2021-069 DME Vegetation Management ProgramSeptember 3, 2021 Report No. 2020-069
INFORMAL STAFF REPORT
TO MAYOR AND CITY COUNCIL
SUBJECT:
DME Transmission and Distribution Vegetation Management Program (VMP)
EXECUTIVE SUMMARY:
DME operates and maintains approximately 360 miles of aerial distribution lines and
approximately 70 miles of aerial transmission lines. A main component of the DME’s maintenance
program is the VMP. DME is obligated by regulatory oversight bodies to adopt and implement a
VMP that reduces or eliminates the occurrences of vegetation caused system faults.
DISCUSSION:
In 2009, DME drafted and implemented a transmission and distribution vegetation plan. The plan
was based on standard industry practices and met the requirements of OSHA 1910.260 and ANSI
A300 standards. The VMP included with this report continues to meet those requirements and
standards and was also reviewed by the City of Denton’s Park and Recreation Department.
Trimming of resident owned trees in electric easements is a required but sensitive activity. An
important component of the plan is resident communications. To address this need, DME
implemented a 3-method approach to notifying residents of impending trimming activities. DME
utilizes Interactive Voice Response (IVR - phone notification to residents), door hangers placed
prior to trimming activities, and personal contact. DME requires the tree trimming contractor to
have an arborist on site as well as a full time DME employee who oversees the activities of the
tree trimming contractor. DME utilizes herbicides as approved per the Integrated Pest
Management Plan which was adopted by City Council.
CONCLUSION:
DME evaluates the vegetation plan annually and adjusts the plan based on current regulatory and
industry best practices. DME is proud to announce, as was communicated in our budget
presentation to City Council, that we are currently seeking a designation as a Tree Line USA Utility
from the National Arbor Day Foundation. This designation provides acknowledgement that DME
is operating our utility in a manner that has a minimum impact to the existing tree canopy in the
greater Denton area.
ATTACHMENTS:
September 3, 2021 Report No. 2020-069
DME Transmission and Distribution Vegetation Management Plan
Tree Line USA Utility Application and Program Information Link
STAFF CONTACT:
Chris Lutrick
DME Executive Manager of Operations
Chris.lutrick@cityofdenton.com
940-349-7152
REQUESTOR:
Staff Initiated
PARTICIPATING DEPARTMENTS:
Parks and Recreation – Gary Packan, Director of Parks and Recreation; and Haywood Morgan,
Urban Forester.
STAFF TIME TO COMPLETE REPORT:
2 Hours
DME
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Denton Municipal Electric
Vegetation Management Program
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Vegetation Management Program of Denton Municipal Electric
TVMP Section Table of Contents
Section I – Objectives
Section II – Customer Relations
Section III - Trimming Practices, Procedures and Definitions
Section IV – Removal and Trimming Standards – Work Specifications
Section V – Document Control
SECTION I Objectives
The objectives of the Transmission Vegetation Management Program (TMVP) of Denton
Municipal Electric (DME) are to provide a safe system environment for DME’s customers and
the general public and to minimize tree-related outages caused during high wind, snow and ice
storms, and trees losing their branches form disease or old age. The objectives are to be
achieved while maintaining positive relations and utilizing sound environmental practices.
To establish a comprehensive and consistent program for performing vegetation
management of the DME transmission system and distribution right-of-ways and
easements in compliance with NERC Standard FAC-003-1. This program defines the
responsibilities of DME personnel and contractors, identifies procedures to be followed by
contractors performing all work and defines the clearance requirements between
conductors and vegetation acceptable to DME for maintaining a reliable transmission and
distribution service.
NOTE: This program will be reviewed annually for accuracy and revisions by the
Vegetation Management Subject Matter Expert (SME)(Currently Brad Watts).
SECTION II Customer Relations
Customer Contact Steps
1. IVR (Interactive Voice Response) will make contact by telephone informing the customer
when tree trimming will be done at their property and or neighborhood.
2. Door hangers are to be placed on all addresses affected by the tree trimming job.
3. All attempts shall be made to contact customers in person by a DME employee or
contractor working for DME before entering a customer property to trim trees.
DME SETTLEMENT STRATEGY
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DME will make direct contact with the land owner and or current resident.
We will state the fact of the important need to access the land with the respect of the land owner
and his property staying within the boundaries of our acquired easements.
DME and its contractors will restore any property damage that occurs from the direct result of
DME crews back to its original state at which we entered the property.
All other matters will be processed through our legal department in a timely manner.
SECTION III Trimming Practices, Procedures, and Definitions
Brush - a woody plant that is less than 3 inches diameter at breast height (dbh), that is not part
of an existing tree, and that may reach the conductor at maturity.
Brush work – trimming, clearing brush and applying an herbicide to the cut stems, or only
applying herbicide to brush.
Clearance 1 — The Transmission Operator (TO) shall determine and document appropriate
clearance distances to be achieved at the time of transmission vegetation management work
based upon local or regional conditions and the expected time frame in which the TO plans to
return for future vegetation management work. Local or regional conditions may include, but are
not limited to: operating voltage, appropriate vegetation management techniques, fire risk,
reasonably anticipated tree and conductor movement, species types and growth rates, species
failure characteristics, local climate and rainfall patterns, line terrain and elevation, location of
the vegetation within the span, and worker approach distance requirements. Clearance 1
distances shall be greater than those defined by Clearance 2 below.
Clearance 2 — The TO shall determine and document specific radial clearances to be
maintained between vegetation and conductors under all rated electrical operating conditions.
These minimum clearance distances are necessary to prevent flashover between vegetation
and conductors and will vary due to such factors as altitude and operating voltage. These TO-
specific minimum clearance distances shall be no less than those set forth in the Institute of
Electrical and Electronics Engineers (IEEE) Standard 516-2003 (Guide for Maintenance
Methods on Energized Power Lines) and as specified in its Section 4.2.2.3, Minimum Air
Insulation Distances Without Tools in the Air Gap.
o Where transmission system transient overvoltage factors are not known,
clearances shall be derived from Table 5, IEEE 516-2003, phase-to-ground
distances, with appropriate altitude correction factors applied.
o Where transmission system transient overvoltage factors are known, clearances
shall be derived from Table 7, IEEE 516-2003, phase-to-phase voltages, with
appropriate altitude correction factors applied.
Coniferous - any cone-bearing trees or shrubs, mostly evergreens.
Danger tree - any dead, dying, weak, diseased, or leaning tree (on or off the right-of-way) that
could fall onto the conductors.
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Diameter at Breast Height (dbh) – the diameter of individual tree trunks or individual stems of
brush measured at a point 4.5 feet above ground.
Deciduous - any perennial plant that sheds its leaves annually or at the end of a growing season
Demand tree trimming -trimming or removing the trees on a customer requested or emergency
basis. Also may include tree work associated with line construction projects. This is typically
required when trees have grown into the conductors, or are close to the conductors, and have
created a potentially dangerous situation. This may also include special trimming or chipping
work when requested by Denton Municipal Electric. Customer requested demand tree work
should only be assigned by Denton Municipal Electric.
Directional trimming - a form of natural trimming (pruning) used to encourage tree re-growth
away from the conductor. It is accomplished by removing limbs growing toward the conductors
entirely at the branch collar near the trunk of the tree, or by pruning to lateral branches that are
at least one-third the diameter of the limb being cut and are growing away from the conductor.
Drop-crotching - generally speaking, is a crown reduction technique in which a tree trimmer
makes the proper pruning cuts at crotches, removing the larger limb and favoring the smaller.
For electric line clearance, the trimmer would remove limbs growing toward the conductors and
favor those growing away from the conductors. This usually results in a "V" shaped appearance
of the tree crown and is frequently referred to as "V-trimming". See definition of "natural
pruning" for further description.
Evergreen - any plant that retains its leaves/needles year-round.
Herbicide - a chemical pesticide used to control, suppress, or kill plants, will have a colored die
for recognition. - BASAL SUMP MIX #1
E.P.A # 228-385
INGREDIENTS
Tahoe 4E
(Triclopyr)……………………20%
Dye………………….……….05%
Basal Oil…………………..79.5%
Natural pruning -a method by which branches are cut to the branch collar at a suitable parent
limb, the trunk of the tree, or an appropriately sized lateral branch. This method of pruning is
sometimes called "drop-crotching", “proper pruning”, the “Shigo method” or "lateral trimming."
Preventative maintenance - trimming or removing vegetation on a systematic basis typically by,
but not limited to, circuit or grid, and in a manner intended to achieve system reliability.
Pruning - the removal of dead, dying, diseased, interfering, objectionable, and/or weak branches
of trees or shrubs using proper arboricultural techniques.
Removal - completely removing an entire tree as close as practical to ground level and applying
herbicide to the cut stump.
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Right-of-way - a transmission or distribution right-of-way, an easement, a utility easement, or
any other corridor of land paralleling, on both sides, an overhead transmission or distribution
line, and in respect of which DME has certain rights.
Safety zone work – removing all overhangs by cutting back limbs to a minimum clearance of 10
feet from energized conductor.
Selective herbicide - an herbicide that, when applied to a mixed population of plants, will control
specific species without injury to others.
Shearing -the making of many small cuts so that a tree adjacent to the conductors is sheared in
a uniform line. This is not a generally acceptable practice.
Side pruning - using natural pruning methods to cut back or removing side branches that are
threatening the conductors; required where trees are growing adjacent to conductors.
Topping - cutting back the upper crown of a tree to a uniform horizontal line, leaving multiple
stubs. This is an improper and unacceptable trimming technique.
Tree - a perennial plant with a woody trunk measuring at least four (3) inches (dbh), and having
one set of annual rings at ground level or more than one set of annual rings not separated by
included bark. Trees that grow adjacent to one another and share an apparent common base
completely separated by "included bark" are considered to be distinct trees. "Included bark" is
bark that is included within the wood of a tree, or between the woody stems of separate trees,
creating a physical separation between the trees.
Tree crown - the upper portion of the tree, the branches or leaf area.
Trimming - cutting back tree branches or shrubs to shape or reduce the size of the tree or
shrub.
V-trim - using natural pruning methods to cut back large portions of the upper crown of a tree.
This is required when trees are located directly beneath a conductor. Also known as crown
reduction pruning or drop crotching.
Vegetation - all the plant (flora) life in a particular region. A plant community, assemblage or
aggregation with distinguishable characteristics.
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SECTION IV REMOVAL & TRIMMING STANDARDS – Work Specifications
Native Trees for North Texas & Growth Rate
Manual of Woody Landscape Plants, by Michael Dirr.
Scientific Name Common Name Growth Rate Type
* “Rate of growth refers to the vertical increase in growth unless specified differently. Rate, as
is true for size, is influenced by numerous variables such as soil, drainage, water, fertility, light,
exposure, ad infinitum.
Slow – Tree can grow up to 12” per year.
Medium – Tree can grow from 13” to 24” per year.
Fast – Tree can grow 25” or more per year.
Type of tree refers to tree being Deciduous or Evergreen:
Deciduous trees are trees whose leaves lose their green coloring and turn orange, red or
Pinus ponderosa Ponderosa Pine Medium Evergreen
Pinus nigra Austrian Pine Medium Evergreen
Carya illinoinensis Pecan Fast Deciduous
quercus virginiana Live Oak Medium Evergreen
Quercus marilandica Blackjack Oak Slow Deciduous
Quercus stellata Post Oak Slow Deciduous
Quercus alba White Oak Slow Deciduous
Celtis laevigata Hackerry Fast Deciduous
Ulmus americana American Elm Fast Deciduous
Ulmus crassifolia Cedar Elm Fast Deciduous
Prosopis glandulosa Mesquite Medium Deciduous
Populus deltoides Cottonwood Fast Deciduous
Juniperus ashei Texas cedar Medium Evergreen
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brown before they are shed at the end of the growing season, generally in autumn.
Evergreen trees carry their leaves throughout the year. Evergreens do shed their leaves, but
only a few at a time and over a long period, so there is never a noticeable change. For most
evergreen trees, the leaves don't change color.
A. Distribution Clearance Work Specifications Based on Growth Chart for Native Trees in
North Texas.
1. General Guidelines
Effective tree to conductor clearance is determined by: OSHA Tree Trimming Standards
1910.269(a)(1)(i)(E); 1910.269(a)(2)(ii); 1910.269(r)
American National Standards Institute A300 Pruning Standards
a. Voltage, tree location, and importance of the individual line
b. Ambient air temperature and the height of the poles and line
c. The species and growth habit.
d. The trimming cycle
2. Under and Side-clearance
Any tree affecting or potentially affecting a primary distribution line
Shall be trimmed to prevent any involvement with the line (see table 1. “DME Minimum
Clearance Requirements”).
Note: (1) Where the amount to be removed in order to obtain adequate clearance will
have an adverse impact on the overall long term health of the tree, the tree will be
considered for removal; (2) The neutral wire has the potential to carry primary voltage,
which contractor shall take into consideration when clearing primary lines; and (3) Open-
Wire Secondary Conductor and neutral shall have a minimum 5' of clearance. All poles
will have a minimum 5’ of clearance around the bottom of the pole.
3. Overhang Clearance
When at all possible, overhangs shall be removed. When not removed, clearance shall be a
minimum of 15 feet. Note: Overhang clearance shall be increased where circuits have
experienced historical exposure to snow and ice.
4. Other Clearances
Secondary Conductors, Service Drops, Streetlight Circuits, DME Fiber-optic and Guy Wires
shall be cleared on a case by case basis as determined necessary by DME during field
inspection, to free them from weight, strain, or displacement caused by contact with trees.
5. Vine Clearance:
Unless otherwise instructed, vines ascending all poles and guy wires shall be
Cut off at ground level.
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Tree Trimming Clearances are established and based on the following
IEEE Table 5 and Table 7, of 516-2003
OSHA Tree Trimming Standards (1910.269)
American National Standards Institute (ANSI) A300 Pruning Standards, which are
industry trimming standards developed by the Tree care Industry Association (TCIA) and
accepted by industry leaders, including the International Society of Arboriculture, the
American Society of Consulting Arborist, the Utility Arborist Association, the US Forest
Service and other tree care organizations. The standards include use of natural lateral or
directional trimming methods that promote growth of the tree away from the electrical
facilities. These trimming methods ideally allow a tree to retain as much of its natural
form as possible while requiring less trimming in the future.
a standard 75’ R.O.W for transmission lines
applicable City of Denton codes
Clearance from
vegetation Conductor Type 0 to 480 V 2‐ 25 KV 69 KV 138 KV
SIDE PRIMARY 5 FEET 10 FEET 15 FEET 30 FEET
OVERHANG PRIMARY 5 FEET 15 FEET NONE NONE
*All clearances are at the time of trimming.
Mitigation Measures – if sufficient clearances cannot be achieved for the protection of
transmission facilities due to various restrictions, then the TVMP SME shall notify Engineering
and System Operations to create a plan to deal with the insufficient clearance.
B. Inspection Process – Approved Procedures
1. All DME transmission circuits are trimmed on a five year trim cycle.
2. Upon completion of a trim, the Contractor Coordinator will inspect the circuit.
3. All DME transmission circuits are inspected on a Quarterly basis.
4. For IMMINENT THREAT of a transmission line outage due to vegetation:
a. inspector shall as soon as practical notify TVMP SME
b. SME will notify System Operations as soon as practical
c. An action plan shall be determined based on consultation with Engineering,
System Operations, TVMP SME, and if necessary, outside entities such as
neighboring entities or ERCOT
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C. DME Transmission Circuits and Types of Growth - Schedule
DME Vegetation Management Maintained Transmission Circuits
Circuit and Circuit Location KV Length/Miles
Growth Types/ Inspection
Denton West to ONCOR Fly Tap 345 KV 8.9 Native Trees/Quarterly
Denton West to Jim Christal 138 KV 3.2 Native Trees/Quarterly
Denton West to RD Wells 138 KV 4.47 Native Trees/Quarterly
Denton West to Fort Worth 138 KV 4.06 Native Trees/Quarterly
Jim Christal to Masch Branch 138 KV 2.95 Native Trees/Quarterly
Masch Branch to Denton North 138 KV 4.38 Native Trees/Quarterly
Denton North to North Lakes 138 KV 1.87 Native Trees/Quarterly
Denton North to Arco 138 KV 5.9 Native Trees/Quarterly
Denton North to Kings Row 138 KV 2.84 Native Trees/Quarterly
Kings Row to Cooper Creek 138 KV 2.13 Native Trees/Quarterly
Arco to Cooper Creek 138 KV 1.63 Native Trees/Quarterly
Cooper Creek to Mc Kinney 138 KV 1.47 Native Trees/Quarterly
Cooper Creek to Brinker 138 KV 2.28 Native Trees/Quarterly
McKinney to Brinker 138 KV 0.89 Native Trees/Quarterly
Spencer Interchange to Pockrus 138 KV 2.17 Native Trees/Quarterly
Pockrus to Corinth 138 KV 1.37 Native Trees/Quarterly
Pockrus to Teasley 138 KV 2.9 Native Trees/Quarterly
Teasley to Fort Worth 138 KV 4.05 Native Trees/Quarterly
Locust to DME Node 138 KV 1.68 Native Trees/Quarterly
Woodrow to DME Node 138 KV 0.08 Native Trees/Quarterly
Spencer Interchange to DME Node 138 KV 0.44 Native Trees/Quarterly
Brinker to Industrial 138 KV 0.22 Native Trees/Quarterly
Brinker to Woodrow 138 KV 0.47 Native Trees/Quarterly
Industrial to Spencer Interchange 138 KV 0.33 Native Trees/Quarterly
RD Wells to Hickory 69 KV 1.73 Native Trees/Quarterly
Hickory to Bonnie Brae 69 KV 0.95
Native Trees/Quarterly
Bonnie Brae to North Lakes 69 KV 1.64
Native Trees/Quarterly
Spencer Interchange to Spencer Switch 69 KV 0.23
Native Trees/Quarterly
Total Miles per KV Rating
345 KV 8.9
138 KV 51.78
69 KV 4.55
Total Miles Inspected 65.23
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NOTE: the above schedule can be adjusted for changing conditions. The schedule is based on
anticipated growth of vegetation and other environmental and operational factors. These may
include operating voltage, appropriate vegetation management techniques, fire risk, reasonably
anticipated tree and conductor movement, species types and growth rates, species failure
characteristics, local climate and rainfall patterns, line terrain and elevation, location of the
vegetation within the span, and worker approach distance requirements.
A schedule based on the above shall be created, with adjustments to the schedule documented
as they occur. The schedule considers the amount of time needed to gain applicable
permissions and permits.
The TVMP SME is responsible for ensuring that the vegetation management work has been
completed according to the work schedule and work specifications.
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SECTION V Document Control
Prepared by:
DME 12/18/2009
Change History:
The change history below reflects changes to the Manual or its structure.
Version Description of change Date
V 00.01 Initial version 12/18/2009
V00.01 Minor editorial corrections, formatting changes 3/10/2011
V00.02 NOT USED N/A
V00.03 Clarified section titles 1/24/2013
Review Log:
Reviewed By Title Date
Brad Watts Operations Line Superintendent 11/15/2010
Brad Watts Operations Line Superintendent 3/10/2011
Brad Watts Operations Line Superintendent 2/24/2012
Brad Watts Operations Line Superintendent 1/24/2013
Brad Watts Operations Line Superintendent 12/17/2014
Brad Watts Operations Line Division Manager 8/25/2021
Approved By Title Date
Chris Lutrick Executive Manger of Operations 8/26/2021