The California Department of Toxic Substances Control defines treated wood waste (TWW) as wood that has been treated with chemical preservatives. These chemicals help protect the wood from insect attack and fungal decay while it’s being used. Fence posts, sill plates, landscape timbers, pilings, guardrails, decking and grape stakes are all examples of chemically treated wood.

TWW contains hazardous chemicals that pose a risk to human health and the environment. Arsenic, chromium, copper, creosote and pentachlorophenol are among the chemicals used to preserve wood and are known to be toxic or carcinogenic. Harmful exposure to these chemicals may result from touching, inhaling or ingesting TWW particulate (e.g., sawdust and smoke).

Note:  The statute (HSC § 25150.7) and regulations (22 CCR § 67386.1 et seq.) that allow treated wood waste to be handled with alternative management standards are due to expire after December 31, 2020. After that date, all hazardous treated wood waste (not exempted by HSC § 25143.1.5 as utility generated) managed in California will have to be stored and manifested as hazardous waste and transported to Class I hazardous waste landfills for disposal.  For more information, visit https://dtsc.ca.gov/toxics-in-products/treated-wood-waste/