RCRA DELISTING
 

TECHNICAL SUPPORT DOCUMENT
 

Office of Solid Waste 

Prepared by 

Multimedia Planning and Permitting Division
 

U.S. Environmental Protection Agency
 

Region 6
 

Dallas, TX 75202
 

January 10, 2002 

Updated by
 

Land and Chemicals Division
 

U.S. Environmental Protection Agency
 

Region 5
 

Chicago, IL 60404
 

October 31, 2008 
DISCLAIMER 

This document provides describes to U.S. Environmental Protection Agency (U.S. EPA) regions and 

states on how to use the U.S. EPA Delisting Risk Assessment Software (DRAS) as a tool for the 

evaluation of hazardous waste delisting petitions. The document is not a substitute for U.S. EPA 

regulations, nor is it a regulation itself. Thus, it cannot impose legally binding requirements on U.S. 

EPA, states, or the regulated community. It may not apply to a particular situation based on the 

circumstances. U.S. EPA may change the DRAS in the future, as appropriate. 

i 
ACKNOWLEDGMENTS 

The Region 6 Delisting Team and Dr. Michael Morton (U.S. EPA Region 6), the primary author and 

editor of the Delisting Technical Support Document (DTSD) and the interactive, Windows-based 

Delisting Risk Assessment Software (DRAS), would like to acknowledge that development of the 

(RCRA) delisting risk-based program could not have been accomplished without the support, input, and 

work of a multitude of U.S. EPA and support contractor personnel. The foundation for the procedures 

and methodologies outlined in the DRAS and DTSD was first developed by the Office of Research and 

Development (ORD) and the Office of Solid Waste (OSW) in previous RCRA delisting risk assessment 

procedures. The risk assessment approach was originally initiated in response to the desire of the Region 

6 Multimedia Planning and Permitting Division to implement an up-to-date and technically sound RCRA 

delisting risk assessment program. The DRAS, which performs risk assessments for wastes petitioned for 

RCRA delisting, has been developed to facilitate the risk-based evaluation of the wastes by nontechnical 

personnel. The DTSD was written to describe the technical methodology used by the DRAS to generate 

risk-based information on wastes petitioned for RCRA delisting. 

The development of this document was significantly enhanced by capable organizations and personnel 

within U.S. EPA. Chichang Chen and Shenyi Yang of the Hazardous Waste Identification Division are to 

be commended for their technical comments on the overall methodologies presented in the DTSD and 

their insightful ideas for the DRAS, which led to a more user-friendly software product. In addition, 

Stephen Kroner and David Cozzie of the Economic Methods and Risk Analysis Division provided 

significant policy and technical comments on the DTSD and DRAS. 

The U.S. EPA regional offices contributed valuable comments that have significantly improved the 

usability of both the risk-based software and the supporting document. The authors would be remiss if 

they did not acknowledge significant contributions from Judy Sophianopoulos of Region 4, Todd Ramaly 

of Region 5, Michael Gansecki of Region 8, and Patrick Wilson of Region 9. Cheryl Overstreet of the 

Region 6 Base Closure Team also contributed a valuable review of the DTSD. 

In addition, Terry Allison of Allison Geoscience Consultants, Inc., provided a significant review of the 

methodologies used to incorporate waste volume into groundwater fate and transport modeling. 

This work could not have been completed without valuable support from contractor personnel. Tetra 

Tech EM Inc. (Doug Czechowski) and Tech Law (Wally O’Rear) performed the bulk of the project’s 

oversight and coordination. HydroGeoLogic, Inc., under subcontract, provided technical improvements 

in the modeling approaches used in the risk-based process, such as the EPA’s Composite Model for 

Leachate Migration with Transformation Products (EPACMTP) ground water fate and transport model 

advancements. HydroGeoLogic, Inc., led by Sam Figuli and Darren Baird, developed the software code 

that forms the foundation of the Windows-based Delisting Risk Assessment Software (DRAS) program. 

The work of these contractors was performed under the technical direction of Region 6 Delisting Team 

staff as well as key Agency project and contracting officers. 

More recently, the DRAS has been extensively modified to incorporate updated groundwater modeling, 

Updated adsorption isotherms for metals from the Metal Speciation Equilibrium Model for Surface and 

Ground Water (MINTEQA2), new toxicity data, and other technical upgrades or corrections have been 

incorporated intoDRAS version 3 by the joint efforts of Regions 5 and 6 under the direction of Todd 

Ramaly (R5) and Michelle Peace (R6) . The improvements were made possible by the generous 

contribution of technical, financial, and contractor support of other EPA Regions including Region 3's 

ii 
Dave Friedman, Region 7's Jim Seiler, and Region 9's Cheryl Nelson. The revised groundwater modeling 

was provided by HydroGeoLogic, Inc., led by Dr. Varut (Dua) Guvanasen with computer programming 

changes under subcontract to AMEC’s Darren Baird. The work was continued by TechLaw, Inc. led by 

Kristi Hogan and Nicole Guyer with updates to the software code by Amy Lu. 

All remaining updates were finalized by Dr. Guvanasen of HydroGeoLogic, Inc. in 2008 with major 

contributions from his team members Prashanth Khambhammettu (programming) and Dr. Xinyu Wei 

(calculation verification). 

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RCRA Delisting Technical Support Document 

Contents Revised October 2008 

CONTENTS 

Chapter	 Page 

CONTENTS.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
 

ACRONYMS AND ABBREVIATIONS. ................................................. x
 

VARIABLES....................................................................... xiv
 

1 INTRODUCTION. ........................................................... 1-1
 

1.1 	 DOCUMENT OBJECTIVES. ............................................ 1-3
 

1.2 	 BACKGROUND....................................................... 1-3
 

1.2.1	 U.S. EPA OSW Hazardous Waste Delisting Program. . . . . . . . . . . . . . . . . . . . 1-4
 

1.2.2 	 Regional Authorization.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
 

1.2.3 	 Regional Program Modifications.................................... 1-5
 

1.2.4 	 DRAS......................................................... 1-7
 

1.2.4.1 Calculating Delisting Levels for Multi-year Delistings.. . . . . . . . . . . 1-8
 

1.2.4.2 Calculating Aggregate Risks and Hazards.. . . . . . . . . . . . . . . . . . . . . 1-8
 

1.3	 DELISTING REFERENCE DOCUMENTATION.. . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9
 

1.3.1 	 Delisting Process Documents....................................... 1-9
 

1.3.2 	 Delisting Docket Materials. ...................................... 1-10
 

1.3.3	 Other Relevant Reference Documents .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-11
 

1.4 	 DOCUMENT ORGANIZATION......................................... 1-13
 

2	 ESTIMATION OF CHEMICAL RELEASES AND MEDIA CONCENTRATIONS.. . . . . . . . 2-1
 

2.1 	 SOURCE RELEASE SYSTEMS. ......................................... 2-1
 

2.1.1	 Liquid-Phase Waste (Surface Impoundment). . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
 

2.1.2 	 Solid-Phase Waste (Landfill)....................................... 2-2
 

2.2	 RELEASES TO GROUNDWATER (EPACMTP). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
 

2.2.1	 Methodology for Estimation of Waste Constituent Concentration in 


Groundwater.................................................... 2-3
 

2.2.2 	 Overview of EPACMTP.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
 

2.2.2.1 Contaminant Release and Transport Scenario. . . . . . . . . . . . . . . . . . . 2-6
 

2.2.2.2 EPACMTP Modeling Assumptions and Input Parameters.. . . . . . . . . 2-7
 

2.2.2.3 Modification of EPACMTP to Derive Waste Volume-Specific 

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Contents Revised October 2008 

CONTENTS (Continued) 

Chapter	 Page 

 DAFs.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13
 

2.2.2.3.1 	 Landfills.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13
 

2.2.2.3.2	 Surface Impoundments. . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15
 

2.2.3 Calculation of Groundwater Waste Constituent Concentration at the POE. . . 2-15
 

2.3 RELEASES TO SURFACE PATHWAYS.................................. 2-19
 

2.3.1 Calculation of Waste Constituent Concentration in Air — Particulates.. . . . . 2-19
 

2.3.1.1	 Estimation of Particulate Emissions. . . . . . . . . . . . . . . . . . . . . . . . . 2-20
 

2.3.1.2	 Calculation of Particulate Constituent Concentration in Air at 


 the POE.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-28
 

2.3.1.3	 Calculation of Air Deposition Rates and Resulting Soil 


 Concentrations at the POE. ............................... 2-30
 

2.3.2 Calculation of Chemical Concentration in Air at the POE-Volatiles. . . . . . . . 2-32
 

2.3.2.1 	Calculation of Volatile Emissions from a Landfill Using 


 Farmer's Equation. ...................................... 2-32
 

2.3.2.2	 Calculation of Downwind Volatile Waste Constituent 


 Concentration in Air at the POE—Landfill. . . . . . . . . . . . . . . . . . . . 2-34
 

2.3.2.3	 Calculation of Volatile Emissions from a Hypothetical 


 Surface Impoundment.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-35
 

2.3.2.4	 Calculation of Downwind Waste Constituent Concentration in 


 Air at the POE —Surface Impoundment. . . . . . . . . . . . . . . . . . . . . . 2-39
 

2.3.3 Calculation of Waste Constituent Concentration in Surface Water. . . . . . . . . 2-40
 

2.3.3.1	 Computing the Amount of Soil Delivered to Surface Water. . . . . . . 2-42
 

2.3.3.2	 Determining the Volume of Surface Water. . . . . . . . . . . . . . . . . . . . 2-43
 

2.3.3.3	 Computing the Waste Constituent Concentration in Surface


 Water. ................................................ 2-43
 

2.3.4 Calculation of Dissolved Phase Waste Concentration in Surface Water. . . . . 2-44
 

2.3.4.1	 Partitioning Coefficients for Suspended Sediment-Surface Water 


and TSS. ............................................. 2-45
 

2.3.4.2	 Concentration of Waste Constituent in Fish. . . . . . . . . . . . . . . . . . . 2-46
 

2.3.4.3	 Calculation of Fish Concentration from Bioconcentration Factors 


Using Dissolved Phase Water Concentration. . . . . . . . . . . . . . . . . 2-47
 

2.3.4.4	 Calculation of Fish Concentration from Bioaccumulation Factors
 

Using Dissolved Phase Water Concentration. . . . . . . . . . . . . . . . . 2-47
 

EXPOSURE SCENARIO SELECTION. .......................................... 3-1
 

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RCRA Delisting Technical Support Document 

Contents Revised October 2008 

CONTENTS (Continued) 

Chapter Page 

3.1 DEFAULT EXPOSURE SCENARIOS.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
 

3.1.1 Adult Resident. ................................................. 3-2
 

3.1.2 Child Resident.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
 

3.1.3 Special Subpopulation Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
 

3.2 EXPOSURE SCENARIO LOCATIONS. ................................... 3-4
 

3.2.1 Downgradient Groundwater-Drinking Water Well POE . . . . . . . . . . . . . . . . . 3-4
 

3.2.2 Downgradient Surface Water Body POE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
 

3.2.3 Downwind POE. ................................................ 3-6
 

3.3 QUANTIFICATION OF EXPOSURE. ..................................... 3-6
 

3.3.1 Generic Exposure Rate Equation. ................................... 3-6
 

3.3.2 Contact Rate.................................................... 3-7
 

3.3.2.1 Groundwater and Surface Water Exposure Pathway Parameters. . . . . 3-7
 

3.3.2.2 Air Pathways.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9
 

3.3.3 Exposure Frequency............................................. 3-10
 

3.3.4 Exposure Duration. ............................................. 3-11
 

3.3.5 Averaging Time. ............................................... 3-11
 

3.3.6 Body Weight.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11
 

3.3.7 Fish Consumption.. . . .. . . .. . . .. . . .. . . .. . . .. . . .. . . .. . . .. . . .. . . .. . 3-12
 

3.3.8 Age-adjusted Contact Rates....................................... 3-12
 

RISK AND HAZARD ASSESSMENT............................................ 4-1
 

4.1 INDIVIDUAL RISK AND HAZARD ESTIMATION. . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
 

4.2 TARGET RISK LEVELS................................................ 4-3
 

4.2.1 Target Risk .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
 

4.2.2 Target Hazard................................................... 4-5
 

4.2.3 Delisting Levels ................................................. 4-8
 

4.2.4 DRAS Aggregate Risk .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10
 

4.2.5 Special Limitations and Exceptions.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10
 

4.2.5.1 Waste Constituent Concentration Ceiling.. . . . . . . . . . . . . . . . . . . . . 4-11
 

4.2.5.2 Soil Saturation Evaluation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
 

4.2.5.3 Estimation of Potential Health Effects for Lead. . . . . . . . . . . . . . . . . 4-13
 

4.2.5.4 Estimation of Potential Health Effects for PCDDs and PCDFs. . . . . 4-14
 

4.2.5.5 Estimation of Potential Health Effects for PCBs.. . . . . . . . . . . . . . . 4-16


 4.2.5.5.1 Coplanar PCBs.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-17


 4.2.5.5.2 Other PCBs. ................................... 4-18
 

4.2.5.6 Toxicity Characteristic Rule Evaluation. . . . . . . . . . . . . . . . . . . . . . 4-19
 

4.2.5.7 MCL Evaluation. ....................................... 4-21
 

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CONTENTS (Continued) 

Chapter	 Page 

4.2.5.8 	 Detection Limit Evaluation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-21
 

4.2.5.9	 Estimation of Ecological Effects. . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-22
 

4.3 QUANTITATIVE ESTIMATION OF RISK. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-25
 

4.3.1 Groundwater Exposure Pathways.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-26


 4.3.1.1. 	 Ingestion of Groundwater. ................................ 4-26


 4.3.1.1.1 Delisting Level Analysis .. . . . . . . . . . . . . . . . . . . . . . . . . 4-26


 4.3.1.1.2 Risk Analysis................................... 4-27
 

4.3.1.2. Adult and Child Dermal Contact with Groundwater During 


 Bathing................................................ 4-28


 4.3.1.2.1 Delisting Level Analysis.. . . . . . . . . . . . . . . . . . . . . . . . . 4-28


 4.3.1.2.2 Risk Analysis. ................................. 4-31
 

4.3.1.3 	Adult Inhalation of Volatiles from Groundwater During 


 Showering. ............................................ 4-33


 4.3.1.3.1 Delisting Level Analysis.. . . . . . . . . . . . . . . . . . . . . . . . . 4-34


 4.3.1.3.2 Risk Analysis. ................................. 4-36
 

4.3.2 Surface Water Exposure Pathways.................................. 4-44
 

4.3.2.1 Ingestion of Surface Water................................. 4-44


 4.3.2.1.1 Delisting Level Analysis.. . . . . . . . . . . . . . . . . . . . . . . . . 4-45


 4.3.2.1.2 Risk Analysis. ................................. 4-46
 

4.3.2.2 Ingestion of Fish......................................... 4-47


 4.3.2.2.1 Delisting Level Analysis.. . . . . . . . . . . . . . . . . . . . . . . . . 4-47


 4.3.2.2.2 Risk Analysis. ................................. 4-49
 

4.3.3 Air Exposure Pathways.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-50
 

4.3.3.1 Delisting Level Analysis.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-51
 

4.3.3.2 Risk Analysis. .......................................... 4-57
 

4.3.4 Soil Exposure Pathway........................................... 4-61
 

4.3.4.1 Delisting Level Analysis.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-61
 

4.3.4.2 Risk Analysis. .......................................... 4-63
 

4.4 QUANTITATIVE ESTIMATION OF POTENTIAL NONCANCER EFFECTS. . . . 4-65
 

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CONTENTS (Continued) 

Chapter	 Page 

4.4.1 Groundwater Exposure Pathways.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-66


 4.4.1.1 	 Adult Ingestion of Groundwater. . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-66


 4.4.1.1.1 Delisting Level Analysis. . . . . . . . . . . . . . . . . . . . . . . . . 4-67


 4.4.1.1.2 Hazard Analysis.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-68


 4.4.1.2 	Adult and Child Dermal Contact with Groundwater During 


 Bathing............................................... 4-68


 4.4.1.2.1 Delisting Level Analysis. . . . . . . . . . . . . . . . . . . . . . . . . 4-68


 4.4.1.2.2 Hazard Analysis.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-70
 

4.4.1.3 	Adult Inhalation of Volatiles from Groundwater During 


 Showering. ............................................ 4-71


 4.4.1.3.1 Delisting Level Analysis.. . . . . . . . . . . . . . . . . . . . . . . . . 4-72


 4.4.1.3.2 Hazard Analysis................................ 4-74
 

4.4.2 Surface Water Exposure Pathways.................................. 4-75
 

4.4.2.1 Ingestion of Surface Water................................. 4-76


 4.4.2.1.1	 Delisting Level Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . 4-76


 4.4.2.1.2 	 Hazard Analysis.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-77
 

4.4.2.2 Ingestion of Fish......................................... 4-78


 4.4.2.2.1	 Delisting Level Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . 4-78


 4.4.2.2.2 	 Hazard Analysis.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-80
 

4.4.3 Air Exposure Pathways.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-81
 

4.4.3.1 Delisting Level Analysis................................... 4-81
 

4.3.3.2 Hazard Analysis.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-85
 

4.4.4 Soil Exposure Pathway........................................... 4-86
 

4.4.4.1 Delisting Level Analysis................................... 4-86
 

4.4.4.2 Hazard Analysis.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-88
 

5.0 UNCERTAINTY. ............................................................ 5-1
 

5.1 UNCERTAINTY IN THE DELISTING RISK-BASED PROCESS.. . . . . . . . . . . . . . . 5-2
 

5.1.1 Use of Risk Assessment Algorithms for Delisting Evaluations. . . . . . . . . . . . . 5-3
 

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CONTENTS (Continued) 

Chapter 

5.1.2 

Page 

Disposal, Release, and Exposure Scenarios. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4 

5.2 TYPES OF UNCERTAINTY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5 

5.2.1 Variability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7 

5.3 UNCERTAINTY IN SAMPLE ANALYSES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7 

5.3.1 

5.3.2 

The TCLP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8 

Use of a Delisted Material. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9 

REFERENCES.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1
 

Appendix 

A Chemical-Specific Parameters 

A-1 Chemical-Specific Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1-1 

A-2 National Primary Drinking Water Standards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-2-1 

A-3 Soil Saturation Concentrations and Physical States at Ambient Temperature of 

Chemicals Considered for Delisting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-3-1 

A-4 Target Organs and Critical Effects for Compounds with Reference Dose Values. . . A-4-1 

A-5 Default Variables: Abbreviations, Units, and Values. . . . . . . . . . . . . . . . . . . . . . . . . A-5-1 

A-6 Application of CMTP and MINTEQA2 for determining DAFs. . . . . . . . . . . . . . . . . A-6-1 

B Parameters Used for Surface Pathway Release and Risk Calculations.. . . . . . . . . . . . . . . . . . . B-1
 

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Acronyms and Abbreviations Revised October 2008 

FIGURES 

Figure 

2-1 DAF Scaling Factors for Landfills............................................... 2-15
 

2-2 DAF Scaling Factors for Surface Impoundments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17
 

TABLES
 

Table
 

2-1 EPACMTP Modeling Assumptions and Input Parameters.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
 

4-1 TC Rule Regulatory Levels.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-23
 

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Acronyms and Abbreviations Revised October 2008 

ACRONYMS AND ABBREVIATIONS 

ìg Microgram 

ìm Micron 

AADM Ambient Air Dispersion Model 

ADD Average daily dose 

AP-42 “Title” 

API American Petroleum Institute 

AT Averaging time 

atm Atmosphere 

BAF Bioaccumulation factor 

BaP Benzo(a)pyrene 

BCF Bioconcentration factor 

BOD Biochemical oxygen demand 

BSAF Biota-sediment bioaccumulation factor 

BW Body weight 

CAS Chemical Abstracts Service 

CFR Code of Federal Regulations 

CLP Contract Laboratory Program 

cm Centimeter 

CSF Cancer slope factor 

DAD Personally absorbed dose 

DAF Dilution attenuation factor 

DF Dilution factor 

DRAS Delisting Risk Assessment Software 

DTSD Delisting Technical Support Document 

DW Dry weight of soil or plant or animal tissue 

EFH Exposure Factors Handbook 

EPACML U. S. EPA Composite Model for Landfill 

EPACMTP U. S. EPA Composite Model for Leachate Migration with Transformation Products 

EQL Estimated quantitation limit 

FR Federal Register 

g Gram 

GC Gas chromatography 

HBN Health-based number 

HEAST Health Effects Assessment Summary Tables 

HELP Hydrologic Evaluation of Landfill Performance 

HI Hazard index 

HQ Hazard quotient 

hr Hour 

HSWA Hazardous and Solid Waste Amendments 

ACRONYMS AND ABBREVIATIONS (Continued) 

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Acronyms and Abbreviations Revised October 2008 

HWIR Hazardous Waste Identification Rule 

IDL Instrument detection limit 

IEUBK Integrated Exposure Uptake Biokenitc Model 

IRIS Integrated Risk Information System 

ISC Industrial Source Complex 

ISCST3 Industrial Source Complex Short Term 3 

ISCSTDFT Industrial Source Complex Short Term Draft 

K Kelvin 

kg Kilogram 

km Kilometer 

L Liter 

LADD Lifetime average daily dose 

lb Pound 

m Meter 

MCL Maximum contaminant level 

MCLG Maximum contaminant level goal 

MDL Method detection limit 

Mg Megagram 

mg Milligram 

MIR Maximum individual risk 

mL Milliliter 

mm Millimeter 

MSWLF Municipal solid waste landfill 

NAPL Nonaqueous-phase liquid 

NCP National Oil and Hazardous Substances Pollution Contingency Plan 

NCEA U. S. EPA National Center for Environmental Assessment 

NPDES National Pollutant Discharge Elimination System 

NRC National Research Council 

NWT Nonwastewater leachate 

OAQPS U. S. EPA Office of Air Quality Planning and Standards 

OPPI U. S. EPA Office of Policy Planning and Implementation 

ORD U. S. EPA Office of Research and Development 

OSW U. S. EPA Office of Solid Waste 

PAH Polynuclear aromatic hydrocarbon 

PCB Polychlorinated biphenyl 

PCDD Polychlorinated dibenzo(p)dioxin 

PCDF Polychlorinated dibenzofuran 

PDF Probability density function 

pg Picogram 

PM Particulate matter 

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RCRA Delisting Technical Support Document 

Acronyms and Abbreviations Revised October 2008 

ACRONYMS AND ABBREVIATIONS (Continued) 

PM10 Particulate matter less than 10 microns in diameter 

POE Point of exposure 

ppb Parts per billion 

ppm Parts per million 

ppmv Parts per million by volume 

ppt Parts per trillion 

PQL Practical quantitation limit 

QA Quality assurance 

QAPP Quality assurance project plan 

QC Quality control 

RAEPE	 “Rapid Assessment of Exposure to Particulate Emissions from Surface Contamination 

Sites” 

RAGS	 “Risk Assessment Guidance for Superfund” 

RCRA	 Resource Conservation and Recovery Act 

RfC	 Reference concentration 

RfD	 Reference dose 

RMC	 Reynolds Metals Company 

RME	 Reasonable maximum exposure 

RPF	 Relative potency factor 

s	 Second 

SIMS	 Surface Impoundment Modeling System 

SQL	 Sample quantitation limit 

STORET	 Database Utility for STOrage and RETrieval of Chemical, Physical, and Biological Data 

for Water Quality 

SVOC	 Semivolatile organic compound 

SW-846	 “Test Methods for Evaluating Solid Waste” 

TCDD Tetrachlorodibenzo(p)dioxin 

TCLP Toxicity characteristic leaching procedure 

TC Rule Toxicity characteristics Rule 

TDA Toluenediamine 

TDI Toluene diisocyanate 

TEF Toxicity equivalent factor 

TEQ Toxicity equivalent quotient 

Tetro Tech Tetro Tech EM Inc. 

THQ Target hazard quotient 

TIC Tentatively identified compound 

TLV Threshold limit value 

TOC Total organic carbon 

TSD Treatment, storage, or disposal 

TWA Time-weighted average 

UCL95	 95th percentile upper confidence limit 

U. S. DOE	 U. S. Department of Energy 

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RCRA Delisting Technical Support Document 

Acronyms and Abbreviations Revised October 2008 

ACRONYMS AND ABBREVIATIONS (Continued) 

U.S. EPA U.S. Environmental Protection Agency 

USGS U.S. Geological Survey 

USLE Universal soil loss equation 

VOC Volatile organic compound 

WQC Water quality criteria 

yd Yard 

yr Year 

xiv 
 

 

RCRA Delisting Technical Support Document 

Variables Revised October 2008 

VARIABLES 

A = area of waste management unit (acres) 

a = coefficient for Stability Class D = 32.093 

Aeroded = amount of soil and waste eroded (tons/acre/yr) 

Aexposed = area of waste management unit exposed (acres) 

A s = waste mass delivered to surface water (kg/acre/yr) 

Asi = area of surface impoundment (m )2 

Askin = exposed skin surface area (cm )2 

A w = rate of waste erosion from landfill (kg/acre/yr) 

ADD = average daily dose (mg waste constituent/kg BW/day) 

ADD c,p = average daily dose for waste constituent c for pathway p (mg/kg-day) 

AT = averaging time (days or yrs) 

â = Proportionality constant (cm/sec)-1/3 

B = Bunge constant (unitless) 

b = coefficient for Stability Class D = 0.81066 

BAF = bioaccumulation factor (L/kg) 

BD = soil dry bulk density (g soil/cm soil) 3 

BW = body weight (kg) 

C = constant (m /s) 2 -2/3 

Cair = constituent’s maximum allowable respirable air concentration at POE (mg/m )3 

Cair-I = constituent air concentration from compartments: shower, bathroom, and house 

(mg/L) 

Cair-max = maximum possible air concentration of waste constituent based on Henry’s Law 

(mol/L) 

C avg = downwind concentration of waste constituent at POE (mg/m )3 

C avg,s = average constituent air concentration in shower (mg/L) 

Cavg,b = average constituent air concentration in bathroom (mg/L) 

Cavg,h = average constituent air concentration in house (mg/L) 

Cdl-air-p = pathway total concentration delisting level for respirable landfill air particulates 

(mg/kg) 

Cdi-air-si = pathway leachate concentration delisting level for volatiles from surface 

impoundment (mg/L) 

Cdl-air-v = pathway total concentration delisting level for volatiles from landfill (mg/L) 

Cdl-dermal = pathway leachate concentration delisting level for groundwater dermal contact 

(mg/L) 

Cdl-fish = pathway total concentration delisting level for fish ingestion (mg/kg) 

Cdl-ingest = pathway leachate concentration delisting level for groundwater ingestion (mg/L) 

Cdl-inhale = pathway leachate concentration delisting level for shower inhalation (mg/L) 

Cdl-soil = pathway total concentration delisting level for soil ingestion (mg/kg) 

Cdl-water = pathway total concentration delisting level for ingestion of surface water 

(mg/kg) 

Cdw = dissolved-phase water concentration (mg waste constituent/L water) 

Cfish = maximum allowable concentration of waste constituent in fish tissue (mg/kg) 

C5th-stream = concentration of waste in fifth-order stream (kg/L) 

xv 
 

 

RCRA Delisting Technical Support Document 

Variables Revised October 2008 

VARIABLES (Continued) 

Cgen = generic constituent concentration — the medium average concentration contacted 

over the exposure period (for example, mg/kg for soil and mg/L for water) 

Cgw = waste constituent concentration in groundwater (mg/L) 

Cgw-dermal = maximum allowable constituent concentration in groundwater for dermal 

exposure (mg/L) 

Cgw-ingest = maximum allowable constituent concentration in groundwater for ingestion 

(mg/L) 

Cgw-inhale = maximum allowable constituent concentration in groundwater used for 

showering (mg/L) 3 Ci = vapor-phase concentration of I in landfill (g/m ) 3 ci = maximum allowable vapor-phase concentration of constituent in landfill (g/m )


Cinh = mass of waste constituent inhaled (mg/day)
 

CL = leachate concentration (TCLP concentration) (mg/L)
 -3 Cl = Concentration of constituent I in liquid phase (mol.m )


CLMAX = maximum allowable waste leachate (TCLP) concentration (mg/L)
 3 Cs = vapor-phase concentration of constituent I at surface (g/m )


Csat = soil saturation concentration (mg/kg)
 

Csoil = resulting soil concentration (mg/kg soil/yr)
 

Csoluble = concentration of soluble fraction of constituent in waste (mg/kg)
 

Csw = concentration of waste constituent in surface water (mg/L)
 

Ctotal waste = total concentration of constituent in waste (mg/kg)
 

Cancer Riski = individual lifetime risk indirect exposure to waste constituent I (unitless)
 

Cancer Riskinh(I) = individual lifetime cancer risk from direct inhalation of carcinogen waste
 

constituent I (unitless) 

CM = USLE cover management factor (unitless) 

CR = water consumption rate (L/day) 

CRfish = fish water consumption rate (kg/day) 

CRgen = contact rate — the amount of contaminated medium contacted per unit time or 

per event (for example, kg/day for soil and L/day for water) (upper-bound value) 

CRsoil = soil consumption rate (mg/day) 

Cs = average soil concentration over exposure duration (mg waste constituent/kg soil) 

Csi = saturation vapor concentration of I in landfill 

CSF c = cancer slope factor for waste constituent c (mg/kg day)-1 

CSFinhal = constituent inhalation cancer slope factor (mg/kg day)-1 

CSForal = constituent oral cancer slope factor (mg/kg day)-1 

D = 100, distance to stream or river (m) 

d = depth of soil cover (m) 2 Da = diffusivity of constituent in air (cm /s) 2 Dair = diffusion coefficient of constituent in air (m /s)

de = effective diameter of surface impoundment (m) 2 Dether = diffusion coefficient of ether (cm /s) 2 Di = gas-phase diffusion coefficient (m /s)2 Dl = diffusivity in water of a chemical (m /s) 2 Dw = diffusion coefficient in water (cm /s) 2 DA = dose absorbed per unit area per event (mg/cm -event) event 

xvi 
 

 

 

 

 

 

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Variables Revised October 2008 

VARIABLES (Continued) 

DAD = dermally absorbed dose (mg/kg-day)
 

DAF = dilution attenuation factor (unitless)
 

DAFsf = DAF scaling factor (unitless)
 

DAF va = waste volume-adjusted DAF (unitless)
 

DH = drop height of material from truck (m)
 

dp = droplet diameter (cm)
 

Ei = landfill volatile emission flux of constituent (g/s)
 

El = particulate emissions from waste loading and unloading operations (kg/ton)
 

El10 = waste loading and unloading emission rate of particulates up to 10 ìm (kg/ton)
 

El30 = waste loading and unloading emission rate of particulates up to 10 ìm (kg/ton)
 

ET = total emission rate of particulates that may be inhaled (g/hr)
 

ET10 = total emission rate of particulates up to 10 ìm (g/hr)
 

ET30 = total emission rate of particulates up to 30 ìm (g/hr)
 

Ev = particulate emissions from vehicle travel (g/hr)
 

Ev10 = vehicle travel emission rate of particulates up to 10 ìm (g/hr)
 

Ev30 = vehicle travel emission rate of particulates up to 30 ìm (g/hr)
 

Ew = particulate emissions from wind erosion (g/hr) 


Ew10 = wind erosion emission rate of particulates up to 10 ìm (g/hr) 


Ew30 = wind erosion emission rate of particulates up to 30 ìm (g/hr)
 

ED = exposure duration (yr)
 

EF = exposure frequency (days/yr)
 

ETcomp = exposure time in each compartment (bath, shower, or house) (days/shower)
 

EV = event frequency (events/day)
 

F = frequency that wind blows from sector of interest (unitless)
 

Fc = fraction contaminated (unitless)
 

fem,b = fraction of constituent emitted from bathroom water use (unitless)
 

femh = fraction of constituent emitted from house water use (unitless)
 

fem,s = fraction of constituent emitted from shower water use (unitless)
 

Fexposed = fraction of area exposed to erosion (unitless)
 

Finhal = fraction of particulates inhaled (Unitless)
 

foc = fraction organic carbon content of soil (g/g)
 

fsat, I = Fraction of gas phase saturation for each shower inhalation compartment I
 

F(X) = dimensionless function obtained from plot in RAEPE
 

h = nozzle height (cm) 3 H = Henry’s Law constant (atm-m /mol)


H' = dimensionless Henry’s Law constant
 

HBN = health-based number (or MCL) (mg/L)
 

HI = hazard index (unitless)
 

HIp = total hazard index for all waste constituents for specific exposure pathway p
 

HQ = hazard quotient (unitless)
 

HQc,p = hazard quotient for waste constituent c for exposure pathway p (unitless)
 

HIcum = aggregate hazard index for all constituents and all exposure pathways
 

VARIABLES (Continued) 

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RCRA Delisting Technical Support Document 

Variables Revised October 2008 

I =	 intake — amount of constituent at exchange boundary (mg/kg-day); for 

evaluating exposure to noncarcinogenic constituents, this intake is referred to as 

ADD; for evaluating exposure to carcinogenic constituents, this intake is referred 

to as LADD 

Ib =	 bathroom water use (L/min) 

Ih =	 house water use (L/min) 

Is =	 shower water use (L/min) 

IFAadj =	 inhalation factor, age-adjusted ([m 3

-year]/[kg-day]) 

IFSadj =	 soil ingestion factor ([mg-year]/[kg-day]) 

IFWadj =	 water ingestion factor, age-adjusted [L Cyear]/[kgCday] 3 3 IR =	 inhalation rate (m /day or m /hr)

2 Ji =	 volatile emission flux of constituent (g/m /s)

k = constant— 0.36 for particulates up to 10 ìm and 0.8 for particulates up to 30 ìm 

K = overall mass transfer coefficient (m/s) 3 Kd =	 soil-water partition coefficient (cm water/g or L/kg)

Kef =	 USLE erodibility factor (ton/acre) 

Keq =	 equilibrium constant (unitless) 

KG =	 gas-phase transfer coefficient (m/yr) 

Kg =	 gas-phase mass transfer coefficient (m/s) 

KL =	 liquid-phase transfer coefficient (m/yr) 

Kl =	 liquid-phase mass transfer coefficient (m/s) 

Koc =	 soil organic carbon-water partition coefficient (mL water/g soil) 

koc =	 normalized distribution coefficient (L/kg) 

Kol =	 overall mass transfer coefficient (cm/sec) 

Kow =	 octanol-water partition coefficient (mg waste constituent/L octanol)/(mg waste 

constituent/L water) 

Kp =	 batch drop particle size multiplier (dimensionless) 

Kp

w =	 skin permeability constant in water (cm/hr) 

Ke =	 equilibrium coefficient (s/cm-yr) 

L =	 distance from center of uncovered waste area to compliance point 1,000 feet 

(304.8 m) downwind (km) 

L' = virtual distance (the distance necessary to convert from an ideal point source to a 

volume source) (km) 

Lv = distance from virtual point to compliance point located 1,000 feet (304.8 m) 

downwind (m) 

LADD = lifetime average daily dose (mg waste constituent/kg BW/day) 

LADD c,p = lifetime average daily dose for waste constituent c (mg/kg-day) via pathway p 

LS = USLE length-slope factor (unitless) 

M =	 moisture content of waste (percent) -1 Mi = molecular weight (g.mol )

MW = molecular weight 

n =	 total soil porosity (L pore /Lsoil) 

VARIABLES (Continued) 

Np = number of days per year with at least 0.01 inch of precipitation (days per year) 

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RCRA Delisting Technical Support Document 

Variables Revised October 2008 

P = support practice factor (dimensionless) 

p = Pasquill Stability coefficient for Category D (unitless) 

P a = air-filled sand porosity (dimensionless) 

P p = partial pressure of constituent (atm) 

PT = total sand porosity (dimensionless) 

PF = USLE supporting practice factor (unitless) 

q = Pasquill Stability coefficient for Category D (unitless) 

qd = rate of deposition (mg/m /s) 2 

Q gs = volumetric gas exchange rate between shower and bathroom (L/min) 

Qgb = volumetric gas exchange rate between bathroom and house (L/min) 

Qgh = volumetric gas exchange rate between house and atmosphere (L/min) 

Q p = emission rate of waste constituent particluates (mg/s) 

Qp10 = emission rate of waste constituent particulates up to 10 ìm (mg/s) 

Qp30 = emission rate of waste constituent particulates up to 30 ìm (mg/s) 

Q v = volatile emission rate (mg/s) 

Q2nd = flux of water in second-order stream (L/year) 

Q stream = volumetric flow of stream (L/year) 

R = universal gas constant (atm-m /mol-K) 3 

RF = rainfall erosion factor (1/year) 

RfC = reference concentration (mg/kg) 

RfD = reference dose (mg/kg-day) 

RfD c = reference dose for waste constituent c (mg/kg-day) 

Risk = cancer risk for carcinogens (unitless) 

Risk c,p = risk for waste constituent c for specific exposure pathway p 

Risk cum = aggregate risk for all constituents and all exposure pathways 

Risk p = total risk for all constituents for specific exposure pathway p 

S = mean vehicle speed (km/hr) 

s = silt content of waste (percent) 

S cg = Schmidt number on gas side (unitless) 

Sd = sediment delivery ratio (unitless) 

SF = slope factor (mg/kg-day)-1 

Sol = solubility in water (mg/L water) 

T = standard temperature (K) 

t = soil thickness from which particles can be ingested (m) 

t+1 t (t - t ) = calculational time step (min) 

event t = duration of event (hr/event) 

TCLP = TCLP concentration of waste constituent (mg/L) 

tf = o time for constituent concentration to reach 1 percent of C 

THQ = target hazard quotient (unitless) 

TPDmin = minimum round trips per day 

TR = individual target risk level (unitless) 

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RCRA Delisting Technical Support Document 

Variables Revised October 2008 

VARIABLES (Continued) 

TSS = total suspended solids concentration (mg/L) 

U = mean annual wind speed (m/s) 

U10 = wind speed at 10 m (m/s) 

U t = threshold value of wind speed at 7 m (m/s) 

V = volume of landfilled waste (yd )3 

Vb = volume of bathroom (L) 

Vh = volume of house (L) 

V s = volume of shower (L) 

Vsi = volume of liquid in surface impoundment (m )3 

vd = deposition velocity (m/s) 

vt = terminal velocity (cm/sec) 

Vf = fraction of disposal site covered with vegetation (unitless) 

VKT = vehicle kilometers traveled-km trip x number of trips 

VR comp = ventilation rate for compartment (shower, bathroom, house) (L/hr) 

W = mean vehicle weight (tons) 

w = mean number of wheels per vehicle 

W comp = water used in one of three compartments (shower, bathroom, house) (L/hr) 

X = dimensionless ratio 

x = 1⁄2 width of area exposed (m) 

yb,t = gas phase constituent concentration in the bathroom (mg/L) 

yh,t = gas phase constituent concentration in the house (mg/L) 

ys,t 

Yd 

= 

= 

gas phase constituent concentration in the shower (mg/L) 

dumping device capacity (m )3 

á 

Ö 

Ö Rn

= 

= 

= 

mass fraction of constituent in waste (unitless) 

mass transfer efficiency of chemical (unitless) 

mass transfer efficiency of radon (unitless) 

a r = density of air (g/cm )3 

ñb = soil bulk density (mg/m )3 

ñdb = dry soil bulk density (kg/L) 

ñ s = soil particle density (kg/L) 

ñ w

È a

È w

= 

= 

= 

waste density (tons per cubic yard) 

air soil air-filled soil porosity (L /L ) 

water-filled soil porosity (L /L ) water soil

ô = lag time (hr) 

m a = viscosity of air (gm/cm-s) 

3z = vertical dispersion coefficient (m) 

10 -2 = unit conversion factor (kg-cm /mg-m ) 2 2 

10-3 = unit conversion factor (kg-ìg/g ) 2 

10-4 = unit conversion factor (m /cm ) 2 2 

10-6 = unit conversion factor (g/ìg) 

10-6 = unit conversion factor (kg/mg) 

0.001 = unit conversion factor (g/mg) 

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RCRA Delisting Technical Support Document 

Variables Revised October 2008 

0.004047 = unit conversion factor (km /acre) 2 

0.31536 = unit conversion factor (m-g-s/cm-ìg-yr) 

365 = unit conversion factor (days/yr) 

907.18 = unit conversion factor (kg/ton) 

3.1536 × 10 7 = unit conversion factor (s/yr) 

xxi 
 

RCRA Delisting Technical Support Document 

Chapter 1: Introduction Revised October 2008 

Chapter 1 

Introduction 

What’s covered in Chapter 1: 

� Document Objective and Purpose 

� Background 

� Delisting Reference Documentation 

� Document Organization 

Under the regulations implementing Subtitle C of the Resource Conservation and Recovery Act (RCRA), 

wastes are designated as hazardous in two ways: (1) solid wastes that exhibit certain characteristics (those 

listed in 40 Code of Federal Regulations [CFR] Part 261, Subpart C) and (2) solid wastes that are specifically 

listed as hazardous (those listed in 40 CFR Part 261, Subpart D). As set forth in Subpart C, wastes that are 

characteristically hazardous remain so until they no longer exhibit any characteristic for which they are listed. 

Toxicity is one of the characteristics for which Subtitle C wastes are listed as hazardous. This document 

outlines a risk assessment procedure for determining whether a Subtitle C listed waste exceeds the U.S. 

Environmental Protection Agency (U.S. EPA) criteria for toxicity, a characteristic of RCRA listed wastes. 

Risk assessment is a science used to evaluate the carcinogenic risks and noncarcinogenic hazards to human 

health that are attributable to releases of hazardous chemicals. Risk assessments conducted for the delisting 

include evaluation of risks associated with direct and indirect exposures to waste constituents. The following 

definitions are adopted from the National Research Council’s (NRC) 1983 report titled “Risk Assessment 

in the Federal Government: Managing the Process” (NRC 1983) for use throughout this guidance: 

Risk assessment The scientific evaluation of potential health impacts that may result from 

exposure to a particular substance or mixture of substances under specified 

conditions 

Hazard An impact to human health by waste constituents of concern 

Risk An estimation of the probability that an adverse health impact may occur as 

a result of exposure to chemicals in the amount and by the pathways 

identified 

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RCRA Delisting Technical Support Document 

Chapter 1: Introduction Revised October 2008 

Dose	 Constituent mass administered into the body per unit body weight per unit 

time (for example, in milligrams per kilogram per day) 

Exposure	 Exposure of identified receptors to chemicals via relevant pathways 

Direct exposure	 Exposure via immediate inhalation from a contaminated source 

Indirect exposure	 Exposure resulting from contact of human and ecological receptors with soil 

or water bodies on which an emitted chemical has been deposited or into 

which an emitted chemical has leached 

Secondary exposure	 Synonymic phrase for indirect exposure 

This Delisting Technical Support Document (DTSD) was developed to be an integral part of and to provide 

the technical background for the Delisting Risk Assessment Software (DRAS). The DRAS can aid in 

determining whether a waste qualifies as being not characteristically toxic for the purposes of delisting under 

40 CFR 260.20 and 260.22. The DRAS was developed to compute the risks and hazards associated with a 

specific waste stream for which a delisting petition has been submitted. The DRAS assesses the toxicity of 

a petitioned waste by estimating (1) chemical- and waste volume-specific screening exit values and (2) 

aggregate cancer risks and noncarcinogenic hazard indices (HI). To calculate the potential risks associated 

with a particular waste stream petitioned for delisting, specific information about the petitioned waste is 

required. U.S. EPA requires the following waste-specific information for DRAS in order to estimate risks 

and hazards associated with potential exposure to the petitioned waste stream: 

•	 The maximum annual or total waste volume of the petitioned waste; 

•	 The maximum total concentration of each chemical constituent in the petitioned waste; 

•	 The maximum Toxicity Characteristic Leaching Procedure (TCLP) concentration of each 

chemical constituent in the petitioned waste; and 

•	 The number of years the petitioned waste is projected to be generated 

Section 1.1 discusses the objectives and purpose of this document. Section 1.2 provides background on the 

Hazardous Waste Delisting Program. Section 1.3 summarizes delisting reference documentation. An 

overview of the organization of this DTSD is provided in Section 1.4. 

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RCRA Delisting Technical Support Document 

Chapter 1: Introduction Revised October 2008 

1.1 DOCUMENT OBJECTIVES 

The objectives of the DTSD are to (1) describe the human health risk-based delisting methodology developed 

to perform a screening-level analysis and to compute aggregate risks and HIs for petitioned wastes and 

(2) provide documentation of data and default parameters selected for the risk analysis. The DTSD provides 

background information about the algorithms and equations used in conjunction with dilution attenuation 

factors (DAF) to compute cancer risks and hazard quotients (HQ) for individual chemicals. This information 

is intended to assist regulatory authorities, petitioners, and decision-makers in making hazardous waste 

delisting determinations. 

1.2 BACKGROUND 

Section 1004(5) of RCRA as amended by the Hazardous and Solid Waste Amendments (HSWA) of 1984 

defines “hazardous waste” as “a solid waste, or combination of solid waste, which because of its quantity, 

concentration, or physical, chemical, or infectious characteristics may (a) cause, or significantly contribute 

to an increase in the mortality or an increase in serious irreversible, or incapacitating reversible, illness; or 

(b) pose a substantial present or potential hazard to human health or the environment when improperly 

treated, stored, transported, or disposed of, or otherwise managed.” 

Section 3001 of RCRA requires U.S. EPA to identify those wastes that should be classified as “hazardous.” 

The Agency’s hazardous waste identification rules designate wastes as hazardous in one of two ways. First, 

the Agency has established four hazardous waste characteristics that identify properties or attributes of wastes 

that would pose a potential hazard if the wastes are improperly managed (see 40 CFR 261.21 through 261.24). 

Any generator of a solid waste is responsible for determining whether a solid waste exhibits any of these 

characteristics (see 40 CFR 262.11). Any solid waste that exhibits any of the characteristics remains 

hazardous until it no longer exhibits the characteristics (see 40 CFR 261.4(d)(1)). 

The other mechanism that U.S. EPA uses to designate wastes as hazardous is “listing.” The Agency has 

reviewed data on specific waste streams generated from a number of industrial processes and has determined 

that these wastes, if mismanaged, would pose hazards for one or more reasons, including (1) the presence of 

significant levels of hazardous constituents listed in Appendix VIII to 40 CFR Part 261, (2) manifestation of 

one or more of the hazardous waste characteristics, or (3) the potential to impose detrimental effects on the 

environment (see generally 40 CFR 261.11). U.S. EPA has generally determined that these wastes contain 

toxic constituents at concentrations that potentially pose risks that are unacceptable for human or 

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RCRA Delisting Technical Support Document 

Chapter 1: Introduction Revised October 2008 

environmental exposure and that these constituents are mobile and persistent to the degree that they can reach 

environmental or human receptors. 

As part of its RCRA Subtitle C hazardous waste regulations, U.S. EPA’s Office of Solid Waste (OSW) gives 

facilities the flexibility to petition the Agency to exempt low-risk listed hazardous wastes that may not 

actually pose a threat to human health or the environment under the provisions of 40 CFR 260.20 and 260.22. 

This process is referred to as the “delisting” of a specific generator’s listed waste. U.S. EPA’s OSW was 

directed by statute to review petitions in order to determine whether the wastes may be delisted. The overall 

intent of the delisting process is to ease the regulatory burden on handlers of listed wastes that may have been 

improperly classified as hazardous by the broad listing definitions. In addition, the delisting process can be 

used to exclude listed wastes that are sufficiently treated, that they no longer pose a threat to human health 

or the environment. Listed hazardous wastes that exhibit any of the characteristics will continue to be 

regulated as hazardous wastes until the characteristic is removed. In a number of cases, wastes were listed 

because they contained toxic hazardous constituents and exhibited one or more of the hazardous waste 

characteristics that do not relate to chemical toxicity (for example, ignitability, corrosivity, and reactivity). 

If such a waste still exhibits any characteristic after the delisting criteria described herein have been applied, 

it must continue to be managed as a characteristically hazardous waste. 

1.2.1 U.S. EPA OSW Hazardous Waste Delisting Program 

The U.S. EPA OSW developed the Hazardous Waste Delisting Program to allow facilities that generate 

Subtitle C hazardous wastes to petition to have their wastes exempted from the requirements of the Subtitle 

C hazardous waste program (see 40 CFR 260.22). The delisting process evaluates whether a waste would 

release hazardous chemicals to groundwater at concentrations exceeding acceptable levels (health-based 

numbers or HBNs). Generally, the greatest risks determined for waste constituents considered for delisting 

resulted from potential groundwater exposure—that is, chemical releases to groundwater and subsequent 

exposure via groundwater exposure pathways. The U.S. EPA OSW originally applied the U.S. EPA 

Composite Model for Landfills (EPACML) fate and transport model to estimate constituent concentrations 

in groundwater at a receptor well located downgradient from a landfill or surface impoundment (U.S. EPA 

1990c and 1990h). The EPACML fate and transport model was used to determine a Dilution-Attenuation 

Factor (DAF), which estimates the degree of dilution and attenuation that a constituent would undergo as it 

leaches from a waste management unit and is transported in the subsurface, into the saturated zone, and to 

a theoretical downgradient receptor well. The results of the EPACML analyses, the DAFs, were used to 

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RCRA Delisting Technical Support Document 

Chapter 1: Introduction Revised October 2008 

compute the maximum acceptable constituent concentration (that is, the exit level) in the leachate of a waste 

proposed for delisting. 

The EPACML was originally developed to compute DAFs and set regulatory levels for specific constituents 

for the Toxicity Characteristics Rule (TC Rule) (U.S. EPA 1990d). Since the application of the EPACML 

to the TC Rule and to delisting, the Agency has developed a number of improvements in the modeling method 

and the input data. The U.S. EPA Composite Model for Leachate Migration with Transformation Products 

(EPACMTP) is the product of these improvements made to the EPACML fate and transport model. 

1.2.2 Regional Authorization 

On October 10, 1995, U.S. EPA Administrator Carol M. Browner delegated authorization of the Hazardous 

Waste Delisting Program to U.S. EPA’s 10 regional offices (61 Federal Register [FR] 32798). The U.S. EPA 

OSW in Washington, DC, had previously administered the Delisting Program. As a result of the 

Administrator’s action, delisting petitions that require a federal decision are now being reviewed by the 

appropriate U.S. EPA regions, and the regions, as of October 10, 1995, have the authority to make decisions 

on delisting petitions. The Agency believes that decentralizing the delisting authority to the Regional 

Administrators will result in more timely responses to delisting petitions. 

Under RCRA, states authorized to administer a delisting program in lieu of the federal program also may 

exclude wastes from hazardous waste regulations. Facilities that manage their wastes in a state with RCRA 

delisting authorization should petition that state rather than U.S. EPA for an exclusion. Even in unauthorized 

states, U.S. EPA encourages petitioners to contact state authorities to determine what procedures might be 

necessary for delisting under state laws. 

1.2.3 Regional Program Modifications 

Previously, U.S. EPA OSW delisting evaluations applied the EPACML fate and transport model for 

determining potential chemical releases to groundwater (U.S. EPA 1991b). However, the EPACML had 

limitations, such as the inability to predict DAFs on a chemical-specific basis. After receiving authority to 

administer the Delisting Program, U.S. EPA Region 6 initially made two enhancements to the delisting 

process: (1) application of a new fate and transport model to calculate waste volume-specific DAFs, and (2) 

evaluation of additional exposure pathways. U.S. EPA Region 6 maintained the U.S. EPA OSW requirement 

to evaluate petitioned wastes on the basis of waste volume and investigated improvements made to the 

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EPACML that had been incorporated into the EPACMTP. Following review of the EPACMTP and the 

available literature, U.S. EPA Region 6 adopted the EPACMTP fate and transport model to develop DAFs 

in order to estimate the risk associated with exposure via groundwater pathways for delisting purposes. 

The EPACMTP has been used to compute DAFs for the proposed Hazardous Waste Identification Rule 

(HWIR) (U.S. EPA 1995a) and the proposed Petroleum Refining Listing Rule (U.S. EPA 1998c). For the 

HWIR, the EPACMTP was used to determine (for 192 chemicals) waste volume-generic DAFs, which are 

based on a range of waste management unit areas (waste volumes) identified in a national survey of waste 

management units (including landfills and surface impoundments). A DAF represents the amount of dilution 

and attenuation expected to occur in groundwater as a chemical migrates to a potential exposure point at a 

downgradient receptor well. 

The U.S. EPA evaluates petitions on the basis of a specific volume of waste. To do so, U.S. EPA Region 6 

revised the EPACMTP to develop waste volume-specific DAFs. This was accomplished by using the 

EPACMTP to compute DAFs for a range of waste volumes for each waste disposal scenario (landfill and 

surface impoundment) and then developing regression equations for each disposal scenario that can be used 

to compute a DAF as a function of a specific waste volume (see Section 2.2.4). The U.S. EPA Region 6 

Delisting Program performs two analyses of a petitioned waste: (1) a screening analysis that uses waste 

volume-specific DAFs to back-calculate maximum TCLP waste constituent concentrations at the prescribed 

risk levels for groundwater exposure pathway analyses and (2) an aggregate risk and hazard analysis that uses 

the waste volume-specific DAFs described herein. For further information on the development of waste 

volume-specific DAFs, refer to the document titled “Application of EPACMTP to Region 6 Delisting 

Program: Development of Waste Volume-Specific Dilution Attenuation Factors” (U.S. EPA 1996a). 

In developing DRAS version 3, the EPACMTP was rerun with updated parameters, databases, and algorithms 

consistent with OSW use of the model. In addition, MINTEQA2 adsorption isotherms were used in 

conjunction with EPACMTP, resulting in some DAFs that vary based on the initial leachate concentration 

in the landfill or surface impoundment. The algorithms in DRAS have been modified accordingly to handle 

DAFs that vary by input concentration. 

In a second enhancement to the delisting process, U.S. EPA Region 6 included additional exposure pathways 

in the delisting petition evaluation process to ensure that all potential exposure scenarios are addressed in the 

risk assessment. These additional pathways include (1) dermal contact with and inhalation of volatiles during 

bathing or showering with groundwater, (2) ingestion of drinking water from surface water bodies, (3) 

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ingestion of contaminated fish, (4) inhalation of windblown particulates and volatiles from a waste 

management unit, and (5) ingestion of soils contaminated with windblown waste constituent particulates. 

These additional pathways allow a more complete evaluation of potential human health risks resulting from 

potential chemical releases of delisted wastes. For each exposure pathway, the appropriate chemical-specific 

factors are used to predict the risk to the sensitive receptor from the potential exposure to chemical 

contaminants. For instance, the effects of indoor inhalation exposure to volatile constituents may be 

comparable to or greater than those of ingestion exposure through drinking water (McKone 1987), and 

exposure from ingestion of contaminated fish may be significant because of bioaccumulation of each 

chemical constituent in fish tissue. 

1.2.4 Delisting Risk Assessment Software (DRAS) 

To evaluate delisting petitions in a timely manner, the U.S. EPA Region 6 Delisting Program developed a 

Windows-based program called the Delisting Risk Assessment Software ( DRAS), that analyzes the risks and 

hazards posed by the constituents of a waste petitioned for delisting. Specifically, the DRAS performs two 

types of analyses: screening-level analyses and aggregate risk and hazard analyses. The results of these 

analyses may be viewed on screen, imported directly to word processing software, or printed in documentready form. The screening-level analyses compute chemical-specific exit values or “delisting levels” for 

multi-year delistings. The aggregate risk and hazard analyses compute the aggregate carcinogenic risk and 

noncarcinogenic hazard indices (HI) for a waste petitioned for a one-time delisting. The delisting levels and 

aggregate risk and hazard estimates are calculated using modeled, medium-specific chemical concentrations 

and standard U.S. EPA exposure assessment and risk characterization algorithms. 

Sections 1.2.4.1 and 1.2.4.2 provide additional discussion regarding calculation of delisting levels and 

calculation of aggregate risks and hazards, respectively. 

1.2.4.1 Calculating Delisting Levels for Multi-year Delistings 

In addition to alerting the user to the most limiting and most sensitive combination of exposure pathway and 

receptor, the DRAS provides the calculated chemical-specific delisting level for that combination. A delisting 

level is the maximum allowable concentration for each constituent of a waste petitioned for a multi-year 

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delisting. For each waste constituent, the DRAS computes a total delisting level (in milligrams per kilogram) 

and a TCLP delisting level (in milligrams per liter). The TCLP delisting levels for the groundwater exposure 

pathways are calculated with standard risk assessment algorithms and with groundwater chemical 

concentrations at the point of exposure (POE) derived from waste volume-specific DAFs using the 

EPACMTP fate and transport model. The chemical-specific total delisting levels for the surface exposure 

pathways are calculated with standard risk assessment algorithms and with predicted chemical concentrations 

at the POE. 

The analysis identifies the pathway-receptor combination that is the limiting combination or, in the case of 

multiple pathway-receptor combinations that fail the screening analysis, the most sensitive combination of 

pathway and receptor. This analysis shows the user the degree to which the waste’s TCLP or total waste 

concentration exceeds the delisting level. The program also provides (in a print-ready summary table) all the 

calculated delisting levels for all pathway-receptor combinations. 

1.2.4.2 Calculating Aggregate Risks and Hazards 

In addition to calculating delisting levels for multi-year standard delistings, the DRAS performs a aggregate 

risk assessment for disposal of petitioned wastes in a landfill or surface impoundment waste management unit 

as a one-time delisting. If the delisting petition is for a one-time exclusion, the results of the aggregate risk 

assessment may be used in lieu of the delisting levels. A one-time delisting does not require the Agency to 

establish monitoring concentrations that must be met by each batch of waste to be managed under a 

promulgated exclusion. Therefore, the user may bypass the delisting levels, which are set at relatively 

conservative risk levels, in favor of the aggregate risk assessment process that employs the Agency’s target 

risk levels (see Chapter 4 on target levels). 

Computing the aggregate risk for a petitioned waste provides the user with detailed analysis of the petitioned 

waste. The DRAS indicates which chemicals and which pathways and/or receptors are driving the risk for 

a particular waste. The DRAS computes the aggregate carcinogenic risk by summing the carcinogenic risks 

for all waste constituents for a given exposure pathway and then summing the carcinogenic risks for each 

pathway analyzed in the delisting risk assessment. The DRAS computes the aggregate noncarcinogenic risk 

by summing the noncarcinogenic HQs for all waste constituents for a given exposure pathway and then 

summing the noncarcinogenic hazards associated with each exposure pathway analyzed. If the aggregate 

noncarcinogenic hazard exceeds the allowable level, the user should refer to Appendix A-4. Chemicalspecific hazards may be apportioned by target organ. 

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1.3 DELISTING REFERENCE DOCUMENTATION 

A number of delisting process documents have been developed to provide guidance specific to elements of 

the delisting process, including delisting petition preparation, waste sampling, sample quality 

assurance/quality control (QA/QC), and risk and hazard assessment. Delisting docket materials and other 

relevant reference documents are available and have also been used to support the delisting process. These 

documents and materials are briefly described below. 

1.3.1 Delisting Process Documents 

Documents available to guide a user through the delisting process are described below. 

Delisting Guidance Manual. The “U.S. EPA Region 6 RCRA Delisting Program Guidance Manual for the 

Petitioner” (U.S. EPA 1996e) provides guidance to individuals who may be interested in submitting a petition 

to exclude or “delist” a listed hazardous waste generated at a particular facility from the lists of hazardous 

wastes in 40 CFR Part 261, Subpart D. U.S. EPA recognizes that a specific listed waste generated at a 

particular facility may not meet the criteria for which the waste was originally listed. The manual provides 

guidance on how to satisfy the procedures set forth in 40 CFR 260.20 and 260.22 whereby any individual can 

petition the Agency for a regulatory amendment to exclude a listed waste generated at a particular facility. 

Risk Assessment Software User’s Manual. U.S. EPA Region 6 has developed a separate user’s manual to 

support the DRAS. The “U.S. EPA Region 6 RCRA Delisting Risk Assessment Software User’s Manual” 

(U.S. EPA 1998a) provides the user with the necessary information for installing and running the Windowsbased risk assessment software. The user may access this manual directly through the Windows-based risk 

assessment software or may refer to a hard copy. 

Application of Waste Volume-Specific DAF Document. U.S. EPA developed the report titled “Application 

of EPACMTP to Region 6 Delisting Program: Development of Waste Volume-Specific Dilution Attenuation 

Factors” to describe its approach for adapting the EPACMTP to the U.S. EPA Region 6 Delisting Program 

(U.S. EPA 1996a). The EPACMTP model computes individual DAFs that represent the decrease in 

concentration of a chemical as a result of its leaching from a waste management unit and its subsequent 

transport in the subsurface unsaturated and saturated zones to a receptor well. The EPACMTP was 

developed to compute DAFs as a function of a number of input parameters, including waste management unit 

area. However, waste volume is typically a derived input parameter, and the Delisting Program evaluates 

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wastes based on specific waste volumes. Therefore, U.S. EPA Region 6 modified the EPACMTP model to 

compute DAFs for the range of waste volumes typically encountered in the evaluation of hazardous waste 

delisting petitions. The modifications to the EPACMTP and the analyses performed to derive 90th percentile 

DAFs for 192 chemicals (those listed in the proposed HWIR [U.S. EPA 1995a]) as a function of waste 

volume for wastes disposed of in landfills and surface impoundments are summarized in the 1996 report. 

1.3.2	 Delisting Docket Materials 

Three delisting risk assessment evaluations have been performed to date by the U.S. EPA OSW to determine 

the risks and hazards associated with disposing of delisted wastes in nonhazardous waste management units. 

Specifically, the Agency has evaluated risks and hazards associated with contaminant releases to 

groundwater, surface water, and air and has documented the calculations performed in these evaluations in 

the dockets associated with each petition review. These three delisting risk evaluations performed by U.S. 

EPA are addressed in the following documents: 

•	 U.S. EPA. 1993a. “Docket Report on Evaluation of Contaminant Releases to Surface Water 

Resulting from Conversion System’s Petitioned Waste.” August 27. 

•	 U.S. EPA. 1993c. “Docket Report on Evaluation of Air Emissions Resulting from 

Conversion Systems, Inc.’s, Petitioned Waste.” September 9. 

•	 U.S. EPA. 1994a. “Docket Report on Evaluation of Contaminant Releases to Air from 

U.S. Department of Energy Hanford’s Petitioned Waste.” May 27. 

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1.3.3	 Other Relevant Reference Documents 

The algorithms that the U.S. EPA Region 6 DRAS uses to compute the potential risks to human health 

associated with a waste petitioned for delisting are adapted from the following documents: 

•	 U.S. EPA. 1988a. “Risk Assessment Guidance for Superfund (RAGS), Volume I: Human 

Health Evaluation Manual (Part A).” Office of Emergency and Remedial Response. 

Washington, DC EPA/540-1-89/002. 

•	 U.S. EPA. 1991a. “Risk Assessment Guidance for Superfund (RAGS) Volume I: Human 

Health Evaluation Manual (Part B, Development of Risk-Based Preliminary Remediation 

Goals)” (hereinafter referred to as RAGS Part B). Office of Emergency and Remedial 

Response. Washington, DC Publication No. 9285.7-013. 

For dermal pathways, which are not covered in RAGS Part B, the DRAS uses the algorithms presented in the 

following document: 

•	 U.S. EPA. 1992b. “Dermal Exposure Assessment: Principles and Applications, Interim 

Report.” Office of Health and Environmental Assessment. Washington, DC. EPA/600/8­

91/011B. January. 

Additional exposure and risk assessment algorithms for shower inhalation of groundwater were obtained from 

the nongroundwater pathway risk assessment addressed in the following document: 

•	 U.S. EPA. 1997a. “Supplemental Background Document; NonGroundwater Pathway Risk 

Assessment; Petroleum Process Waste Listing Determination.” OSW. Research Triangle 

Park, North Carolina. March 20. 

This background document contains the assumptions and equations used to evaluate the shower, bathroom, 

and house inhalation pathways for groundwater that were in turn used to determine the risks associated with 

specific petroleum refinery wastes. The docket materials contain the equations and assumptions that the U.S. 

EPA Headquarters Delisting Program used to evaluate delisting petitions with regard to the surface water and 

air exposure pathways. 

Additional information on multipathway risk assessment algorithms and the EPACMTP fate and transport 

model used for the proposed HWIR (U.S. EPA 1995a) is provided in the following FR notice and background 

document for the HWIR: 

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•	 U.S. EPA. 1995a. “Hazardous Waste Management System: Identification and Listing of 

Hazardous Waste—Hazardous Waste Identification Rule (HWIR).” OSW. Washington, DC 

60 FR 66344. 

•	 U.S. EPA. 1995b. “Technical Support Document for HWIR: Risk Assessment for Human 

and Ecological Receptors.” Volumes I and II. OSW. Washington, DC 

Details on the assumptions and input parameters used for the EPACMTP are provided in the following 

documents: 

•	 U.S. EPA. 1997e. EPA's Composite Model for Leachate Migration with Transformation 

Products, EPACMTP: User's Guide. Office of Solid Waste, Washington, D.C. 

•	 U.S. EPA. 1996b. EPACMTP Background Document. Office of Solid Waste. 

Washington, D.C. September. 

•	 U.S. EPA. 1996c. EPACMTP Background Document for the Finite Source Methodology 

for Chemicals with Transformation Products and Implementation of the HWIR. Office of 

Solid Waste. Washington, D.C. September. 

•	 U. S. EPA. 1997h. Analysis of EPA's Industrial Subtitle D Databases used in 

Groundwater Pathway Analysis of the Hazardous Waste Identification Rule (HWIR). 

Office of Solid Waste, Washington, DC. September. 

•	 U.S. EPA. 1996d. Background Document for EPACMTP: Metals Transport in the 

Subsurface, Volume 1: Methodology. Office of Solid Waste. Washington, D.C. August. 

•	 U.S. EPA. 1999. EPA's Composite Model for Leachate Migration with Transformation 

Products (EPACMTP) Background Document for Metals; Volume 2: Sorption Isotherms. 

Office of Solid Waste, Washington, DC. August. 

Every effort was made to maintain consistency with the U.S. EPA Region 6 “Human Health Risk Assessment 

Protocol for Hazardous Waste Combustion Facilities - Peer Review Draft” (U.S. EPA 1998b) at the time 

DRAS was first released. The contaminant release and risk assessment algorithms and parameter values used 

for the DRAS have been compared to the draft Human Health Risk Assessment Protocol for Hazardous Waste 

Combustion Facilities (HHRAP) in order to ensure consistency between the two approaches. The HHRAP 

has since been finalized with a number of modifications and updates (U.S. EPA 2005), however, the changes 

do not impact the methodology used in the DRAS. 

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1.4	 DOCUMENT ORGANIZATION 

This section presents an overview of the DTSD’s organization. The DTSD is arranged in a user-friendly 

format to present the technical procedures used to conduct a risk assessment for a petitioned waste: 

•	 Chapter 1 describes the objectives of this DTSD and provides background and reference 

information for the U.S. EPA Delisting Program. 

•	 Chapter 2 describes the methods used to estimate chemical releases from waste management 

units to groundwater, soils, air, and surface water as well as the calculation of contaminant 

concentrations in each of these media. 

•	 Chapter 3 describes the selection of exposure scenarios, including the receptor locations, and 

the parameters and assumptions used to quantify exposure. 

•	 Chapter 4 describes the methodology used to compute target carcinogenic risks and HQs as 

well as aggregate carcinogenic risks and HIs. 

•	 Chapter 5 discusses the uncertainties involved in the risk and hazard analyses performed for 

the U.S. EPA Delisting Program. 

•	 Chapter 6 contains full citations to the items referenced throughout the DTSD. the U.S. EPA 

Delisting Program. 

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