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 TM 5-684/NAVFAC MO-200/AFJMAN 32-1082
Table 4-l. Sapwood thickness in poles (continued)
Sapwood thickness
Sapwood thickness
Natural heartwood
Species
-
decay resistance
(inches)
(millimeters)
Low to moderate
2.0
Southern yellow pine.
to
4.25
51
to
108
Low
Lodgepole pine.
0.5
to
2.0
13
to
51
Low
Ponderosa pine
2.0
to
51
200
3.5
(b) Condition rating. For practical purposes,
should be given to the vicinity of any separation
the condition of a pole should be rated on its wood
checks. If the ground is wet, the wood may be soft
integrity or on the extent of any decay. While the
but not decayed, so examine a sliver of the wood to
see if it breaks easily or crumbles. Look and smell
amount of preservative present in one pole as com-
for preservative on the surface of the pole (a musty
pared with another should be taken into consider-
smell often indicates active decay). Remove as much
ation in the rating, a high degree of accuracy in this
decayed wood as possible with the spade and clean
respect requires laboratory methods or special ap-
the surface with a wire brush. Open pockets of de-
paratus.
cay and determine their extent by probing. Interior
(c) Effect of sapwood thickness. Table 4-l
decay at the ground line may be checked by taking
shows the average thickness of the sapwood in the
borings.
timber species which are most often used for facility
(3) Measuring pole circumference. After re-
poles. It will be noted that the species with thin
moval of all decayed wood, the remaining circumfer-
sapwood, which consequently receive a shallower
ence of the pole just below ground line should be
penetration of preservative, generally have a more
measured. Deduction from this measured circum-
durable heartwood. However, long life in poles is
ference is made for any external or internal decay
more dependent upon effective preservative treat-
ment. Since the thicker sapwood species are capable
pockets in order to determine whether the pole
meets the minimum circumference permitted by the
of a deeper treatment, they will often yield the long-
NESC.
est average life.
c. Groundline inspection. If the inspection of the
(a) If the ground-line circumference is below
above-ground portion of the pole indicates that re-
the permissible minimum, the pole should be
placement is necessary, there is no need for below-
promptly replaced or reinforced.
ground inspection. However, if the above-ground
(b) If the ground-line circumference is above
portion is substantially intact or adequate for treat-
the permissible minimum, the pole should be
ment in place, continue with the below-ground in-
ground-line treated as covered in section VI.
spection. Sampling procedures may be used if the
4-16. Determination of wood pole adequacy.
poles can be grouped by species and class, age, and
conditions of exposure to damage. Every third or
When inspections reveal heart rot; splits; lightning,
fourth pole should be inspected below the ground
insect, bird, or vehicle damage; or other apparent
line. Any unsatisfactory conditions found during
weaknesses, these conditions should be reported so
sampling will indicate the need for inspecting more
that the adequacy of the pole to sustain its loads
or all of the poles in the group. Use the following
may be evaluated by engineering personnel. When-
method for below-ground inspections:
ever the condition requires backfilling to any degree
(1) Excavation. If the sound test indicates no
more than that for spot inspection, provide
serious internal decay above ground (verified by
groundline treatment as covered in section VI. Test
borings when in doubt), the next step is excavating
wood pole stubs, as required for the wood poles they
the soil to about 18 inches (450 millimeters). It may
help support. Steel stubs should be inspected to see
be necessary to excavate deeper in dry or porous
that the installation is in good condition and hold-
soils, and this can be determined as the work
ing properly.
progresses. When there is danger of toppling the
a. Replacement. If the diameter of the pole has
pole by digging, provide temporary propping of
decreased more than about 15 percent due to dam-
poles. The hole should be wide enough to permit use
age or decay at the ground line, or if the diameter of
of the borer below the ground line. Care must be
the heart-rotted section as determined by boring is
taken not to cut or disturb the ground wire.
more than about 30 percent of the total diameter of
(2) Inspection. With a blunt tool, probe the sur-
the pole, it should be scheduled for replacement as
soon as possible.
face of the pole gently below the ground line to see if
b . Reinforcement. In many cases, a pole will de-
the wood is intact and firm or if decay is present as
evidenced by soft, spongy wood. Close attention
cay at the ground line but the wood above will be
4-9
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