Counting dangerous waste

If your business generates dangerous waste, you are required to know how much of this waste you generate each month — we call this “counting.”

Counting means you know the weight of your dangerous waste. This can include wastes that you:

Generate.
Accumulate.
Dispose of.
Treat.
Recycle.
Ship off-site on a manifest.

You may have to count some wastes you haven't thought of — for example, still bottoms.

Read our publication, Counting dangerous waste under the Dangerous Waste Regulations for detailed guidance.

Health care facilities and pharmaceuticals

If you are a health care facility, please go to our Pharmaceutical Waste Management page for more detailed instructions on counting your waste.

Health care facilities must count both pharmaceuticals and non-pharmaceutical waste.

I want to:

Learn how to designate waste

Learn about proper containment

Click to go to our Pharmaceutical Waste Management webpage.

Count pharmaceutical waste

Why count dangerous waste?

The type and amount of waste you generate each month determines your generator category. Your generator category determines which rules apply to your business. It is also needed to fill out your:

Dangerous Waste Annual Report.
Pollution Prevention Plan (if required).

Click to read Counting Dangerous Waste Under the Dangerous Waste Regulations. — Read our Counting Dangerous Waste publication.

How do you count or find the weight of your waste?

Count your dangerous waste each month.
The highest amount you generate (or accumulate) in any month is what determines your generator category.
Do not average multiple months over time.

Here are three ways to find the weight of your waste:

1. Weigh and multiply

Option A: Weigh a smaller amount and multiply by the total gallons you have.

For example: Weigh 1 gallon of your waste. Then, multiply that by the total number of gallons you have.

Option B: Weigh your waste containers before and after adding waste. The difference equals the weight of your waste.

2. Calculate with density

220 pounds equals one half of a 55 gallon drum

If you know the density (or how many pounds are in one gallon) of your liquid waste, you can calculate the weight. For instance, 1 gallon of water weighs 8.34 pounds.

Start by estimating.
Then calculate if you are close to the limit.

For example:

A 55-gallon drum full of water weighs about 458 pounds (8.34 x 55 = 458).
If you have a 55-gallon drum of liquid waste that is half full AND it has a density similar to water, you probably have a little over 220 pounds of waste (8.34 x 27.5 = 229).

Note: Some wastes have a significantly different density than water. A waste sludge may weigh much more.

3. Calculate with specific gravity

If you know the specific gravity of your waste, you can calculate the weight. The specific gravity is often listed on Safety Data Sheets (SDS or MSDS) for products that become waste.

For example:

Multiply the specific gravity of the waste by 8.34 (the density of 1 gallon of water) to get the density of your waste in pounds per gallon.
Then, multiple that density by the number of gallons you have.

Read our Counting Dangerous Waste publication for more detailed information.

What not to count

Conditionally excluded wastes

The Dangerous Waste Regulations conditionally exclude some dangerous wastes. See excluded categories of waste at WAC 173-303-071. Excluded wastes remain solid wastes, but they are not subject to most of the dangerous waste rules, including counting and annual reporting requirements. Usually, the waste must meet a set of specific conditions in order to qualify for the exclusion.

These wastes may be excluded because:

They are regulated under other state and federal programs.
They are recycled in ways that don’t harm human health or the environment.

For example, a household hazardous waste exclusion removes household waste from dangerous waste regulation. Other exclusions include treated wood waste, polychlorinated biphenyls (PCBs), and waste reclaimed and reused in a closed loop system. Many other wastes are excluded in the regulations. The wastes mentioned here are some of the most common ones.

Domestic sewage exclusion

This exclusion allows dangerous waste to be discharged to a publicly-owned treatment works. Washington state’s version of the domestic sewage exclusion is more stringent than the federal exclusion. Important conditions include:

Waste treated or stored prior to discharge is counted
Waste directly discharged to the sanitary sewer is not counted
The waste must be treatable at the treatment works
The discharger has a permit that allows that activity
The waste is excluded only after it enters the sanitary sewer system

Learn more in Domestic Sewage Exclusion.

Special wastes

Special Wastes are state-only excluded wastes with their own set of management requirements. See conditional exclusion of special wastes at WAC 173-303-073. Special wastes includes:

Category D toxic wastes (D004-D043 waste codes)
Solid corrosive waste
Low-level persistent waste:
- Halogenated organic compounds (HOCs)
- Polycyclic aromatic hydrocarbons (PAHs)

Special wastes pose a relatively low hazard to the environment. Subject to approval, they may be disposed in municipal landfills or recycled. Learn more in Managing Special Waste.

The special waste category also includes waste generated from the salvaging, rebuilding, or discarding of transformers, capacitors, or bushings as listed in WAC 173-303-9904.

Contact information

Need help?
Contact a dangerous waste inspector in your region.