Good Wood Gone Bad – The effects of arsenic leaching from CCA-treated wood are creating very real concerns for the waste industry.

Solid waste managers take in the world’s undesirables every day, but in doing so, a potential bomb – chromated copper arsenate (CCA)-treated wood – is waiting to drop on the industry. In approximately 15 years, the amount of CCA-treated wood headed for disposal is expected to peak. And like an unwelcome mother-in-law, over time, the effects of arsenic leaching from the wood could wind up being a nagging problem.



CCA-treated wood recently has received much attention over soil and water contamination from structures made from this common building material; the possible effects on those working with the wood; and the potential danger to children who play on treated wood structures. These issues continue to unfold.



However, for the past five years, a team of researchers led by Helena Solo-Gabriele of the University of Miami, Fla., and Timothy G. Townsend of the University of Florida, Gainesville, with funding from the Florida Center for Solid and Hazardous Waste Management, a statewide research center located at the University of Florida, have been studying the implications of the material’s disposal.



“The research has been good and quite strong, and there is a bona fide concern,” says Bill Hinkley, chief of the bureau of solid and hazardous waste for the Florida Department of Environmental Protection (FDEP), Tallahassee. “The bottom line is that there’s no arguing that arsenic leaches out of CCA-treated wood, and there’s no doubt that the burden is going to fall on the waste industry to sort out. The dispute centers on what we are going to do about it.”



While all aspects of CCA-treated wood use currently are facing scrutiny in the state, Florida research primarily has focused on the effects of discarded CCA-treated wood. In fact, it was a waste management issue that began the interest in this subject, Townsend says [See “More than Child’s Play”].





Basic Facts



Preserved or treated wood is a common component of the solid waste stream. A 1998 U.S. Environmental Protection Agency (EPA) study estimated that 136 million tons of building-related construction and demolition (C&D) debris were generated in 1996, with wood representing the largest component.



According to the report, approximately 500 wood processing facilities in the United States derive wood from C&D.



Because preserved wood products are treated by applying pesticide to the wood to prevent fungal or microbial decay, questions often arise as to how to best manage discarded treated wood, from both from a regulatory and an environmental perspective.



Common U.S. wood preservatives include creosote and pentachlorophenol. But the predominant preservative used today is CCA, which introduces concentrations of copper, chromium and arsenic to the wood.



As part of the CCA wood treatment process, wood first is dried in a kiln. The dried wood then is placed in a vessel where a vacuum is applied to the wood’s pore space. CCA solution is introduced into the vessel, which then is placed under pressure. This causes the CCA solution to enter the wood’s pore space. A vacuum extracts the excess solution. And after the wood is removed from the vessel, it dries over a drip pad.



CCA solutions vary among wood treaters, but there are three typical formulations, as defined by the American Wood Preservers Institute (AWPI), Fairfax, Va., based on the solution composition by percent mass of the metal compounds used [See “CCA-Treated Wood Types and Requirements”]. Of types A, B and C, C is most commonly used. The concentration of CCA remaining in the wood after treatment is rated in pounds of CCA per cubic foot of wood, defined as the standard retention value.



Typical CCA-treated wood applications include telephone poles, fence posts, decks, and components of home construction [See “Standard Retention in Various CCA-treated Wood Products”].



At low retention values, CCA-tr