The evaluation addresses the waste reduction/pollution prevention and economic issues involved in replacing chromated copper arsenate (CCA) with ammoniacal copper/quaternary ammonium (ACQ) as a way to preserve wood. The most obvious pollution prevention benefit gained by using ACQ is eliminating the use of arsenic and chromium, both of which generate hazardous wastes and a risk of contaminating the environment via chemical spills. Because most treatment plants are self-contained in that they reuse all wastewater produced within the plant and on the drip pads, no liquid waste problems were addressed for either the CCA or the ACQ treating process. The ACQ system generates more air pollution than does the CCA system, mainly as ammonia (NH3). For a plant with an annual production of 1 million cu ft (or about 20 million board feet), 90,000 lb of NH3 would be released per year from the ACQ treatment operations and the ACQ-treated wood. The treated wood, after being transferred from the drip pads to the outside storage yard, could become a major source of contamination.