Commentary: Treated wood waste brings specific disposal rules

Issue Date: March 15, 2017
By Sharla Moffett
Sharla Moffett
Starting later this year, the California Department of Toxic Substances Control will inspect facilities that generate treated wood waste, including farms, as part of a study to determine whether the waste is being properly handled and disposed.

Farms and agricultural facilities throughout California utilize treated wood in their operations, from fence posts and crop stakes to retaining walls. When a farm is finished with this wood, it's more important than ever to dispose of it properly.

California farmers, ranchers and agricultural businesses should be aware of recent changes in state law regarding treated wood waste disposal and make sure their operations are in compliance.

In 2015, Senate Bill 162, sponsored by Sen. Cathleen Galgiani, D-Stockton, extended the law allowing treated wood waste to be disposed in a composite-lined Class II or Class III landfill. A new provision in the law, however, required a compliance study to determine whether treated wood waste was being properly handled and disposed.

The study will be conducted by the California Department of Toxic Substances Control, or DTSC, and will include inspections of those generating treated wood waste, including farms, starting later this year. The compliance study must be submitted to the Legislature by July 1, 2018.

So, what is treated wood waste and what do the regulations require? First, it may be helpful to clarify what isn't TWW. Wood that has been painted, stained or coated does not meet the definition of TWW, unless it has also been pressure treated with wood preservatives.

Treated wood is wood that has been treated with any wood preservatives containing pesticides or fungicides and registered by the U.S. Environmental Protection Agency to be used for that purpose. This wood is used for fencing, stakes, animal enclosures, trellises and other structures that are exposed to weather and the elements.

Treated wood waste really comes in two varieties: old and new. Old TWW is generated when wood is removed from service at the end of its useful life or is replaced for other purposes. In agricultural applications, removal of fence posts, crop stakes, building poles or plywood panels are some of the items that could become treated wood waste.

New TWW is typically generated during construction activities. Building new structures or replacing existing ones utilizing treated wood almost always generates TWW when the wood is cut or drilled. The resulting sawdust, chips or shavings are considered treated wood waste and must be disposed properly, according to the state law.

"Generators" under the law include any company or individual who generates TWW. This includes large and small agricultural enterprises, construction companies, railroads, various state agencies, even the weekend do-it-yourselfer.

The law is pretty clear: Everyone must dispose of treated wood waste properly. Large generators, which dispose of more than 10,000 pounds per year, must register with the DTSC and report treated wood waste semi-annually.

If there is treated wood at your facility, you are likely going to generate TWW. As such, it's critical to make sure treated wood and untreated wood are separated for disposal. Before disposing of TWW, report it to landfill and transfer station operators. Finally, make sure TWW is disposed of in a Class II or Class III, composite-lined landfill approved by the applicable Regional Water Quality Control Board.

Preparing your facilities for a compliance inspection on treated wood waste will go a long way in avoiding issues or costly enforcement actions. Here are some suggestions to have in place when it comes to TWW at your facility:

  • Have a list of procedures for separating TWW from untreated wood and other materials, and provide adequate training to staff.
  • Review the list of landfills that accept TWW (see links below) and call ahead to confirm it is still accepted.
  • Small generators may store 1,000 pounds or less for no more than 30 days, or be subject to additional requirements.
  • Cover stored TWW to prevent impacts from runoff.
  • Do not burn treated wood waste for disposal.
  • Label all TWW shipments going to disposal and identify it to disposal facility personnel.
  • Notify DTSC if the facility generates more than 10,000 pounds of TWW per year, and review the specific storage and disposal requirements for large generators.
  • Use containment methods when cutting and drilling treated wood, and do such work away from water.

For more information on TWW disposal, contact the Western Wood Preservers Institute at 360-693-9958 or visit our website at Also, visit these websites:

TWW Disposal - What You Need to Know:

TWW Regulations:

Requirements for Generators of TWW:

List of Approved Class II & Class III Landfills:

(Sharla Moffett is the government affairs director for the Western Wood Preservers Institute in Vancouver, Wash., which represents the treated wood industry in the 17 Western states and Canadian provinces.)

Permission for use is granted, however, credit must be made to the California Farm Bureau Federation when reprinting this item.