An Approach To Evaluating
Hazardous Waste Combustion Residues For Delisting
Compliance Strategies &
Solutions, Inc.
ABSTRACT
Residues from hazardous waste combustion units (e.g., ash, spent lime, scrubber water, etc.) are often classified as listed hazardous waste under the regulations implementing the Resource Conservation and Recovery Act (RCRA). As listed hazardous wastes, combustion residue management remains subject to stringent and costly regulations from the point of generation through the ultimate point of disposal. The U.S. Environmental Protection Agency’s (hereafter, EPA) streamlined hazardous waste delisting petition process has allowed several hazardous waste combustion facilities to greatly reduce their regulatory and financial burdens by re-classifying listed combustion residues as non-hazardous wastes, even though the residues are derived from waste streams that carry multiple waste codes. To illustrate how other facilities may be able to reduce their regulatory and financial burdens, this paper will review the pre-petition waste evaluation process that a facility used to determine if a delisting petition was a viable option for its combustion residues. In addition, this paper will identify potential candidates, the timeframe, and the projected costs for the delisting petition process administered by the EPA Regional Offices and State Agencies.
The RCRA regulations contain provisions that allow
the petitioning of the governing Agency to exclude or “delist” a listed
hazardous waste from the universe of regulated hazardous wastes. These provisions are provided in 40 CFR
260.20 and 260.22. For many years
delistings were considered virtually unachievable and economically
unfeasible. On March 23, 2000, however,
the EPA published a guidance document on delisting entitled EPA RCRA
Delisting Program Guidance Manual for the Petitioner (hereafter, Delisting
Guidance).1 This guidance
document has provided a streamlined framework that, when followed, can provide
significant regulatory relief to the successful petitioner. By delisting a listed hazardous waste, RCRA
regulated entities benefit by minimizing their cost, liability, and regulatory
burden.
To successfully delist a particular waste stream, the
generator must demonstrate to the Agency that the waste stream does not meet
the criteria for which it was listed, exhibit any characteristics of hazardous
waste, or exhibit any other factor that could cause it to be hazardous. This demonstration must be supported by waste
analysis data that accurately characterizes the physical and chemical
composition of the waste stream. Upon
receipt of the data, the Agency will evaluate the waste stream to determine if
future management of the waste has the potential to threaten human health or
the environment.
A major component of the Agency’s risk evaluation
involves the performance of a delisting risk assessment using the Delisting
Risk Assessment Software (DRAS). The DRAS is an Agency tool that computes
chemical-specific exit values or “delisting levels” based on the default cancer
risk level of 1 x 10-5 (i.e., 1 in 10,000) and a noncancer hazard
index of 0.1. Waste streams with
constituent concentrations that do not exceed the delisting levels are prime
candidates for the streamlined delisting process.
Petitioners, who want to determine if a waste stream
meets the delisting levels may use the DRAS to evaluate the potential risk
posed by the waste stream before submitting a delisting petition. The following sections of this paper present
a review of a pre-petition waste evaluation strategy that a petitioner has used
to support a decision to pursue a delisting petition.
Anyone who is considering pursuing a delisting
petition should have a sound basis for determining that the waste stream is
worthy of the time and resources that will be invested in preparing the
petition. A petitioner can gain a
higher level of confidence in a waste’s potential for delisting by implementing
a pre-petition evaluation strategy. The
components of such a strategy include:
Further discussion of each component of the
preliminary evaluation strategy is provided in the following sections of this
paper.
Owners and operators of hazardous waste combustion
facilities are required to characterize combustion residues to determine if
they are RCRA hazardous wastes. This
characterization must be supported by process knowledge and/or waste analysis
data maintained in the facility’s operating record. Facilities with existing waste analysis data
may use that data to discern which waste streams generated at the facility are
unlikely to be potential candidates for delisting. For example, combustion residues for which
existing data indicate that the waste exhibits the toxicity characteristic due
to high concentrations of leachable metals will likely have a low probability
of success in the delisting program without further treatment (e.g.,
stabilization).
While existing data may be useful to screen out
waste streams from further delisting consideration, the petitioner should use
extreme caution in making a decision to pursue a delisting petition based
solely on existing waste analysis data.
In most cases, existing data will have been collected for purposes other
than delisting, and the data is not likely to address all analytical or quality
assurance/quality control (QA/QC) requirements of the delisting program. For example, a common concern with existing
waste analysis data is that the minimum detection limits are often too
high. Detection limits that are too high
may falsely indicated that the waste stream is a good candidate for delisting. The petitioner may then make the mistake of
relying on the existing data to make a decision to pursue a delisting
petition. However, when new data is
collected to support the delisting petition, the Agency may require detection
limits that are lower than the detection limits in the existing data. Consequently, the delisting data may identify
constituent concentrations in the waste stream that exceed the delisting levels
computed by the DRAS. Existing data,
therefore, should be used with caution when making a decision to pursue a
delisting petition. For many waste
streams, it may be necessary to collect additional preliminary data to support
a more rigorous preliminary risk evaluation.
Collecting Additional Preliminary Data
Prior to performing a preliminary evaluation on the
waste stream, the petitioner should consider collecting additional preliminary
waste analysis data. The data should
closely resemble the data requirements necessary to support the delisting
petition. Most importantly, the data
should be representative of the waste stream and should be based on the lowest
possible detections limits for the constituents of concern. As a general guideline, data for the
preliminary evaluation should address the following:
As mentioned, the detection limits for the
constituents of concern should be sufficiently low such so that the detection
limits for individual analytes do not exceed the delisting levels that will be
calculated by the DRAS. For most
analytes, the detection limits should be less than, or equal to, the practical
quantitation limits provided in Appendix IX to 40 CFR 264. Data that meet these criteria and closely
resemble data required for the delisting petition will better serve the
preliminary risk assessment component of the pre-petition evaluation
strategy. The data will also provide the
petitioner with a more realistic view of the waste’s potential for delisting.
Once a petitioner has obtained data that is
representative of the waste stream, a preliminary risk evaluation should be
performed using EPA’s DRAS. DRAS v 2.0
was released by EPA in April 2002, and is designed to determine whether a waste
qualifies as “not characteristically toxic” for the purpose of delisting.2
Each risk evaluation performed using the DRAS is
based on a waste disposal scenario in either a landfill for solid wastes or a
surface impoundment for liquid wastes.
The DRAS computes chemical-specific exit values or “delisting levels”
based on the default cancer risk level of
1 x 10-5 and a noncancer hazard index of 0.1. The constituent concentrations of the
specific waste stream should not exceed the established delisting levels. In determining the allowable constituent
concentrations for a petitioned waste, the DRAS sets two delisting levels for
each constituent: 1) a total concentration delisting level, and 2) a leachate
concentration delisting level. The total
concentration delisting level is the maximum allowable concentration of a
constituent in the whole waste. The
total concentration of each constituent in the waste should not exceed the
total concentration delisting level. The
leachate concentration level is the maximum allowable concentration of a
constituent in leachate derived from the waste using the TCLP. The TCLP concentration of each waste
constituent should not exceed the leachate concentration delisting level.
The DRAS back-calculates a delisting level for each
waste constituent and each exposure pathway that the delisting program
addresses. The DRAS generates leachate
concentration delisting levels for all groundwater exposure pathways (ingestion
of groundwater, dermal absorption while bathing with groundwater, and inhalation
of groundwater volatiles while showering) and for two of the air inhalation
exposure pathways (inhalation of volatiles from a landfill and inhalation of
volatiles from a surface impoundment).
The DRAS generates total concentration delisting levels for the
remaining air inhalation exposure pathways (inhalation of particulates from a
landfill), the surface water exposure pathways (ingestion of surface water and
ingestion of fish), and the soil ingestion exposure pathway.
To develop the final leachate concentration
delisting level for a waste constituent, the DRAS calculates the constituent’s
pathway-specific leachate concentration delisting levels for the groundwater
pathways and the two relevant air exposure pathways, and then selects the lowest
of the pathway specific values as the final leachate concentration delisting
level. Similarly, to develop the final
total concentration delisting level for a waste constituent, the DRAS computes
pathway-specific values for the relevant pathways, and then chooses the lowest
as the final total concentration delisting level.
For carcinogenic waste constituents, delisting
levels are computed using a moderately conservative default target risk level
of 1 x 10-5. For
noncarcinogenic waste constituents, delisting levels are based on a moderately
conservative default Hazard Quotient (HQ) of 0.1. The default risk level and the HQ values
provide an order of magnitude of safety above the established target risk level
of 1 x 10-4 for carcinogens and the established Hazard Index (HI) of
1.0 for noncarcinogens. The delisting
levels for each waste constituent are the maximum concentrations (total and
TCLP) allowed for the constituent in the petitioned waste, which are based on the
most sensitive exposure pathway. If the
concentration of each constituent in a petitioned waste is less than the total
concentration delisting level, and if the TCLP concentration for each
constituent is less than the leachate concentration delisting level, the waste
may qualify to exit the hazardous waste management program. No single constituent concentration in the
waste or TCLP concentration should exceed its delisting level.3
Having performed a preliminary risk evaluation using
the DRAS, a petitioner can proceed with the delisting petition process with an
increased level of confidence that the waste will be excluded from RCRA
regulations as hazardous waste. However,
before submitting the delisting petition, the petitioner must attend a
pre-petition scoping meeting with the Agency and execute an Agency-approved
Sampling and Analytical Plan.
A petitioner who is confident in the preliminary
risk evaluation results and wants to continue pursuing a delisting petition
will need to attend a pre-petition scoping meeting with the Agency. In general, the purpose of the meeting is to
discuss with the Agency the nature and extent of site-specific information that
must be included in the delisting petition.
The meeting also provides an opportunity for the petitioner to seek
clarification on issues such as the minimum sampling and analytical
requirements that will be acceptable to the Agency.
The petitioner should prepare for the meeting by
developing written responses to the Pre-Petition Scoping Meeting Checklist
items provided in Appendix D of the Delisting Guidance.1 This information includes:
The next component of the pre-petition evaluation
strategy is developing and executing an Agency-approved sampling and analytical
plan. The purpose of the sampling and
analytical plan is to define a list of constituents of concern and generate
representative data to support the delisting petition. The objectives of the plan should include:
The sampling and analytical plan is a necessary part
of the pre-petition evaluation process, because it will guide the petitioner in
the collection of data that the Agency will use as a basis for granting a
delisting petition. The petitioner will
also benefit from implementing the Sampling and Analytical Plan, because the
analytical data to be collected will provide the petitioner an opportunity to
re-evaluate the risks posed by the waste before the petition is submitted to
the Agency.
Re-evaluating Risks Based on Data to be Included in
the Delisting Petition
Before a petitioner proceeds with developing and
submitting a delisting petition, the preliminary risk evaluation should be
repeated using the data that will support the delisting petition in the
DRAS. This last component of the
pre-petition evaluation strategy will provide the petitioner with another
opportunity to ensure that the waste constituent concentrations do not exceed
the delisting levels or raise irresolvable issues during the Agency’s review of
the delisting petition.
HAZARDOUS
WASTE COMBUSTION RESIDUES
THAT
ARE POTENTIAL CANDIDATES FOR DELISTING
Hazardous waste combustion residues are often
regulated as listed hazardous waste if they are derived from the treatment of
listed hazardous wastes. However, for well-operated
combustion units, the residues are not likely to exhibit the same physical and
chemical characteristics as the listed hazardous wastes that were burned in the
unit. As a result, combustion residues
generated by units that routinely burn the same waste stream may qualify as
potential candidates for delisting. Such
residues can include: ash, spent lime, spent carbon, scrubber waters, baghouse
dust, and wastewater treatment sludges.
These same wastes may not be good candidates for delisting when they are
generated by commercial and on-site hazardous waste combustion units that burn
highly variable wastes from different sources.
PROJECTED
PROJECT SCHEDULE
According to the EPA’s streamlined delisting process
outlined in the Delisting Guidance, a final Agency decision on a delisting
petition typically takes about 180 working days after a complete petition is
submitted. During this period, the
Agency will perform a technical review of the delisting petition, and the
petitioner will have to respond to any minor deficiencies identified by the
Agency. If major deficiencies are
identified by the Agency, the petition will be denied by the Agency or required
to be withdrawn by the petitioner. After
all minor deficiencies have been addressed to the Agency’s satisfaction, a
Federal Register notice will be published to provide a 30-45 day public comment
period on the delisting petition. If
public comments are received, they must be addressed and incorporated into a subsequent
Federal Register notice announcing the Agency’s final decision on the delisting
petition.
ESTIMATED COST OF DELISTING A WASTE STREAM
For each delisting petition submitted to the Agency,
the petitioner will incur costs associated with gathering the necessary data
and preparing the petition. These costs
may be as high as $80,000 to $100,000, but can be substantially less.4 If the delisting effort is successful, the
return on the petitioner’s investment will result in significant hazardous
waste management cost savings.
CONCLUSIONS
A prospective petitioner can gain a significant
degree of confidence in a waste’s ability to be delisted by following the
pre-petition evaluation strategy outlined in this paper. Each component of the strategy should be
implemented by a prospective petitioner to minimize irresolvable issues that
may arise after the petition is submitted.
If the outcome of the preliminary evaluation strategy indicates a
favorable delisting scenario (i.e., that the waste does not exceed delisting
levels), the delisting program can serve as a streamlined process to exclude
the hazardous waste from RCRA Subtitle C regulations.
1. U.S. EPA, EPA RCRA Delisting Program
Guidance Manual for The Petitioner, March 23, 2002.
2. U.S. EPA, User’s Guide for the U.S. EPA Region
6 Delisting Risk Assessment Software (DRAS), April 2002.
3. U.S. EPA, RCRA
Delisting Technical Support Document, May 2000.
4. U.S. EPA, RCRA
Hazardous Waste Delisting: The First 20 Years, June 2002.