The Science of CCA

Around the world, CCA (chromated copper arsenate) poles have weathered almost every soil and environmental condition imaginable with the same results: long service life, reliability and dependability.

CCA is a mixture of copper, chromium and arsenic - chemical elements that occur naturally throughout the earth's crust and atmosphere. Copper becomes an effective fungicide when combined with the other elements. Chromium, also toxic to certain fungi, plays an important role in helping the preservatives to chemically bond or "fix" to the wood fibre. Inorganic pentavalent arsenic is used in CCA because of its effectiveness against wood-destroying insects. Unlike the highly toxic trivalent arsenic, pentavalent arsenic is a naturally occurring trace element present in soil, water, air, plants and in the tissues of most living creatures, including humans.

Together, the chemical elements of CCA give utility poles durability by rendering the wood fibre useless as a food source for fungi and termites.

This corrects the one shortcoming that makes wood the ideal material for utility poles - the fact that it is biodegradable. With CCA, the poles are easily and cost-effectively protected against these two natural hazards.

Fixation Prevents Leaching

CCA is extremely leach-resistant because if becomes "fixed" in the wood fibres. The preservative is a mixture of stable metallic oxides that react chemically with wood sugars and, upon contact, form insoluble precipitates in the wood cells. Once these precipitates become fixed in the wood, they do not migrate or evaporate.

CCA is injected into the wood under pressure. This process forces preservatives deep into the wood's cellular structure. How quickly it fixes depends on several variables, including the temperature, humidity and the species of wood. Accelerated fixation can be accomplished in a matter of hours.

Environmental Impact

When compared with alternate building products, wood is a natural choice. CCA enables the utility industry to gain the maximum benefits from wood, since preservative treatment enables wood to retain its structural integrity 10 to 20 times longer than untreated wood.

It is important for anyone who specified building materials to consider the environmental impact of their decisions. But how does one measure environmental effects? The internationally accepted method if life- cycle analysis. This quantifies energy and material usage as well as environmental releases at several stages, including: resource extraction, manufacturing, construction, service and post-use recycling or disposal.

An extensive survey by North American researchers found that overall wood was considered the most environmentally friendly building material. Masonry ranked second, concrete third and steel fourth.

Safety Concerns

"Concerns about CCA-treated wood stem from a failure to distinguish between the wood that has been treated with the preservative and the preservative itself." This statement was part of a 1995 article in the magazine "Priorities", published by the American Council on Science and Health (ACSH). This independent, non-profit group was founded in 1978 by a group of scientists concerned that many important public policies related to health and the environment did not have a sound scientific basis.

The article went on to state: "In solution, CCA is a potentially hazardous material. CCA-treated wood, however, is not classified as hazardous, because CCA 'fixes' to the wood in a way that makes the chemical highly soluble and leach resistant. There are few limitations to the use of CCA-treated wood and it can be disposed of as ordinary trash."

CCA Is Safe - Even for Playgrounds and Gardens

Linemen have long known that CCA poles are clean to the touch and non-staining. Because CCA is so safe, it is widely used for playground equipment and decking. In fact, a report by the American Wood Preservers Institute says that there is no reason to avoid using treated wood in the playground or to avoid walking barefoot on pressure-treated decks.

Study after study conducted by groups around the world has verified the harmlessness of treated wood. Commercial farms commonly use treated wood for tomato stakes, grape supports and mushroom trays. There have been no reports of CCA leaching out and being absorbed by vegetables. Experience, as well as research, shows that treated wood is fine for use in gardens.

Low Corrosivity and Conductivity

The CCA used in Canada is an oxide formulation rather than a salt formulation, so there is no threat of corrosion to galvanized bolts or metal steps and screws. There are also no by-products to increase conductivity. Dry CCA poles actually provide protection against the effects of current leakage, thereby increasing lineman safety.

No Loss of Strength

Full-scale testing proves it. Bending strength is not significantly affected by CCA treatment. In fact, some species of wood show a slight increase in strength.

While the increase in modulus of rupture is not sufficient to impact the calculation of design stress, it should eliminate concerns about the loss of strength - while providing an extra cushion in the engineering and construction of a utility pole line.

Proven Performance Over 55 Years

The first large-scale use of CCA wood poles by a utility company took place in 1940 and 1941. Bell Telephone System installed tens of thousands of pine poles. While these poles have lived up to their service life expectations, some have been removed due to line obsolescence or accidents.

Easier Pole Handling

Wood poles are naturally resilient to rough handling. Poles made from alternative materials, however, must be handled more carefully to avoid the risk of crushing them or damaging their protective coatings. This extra measure of caution can slow the handling process, in turn, increasing costs. Because wood poles need not be handled "with kid gloves", loading, unloading and installation may be carried out using conventional equipment with little fear of damage.

Improved Climbability

Climbability can be an issue with some utility companies. As a result, CCA pole manufacturers developed additives which are now used to treat the outside layer of the poles. The additives improve gaff penetration, resulting in a better grip. The poles become easier to climb and the preservative properties of the CCA treatment are not affected.