States United Environmental Protection Agency Superfund
Office of Solid Waste and Emergency Response Washington, DC 20460
Publication 9355.4-23 July 1996
Soil Screening Guidance: Users Guide
Second Edition
EPA/540/R-96/018 July 1996
Soil Screening Guidance: Users Guide
Second Edition
Office of Emergency and Remedial Response U.S. Environmental Protection Agency Washington, DC 20460
ACKNOWLEDGMENTS
The development of this guidance was a team effort led by the staff of the Office of Emergency and Remedial Response. David Cooper served as Team Leader for the overall effort. Marlene Berg coordinated the series of Outreach meetings with interested parties outside the Agency. Sherri Clark, Janine Dinan and Loren Henning were the principal authors. Paul White of EPA's Office of Research and Development provided tremendous support in the development of statistical approaches to site sampling. Exceptional technical assistance was provided by several contractors. Robert Truesdale of Research Triangle Institute (RTI) led their team effort in the development of the Technical Background Document under EPA Contract 68-W1-0021. Craig Mann of Environmental Quality Management, Inc. (EQ) provided expert support in modeling inhalation exposures under EPA Contract 68-D3-0035. Dr. Smita Siddhanti of Booz-Allen & Hamilton, Inc. provided technical support for the final production of the Users Guide and Technical Background Document under EPA Contract 68-W1-0005. In addition, the authors would like to thank all EPA, State, public and peer reviewers whose careful review and thoughtful comments contributed to the quality of this document.
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DISCLAIMER
Notice: The Soil Screening Guidance is based on policies set out in the Preamble to the Final Rule of the National Oil and Hazardous Substances Pollution Contingency Plan (NCP), which was published on March 8, 1990 (55 Federal Register 8666). This guidance document sets forth recommended approaches based on EPAs best thinking to date with respect to soil screening. This document does not establish binding rules. Alternative approaches for screening may be found to be more appropriate at specific sites (e.g., where site circumstances do not match the underlying assumptions, conditions and models of the guidance). The decision whether to use an alternative approach and a description of any such approach should be placed in the Administrative Record for the site. Accordingly, if comments are received at individual sites questioning the use of the approaches recommended in this guidance, the comments should be considered and an explanation provided for the selected approach. The Soil Screening Guidance: Technical Background Document (TBD) may be helpful in responding to such comments. The policies set out in both the Soil Screening Guidance: Users Guide and the supporting TBD are intended solely as guidance to the U.S. Environmental Protection Agency (EPA) personnel; they are not final EPA actions and do not constitute rulemaking. These policies are not intended, nor can they be relied upon, to create any rights enforceable by any party in litigation with the United States government. EPA officials may decide to follow the guidance provided in this document, or to act at variance with the guidance, based on an analysis of specific site circumstances. EPA also reserves the right to change the guidance at any time without public notice.
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TABLE OF CONTENTS
1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Role of Soil Screening Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Scope of Soil Screening Guidance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.0 SOIL SCREENING PROCESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Step 1: Developing a Conceptual Site Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.1 Collect Existing Site Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.2 Organize and Analyze Existing Site Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.3 Construct a Preliminary Diagram of the CSM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.4 Perform Site Reconnaissance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Step 2: Comparing CSM to SSL Scenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.1 Identify Pathways Present at the Site Addressed by Guidance . . . . . . . . . . . . . . . . . . . . . . . . 2.2.2 Identify Additional Pathways Present at the Site Not Addressed by Guidance . . . . . . . . . . . . . . 2.2.3 Compare Available Data to Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Step 3: Defining Data Collection Needs for Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.1 Stratify the Site Based on Existing Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.2 Develop Sampling and Analysis Plan for Surface Soil. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.3 Develop Sampling and Analysis Plan for Subsurface Soils . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.4 Develop Sampling and Analysis Plan to Determine Soil Characteristics . . . . . . . . . . . . . . . . 2.3.5 Determine Analytical Methods and Establish QA/QC Protocols . . . . . . . . . . . . . . . . . . . . . . 2.4 Step 4: Sampling and Analyzing Site Soils & DQA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4.1 Delineate Area and Depth of Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4.2 Perform DQA Using Sample Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4.3 Revise the CSM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 Step 5: Calculating Sitespecific SSLs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5.1 SSL Equations--Surface Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5.2 SSL Equations--Subsurface Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5.3 Address Exposure to Multiple Chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6 Step 6: Comparing Site Soil Contaminant Concentrations to Calculated SSLs . . . . . . . . . . . . . . 2.7 Step 7: Addressing Areas Identified for Further Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1 1 2 3 5 5 5 5 5 7 7 7 8 8 9 9 12 14 17 18 18 20 20 20 20 21 23 32 33 36 37
ATTACHMENTS A. Conceptual Site Model Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1 B. Soil Screening DQOs for Surface Soils and Subsurface Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1 C. Chemical Properties for SSL Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1 D. Regulatory and Human Health Benchmarks Used for SSL Development . . . . . . . . . . . . . . . . . . . . D-1
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LIST OF EXHIBITS
Exhibit 1 Exhibit 2 Exhibit 3 Exhibit 4 Exhibit 5 Exhibit 6 Exhibit 7 Exhibit 8 Exhibit 9 Exhibit 10 Exhibit 11 Exhibit 12 Exhibit 13
Conceptual Risk Management Spectrum for Contaminated Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Exposure Pathways Addressed by SSLs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Key Attributes of the Users Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Soil Screening Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Data Quality Objectives Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Defining Study Boundaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Designing Sampling and Analysis Plan for Surface Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Designing Sampling and Analysis Plan for Subsurface Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 U.S. Department of Agriculture Soil Texture Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 Site-Specific Parameters for Calculating Subsurface SSLs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Q/C Values by Source Area, City, and Climatic Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Simplifying Assumptions for SSL Migration to Ground Water Pathway . . . . . . . . . . . . . . . . . . . . 29 SSL Chemical with Non-carcinogen Toxic Effects on Specific Target Organ/Systems . . . . . . . . . . . . 34
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LIST OF ACRONYMS
ARAR ASTM CERCLA CLP CSM CV DAF DNAPL DQA DQO EA EPA HBL HEAST HELP HHEM HQ IRIS ISC2 MCL MCLG NAPL NOAEL NPL NTIS OERR PA/SI PCB PEF PRG Q/C QA/QC QL RAGS RCRA RfC RfD RI RI/FS RME ROD SAB SAP SPLP SSL TBD TCLP USDA VF VOC
Applicable or Relevant and Appropriate Requirement American Society for Testing and Materials Comprehensive Environmental Response, Compensation and Liability Act Contract Laboratory Program Conceptual Site Model Coefficient of Variation Dilution Attenuation Factor Dense Nonaqueous Phase Liquid Data Quality Assessment Data Quality Objective Exposure Area Environmental Protection Agency Health Based Limit Health Effects Assessment Summary Table Hydrological Evaluation of Landfill Performance Human Health Evaluation Manual Hazard Quotient Integrated Risk Information System Industrial Source Complex Model Maximum Contaminant Level Maximum Contaminant Level Goal Nonaqueous Phase Liquid No-Observed-Adverse-Effect Level National Priorities List National Technical Information Service Office of Emergency and Remedial Response Preliminary Assessment/Site Inspection Polychlorinated Biphenyl Particulate Emission Factor Preliminary Remediation Goal Site-Specific Dispersion Model Quality Assurance/Quality Control Quantitation Limit Risk Assessment Guidance for Superfund Resource Conservation and Recovery Act Reference Concentration Reference Dose Remedial Investigation Remedial Investigation/Feasibility Study Reasonable Maximum Exposure Record of Decision Science Advisory Board Sampling and Analysis Plan Synthetic Precipitation Leaching Procedure Soil Screening Level Technical Background Document Toxicity Characteristic Leaching Procedure U.S. Department of Agriculture Volatilization Factor Volatile Organic Compound
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1.0 INTRODUCTION
1.1
Purpose
The Soil Screening Guidance is a tool that the U.S. Environmental Protection Agency (EPA) developed to help standardize and accelerate the evaluation and cleanup of contaminated soils at sites on the National Priorities List (NPL) with future residential land use.1 This guidance provides a methodology for environmental science/engineering professionals to calculate risk-based, site-specific, soil screening levels (SSLs) for contaminants in soil that may be used to identify areas needing further investigation at NPL sites. SSLs are not national cleanup standards. SSLs alone do not trigger the need for response actions or define unacceptable levels of contaminants in soil. In this guidance, screening refers to the process of identifying and defining areas, contaminants, and conditions, at a particular site that do not require further Federal attention. Generally, at sites where contaminant concentrations fall below SSLs, no further action or study is warranted under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA). (Some States have developed screening numbers that are more stringent than the generic SSLs presented here; therefore, further study may be warranted under State programs.) Generally, where contaminant concentrations equal or exceed SSLs, further study or investigation, but not necessarily cleanup, is warranted. SSLs are risk-based concentrations derived from equations combining exposure information assumptions with EPA toxicity data. This Users Guide focuses on the application of a simple sitespecific approach by providing a step-by-step methodology to calculate site-specific SSLs and is part of a larger framework that includes both generic and more detailed approaches to calculating screening levels. The Technical Background Document (TBD) (EPA, 1996), provides more information about these other approaches. Generic SSLs for the most common contaminants found at NPL sites are included in the TBD. Generic SSLs are calculated from the same equations presented in this guidance, but are based on a number of default
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assumptions chosen to be protective of human health for most site conditions. Generic SSLs can be used in place of site-specific screening levels; however, in general, they are expected to be more co...
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