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Many alternatives exist to prolong pole life compared to a standard treated wooden pole. In this article, we’ll be exploring the available options and giving an overview of their effects on safety, maintenance and overall environmental impact. Furthermore, this article will provide an overview of readily available solutions designed to protect a treated wooden pole.
The following information is from a report published by AquAeTer, Inc regarding an environmental lifecycle assessment of wooden, steel, concrete and composite poles (Full report available on request). The products used in the report represent general product categories, which are subject to different designs and material contents. Three of the most commonly used alternatives to wooden poles are steel, steel-reinforced concrete and composite/plastic. The composite poles use a fibreglass construction, sometimes featuring an outer plastic coating. From an initial cost standpoint, all of the above options, as a general rule, incur a more significant initial purchase cost, with composite being particularly high due to its resource requirement for production.
While we might assume that these more costly alternatives provide better grid strengthening, they are subject to many of the same issues of failure as wooden poles. Although traditional leaching and decay that we see in wooden poles are not present, both concrete and steel poles suffer from ground line corrosion. Using life cycle assessment methodologies (LCA and following ISO 14044) steel poles, in particular, are vulnerable to the effects of wetting and rusting despite galvanisation. Likewise, steel-reinforced concrete poles are also subject to internal corrosion over time, leading to failure and increased potential danger due to their weight and structure. Similarly, composite materials may suffer from osmosis within the fibreglass structure leading to a possible pole failure and increased hazards from a safety perspective. The lifespan of a composite pole is currently unproven, but concrete and steel poles have an estimated lifespan of 40 years, with regular inspection and remediation work often required.
Let’s focus on steel and concrete poles; our industry research indicates that not only are steel and concrete subject to corrosion, but they can be heavy and more challenging to handle versus a traditional wooden pole. The greater mass of these poles has the potential to cause a variety of new challenges in conducting a safe and efficient installation process. As a result, not only is the pole cost higher but likely the installation cost as well resulting from risk assessments and safety considerations being both time consuming and costly. In addition, they can be harder to climb and even conductive, posing a higher risk to employees and the public if they fail. The alternatives of steel, concrete and composite also require inspection incurring yet further costs. Maintenance of poles and power lines to ensure grid security is another essential factor to consider. Whereas maintenance to overhead cables of conventional wooden poles is carried out via climbing, composite, steel and concrete pose new and additional challenges to utilities and their employees.
There are several issues with alternative pole methods, but perhaps the most pressing is the environmental impact of the alternative materials. The study mentioned above conducted by AquAeTer Inc states precise data for the ecological effects of alternative pole use. The following values are normalised to a value between 0-1 to allow the demonstration of environmental impact from cradle to grave.
The environmental impacts of alternative materials fall under specific key categories for quantification. These include Fossil fuel use, Greenhouse gas, Acid rain, water use, bi-product of smog production, eutrophication and ecotoxicity.
In a summary of figures, steel and composite poles required the highest use of fossil fuels in production at 1 and 0.94 respectively. Steel and composite share similar figures for net greenhouse gas emissions, with concrete coming in at 0.58. In comparison, an ACZA-treated pole consumes a fossil fuel value of 0.072 and emits net greenhouse gas emissions of 0.22, proving to be dramatically lower than the alternatives. Similar figures are valid for wood across the remaining variables, strongly indicating that a treated wooden pole is by far the most advantageous solution in the face of reducing environmental impact. Furthermore, wooden products absorb an estimated 320kg of CO2 per pole during the beginning of their lifecycle and if disposed of correctly can be a useful source of energy recovery in permitted facilities with emissions controls.
Wooden poles from an environmental standpoint are therefore a favourable option; however, depending on variables such as climate, treatment regulations, ground conditions etc. are subject to often varying lengths of life cycles.
Industry findings have shown the advantages of wooden pole use; however, differing regional regulations for treatment, effects of climate, and ground conditions all contribute to potentially unfavourable premature pole failure. See our customer profile case studies for real industry data. Conventional wood treatments fall under two main categories of water-based and water repellent treatments. Water-based treatments include CCA, water-based copper etc. with copper as the primary biocide plus co biocides and fixatives. In contrast, water repellent treatments include creosote, Pentachlorophenol, copper in oil etc. Initially these preservatives provide total protection from decay but lose effectiveness overtime at the critical ground line section of the pole as a result of leaching and oxidation. These preservatives only penetrate the outer sapwood of the pole which is sufficient for parts of the pole both above ground and deep underground; the decay in the 8 inches or so below the ground line, however, is the area that needs the most significant protection. As the preservative suffers from leaching over time, the timber can become exposed to over 30,000 different types of wood-decaying organisms. Combined with potentially high moisture content and oxygenated topsoil, this is a perfect environment for decay.
Barrier products provide additional protection to a wooden pole at the vulnerable ground line section and work in conjunction with a treated pole to compliment the life expectancy. These barrier systems can feature both partial and fully sealed protection depending on product specification. Partial barriers are available in many forms such as a simple ground line wrap, self-adhesive tape, heat shrink tube, wrap with a metal foil behind the outer wrap or a complete pull-on “bag” that covers the whole in-ground section of the pole. The issue with partial barriers is that they do not seal the surface of the pole behind the sleeve or bag. All causes of decay can access the pole behind the barrier creating a wet band at the top of the bag or sleeve allowing decay to occur at the top of the barrier or behind the barrier itself. Without entirely excluding moisture, organisms and nutrients, there is still exposure to decay.
To exclude the potential for rot, the outer surface at the ground line must have an entirely protective seal, preventing leaching and decay. Our research shows that the moisture content of 25% is required for decay to begin. A fully-sealed barrier protection system lowers the entry point for moisture from the ground, ensuring the wood in the upper part of the sleeve remains below the level at which decay can start. The barrier ensures that conventional ground line decay becomes impossible. Full barrier protection from a Polesaver sleeve, for example, can not only guarantee a 40-year life expectancy on the sleeve but also enables decay testing to be easily carried out. Polesaver sleeves are compatible with all forms of pole testing, including hammer testing, spike or probe, resistograph and sound wave-based systems without affecting test results. High-performance sealing tape is also available to re-seal holes made when a test hole penetrates through the Polesaver sleeve to ensure decay becomes impossible.
Alternative pole types of concrete, steel and composite may be advantageous in certain respects; however, wooden poles have shown to be more appealing from the viewpoint of cost, maintenance and environmental impact. With the potential for a greatly extended lifespan resulting from full barrier protection, wooden poles are quickly becoming a favourable option. Look out for our next article where we explore the different options of barrier sleeves available!
Richard is the founder and CEO of Polesaver. With over 26 years of experience in developing and testing Polesaver products, Richard is an expert when it comes to wood preservation.
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Polesaver manufacturers and supplies guaranteed products that are proven to extend the life of utility poles. With over 7 million sleeves supplied to date, our patented ground-line barrier sleeves have been proven in volume use since 1994.
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Polesaver uses long term independent test data on the effectiveness of barrier sleeves and fire protection fabric to reach all the conclusions given on this website (test data available on request). Based on this data, Polesaver believes longer life, maintenance of strength over time, improved safety and reliability, extended inspection periods and reduced maintenance requirements are reasonable claims. This is subject to Polesaver products being correctly applied as per our instructions and used on correctly preservative treated (for long term in-ground use - use class 4 or higher) wooden utility poles that are free of decay at the time of sleeve application. The claims made, real or implied are not warranties. It is the responsibility of the user to evaluate and satisfy themselves that the performance of the product meets their specific safety, reliability, extended inspection, repair and any other performance or cost-benefit criteria before using Polesaver sleeves or fire protection fabric.