2023-025 Effective Vegetation Management for Telecommunication Providers March 10, 2023 Report No. 2023-025
INFORMAL STAFF REPORT
TO MAYOR AND CITY COUNCIL
SUBJECT:
Effecting vegetation management onto telecommunication providers in the City of Denton.
BACKGROUND:
Ice Storm Mara crossed the State of Texas at the end of January 2023 and left a path of ice and
bitter cold from North Texas to the southern Hill Country. The City of Denton experienced
crippling ice on its roadways that made travel dangerous while Denton Municipal Electric's
(DME) electric distribution system remained solid with minimal outages. However, electric
utilities in the Hill Country suffered ice loading on transmission and distribution circuits, leading
to widespread damage and multiple outages over a broad service area leaving some without power
for days. News reports and board meetings from Hill Country area electric providers pointed to at
least one common causal contributor — ice loaded trees. Ice loaded trees falling on the pole
attachments of telecommunication providers brought down segments of the electric distribution
network.
Since January 2021, Engage Denton has recorded 19 citizen concerns of"lines in trees." After
DME's investigation,each of the concerns were identified as telecommunication cables in the trees
— not DME lines. DME has established a Vegetation Management program that outlines the
clearances DME strives to achieve and maintain on its electric transmission and distribution
circuits. The preventive nature of this program has assisted the utility in minimizing outages due
to vegetation getting into its transmission and distribution lines. DME recommends these required
vegetation clearances should extend to telecommunication providers who have attachments on
DME's poles. This action will not fully eliminate all potential issues as seen in the Hill Country,
but it is anticipated to reduce the risk of a large falling tree limb taking down a DME pole therefore
cause an electric outage, along with reducing the number of requests for service that DME's crews
investigate.
DISCUSSION:
DME will distribute the letter attached to known contact emails and addresses for the
telecommunication providers in Denton during the week of March 20, 2023. In an upcoming City
Council meeting, Council will also receive a consent item to approve an ordinance requiring all
telecommunication companies to comply with the vegetation management program established by
DME. If telecommunication companies fail or refuse to comply with the ordinance, DME will use
staff and/or contractor resources to trim vegetation from a telecommunication line and bill the
telecommunication cable owner for these services with an appropriate service charge.
CONCLUSION:
DME believes it is important to take this action for the benefit of the health, safety, and welfare of
the public.Requiring telecommunication companies to proactively initiate vegetation management
practices should lead to reduced maintenance costs for DME and help support transmission and
distribution line safety in case of ice storms.
March 10,2023 Report No. 2023-025
ATTACHMENTS:
1. Attachment 1: Letter to Telecom Providers
STAFF CONTACT:
Jerry Fielder, P.E.
Engineering Division Manager, Denton Municipal Electric
Jerry.fielder@cityofdenton.com
(940) 349-7173
REQUESTOR: Staff Initiated
STAFF TIME TO COMPLETE REPORT: 1 hour
Attachment 1
Name
Address
City, State Zip code
Dear Telecom Provider in the City of Denton,
As a result of recent winter storm events and historical challenges faced by DME regarding trees
in communication lines, there is a need for a more proactive approach to mitigate this hazard. As
such, DME is proposing to implement the same Vegetation Management Program standards used
around energized lines to communication lines. The task of following these standards is your
responsibility. Excerpts from the program have been included in Attachment A.
DME is requesting your cooperation in implementing these standards which we believe will help
mitigate impacts to the delivery of energy to our customers while also ensuring the continuity of
your service to your customers.
DME requests your response to this proposal with a date certain for implementation and
identification of a primary contact with your company for this matter.
Sincerely,
Jerry Fielder, P.E.
Engineering Division Manager
Denton Municipal Electric
Attachment 1
Native Trees for North Texas & Growth Rate'
Scientific Name Common Name Growth Rate* Type
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 laegigata Hackberry 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
*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 inches per year.
Medium—Tree can grow from 13 to 24 inches per year.
Fast—Tree can grow 25 inches or more per year.
Deciduous trees' leaves lose their green coloring and turn orange, red, or brown before they shed
at the end of the growing search, generally in autumn.
1 Manual of Woody Landscape Plants by Michael Dirr
Attachment 1
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 do not change color.
Distribution Clearance Work Specifications Based on Growth Chart for Native Tress in
North Texas
1. General Guidelines
Effective tree to conductor clearance is determined by OSHA Tree Trimming Standards
1910.269(a)(1)(E), 1910.269(a)(2)(ii), and 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 height of the poles and line
c. The species and growth habit
d. The trimming cycles
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 erm 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 within 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, overhands shall be removed. When not removed, clearance shall be a
minimum of 15 feet.
Note: Overhand clearance shall be increased where ere circuits have experienced historical
exposure to snow and ice.
4. Other Clearances
Secondary conductors, service drops, streetlight circuit, DME fiber-optic and guy wires shall
be cleared on a case-by-case basis as determine necessary by DME during field inspection, to
free them from weight, strain, or displacement cause b contact with trees.
5. Vine Clearance
Unless otherwise instructed, vines ascending all poles and guy wires shall be cut off at ground
level.
Tree trimming clearances are established and based on the following:
• IEEE Table 5 and Table 7 (516-2003)
• OSHA Tree Trimming Standards (1910.269)
• ANSI A 300 Pruning Standards which are industry trimming standards developed by the
Tree Care Industry Association and accepted by industry leaders, including the
International Society of Arboriculture, American Society of Consulting Arborist, Utility
Arborist Association, US Forest Service, and other tree care organization. The standards
Attachment 1
include use of natural lateral or directional trimming methods that promote growth of the
tree away for 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.
• Applicable City of Denton codes
Clearance from
Conductor Type 0 to 480V 2 to 25 kV
Vegetation*
Side Primary 5 feet 10 feet
Overhang Primary 5 feet 15 feet
*All clearances are at the time of trimming