January 14, 2026

Drip Pad Closure Options When Phasing Out Hazardous Wood Preservatives

Facilities conducting wood preservation operations may find themselves generating hazardous wastes, including some unique to the industry, such as F032, F034, F035, and K001. In the early 2000s, facilities voluntarily phased out the use of chromated copper arsenate (CCA) in the preservation of residential wood products, such as decks, playground equipment, and landscaping timbers. [68 FR 17366] The phase-out was accompanied by a significant drop in the amount of F035 waste generated in the country. To support the industry’s move toward using preservatives that do not generate hazardous waste, EPA published RO 14681. The guidance addresses options for properly managing drip pads regulated under Parts 264 and 265, Subpart W, when converting from CCA to alternative preservatives that do not result in the generation of hazardous waste.

In October 2025, EPA provided additional guidance in RO 14972 explaining how such management options also apply to wood preservers that convert from pentachlorophenol (F032) or creosote (F034) to nonhazardous wood treatment chemicals. The guidance follows the phase-out of pentachlorophenol, which is scheduled to be completed in 2027. [89 FR 13714] As drip pads are a type of hazardous waste accumulation unit, four options exist for managing the units when transitioning to nonhazardous wood treatment chemicals.

Complete closure before converting to nonhazardous chemicals. Facilities can “clean close” the drip pad as a hazardous waste management unit (detailed in §§264.575 and 265.445) before converting the wood treatment plant to the alternative preservative. State and federal regulators should be consulted to determine specific levels of decontamination that are protective of human health and the environment. If “clean closure” cannot be completed, the unit would be subject to post-closure care regulations as a closed hazardous waste landfill.
Continued operation. Facilities can continue to operate under Subpart W and manage all wastewaters, process residuals, preservative drippage, etc., that accumulate on the drip pad as hazardous waste. Any liquids removed from the drip pad would be considered hazardous waste under the mixture rule because the drip pad would not have been decontaminated and the liquids would have been mixed with F-listed waste. Closure requirements would only apply when operations cease.
Phased closure. Facilities can convert to an alternative preservative that does not generate hazardous waste, perform certain closure activities, and postpone complete closure until a future date. Under this option, the drip pad and other containment system components would be cleaned sufficiently such that any liquids that come into contact with the pad would not be considered to have been “mixed” with listed waste. The level of cleaning would have to be determined by the appropriate federal or state regulatory authority.
Discontinued use with delayed closure. Large quantity generators can cease operation of their drip pads, eliminating the generation of hazardous waste from those units, but delay “clean closure” under the flexibility of §262.17(a)(8). This provision allows generators that close only a hazardous waste accumulation unit (as opposed to the entire facility) to place a notice of closure in their operating record and perform clean closure requirements in §262.17(a)(8)(iii) at a later date when the facility closes as a whole.

In addition to the drip pad closure requirements in Subpart W, facilities that use or have previously used chlorophenolic preservatives (thus generating F032 waste) are subject to additional documentation and cleaning requirements in §261.35. Although EPA’s guidance is within the context of drip pads, such closure options would also apply to other hazardous waste accumulation units, such as containers, tanks, and containment buildings.

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This document addresses issues of a general nature related to the federal environmental regulations. Persons evaluating specific circumstances dealing with the environmental regulations should review state and local laws and regulations, which may be more stringent than federal requirements. In addition, the assistance of a qualified professional should be enlisted to address any site-specific circumstances.