In-service condition of selected utility poles in Ghana and efficacy of their residual CCA retention against a brown rot fungus (Gloeophylum striatum)

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CCA treated woods have been used for a long time in Ghana, even before the 1940s. In recent times, there have been some problems with these preserved woods which are being used as utility poles in both the electricity and telecommunication industries. The efficacy of residual CCA wood preservative remaining in utility poles in service after a period of time ranging from 10 years to 38 years was investigated from eight different locations namely, Akosombo, Akropong-Akwapim and Doyumu in the Eastern Region, Barekese, Asokore Effiduase, Kaasi Industrial Area and U.S.T. Campus in the Ashanti Region, and finally Golokwati in the Volta Region. Observation of the external surface of poles showed that areas in Golokwati, Akosombo and Effiduase are the worst affected with decay depth of 6-12cm, 6-12cm and 4-10cm with Kaasi having no decay. Internal decay in poles showed Kaasi poles to have the highest sound portion of 68.5 percent and no advanced decay while areas in Effiduase and Golokwati had advanced decay percentage of 46.1 and 59.8. Cores from these inspected poles were extracted from the groundline region of the pole and assessed visually for the extent of external decay of the pole. Residual retention was determined by x-ray fluorescent analysis. Zone of inhibition (ZOI) and weight loss due to decay on the extracted cores were also determined. Residual retention for the 8 different locations indicated that only Kaasi Industrial Area high voltage poles had 1 9.7kg/m3 of preservative and is considered adequate enough to continue to sustain them in service for about 10 years to 15 years before remedial treatment may be offered. All the other locations had low retention levels ranging from 5.1kg/m3 at Golokwati to11.3 kg/m3 at Akropong-Akwapim. Zone of inhibition values also showed that by the seventh day, Akosombo, Kaasi and Akropong-Akwapim poles had high levels of 7mm, 6mm and 7mm respectively while U.S.T. showed an anomaly with the treated sample being overgrown and the untreated being 2mm from the fungi. Weight loss test also indicated a very low weight loss of 3.6% for Kaasi meaning higher resistance to decay fungi with U.S.T. Effiduase and Golokwati having high values of 37.5%, 376% and 36.0% respectively indicating a high susceptibility to decay fungi. Relating residual retention, zone of inhibition and weight loss values, it can be concluded that Kaasi Industrial Area poles are sound enough to remain in service while poles in U.S.T., Golokwati and Effiduase had serious decay and needed replacement. Poles in Akosombo even though they showed moderate levels of residual retention and weight loss with high levels of Zone of Inhibition (ZOl) needed replacement because of their external conditions which showed 6 to 12cm depth of decay while Akropong-Akwapim, Barekese and Doyumu posts can be offered remedial treatment upon inspection.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of the Degree of Master of Science, 1999