available planting area;
o The anticipated rate of survival of Trees planted;
o The types of Trees proposed.
3.2.1 antities of Replacement Qu D mcnt Trees
Replacement Tree values will be expressed in terms of caliper inches (diameter) measured per standards
outlined in the American Standard of Nursery Stock, a publication prepared by the American Association of
Nurserymen and approved by the American National Standards Institute. Measurements arc to be taken as
follows:
• 6 inches from the ground for Trees up to an including 4 inches diameter
• 12 inches from the ground for Trees 4 1/2 inches up to and including
8 inches diameter
• 4 1/2 feet above the ground for Trees 9 inches diameter and larger.
For Trees with a value greater than 30 points using the criteria in Section 2.1, replacement calculations will
initially require 100% of the diameter of the Tree in question. For example, a Tree svith a 75-inch
circumference (24-inch diameter) will require 24 caliper inches of Replacement Trees, which could be met
by six Trees of 4 inches each or four Trees of 6 inches each.
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For Trees with a value from 20 to 30 points, replacement calculations will initially require 75% of the
diameter of the Tree in question. In this case, a Trce with a 75-inch circumference (24-inch diameter) will
require 18 caliper inches of Replacement Trees.
For Trees with a value from 10 to 19 points, replacement will initially_require 50% of the diameter of the
Tree in question.
In cases where a Tree is dead or judged by the Urban Forester to be in such poor condition that it will not
live more than another year, no replacement is required.
In all cases a reduction shall be allowed in the number and sizes of Replacement Trees, if the applicant
requests a reduction, and if the applicant demonstrates clearly that there arc sufficient remaining, pre-
existing Trees on the affected Subject Site to meet 1.5 times the minimum planting standard set forth in
Section 3.2.5. Notwithstanding the minimum planting standards, each of the remaining pre-existing trees
must be Class I or II Large trees six inches or more in diameter.
3.2.2 Available Plantinf Area: On-site and off-site Replacement
Replacement Trees should be planted on the Subject Site from which existing trees are to be removed. If
this is not feasible, the applicant may either:
o Initiate a proposal to plant Trees off-site if the planting site is in reasonable proximity to the
project area.
o Provide for Replacement Trees through a "replacement inch" certificate from a Tree Trust.
3.2.3 Survival Potential;Irritation and Maintenance
Before approving any replacement option, the Urban Forester will assess the probability that Trees planted
will survive. This typically requires that some type of irrigation and maintenance capability be implemented
for a minimum of 12 months. Irrigation or maintenance may not be required for the full 12 months if it can
be adequately demonstrated that, given the size and type of Trees planted, the planting site and the time of
year the Trees arc planted, the mortality rate is likely to be low. The applicant may be required to conform
to the maintenance guidelines set forth in 3.1.1. Tree Maintenance.
3.2.4 Types of Replacement Trees
In order to enhance the general quality of the urban forest, 75% of the Replacement Trees required must
normally be Class I or Class II species (see Appendix A). The Urban forester may recommend Trees from
other Classes. All Trees must be suitable for the environment of the immediate planting site. The height
rating of the Replacement Tree(s) (as shown in Appendix A) must normally match that of the tree(s) being
removed, although the Urban Forester may approve smaller or larger trees for good cause shown.
3.2.5 Minimum Standards For Total Number of Tires
Regardless of the number of Trees present on a Subject Site before development or construction, each
Subject Site must attain the Minimum Planting Standard whenever there is Major Development. This
standard has been determined by the Urban Forester as a reasonable expectation for property within the
City, given current open space and setback requirements. To satisfy the Minimum Planting Standard
requirement, a Tree must be at least two inches in diameter measured 6 inches above the ground. Pre-
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existing Trees may be of any species, while Trecs planted to meet the Minimum Planting Standard
requirement must be Class I or Class II Trees as set forth in this Criteria Manual. The number of Trees
required depends on the size of the affected Building Site and is set forth in the following table:
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Stzg of Building Stie m square feet Number of Trees required
5,000 or less 2
5,001 to 7,500 3
7,501 to 10,000 4
10,001 to 12,500 5
12,501 to 15,000 6
15,001 or more 7
3.2.6 Enforcement Criteria; Delayed Plantinfs.
The location, size and type of all Replacement Trees and all Trees planted to attain the Minimum Planting
Standard must be shown or referenced in the Tree Disposition Conditions in a manner which will allow
verification of their installation at the time of inspection for certificate of occupancy.
Optimum planting times do not always correspond to project completion. For that reason, planting of
Replacement Trees and Trees planted to attain the Minimum Planting Standard may take place after a
certificate of occupancy is issued, if approved by the Urban Forester, and if: (i) the permittee posts fiscal
security in an amount equal to the going rate for installed Trees with a one-year guarantee,plus 15% to
cover administrative costs, together with all necessary rights of entry, (ii) the permitte provides a "post-
dated' replacement inch certificate to guarantee planting at a specified future date if the permittee fails to
provide the required Trees by that date,and such a certificate can be made returnable to the permittee in
cast the permittee provides the required Trecs,or(iii) the permittee provides other sufficient assurance that
the Trees will be provided. Certificates of occupancy may be issued conditionally in this case.
4. TREE PHYSIOLOGY
The following is a collection of facts regarding tree physiology which provide the basis for the subsequent
design standards for preservation (see Figure 6).
4.4.1 Roots
Roots provide three primary functions: 1) support, 2) intake of nutrients and water and 3) storage of food
reserves. Cutting a large root has the triple effect of reducing the tree's anchorage, destroying the nutrient
intake potential beyond that point and reducing food reserves by a substantial amount.
Tree roots must respire in order to survive. Conditions which restrict the availability of oxygen effectively
suffocate affected roots. Such conditions will also result in the accumulation of carbon dioxide and other
toxic gases in the soil which adversely affect associated soil microfauna as well as the roots. Typical
conditions which inhibit this essential gas exchange arc compaction of the soil, addition of new soil (fill)
and ponding of water.
CRITERIA MANUAL (February 28, 1994) Page CM--16
• •
Trees establish a balance between root and crown areas such that destroying a portion of one may lead to
the destruction of a portion of the other.
Roots of adjacent trees arc typically intermingled through the sharing of rootstock by several stems, grafting
of roots by like species of trees or a general sharing of the same space. It is important to make a clean cut
when severing roots rather than tearing them. A ripping action (as with a dozer) affects roots of one (I) or
more trees far beyond the point of contact. Roots left jagged are also unable to produce the callous growth
necessary to close the wound; thus decay becomes more extensive. In addition, cleanly cut roots can
generate new roots more readily than torn roots.
The soil pH is an important factor in the functioning of the root system. Leaching of the lime from concrete
can increase alkalinity to potentially lethal levels.
Approximately 99 percent of a tree's roots occur within the first three (3) feet of soil and most of the fine
feeder roots which collect the moisture and nutrients arc located in the first twelve (12) inches of soil.
Typically,a tree's root system extends as much as two (2) to three (3) times the distance to the driplinc.
4.4.2 Trunk
A tree's trunk serves as a conduit for nutrients and water going to the leaves and food materials going to the
roots. In addition, it is a major food reserve storage area.
The sapwood contains the cells which serve as the upward transport system for nutrients and water. In most
trees, the sapwood is found within the last few inches of the outer trunk wood.
The phloem, located in a very thin layer of cells just inside the bark, serves as the downward transport
system for food materials, enzymes, hormones and other materials produced by the leaves.
The cambium is the tissue layer located between the phloem and sapwood that creates the cells for both
transport systems.
The proximity of all these important structures to the outer extremities of the trunk and branches make their
protection against injury so critical.
Contrary to popular belief, tree wound dressing is not a corollary to antiseptics used on animal wounds
which prevent infection and promote healing. The only sure cure is prevention where trees are concerned.
Trees never -heal' wounds, but rather, seal off or compartmentalize the affected area provided all conditions
are right for such activity. There are arboricultural techniques which can increase the chances of a tree
successfully compartmentalizing some wounds,but simply applying tree wound dressing is not chief among
them. (Note: Because tree wound dressing masks odors emitted by the wounds which attract insect
vectors, it is a vital procedure in the protection of oak trees against the oak wilt fungus. Tree wound
dressing should be applied to oaks immediately after wounding.)
The root collar is the interface of the tree trunk and root system evidenced by a flaring of the trunk near the
ground surface_ The proximity of this structure to the root system promotes the misconception that the root
flare can be covered with fill such as top soil dressing. This portion of the trunk is not adapted to the same
conditions as the underground roots. In addition to reducing aeration, fill material which tends to keep the
root flare and trunk area moist, can facilitate invasion by soil borne fungi and insects. When this happens,
the tree trunk can be girdled by decay agents, resulting in death. Some species of trees are more susceptible
to this than other; however, covering the root flare should be avoided as a general rule.
CRITERIA MANUAL (February 28, 1994) Page CM--17
•
4.4.3 Crown
The tree's branches and lcavcs make up the crown. Branchcs serve the same transport and food storage
function as the trunk in addition to giving rise to the lcavcs. Leaves manufacture the food and other
substances required to sustain the whole tree.
Removal of more than 30 percent of a tree's crown can severely impact the tree's ability to provide
sufficient food quantities for continued growth or protection against debilitation by disease.
b 14:\o 1472man.54
CRITERIA MANUAL (February 28, 1994) Page CM--18
i •
Appendix A: Classes of Trees
Trees are divided into four Basses. Class one and two trees are considered the most valuable in
enhancing the environment and are the most likely to prosper in this area. Species that are classified as
shade trees will reach a height that will conflict with overhead powerlines, permanent structures, or the
canopy will exceed the limits of a confined space. Species that are classified as ornamentals or shrubs
will not provide the protection or aesthetic impact of a shade tree, yet they are suitable for planting
beneath powerlines or within limited spaces. Following the common and botanical names for each
species, the following information is provided:
Class (one through four)
Origin
N - Native
I - Introduced
Site
1 -Xerophytic(requires little water)
2- Mesic(requires moderate water with good drainage)
3-Aquatic(requires significant water,tolerates poor drainage)
Light
1 - Full Sun
2 - Moderate Sun
3 - Shade
Size
1 - 80 to 100 feet in ultimate height(shade tree)
2 -30 to 80 feet in ultimate height(small tree to shrub)
3- 10 to 30 feet in ultimate height (shrub to bush)
For example, the code for Live Oak is 1/N/2/1/1, which indicates that the Live Oak is a Bass one
species that is native to Texas, requires moderate water with good drainage,demands or tolerates full
sun, and will exceed 80 feet in ultimate height. As a shade tree, the Live Oak will provide protection and
an aesthetic impact but the tree is not suitable for planting beneath powerlines or within confined spaces.
COMMON NAME BOTANICAL NAME CLASS tig SITE liGHT si
White Ash Fraxinus americana 1 N 2 1 1
Common Bald Cypress Taxodium distichum 1 N 2 2 1
Cedar Elm Ulmus crassifolia 1 N 2 1 1
Winged Elm Ulmus alata 1 N 2 1 1
Black Hickory Carya texanus 1 N 2 1 1
Shagbark Hickory Carya ovata 1 N 2 1 1
American Holly Ilex opaca 1 N 2 2 2
Southern Magnolia Magnolia grandifolia 1 N 2 1 2
Drummond Red Maple Acer rubrum var. drummondii 1 N 2 1 1
Bur Oak Quercus macrocarpa 1 N 2 1 1
Chinquapin Oak Quercus muhlenbergii 1 N 2 1 1
Live Oak Quercus virginiana 1 N 2 1 1
Nuttall Oak Quercus nuttallii 1 N 2 1 1
Page CM-19
• •
COMMON NAME BOTANICAL NAME CLASS Ni SITE LIGHT SIZE
Overcup Oak Quercus lyrata 1 N 2 1 1
Shumard Red Oak Quercus shumardii 1 N 2 1 1
Swamp Chestnut Oak Quercus prinus 1 N 3 1 1
Water Oak Quercus myrtifolia 1 N 2 1 1
White Oak Quercus alba 1 N 2 1 1
Willow Oak Quercus phellos 1 N 2 1 1
Texas Palm Sabal texana 1 N 2 1 1
Pecan Carya illinoensis 1 N 2 1 1
American Sweetgum Liquidambar stryaciflua 1 N 2 1 1
Eastern Black Walnut Juglans nigra 1 N 2 1 1
Red Bay Persea borbonia 1 N 2 2 2
Mexican Buckeye Ungnada speciosa 1 N 2 1 2
Scarlet(Red) Buckeye Aesculus pavia 1 N 2 2 3
Carolina Buckthorn Rhamnus caroliniana 1 N 2 1 3
Possumhaw Holly Ilex decidua 1 N 2 1 2
American Hombeam Carpinus caroliniana 1 N 2 2 2
Sweet-Bay Magnolia Magnolia virginiana 1 N 2 2 2
Texas Mountain-Laurel Kalmia latifolia 1 N 1 1 3
Palmetto Sabal minor 1 N 3 3 3
Texas Persimmon Diospyros texana 1 'N 1 1 3
Texas Pistache Pistacia texana 1 N 1 1 3
Tulip-Tree Liriodendron tulipifera 1 N 2 2 2
Arrow-wood Virbumum Viburnum dentatum 1 N 2 2 3
Rusty Blackhaw Viburnum Viburnum rufidulum 1 N 2 2 3
Wax Myrtle Myrica cerifera 1 N 2 1 3
Anacua Ehretia anacua 2 N 2 1 3
Green Ash Fraxinus pennsylvanica 2 N 3 2 1
River Birch Betula nigra 2 N 3 2 2
American Elm Ulmus americana 2 N 2 1 1
Black Gum (Water Tupelo) Nyssa aquatica 2 N 3 2 1
Common Honey-Locust Gleditsia triacanthos 2 N 2 1 2
Date Palm Phoenix canariensis 2 1 2 1 1
Desert Palm Washingtonia frlifera 2 I 1 1 1
Common Persimmon Diospyros virginiana 2 N 2 1 2
Snowbell Styrax americana 2 N 2 1 2
Western Soapberry Sapindus drummondii 2 N 2 1 2
Page CM-20
0 •
COMMON NAME BOTANICAL NAME CLASS Nn SITE LIGHT SITE
American Sycamore Plat anus occidentalis 2 N 2 1 1
Wright Acacia Acacia wrightii 2 N 1 1 2
Woollybucket Bumelia Bumelia lanuginosa 2 N 2 2 2
Rough-leaf Dogwood Corn us drummondii 2 N 2 3 3
Parsley Hawthorn Crataegus marshallil 2 N 2 2 3
Yaupon Holly Ilex vomitoria 2 N 2 2 3
Huisache Acacia famesiana 2 N 1 1 2
Indigo-Bush Amorpha fruticosa 2 N 2 2 3
Cherry Laurel Prunus caroliniana 2 N 2 2 3
Chalk Maple Acerleucoderme 2 N 2 1 2
Silver Maple Acer saccharinum 2 N 2 1 2
Paloverde Parkinsonnia aculeata 2 N 1 1 2
Mexican Plum Prunus mexicana 2 N 1 1 3
Lime Prickly-Ash Zanthoxylum fagara 2 N 1 1 2
Eastern Redbud Cercis canadensis 2 N 2 2 2
Sassafras Sassafras albidum 2 N 2 2 2
Virginia Sweetspire ilea virginica 2 N 3 2 3
Weeping Willow Salix babylonica 2 N 2 1 2
Common Witch-Hazel Hamamelis virginiana 2 N 2 1 3
,
Arborvitae Thuja spp. 3 I 2 1 1
Arizona Ash Fraxinus velutina 3 I 2 1 1
Beriandier Ash Fraxinus berlandreriana 3 I 2 1 1
Camphor-Tree Cinnamomum camphora 3 I 2 1 1
Deodar Cedar Cedrus deodara 3 I 2 1 2
Eastern Cottonwood Populus deltoides 3 N 2 1 1
Chinese Elm Ulmus parvifolia 3 I 2 1 1
Siberian Elm Ulmus pumila 3 I 2 1 1
Black Locust Robinia pseudoacacia 3 N 2 1 2
Box-Elder Maple Acer negundo 3 N 2 2 2
Red Mulberry Morus rubra 3 N 2 1 1
White Mulberry Morus alba 3 N 2 1 1
Florida Sabal Palm Sabal spp. 3 I 2 1 1
Common Pear Pyrus communis 3 N 2 1 2
Loblolly Pine Pinus taeda 3 N 2 1 1
Slash Pine Pinus elloittii 3 N 1 1 1
Page CM-21
• i
COMMON NAME BOTANICAL NAME CLASS Nn SiTE LIGHT SIZE
Gulf Black Willow Salix nigra 3 N 3 1 2
Japanese Yew Podocarpus macrophyllus 3 I 2 1 2
Cedar spp. Juniperus spp. 3 I 2 2 2
Common Crapemyrtle Lagerstroemia indica 3 I 2 1 3
American Elderberry Sambucus canadensis 3 N 2 2 3
1 Flowering Crabapple Malus spp. 3 I 2 1 2
Common Fig Ficus carica 3• N 2 1 3
Ornamental Holly Ilex spp. 3 I 2 2 3
Juniper spp. Juniperus spp. 3 I 2 2 2
Loquat Eriobotrya japonica 3 I 2 2 2
• Japanese Maple Acer palmatum 3 I 2 1 3
Mock-Orange Philadelphus spp. 3 I 2 2 3
Russian Olive Eleagnus anigustifo/ia 3 I 2 2 3
Mediteranean Fan Palm Chamaerops humilis 3 I 2 2 3
Mexican Fan Palm Washingtonia robusta 3 I 2 1 3
Sago Palm Cycus revoluta 3 I 2 2 3
Windmill Palm Trachycarpus martianus 3 I 2 2 3
Callery Pear Pyrus calleryana 3 I 2 1 2
Japanese Black Pine Pin us thunbergi 3 I 2 1 2
Ornamental Plum Prunus blireiana 3 I 2 1 3
Purple-leaf Plum Prunus cerasifera 3 I 2 1 3
Pomegranate Punica granatus 3 I 2 1 3
Hercules-Club Prickly-Ash Zanthoxylum clava-herculis 3 N 1 1 2
Rose-of-Sharon (Althea) Hibiscus syriacus 3 I 2 1 3
Vitex Vitex agnus-castus 3 I 2 1 3
Chinese Tallow Sapium sebiferum 4 I 2 1 2
Chinaberry Melia azedarach 4 I 2 1 2
Mimosa (Silktree) Albizia julibrissin 4 I 2 1 3
Oleander Nerium oleander 4 I 2 1 3
Golden Rain-Tree Koelreutera lormosiana 4 I 2 1 2
Sugar Hackberry Celtis Laevigata 4 N 2 1 1
Species of trees that are not induded in the above listing should be valued by the Urban Forester.
Page CM-22
• •
APPENDIX B. WARNING SIGN REQUIRED FOR TREE PROTECTION FENCES
Each warning sign must be weatherproof and printed in black on a white background at least 8.5 x II inches in
size, except for the two lines indicated by "'", which must be red. The print shall be at least as large as shown
below. The phone numbers shall be filled-in with the current phone numbers supplied by the Urban Forester.
TREE PROTECTIOY
FENCING
required by Code of Ordinances
City of West University Place
DO NOT REMOVR !
FINE: $100 OR MORE. JOB MAY BE SHUT DOWN.
FOR PERMISSION FOR TEMPORARY REMOVAL, CALL
. TO REPORT VIOLATIONS, CALL
CERCAS PARA
PROTJiJCCION de ARBOLIiS
Require por Ordenaciones de la
Ciudad de West University Place
FA V OR DR NO R / MOVER *
MULTA DE: $100. 0 MAS. TRABAJO PUEDE SER
TERMINA DO. PA RA PERMISO TEMPORAL DE
REMOVER LLAME: . PARA REPORTAR
VIOLA CLONES LLA ME:
CRITERIA MANUAL (Febwaiy 28, 1994) Page CM--23
• •
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Figure 1. Measurement of various tree configurations _.
CRITERIA MANUAL , b12:\critman7.54(November 1993) Page CM-24
i•
1.:: I . •. ' Critical Root Zone (CRZ) is deemed to
be equal to the average crown spread,
determined as set out below:
' To delormin.(Ito ava(tge sown spry ad of the Iry e,
ss4 traoo an outtino of tho tree's crown on the ground by
t. p(neutp stakes In the z duodty b nvafh(ho outer tips
•
i.
of tho branches. A string with a plumb bob or other
waijttt attached can he used to dooide where to ptac.r
the i<tnkos.
Using an Imaginary lino that would pass through t the
• cantor o(the hunk,moastlr. tho disteno*botwoon the
two stakes (arthost ',pan and tho two stakes c%a oc(
.3 togothor on oppocito aldos of tho (coo. Add thane two
-• moa*urentonts and divide try two for the avora.go width
S . of the tfoo's gown_
V
z1 (1
.
D'
r
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A
worry s (y6 wrc--
I"•
el
v
It Figure lb. Critical Root Zone (CRZ)
s
CRITERIA MANUAL , b12:\criiman7.54(No vent her 1993) Page CM-25
• •
libi8' Live Oak _ _BUILDING
lipp + 9' Live Oak
,
+ 20' Live Oak -}- 9' Live Oak
(Leans Northeast) ��� " - „.�� -' -
+ 8" Cedar Elm
.
-}- 10- Cedar n
04 glii4
p 410,
+ 13' Texas Oa 4
+ 15- Texas Oak
-}- 8' Sugarberry
I
• ,.
fri LIMITS OF CONSTRUCTION
ROTo be fenced during all phases of development.
A: All vegetation beyond this line to remain undisturbed
v. Sr.
- 1 • "thfsiliwer
. .fikt 1.1 lit& .
i a IN:Op I -L'' -I f A JAM.' Pgil
' ' - it .1 1"in.,&..41 Vs. t itawatijiite■- A&/u3 a•oonvosed of 8' to 15' Live Oaks. 2' ,��1 to 4' Yau on Hollies P
ik
'ireatrooprol,frefivorterwortzuwavvw4"-
3" Caliper Live Oak SCALE: 1" - 20'
Replacement Tree
Source: COA
Figure 2. Example of typical Milan graphics
CRITERIA MANUAL , b12:\crihman7.54(Novcmbcr 1993) Page CM-26
• 0
• Figure 4. Retaining .. •
walls to mitigate .�,j• �• •�'?►0••••• ;;1!aw;q
cuts and fills 1,1•�..�.01` r• f; it /n' p
a oti.„„0„t I," ,,&.e„,Li!,0, :....At Ali
�7•1. . a Ii...Noct.oiri:404,48.( wt: •
Retaining Walls V��•1 t� is i,.* e j %�• •�►'�?^tj�'�l�,•41.11r
For Cut and Fill ..:7.0.' ��{,;Ffipip � wmily.t,.# 9 !7.00 '•'
(See City of Austin 4.'
tea.. opp
Standards and Specifications) 4.4
���,,,.,+�`1Nv Figure 3. Aeration systems
,'•rye for trees in fill areas
lika
rte.
f rjanc4 \
lit\
IAAA 44nompAimelloillari%rwonativeta.,wevill
1 - ;$46!fpr...712.ri_."Protes:4;11;4;4 fik.s.a.i. .
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For Fill in the Critical Root Zone = 1 • ::::::::::::::::. ::
. _..so �7 : .
(See City of Austin -
Standards and S
peciii;at�on�) -
source: con
CRITERIA MANUAL , bl2Acritman7.S4(Novcmlicr 1993) Page CM-27
• •
vice _
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I ife4T1 i>"--ea
ft
TRENCHING IMPACTS-
/ #17,411, 66, _ I �
tri , ->-..
L
BORING IMPACTS
Source: con
Figure 5. Minimizing root impact. by ixiring
----------------------------------------------------------
CRITERIA MANUAL , b12:\crilman7"51(Novcnibcr 1991) Page CM-28
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rinor-e G. Tree Slwcture and Physiology
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CRITERIA MANUAL , b12:\critman7.54(November 1993) Page CM-29