Conserving energy by environmentally acceptable practices in maintaining and procuring transmission poles for long service ; August 1989

Evaluations of previously established field trials indicate that\ud chioropicrin, and Vorlex continue to provide protection to Douglas-fir poles,\ud although the degree of protection is diminishing. Reapplication of Vapam 18\ud years after the initial application eliminated fungi which had recolonized the\ud poles. Methylisothiocyanate (MITC) continues to protect Douglas-fir poles 12\ud years after application.\ud Gelatin encapsulation of MITC or chioropicrin appears to have no negative\ud influence on fungitoxicity of these chemicals. Application of water to decompose\ud the gelatin accelerated initial chemical release, but had no longterm effects\ud on performance.\ud A series of laboratory trials have been established to evaluate the\ud performance of sodium n-methyldithiocarbamate (NaMDC), the active ingredient of\ud Vapam. This chemical decomposes more slowly than the liquid formulations and\ud a number of additives are being evaluated to accelerated decomposition. Along\ud with the solid NaMDC, a pelletized formulation of Vapam was evaluated which\ud contained 15 or 40 % NaMDC. These evaluations indicated that the addition of\ud water accelerates release, but the fungal survival in these tests was more\ud variable. The results suggest that a dosage 2 times greater than the liquid\ud formulation is required for effective fungal control; however, further tests are\ud planned to confirm these results.\ud The evaluations of MITC-FUME in Douglas-fir and southern pine poles\ud indicated that MITC has moved to a greater extent in Douglas-fir. Both closed\ud tube bioassays and gas chromatographic analyses of ethyl acetate extracts of wood\ud samples indicated that MITC was present at higher levels in Douglas-fir poles.\ud Southern pine is far more permeable than Douglas-fir and MITC movement should\ud be more rapid in this species. Further tests are planned to identify the nature\ud of this delayed movement.\ud 11\ud Evaluations of Dazomet, a crystalline solid which decomposes tO produce\ud MITC in wood, indicate that detectable levels of this chemical are present in\ud virtually all of the treatment groups. The decomposition rate of this chemical\ud is normally too slow for effective fungal control and these trials are examining\ud the ability of various additives to accelerate decomposition. Further\ud evaluations of pole sections treated with Dazomet and selected additives are\ud underway.\ud A study to evaluate the effect of voids on fumigant effectivness suggests\ud that voids do not adversely affect MITC movement through Douglas-fir pole\ud sections. These results indicate that treatment of voids should be costeffective\ud if the chemical is not applied directly to the void and if the pole\ud retains a sufficient degree of strength.\ud We continue to develop and refine a model for simulating the movement of\ud MITC through Douglas-fir under varying temperature and moisture conditions. The\ud model has been improved to permit three dimensional evaluations, but the times\ud required for computation are still somewhat long. Further evaluations using\ud a variety of environmental conditions are planned.\ud Evaluations of potential replacements for pentachiorophenol for treatment\ud of western redcedar sapwood and field drilled bolt holes have identified several\ud promising alternatives. These chemicals are now under study in several modified\ud field and laboratory tests. Field trials of several potential treatments for\ud field drilled bolt holes indicate that Boracol 40, disodium octaborate\ud tetrahydrate and ammonium bifluoride provided excellent protection over an 8 year\ud period. These formulations all are relatively safe and can be easily applied\ud in the field.\ud 111\ud A laboratory trial to evaluate the effects of selected basidiomycetes on\ud strength of Douglas-fir sapwood and heartwood has concluded. Fungal density,\ud measured as the average number of fungi colonies per beam, gradually increased\ud in all of the beams while longitudinal compression strength (LCS), modulus of\ud rupture (MOR), and modulus of elesticity (MOE) slowly declined. Of the\ud measurements, LCS appeared to be most useful, probably owing to the increased\ud number of sampling sites per beam. The results indicate that the degree of\ud colonization was not a good indicator of wood strength effects.\ud The value of kerfing for decreasing post-treatment checking and improving\ud the service life of Douglas-fir poles was evaluated using a series of inspection\ud reports from a local utility. Kerfed transmission poles had substantially lower\ud rates of internal decay and rejection, but there appeared to be little difference\ud in the rate of decay between kerfed and non-kerfed distribution poles.\ud The evaluation of disodium octaborate tetrahydrate for preventing\ud colonization of air-seasoning Douglas-fir pole sections has been completed.\ud Spraying with a 10 % boric acid equivalent solution (BAE) at 6 month intervals\ud provided the greatest degree of protection, although dipping in a 20 % BAE\ud solution at the start of air-seasoning produced a similar degree of protection.\ud As expected, fungal colonization was far lower at the dryer Oroville site and\ud borate treatment had little influence on the degree of fungal colonization at\ud this site. The results indicate that borate treatment at the start of airseasoning\ud is a viable method for limiting fungal colonization in moist airseasoning\ud sites west of the Cascade Mountains.\ud Evaluations of the tolerance of Stereum sanguinolentum and Peniophora spp.\ud to elevated temperature exposures indicated that both of these fungi were\ud extremely sensitive to elevated temperatures. The lack of long-term survival\ud structures in these fungi probably accounts for this susceptibility to heat.\ud iv\ud A series of trials which measured internal temperatures in Douglas-fir pole\ud sections during treatment with ammoniacal copper arsenate were used to develop\ud a model for predicting internal heating during steaming. The results indicated\ud that previous heating curves were overly optimistic in their prediction of\ud heating. A series of heating curves for various pole diameters and starting\ud conditions are presented.\ud A number of externally applied groundline treatments are under evaluation\ud in a field trial at Peavy Arboretum and a second trial will be established in\ud the San Francisco Bay area. Seven formulations (including standards) are\ud included. The Peavy site will be sampled in the next few months.\ud The performance of copper naphthenate in western wood species is being\ud evaluated in a series of small western redcedar sapwood stakelets which have been\ud treated to a range of retentions and exposed in the fungus cellar. The results\ud will be used to help confirm the performance of copper naphthenate in this\ud species