2.4. RECLAMATION WOOD POLE
UNES. Many Reclamation wood pole
lines were constructed in the late 1940's
and early 1950's. During this period,
most pole suppliers changed from the
use of creosote to pentachlo-rophenol as
a preservative, and adequate quality
control measures had not been
established to ensure optimum
preservative treatment. Also, during that
period, poles were in short supply, and
many species of timber were used for
poles. In some instances poles of
western red cedar, Douglas fir,
Iodgepole or southern pine, and western
larch were used in a given line section.
Throughout this bulletin, two species,
western red cedar and Douglas fir, are
discussed. For our purposes, pine and
larch poles should be considered in the
same category as Douglas fir unless
otherwise indicated.
UNES. Many Reclamation wood pole
lines were constructed in the late 1940's
and early 1950's. During this period,
most pole suppliers changed from the
use of creosote to pentachlo-rophenol as
a preservative, and adequate quality
control measures had not been
established to ensure optimum
preservative treatment. Also, during that
period, poles were in short supply, and
many species of timber were used for
poles. In some instances poles of
western red cedar, Douglas fir,
Iodgepole or southern pine, and western
larch were used in a given line section.
Throughout this bulletin, two species,
western red cedar and Douglas fir, are
discussed. For our purposes, pine and
larch poles should be considered in the
same category as Douglas fir unless
otherwise indicated.
2.5 DESTRUCTIVE FORCES. One of
the most destructive forces affecting
wooden transmission structures is decay.
It will generally progress at a predictable
rate and its advance can be readily
diagnosed in the field at all but the very
early stages.
the most destructive forces affecting
wooden transmission structures is decay.
It will generally progress at a predictable
rate and its advance can be readily
diagnosed in the field at all but the very
early stages.
Also, the damage caused by termites,
beetles, ants, and woodpeckers can be
significant and should receive attention
in proportion to the influence of these
pests upon the poles in a given area.
beetles, ants, and woodpeckers can be
significant and should receive attention
in proportion to the influence of these
pests upon the poles in a given area.
Early detection of decay or damage and
treatment of it is by far the most
important and successful step in
extending pole life.
treatment of it is by far the most
important and successful step in
extending pole life.
III. DECAY
3.1. TYPES OF DECAY.-
3.1.1. Internal decay.-Internal
deterioration of treated poles is due very
largely to development of checks after
treatment that expose the untreated
center portion of the pole to fungi and
insects. Although internal decay may
occur above ground as a result of checks
or holes drilled after treatment, the
deterioration of treated poles is due very
largely to development of checks after
treatment that expose the untreated
center portion of the pole to fungi and
insects. Although internal decay may
occur above ground as a result of checks
or holes drilled after treatment, the
critical groundline zone of poles is most subject
to such deterioration because moisture
conditions near and below groundline are most
favorable to growth of wood-destroying
organisms.
to such deterioration because moisture
conditions near and below groundline are most
favorable to growth of wood-destroying
organisms.
Most wood-destroying organisms are simple
plants, called fungi. They obtain all their food
from the wood they live in. Uke other plants,
fungi develop from spores (seeds) which
germinate, establish extensive root-like systems
within the wood, and eventually produce
microscopic size spores by the millions. Sound
wood may become infected by spores, or by
direct contact with infected material, including
contaminated test equipment.
plants, called fungi. They obtain all their food
from the wood they live in. Uke other plants,
fungi develop from spores (seeds) which
germinate, establish extensive root-like systems
within the wood, and eventually produce
microscopic size spores by the millions. Sound
wood may become infected by spores, or by
direct contact with infected material, including
contaminated test equipment.
During the progress of decay, wood first loses its
luster (looks "dead"), then, as change in color
becomes progressively more pronounced, the
wood loses its characteristic structure and
strength, until only a soft whitish or easily
crumbled brown mass remains. Usually the
decayed wood is wetter than adjacent sound
wood. In cedar poles, internal decay usually
appears as brown pockets of advanced decay
with little surrounding areas of partially decayed
wood
luster (looks "dead"), then, as change in color
becomes progressively more pronounced, the
wood loses its characteristic structure and
strength, until only a soft whitish or easily
crumbled brown mass remains. Usually the
decayed wood is wetter than adjacent sound
wood. In cedar poles, internal decay usually
appears as brown pockets of advanced decay
with little surrounding areas of partially decayed
wood
pockets of advanced decay may be surrounded
by large areas of wood in various stages of decay
by large areas of wood in various stages of decay
section may contain decay in the earlier stages
but with advanced decay limited to a small area.
Most frequently, insects such as termites and
carpenter ants are also present in the decayed
zone.
but with advanced decay limited to a small area.
Most frequently, insects such as termites and
carpenter ants are also present in the decayed
zone.
3.1.2. External decay.-In any species of timber,
external decay results from using a poor
preservative or from a Iow absorption of the
preservative by the timer. In older poles, external
decay is a consequence of gradual loss of most
of the preservative in the sapwood through
leaching, evaporation, and chemical change. In
butt-treated cedar poles, a softening of the
sapwood known as "shell rot' occurs in the upper
untreated portion of the pole. Such decay starts
in the inner sapwood where air and moisture
conditions promote fungus growth, and
eventually extends to the outer sapwood.
external decay results from using a poor
preservative or from a Iow absorption of the
preservative by the timer. In older poles, external
decay is a consequence of gradual loss of most
of the preservative in the sapwood through
leaching, evaporation, and chemical change. In
butt-treated cedar poles, a softening of the
sapwood known as "shell rot' occurs in the upper
untreated portion of the pole. Such decay starts
in the inner sapwood where air and moisture
conditions promote fungus growth, and
eventually extends to the outer sapwood.
3.1.3. Groundline decay.-In most cases, the first
occurrence of decay will be just below the
groundline. This is where the conditions of
occurrence of decay will be just below the
groundline. This is where the conditions of
(FIST 4- 6)
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