Identifying Underlying Hazardous Constituents (UHCs)
One of the most confusing aspects of the land disposal restrictions is the determination of underlying hazardous constituents (UHCs). UHCs are trace amounts of hazardous chemicals (listed in 40 CFR 268.48) found in some hazardous wastes that do not in and of themselves cause the waste to be hazardous, but must be treated before the waste is deposited in a landfill. Due to a convoluted legal history, pre-disposal treatment for UHCs is only mandatory under certain conditions. When do we have to fulfill this requirement, and how do we go about doing it? Let’s walk through the process.
Determining Significant Hazardous Waste Codes
Per 40 CFR 262.11 when you generate solid waste, you must identify if that waste is listed as hazardous (F, K, P, and U codes from 40 CFR 261, Subpart D), and whether that waste exhibits any hazardous characteristics (D codes from 40 CFR 261, Subpart C). As a practical matter, you must also determine which codes are ‘significant’ for treatment purposes, since the treatment standards for listed hazardous waste codes never require treatment for UHCs. And in all but a few cases, the treatment standards for hazardous waste characteristics do require treatment for UHCs.
A hazardous waste will either:
- Be listed and not exhibit any hazardous waste characteristics,
- In which case, all waste codes are significant.
- Not be listed and exhibit one or more hazardous waste characteristics,
- In which case, all listed waste codes are significant.
- Be listed and exhibit one or more hazardous waste characteristics, ?In which case, all listed waste codes are significant, and
- Characteristic waste codes are significant only when the treatment standard for the listed waste code(s) does not already treat for the constituent(s) that caused the waste to exhibit the characteristic. [40 CFR 268.9(b)]
Example 1a: If you have spent solvent acetone that is listed as hazardous waste (F003) and ignitable (D001), the F003 code is significant (all listed codes are significant). But, since the treatment standard for F003 accounts for the ignitable acetone—the constituent that caused the D001 characteristic—the D001 is not a significant code, and you do not need to include it on your LDR notification (commonly referred to as a land ban). [40 CFR 268.7]
Example 2a: If you have that same spent solvent acetone (F003, and D001) that is contaminated with a toxic amount of lead (D008), then the D008 code is significant, because the standard for F003 does not treat for lead.
There are a couple of criteria that also help you determine when you need to treat for UHCs. First, we already mentioned that you must have significant D codes in order to trigger the treatment of UHCs. But in addition to that, you only need to treat for constituents you reasonably expect could be present in your waste, meaning you don’t have to look for every chemical on the list if you do not believe it could be present based on what you know about your waste. And if you have already treated for one of the constituents because it had a significant waste code to begin with, then you don’t have to treat for it a second time.
Why Does It Matter?
In order to comply with 40 CFR Part 268, you must ensure your waste is treated to appropriate standards before it is landfilled. A TSDF will treat the waste on your behalf before it goes to a landfill based on what waste codes and/or UHCs you tell them are present in your waste. TSDFs often charge based on the type of treatment a waste requires. The codes then dictate the amount and type of treatment a waste needs in order to legally go to a landfill. More treatment in turn could mean more money paid to the TSDF for the treatment.
Underlying Hazardous Constituents in Practice
Example 1b: Let’s consider the F003 spent acetone solvent that is a D001 ignitibility waste contaminated with toxic amounts of lead (D008).
- We already determined that this waste does have a significant characteristic waste code—the D008.
- The treatment standard for the D008 at the 40 CFR 268.40 LDR treatment standard table does indicate “…and meet §268.48 standards.” Therefore, we do have to consider UHCs.
In this case, however, lead is NOT a UHC because it will already be treated for by the treatment standard for the significant D008 waste code.
Example 2b: Let’s consider that same F003 spent acetone solvent that is a D001 ignitibility waste contaminated with lead (D008), but this time, it’s also contaminated with 15 mg/L of nickel.
- We already determined that this waste does have a significant characteristic waste code—the D008.
- The treatment standard for the D008 at the 40 CFR 268.40 LDR treatment standard table does indicate “…and meet §268.48 standards.” Therefore, we do have to consider UHCs.
- We know from our previous example that lead is NOT a UHC because it will already be treated for by the treatment standard for the significant D008 waste code.
- The significant waste codes F003 and D008 do not have a treatment standard for nickel, so we must consider it as a potential UHC.
- Since the level of nickel in our waste is above that indicated on the §268.48 table, it is an underlying hazardous constituent.
Now that you’ve seen a few examples, go back and read the criteria you must ask yourself to determine whether or not you must treat your waste for UHCs and they will probably be clearer now.
Determine significant waste codes, learn to use the treatment standards table at 40 CFR 268.40, identify UHCs, and prepare your land disposal restrictions notifications (i.e., land ban form). Demystify the process meeting land disposal restrictions with our online course.
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