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Soil Background and Risk Assessment

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About ITRC
Navigating this Website
1 Introduction
1 Introduction
1.1 Audience
1.2 Purpose
1.3 Use of Background in the Risk Assessment Process
1.4 Limitations
2 Soil Background Definition 
2 Soil Background Definition
2.1 Natural Soil Background
2.2 Anthropogenic Ambient Soil Background
2.3 Additional Background Definitions
3 Establishing Soil Background
3 Establishing Soil Background
3.1 Introduction
3.2 Conducting a Soil Background Study
3.3 Choosing an Area for a Soil Background Study
3.4 Sampling
3.5 Laboratory Analysis
3.6 Using an Existing Soil Background Study
3.7 Background Dataset Analysis
3.8 Establishing Default or Site-Specific Soil Background
3.9 Extracting Site-Specific Background Dataset from an On-site Dataset
4 Using Soil Background in Risk Assessment
4 Using Soil Background in Risk Assessment
4.1 Representative Site Concentration to Compare to a BTV
4.2 Using Default Background
4.3 Using Site-Specific Background
4.4 Use of Background for Remedial Goals
4.5 Additional Considerations
5 Geochemical Evaluations
5 Geochemical Evaluations
5.1 Geochemistry Is Not Statistics
5.2 Uses of Geochemical Evaluations
5.3 General Methodology
5.4 Nondetects
5.5 Key Geochemical Processes
5.6 Extracting Background Data from Existing Data
6 Using Geochemical Evaluations in Risk Assessment
6 Using Geochemical Evaluations in Risk Assessment
6.1 Using Geochemical Evaluations During COPC Selection
6.2 Using Geochemical Evaluations During Risk Characterization
6.3 Considerations
7 Environmental Forensics Related to soil Background
7 Environmental Forensics Related to soil Background
7.1 Introduction
7.2 Polycyclic Aromatic Hydrocarbons
7.3 Total Petroleum Hydrocarbons (TPH)
7.4 Polychlorinated Biphenyls (PCBs)
7.5 Polychlorinated Dibenzo-p-Dioxins and Dibenzofurans (PCDD/F)
7.6 Perfluoroalkyl Substances (PFAS)
7.7 Remote Sensing
8 Conceptual Site Model and Data Quality Objectives
8 Conceptual Site Model and Data Quality Objectives
8.1 Conceptual Site Model
8.2 Data Quality Objectives
9 Sampling
9 Sampling
9.1 Background Reference Areas
9.2 Sample Depth
9.3 Sample Size
9.4 Sample Methods
9.5 Sampling Design
9.6 Sample Collection Methods
9.7 Sample Handling
10 Analytical Methods
10 Analytical Methods
10.1 Introduction
10.2 Obtaining Reliable Analytical Data
10.3 Analytical Limits
10.4 Sample Preparation
10.5 Analytical Test Methods
11 Statistics
11 Statistics
11.1 Data Requirements
11.2 Data Distribution
11.3 Treatment of Nondetects
11.4 Graphical displays
11.5 Outliers
11.6 Confidence Interval Limit, Coefficient, and Limit
11.7 Statistical Values Used to Represent Background
11.8 Statistical Tests to Compare Site and Background Datasets
11.9 Statistical Software
12 Regulatory Framework from State Survey
12 Regulatory Framework from State Survey
12.1 Description of State Survey
12.2 Overview of State Survey Results
12.3 State Survey Results
13 Existing Guidance and Studies
14 Case Studies
14 Case Studies
14.1 Minnesota Pollution Control Agency (MPCA) Soil Background Case Study
14.2 Former Firearms Training Range Soil Background Case Study
14.3 Region 4 RARE Urban Background Study
14.4 Geochemical Evaluation Case Study—Statistical Outlier is an Uncontaminated Soil Sample
14.5 Geochemical Evaluation Case Study—Statistical Outlier Is a Contaminated Soil Sample
14.6 Geochemical Evaluation Case Study–Contaminated Soil Sample Is Not a Statistical Outlier
14.7 Environmental Forensics Case Study—PAHs from Leaked Petroleum Versus Contaminated Fill
Frameworks
Frameworks
Framework 1
Framework 2
Framework 3
Appendices
Appendix A. Upper Limits Used to Estimate Background Threshold Values
Appendix B. Index Plots
Appendix C. Additional Sources of Information for PAHs in Soil
Additional Information
Team Contacts
Glossary
Acronyms
Acknowledgments
References
Document Feedback

 

Soil Background and Risk Assessment
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While there are already guidance documents regarding soil background, there is not a “one-stop-shop” document that provides comprehensive and widely accepted guidance on the state of the science on this topic. This ITRC guidance document fills the gap by providing a consensus-based comprehensive and defensible framework for establishing soil background and using soil background in risk assessments. This guidance also provides references to state, USEPA and other resources, as well as related ITRC documents.

During the initial phases of a site investigation or cleanup project, regulators often use chemical-specific screening values to decide if the presence of chemicals at a site may pose a threat to human health or the environment, or both, and if there is the need for further action. For some chemicals, the screening values are within the range of concentrations found in soils from natural or anthropogenic ambient background. Most regulatory agencies require a response action only when the concentrations of a chemical in soil exceed its background concentrations. Consequently, soil background plays an important role in remedial decisions.

Risk assessors, risk managers, and site investigators, as well as other stakeholders are the target audience of this guidance document.

Training

The SBR Team has developed training to complement the guidance document., which includes four videos and an Internet-Based Training. The videos provide an overview of the information presented in the guidance document; a discussion of sampling and analytical methods; information for establishing and using soil background in risk assessment; and information for using geochemical evaluations and environmental forensics in evaluating soil background.

ITRC Soil Background & Risk Assessment Internet-Based Training

ITRC Soil Background & Risk Assessment Training Videos

  • Overview of the Guidance Document, Introduction, and Definitions
  • Sampling and Analytical Methods
  • Establishing and Using Soil Background in Risk Assessment
  • Geochemical Evaluations and Environmental Forensics
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