Pressure treated, preserved wood, or treated wood waste (including the sawdust), referred to as TWW, has preserving chemicals like arsenic, chromium, copper, creosote, and pentachlorophenol which are carcinogenic (toxic) and has tell-tale indentations. 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 railroad ties are some examples. TWW does not include wood painted with "copper green."
Painted, engineered, stained, laquered, plywood/composite wood may go in the garbage.
What are some things to look for when determining if wood is treated or not?
- Wood manufacturer stamp codes
- Indentations on the surface of the wood (as seen in the photo below)
- When cut, staining is visible around the perimeter only
- Discoloration (e.g. green or dark brown appearance)
- Treated wood may have an end tag that looks like the figure below.
What doesn’t qualify as treated wood?
- Natural wood with no chemical preservatives.
- Natural wood that is painted or has a surface finish such as lacquer, shellac, polyurethane and varnish.
DTSC links and FAQ highlights:
- Requirements for Generators and Handlers of Treated Wood Waste
- List of Landfills approved by the Waterboard to accept TWW
TWW is prohibited from being burned, chipped, ground, or mulched.
Households typically generate TWW when a fence or deck is replaced. Under AMS, households must abide by the following conditions:
- Do not burn the TWW.
- Do not remove or destroy any marking identifying the wood as treated wood.
- Keep TWW segregated from other materials.
- Store less than 1,000 pounds of TWW for no more than 30 days following its removal from use.
- Transport TWW to an authorized TWW facility.
- Identify TWW to TWW facility personnel.
Businesses Same as above and must label TWW bundle/shipments accordingly (see full details here.)
Find resources for about treated wood waste (TWW) specific regulations for households, contractors, businesses, haulers, generators, and landfills at www.TWWDisposal.org. Included are fact sheets and outreach materials on the appropriate handing, disposal, and other management of TWW to facilities that may receive or handle treated wood waste.