Counting dangerous waste

You are required to determine whether the waste your business generates is dangerous waste, a process called designation. You also need to know how much waste you generate — we call that “counting.”

What does counting mean?

Counting is measuring the weight of your dangerous waste, including wastes that you:

  • Generate
  • Accumulate
  • Dispose
  • Treat
  • Recycle
  • Ship off site on a manifest

Counting can get complicated. Not all wastes have to be counted, and you may have to count some wastes you haven't thought of — for example, still bottoms. And when do you count waste in a satellite accumulation area? The guide Counting Dangerous Waste Under the Dangerous Waste Regulations explains how to count waste in a variety of situations.

Why should I count my dangerous waste?

You are required to know how much dangerous waste you generate each month. The type and amount of waste you generate per month determines your "generator status." Your generator status determines which rules apply to your business.

Count your dangerous waste each month. The highest amount you generate (or accumulate) in any month is what sets your generator status. You may not average multiple months over time.

Counting waste is also important for your Dangerous Waste Annual Report and Pollution Prevention Plan.

Know the weight of your waste

You can weigh your waste with a scale or calculate the weight from a known quantity and density. Three ways to get the weight of your waste:

A) Weigh it

Weigh a smaller amount and multiply. For example, weigh one gallon of your waste, then multiply that weight by the total number of gallons you have. You can also weigh your waste containers before and after adding waste. The difference will be the weight of your waste.

B) Calculate with density

Knowing the density, or how many pounds are in one gallon of your liquid waste, can also help you calculate the weight. For example, a gallon of water weighs 8.34 pounds.

Start by estimating, then calculate if you are close to the limit. A 55-gallon drum full of water weighs about 458 pounds. If your 55-gallon drum is almost half full of liquid waste that has a density similar to water, you probably have 220 pounds or more of that waste. Some wastes have a significantly different density than water, so pay careful attention to what you have. A waste sludge may weigh much more.

C) 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.

  1. Multiply the specific gravity of the waste by 8.34 to get the density of your waste in pounds per gallon.
  2. Multiple that density by the number of gallons you have.

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.

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.

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.