Introduction
Platte River Power Authority continually manages vegetation in and near its transmission
right-of-ways to maintain safety and electric reliability.
Fallen trees
and branches are a primary cause of electric power outages; therefore,
vegetation must be kept clear of electric power lines. Additionally,
consideration must be given to vegetation on right-of-ways that would
affect the safety and effectiveness of structure inspections, vehicular
access, structure-to-structure line-of-sight and any vegetation that
poses a potential fire hazard.
Objectives
The primary objectives of vegetation management are:
- To minimize
the risk of trees or branches falling into transmission lines causing
electric service outages.
- To maximize
the safety of all people who, for any reason, need to be in the vicinity
of Platte River’s transmission lines.
- To maintain
sufficient clearance on right-of-ways and access routs to allow for
adequate inspection of facilities and emergency response.
- To meet
all federal regulatory guidelines for vegetation management.
Management
Zones
Platte River acknowledges two zones in managing vegetation near high voltage
power lines. Platte River will manage the wire zone to allow only low-growing
ornamental trees, shrubs and grasses. Vegetation found in the right-of-way
to exceed 15 feet will be removed
The next
zone outward from the wire zone is the “border zone” where
trees are managed on a 45-degree rule. Starting at a height of 15 feet,
where the wire zone ends, trees in the border zone will be pruned at
a 45-degree angle away from the wire zone. This type of management
will prevent trees from falling into and contacting transmission lines.
Click to see a diagram of the wire
and border zones.
Inspection
and Access Requirements
Platte River requires that access to its right-of-ways and facilities provide
for safe and effective inspection of the facilities. To assure safety and effectiveness,
the following guidelines are followed:
- Inspection
of Structures - brush and trees will be completely removed at least
ten feet in each direction from the outer circumference of transmission
structures and down guys.
- Vehicular
Access - access lanes of at least ten to twelve feet in width will
be kept clear of interfering vegetation.
- Structure-to-Structure
Line-of-Sight - brush and trees will be removed to allow visual inspection
from the ground of conductors and structures one span in either direction.
- Fire
Danger - In critical areas, heavy vegetation will be removed from
the right-of-way if damage to facilities is possible from wildfires.
Inspection
Frequency
The need for vegetation management is primarily determined during inspections
by Platte River personnel. Full inspections will occur biannually in the spring
and fall. Follow-up inspections can be triggered by vegetation proximity to
facilities or fast-growing vegetation.
Tree
Removal and Pruning
Any vegetation found to be in violation of clearances during inspections will
be pruned or removed.
Whenever
possible, adequate clearance around facilities will be obtained by
pruning. The goal of pruning is to trim an amount that will maintain
the required clearances for, at least, three to four years.
When
pruning is not adequate or when trees are deemed a high risk to electrical
service or to the safety of the general public, they will be removed
by Platte River. High-risk trees, called “hazard trees”,
are specifically defined by Platte River as any tree located on, or
adjacent to, a transmission line right-of-way or substation that could
damage the facilities should it fall. Such trees generally, but not
always, lean toward the right-of-way or are defective. A number of
things can cause a tree to be defective such as heart rot, shallow
roots, death of all, or part, of the tree, deformities, cracks or splits,
or anything that could result in the tree or a main branch of the tree
falling.
Extreme
conditions such as snow loading, high winds and saturated soils will
be assumed when evaluating trees for potential hazards.
Landowner
Notification and Permission
Attempts will be made to notify landowners of anticipated tasks to be performed
on a right-of-way. This provides property owners time to raise any concerns
they may have. Platte River will perform work if attempts to contact property
owners are unsuccessful when federal regulatory violations are imminent.
Preventative
Approach
Platte River prefers to take a preventative approach to vegetation management
rather than a reactive approach and recommends that any new trees planted on,
or near, transmission right-of-ways have mature heights that comply with the
height requirements as mentioned before.
Planting
according to mature height will reduce the likelihood that trees will
eventually need to be pruned or removed.
For a guide
to trees and their mature heights, go to Colorado State University’s
Cooperative Extension Web site: www.ext.colostate.edu/ptlk/1715.html.
Contact trees@prpa.org with
any questions.
