Wood Pole Inspection, Treatment, and Asset Management
Utility pole asset management is an exciting market in North America that will exceed $100M in 2022. Utility poles are sourced from a variety of different materials including different wood species, painted carbon steel, galvanized carbon steel, stainless steel, and carbon fiber reinforced plastic (FRP). The goal of utility pole asset management is to extend the useful life of the asset maximize the lifetime economically and protect the personnel that maintain, continuity of service, and the end user of the supplied medium. A utility pole’s most critical area and vulnerable area is at the ground line . It is common industry practice now for wood pole owners to adopt a periodic wood pole testing program and remedial ground line treatments. Historical data shows that a proactive wood pole asset management strategy reduces outages, minimizes emergency replacements and enhances customer satisfaction while providing a safer delivery system. The average lifetime of an untreated pole is approximately 30 years. Wood pole treatment has been shown to extend the pole’s life by 15 years or more. Over its lifetime, even with the additional labor and materials cost to adopt a treatment plan, the average annual cost to operate the pole decreases . This article discusses the components of wood pole groundline treatment along with some application guidelines.
Wood Pole Groundline Decay
Most poles fail at the groundline due to decay from approximately 2 inches above the groundline to 18 inches underground. Decay is catalyzed by the four following components: oxygen, moisture, temperature and nutrients in the form of the wood. A wood pole treatment program that eliminated only one of these four catalysts will eliminate decay .
Wood Pole Groundline Treatment
Wood pole ground line treatment consists of excavation, fumigation and external treatment. As noted above the critical 20 inches of wood pole to be treated starts at 2 inches above the ground line to 18 inches below. The wood pole depth must be excavated such that internal treatment conduits may be drilled with an auger drill bit, application of fumigant, external paste and finally a paper wrap.
Figure 1: A wood pole ground line treatment plan included exaction to at least 18 inches, application of an internal fumigant, and an external treatment. Wood pole conduits and reinforcements may complicate the excavation and application of the product.
Internal fumigant treatments are an integral component to controlling ground line wood pole decay. Fumigants are available in granular, liquid and gel formants. In general, fumigant treatments offer much greater distribution properties in the pole compared to other internal treatment methods . Fumigants are known to dissipate up to 8 feet from the application point.
Granular fumigants are applied in treatment holes drilled into the wood pole at degrees downward which are plugged after the fumigant is inserted into the pole. Typically the first hole should start at or slightly below ground line and should be arranged in a spiral pattern covering the treatment zone with about 6 to 12 inches vertically between holes.
Figure 2: Application of wood pole granular fumigants required multiple access points be drilled into the pole below the groundline. Holes are typically spaced 6 inches apart and rotated around the wood pole. The treatment hole is plugged with a tight fitting treated wooden dowel, removable plastic plug or other suitable cap.
A common wood pole external treatment is the MP500 product with Copper Carbonate and Sodium Tetraborate Decahydrate active ingredients . The external treatments are designed for remedial treatment of in-service poles, posts, and other timber members and may be applied by brush, trowel or pump. If selected correctly, the external treatment will halt existing wood decay and offers protection against future decay and wood destroying insects.
Figure 3: Wood pole external treatments are usually applied using a brush from slightly above ground level to 18 inches below.
Wood pole external treatment product is most commonly applied using a brush or trowel to a thickness of 1/16” on poles or timber. The typical wood pole application is from 3” above to 18” below groundline and lower where deeper decay is suspected. Application on poles to be restored must extend the length of wrap-around type repair systems. The treated area is typically wrapped with a moisture barrier such as polyethylene backed kraft paper.
Figure 4: Upon completion of the wood pole internal fumigant and external treatments, the wood pole is wrapped with a polyethylene backed paper.
There are many benefits to a strategic wood pole inspection and treatment program. Through selection of the correct internal fumigant and external groundline treatments, the average pole lifetime of roughly 30 years may double. While there are additional labor and material costs associated with both the wood pole inspection and treatment processes, numerous studies have shown that the annual cost to operate and maintain a pole decreases over its lifetime remedial treatment. TECHKNOWSERV Corporation field technicians and scientists are skilled at applying the correct wood pole treatments for the targeted species in the service climate. Additional benefits include useful and reliable service, safety of maintenance personnel and property owners, and protection of human life.
1. Mike H. Freeman, Kevin W. Ragon, A Review of Wood Pole Testing Equipment Compared to Visual and Excavation Techniques Used in Test and Treat Programs, 2010 Southeastern Utility Pole Conference ~ Technical Forum.
2. Panek, E., and J.O. Blew. Study of Groundline Treatments Applied To Five Wood Pole Species.
3. Morrell, Jeffrey J. 2012. Wood Pole Maintenance Manual: 2012 Edition. Research Contribution 51, Forest Research Laboratory, Oregon State University, Corvallis.
4. Barrier Wrap Technology: Enhancing Preservative Performance In Wood Utility Poles By Mike H. Freeman Independent Wood Scientist Memphis William Abbott Pole Maintenance Company Columbus, NE, 2008.