Quantcast  Internal Void Treatment

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the pesticide's label, with a stiff bristle brush, to all poles marked for ground line treatment and
steel stub reinforcement. All checks and pockets will be thoroughly treated. Preservative shall
be applied to sound wood from 4 inches above to 18 inches or more below ground level. All ex-
ternal decay and loose wood shall first be removed from the treatment zone with a sharp chip-
ping tool. All chips and decayed pieces shall be removed from the hole. Care shall be exercised
to remove the least possible amount of sound wood. Prior to backfilling, a polyethylene-coated
kraft paper shall be tightly wrapped and securely stapled around the treated portion of the pole.
7.1.4.2  Internal Void Treatment,  Liquid preservatives or fumigants may be
used to control decay and/or insect attack within the central core of poles.
Liquid Preservatives. Internal void treatment with liquids is most successful
on cedar and other woods that develop well defined rot pockets and where the transition from rotten
to sound wood is abrupt; they are least effective in Douglas-fir with poorly defined rot pockets. For
Douglas-fir, the use of a fumigant alone or in combination with a water-soluble solution should be
used. To arrest internal decay, water-soluble chemicals or arsenicals and fluorides are forced into
the voids and diffuse through the wet wood. Ants in pole voids can be controlled by injection with
volatile liquids combined with creosote or pentachlorophenol.
NAVFAC TS-20312 specifies the following for internal void treatment:
INTERNAL VOID TREATMENT: Serviceable poles with voids, hollows or insect galleries
shall be internally treated with a liquid pesticide registered by the EPA for such use. Poles shall
be bored with a 3/8 inch drill bit, a sufficient number of times to assure uniform internal
coverage. Preservative shall be pumped into the bottom hole until it runs out the next higher
hole. The hole is then plugged with a preservative-treated plug, and preservative shall be
pumped into the next higher hole until it runs out the hole above. The procedure is repeated
until the entire cavity is flooded or a maximum of one gallon of preservative is used.
Fumigation. (Note: Because of the extreme hazards associated with
fumigants, they shall only be applied by individuals who hold a valid DOD or State Pesticide Ap-
plicator Certification in the Category applicable to fumigation. Consult the cognizant PMC for local
regulations concerning fumigation). Fumigants can control internal decay for at least nine years in
pressure treated Douglas-fir transmission poles. As a result, the use of fumigants to treat Douglas-
fir poles, piles and timbers with internal decay is common technology. However, fumigation treat-
ments aren't as long-lasting in southern pine poles and timbers as they are in Douglas-fir.
Sodium N-methyl dithiocarbamate (Vapam), methylisothiocyanate (Vorlex), and
trichloronitromethane (chloropicrin) are currently registered with the U.S. Environmental Protection
Agency (EPA) for application to wood.
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