Wood poles, the silent guardians of our modern infrastructure, depend on treatments such as CCA, DCOI, and PENTA for utility pole wood treatment, defending against decay and insects. When it comes to wood preservation, these treatments vie for supremacy, each with its unique pros and cons.

In this blog, we’ll tackle how utility wood poles and wood light poles are treated and compare the most common wood pole treatments among each other, ultimately determining the most suitable one.

Wood Light Poles

What is a Utility Pole Wood Treatment?

Utility wood pole treatments help with the longevity of the wood poles. To establish and rely upon the resistance of wood poles against environmental factors, different treatments are applied to protect them from decay, insects, and other forms of deterioration

How are Wood Poles Made?

Durability and longevity are two major components that are crucial when crafting utility poles. Naturally, wood poles are natural materials exposed to outdoor threats such as fungi, mold, decay, and insects like termites. Termites love wood and break down its fiber which reduces its structural integrity. Let’s do a brief rundown on the entire process of creating wood poles.

Selecting the Wood

Where else can we harvest wood other than the forest? Poles are usually made from Douglas Fir, Southern Pine, or Western Red Cedar. Logs that can turn into poles are the ones selected.

When it comes to trees, they’re judged based on their length, straightness, and other characteristics that can factor into load-carrying abilities. About 7% of the trees possess the traits needed to make a utility pole.

After harvesting the suitable candidates, the bark is removed from the tree and reshaped to make it as straight as possible. Every pole is reviewed thoroughly until it’s graded and assigned to a specific class following the ANSI standards. The following criteria are included: presence of decay, knots, and slits, as well as grain orientation.

Pole Preparation

The poles are then incised in preparation for the preserving process. Then, it’s important to make sure that they’re properly conditioned in a way that sustains their strength and durability. Poles are typically dried with air or using a kiln, akin to drying lumber.

When it comes to Southern Pine poles, they are steamed. Douglas Fir poles undergo the Boultonizing process in which the preservative is heated between 180 to 220 degrees Fahrenheit and the retort is pressurized.

Sterilization of the pole is also required, specifically heating it for at least an hour, reaching 150 degrees Fahrenheit at its core.

Pole Preserving Process

The pole-preserving process starts when the poles are placed onto carts and moved into a retort. Either a vacuum or air pressure is applied, depending on the type of treatment. The retort is then filled with the preservatives that will fill the wood fiber.

Preservatives are used among poles (which we’ll discuss further down this blog), pumped from storage tanks, and filling the retort.

Consistent pressure is applied inside the retort to drive the preservative deep into the wood cells. The timeframe of the poles’ exposure to the retort varies based on factors such as size, species, and the specific preservative used. Upon completion of the treatment process, the retort is drained of preservatives, which are then returned to tanks for recycling. The treated poles exit onto a drip pad, where any surplus preservative is collected.

Quality Assurance

Samples are taken from the poles to be thoroughly inspected to meet the standards. Third-party inspection agencies will also do the same during regular visits to review the plant’s quality control practices.

Wood Poles Installed

What is the AWPA Specification for Wood Pole Treatment?

Below is a table that indicates the specifications and guidelines by The American Wood Protection Association (AWPA) for utility wood pole treatments. These requirements are important to maintain the structural integrity of the utility poles and promote consistency in the industry. The information has been sourced from AWPA’s Guidance Document A.

Preservative Efficacy – Laboratory

Basidiomycetes Mandatory
Soft Rot Mandatory
Termites Mandatory

Simulated Field Tests

Fungus Cellar Recommended

Field Tests

Field Stakes Mandatory
Posts Recommended
Termites Mandatory

Field Depletion

Field Stake Mandatory

Preservative Depletion – Laboratory

Water Leaching Mandatory
Soil Leaching Recommended
Evaporative Aging* Mandatory

Physical Properties

Strength Mandatory
Electrical Conductivity** Mandatory
Hygroscopicity Mandatory
Corrosion Mandatory
Preservative Corrosivity Mandatory
Preservation Fixed Rate*** Mandatory

*applicable to preservative systems with one or more organic active ingredients with significant vapor pressure.

**applies only to components of utility line structures and railway ties.

***only applicable to reactive waterborne inorganic wood treatment systems.

A Comparison Overview of Different Utility Wood Pole Treatments

CCA vs DCOI

CCA wood pole treatment has been the most commonly used wood preservative for utility poles for decades. It has copper, chromium, and arsenic compounds. They work together to protect wood from decay and insect infestation. The copper component presents itself as a fungicide while chromium improves the fixation of copper to the wood fibers, and arsenic provides resistance against insects.

There has been criticism against CCA due to environmental concerns. Arsenic, a known carcinogen, raised public health and environmental alarms, causing a shift towards alternative treatments.

On the other hand, DCOI wood pole treatment acts as a replacement for CCA, addressing environmental concerns associated with arsenic. DCOI is a water-based preservative that uses copper to protect wood from decay and insects. It involves immersing the wood in a solution filled with copper oxide particles.

DCOI is considered less toxic than CCA, however, there is still a discussion within the industry regarding its efficacy. Some say that DCOI doesn’t offer the same level of protection against certain wood-deteriorating organisms compared to CCA. Further, the shift towards water-based treatments creates concerns about the leaching of copper into the surrounding environment.

PENTA vs CCA

PENTA wood pole treatment has gained traction as a substitute for CCA. It is a chlorinated phenol compound known for its effectiveness against decay-causing fungi and insects. It’s often applied through pressure treatment, ensuring deep penetration into the wood fibers.

Despite its efficacy, PENTA has come across regulatory challenges. Environmental agencies have shared their concerns about its impact on soil and water. This resulted in banning PENTA for residential use, but it’s still permitted for certain industrial applications, including utility poles.

CCA has a longer and more established history in wood preservation and usage than Penta. However, as mentioned previously, the environmental concerns associated with arsenic have led to a decline in its use.

DCOI vs PENTA

When comparing DCOI and PENTA, utility companies weigh the environmental impact against treatment efficacy. Both treatments have advantages and disadvantages that require careful consideration of the specific needs and regulations applicable to each utility pole installation.

Final Thoughts

Choosing the right wood pole treatment is a critical decision for utility companies. Balance is needed for effective preservation with environmental and regulatory considerations. As regulations evolve and environmental awareness increases, companies must remain informed about the latest developments in wood pole treatments.

Ultimately, the goal is to ensure the longevity and reliability of utility poles while minimizing adverse effects on the environment and public health

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About the Author

Neil Peterson is Chief Operating Officer at LED Lighting Supply. He has been active in the LED industry for over 10 years and is responsible for product planning and management as well as revenue and operations at LED Lighting Supply. Much of Neil’s time is focused on customer engagement for large commercial and industrial lighting requirements. When not working, he enjoys family time, camping, fishing, and sports..

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