York Bridge Concepts
Mentor, Ohio 2002
CCA pressure treated wood is a safe long lasting building material used in decks, fences, retaining walls, picnic tables, docks, and other places where the wood is exposed to rot, insect attack or other forms of biodeterioration. The basic treating process is simple and highly controlled.
The lumber, timbers and plywood to be treated are loaded onto small rail or tram cars. Using a vehicle such as a forklift, the trams are pushed into a large horizontal treating cylinder. The cylinder door is sealed, and a vacuum is applied to remove most of the air from the cylinder and the wood cells. Preservative solution is then pumped into the cylinder and the pressure raised to about 150 pounds per square inch, forcing CCA into the wood.
The total treating time will vary, depending on the species of wood, the commodity being treated, and the amount of preservative to be impregnated but, in all instances, the treating process is a closed system. At the end of the process, excess treating solution is pumped out of the cylinder and back to a storage tank for later reuse. The cylinder door is opened and the trams are pulled out. The wood is wet at that time, so it is kept on a concrete pad. Any drips trickle into a containment area from which they can be either disposed of or reused.
The CCA preservative is a formulation of chromated copper arsenate, a formulation found to be highly effective as a wood preservative. Each of the three elements in CCA is important to its overall performance. Copper is normally associated with piping or perhaps pennies. However, in certain forms, it is an effective fungicide. It is the copper that lends CCA-treated wood its unique greenish cast – which, over time, weathers to a driftwood gray. Chromium, which also helps to protect against certain fungi, plays an important part in the fixation of preservative to the wood fiber.
The arsenic in CCA preservative is pentavalent arsenic, a naturally-occurring trace element in the soil, water, air, plants, and in the tissues of most living creatures, including man. When it is fixed in the wood cells as copper arsenate and chrome arsenate, it is toxic to wood-destroying termites and fungi, but, when used properly in the concentrations found in CCA pressure-treated wood, it is not harmful to people or to animals.
When pressure-impregnated in the wood cells, the CCA mixture of stable metallic oxides is reduced by the wood sugars to form insoluble precipitates. What this means is that the preservative ingredients actually become locked in the cells of the wood – they will not vaporize or evaporate. And unlike wood that has merely been coated with paint or stain, pressure treated wood is protected deep into the wood structure – which is why we confidently offer a lifetime warranty.
CCA treated wood is not only workable, it is clean, odorless, non-staining and, used as directed, safe – safe to handle, safe to work with, and non-irritating to humans, domestic animals, wildlife, plants, and the environment.
The Agency has completed its reregistration eligibility decision (RED) and will continue to work with stakeholders to implement its decision. Pesticide manufacturers to voluntarily phased out certain CCA use for wood products around the home and in children’s play areas. Effective December 31, 2003, no wood treater or manufacturer may treat wood with CCA for residential uses, with certain exceptions.
Environmental Benefits of Pressure Treated Wood
CCA pressure-treated wood is an environmentally responsible choice for exposed construction.