Abstract

Wooden poles and posts have been used for decades as the cheapest and most convenient way to carry electricity, telephone lines, build fences and vineyard trellises. However, a multitude of soil organisms can decay wood, requiring regular replacement of decayed poles and posts. Preservatives such as creosote or CCA are currently used to impregnate timber and extend its in-soil life but these may be environmentally detrimental as leaching can contaminate soil and groundwater. A preserved wooden utility pole should last 25 years in soil before replacement with a concrete, steel or another preserved wooden pole. A physical barrier, a field liner (FL), has been used to encase the base of posts to retain preservative while preventing timber and soil contact. This paper reports on a 26 month accelerated field trial (equivalent to 5.42 years under normal conditions) testing FL’s fitted to lightly preserved (ACQ) and unpreserved posts in Australia. The field liners were calculated to be successful at extending the in-ground life of untreated posts 3.6 fold. Nearly all the sapwood of untreated posts without FL’s had rotted within 26 months, while the sapwood of lightly preserved posts without FL’s are expected to last 35 months in the trial (equivalent to 7.3 years in the field). No decay was found after 26 months with the lightly preserved posts with FL’s. These barriers were thus shown to confer considerable protection on wooden posts (whether preserved or unpreserved) from woodrot fungi in soil. This paper explains (with some quantitative data and modelling as evidence) the significance of this finding in terms of: reduced demand on timber supplies in Australia (in terms of both plantation and old-growth forests); cost saving to the utility companies; and the impact that using FL’s would have on protecting soil and groundwater from preservative leaching.