Administrative Report Or Publication


Conserving energy by environmentally acceptable practices in maintaining and procuring transmission poles for long service ; August 1993 Public Deposited

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  • Evaluation of previously established field trials of internal remedial treatments continues to verify the excellent long-term protection afforded by these treatments. Field trials with gell encapsulated methylisothiocyanate (MITC) demonstrate that gelatin does not interfere with chemical release, nor is addition of supplemental moisture required for release. Field trials have been established to evaluate several new formulations including Basamid plus copper, boron/fluoride rods, and boron rods. Field trials of gelled and pelletized metham sodium indicate that both formulations are moving well through Douglas-fir poles one year after treatment. Evaluations of a copper naphthenate/boron paste for internal treatment indicate that the formulation has moved a short distance from the point of application 3 years after treatment. Boron rod field trials were not fully sampled for residual chemical level this past year; however, evaluation of cores removed from fused borate rod trials in New York indicate that some additional boron diffusion has occurred. Examination of treatment holes suggests that considerable amounts of the boron remain in rod form 2 years after application. In laboratory studies, we have evaluated the use of metham sodium/basamid mixtures and have found that these formulations provide enhanced MITC production over longer periods than either of the components alone. Both formulations were solid, creating the potential for development of safer formulations which provide a rapid release with long term protection. Field trials of these systems will be established in the coming months. Studies also continue with Basamid in an effort to enhance decomposition of this compound. Studies have shown that moisture addition has the most significant effect on decomposition followed by the presence of copper and increasing pH. Further studies on decomposition products are planned to better understand the activity of this molecule. Examination of Douglas-fir timbers treated with metham sodium indicate that MITC levels are similar to those found in poles at similar times after treatment. The presence increased surface area on timbers apparently did not adversely affect diffusion or chemical loss. Evaluation of the fungitoxicity of mixtures of MITC and carbon disulfide is underway in an effort better understand the activity of metham sodium. This compound decomposes to produce a wide array of volatile compounds with varying degrees of toxicity to fungi. Preliminary trials have shown the relatively low toxicity associated with carbon disulfide, a major decomposition product, particularly under acidic conditions. Trials with mixtures will begin shortly. Efforts to develop a three dimensional model of MITC movement are continuing. The model has been evaluated on data collected from small blocks and efforts are underway to verify these results. In addition, full pole grids have been prepared to evaluate the effects of treatment hole geometry and orientation on fumigant movement. Studies to identify alternative treatments for protecting western redcedar sapwood from decay are continuing. A variety chemicals have been shown to be effective 5 years after treatment; however, longer term trials of other formulations suggests that performance declines rapidly at longer time points. Field trials of remedial treatments for field drilled bolt holes continue to demonstrate the performance of diffusible boron and fluoride for preventing fungal attack. These trials will be evaluated again in the coming year. Inspection of the above ground region of Douglas-fir poles in the Pacific Northwest have shown that many poles are colonized by decay fungi far above the groundline. Fungal incidence was greatest in poles near the coast, but decay fungi were also isolated from poles in drier climates. Sampling of additional poles is planned to provide a more detailed analysis of the risk of above ground decay in this region. Efforts are also continuing to evaluate the performance of through-bored Douglas-fir poles to provide better data on the degree of preservative penetration required in the through-bored zone to achieve optimum performance. These trials have shown that most poles are well treated, but no decay has been detected in the through bored zone of poles with as little as 60 % of the through-bored zone treated. Efforts are also underway to evaluate penetration and retention of preservative in poles with various throughboring patterns. Studies to identify optimum conditions for sterilization of air-seasoned Douglas-fir poles are continuing. These trials have evaluated pentachlorophenol in oil treatments. The results illustrate the value of long treatment cycles which incorporate Boulton-seasoning. The data from these trials will be used to construct heating curves for this treatment. Trials of groundline preservative systems on Douglas-fir pole stubs continue to show that more recently developed formulations continue to move through the wood at rates which are similar to those found with older pentachlorophenol based systems. Trials in California on pine, Douglas-fir and western redcedar have provided similar results. Tests are now underway to establish thresholds for mixtures of groundline preservative formulations. Copper naphthenate treated wood continues to perform well in both field and fungal cellar trials. Unweathered western redcedar stakes have tended to perform better than stakes which were weathered prior to treatment. These differences may reflect an increased permeability which enhances leaching.
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