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TPH Risk Evaluation at Petroleum-Contaminated Sites

Navigating this Website
1 Overview
2 Introduction
2 Introduction Overview
2.1 Issues Unique to TPH
2.2 Applicability of Guidance
2.3 Background of Current Approaches
2.4 TPH Risk Characterization Framework
3 Regulatory Framework
3 Regulatory Framework Overview
3.1 History of TPH Regulation
3.2 What is the Legal Basis for Risk-Based Closure of Petroleum Sites?
3.3 TPH-Specific Regulatory Challenges
3.4 TPH-Specific Regulatory Tools
4 TPH Fundamentals
4 TPH Fundamentals Overview
4.1 Petroleum Chemistry and Refining
4.2 Physical and Chemical Properties of Petroleum Constituents, TPH Carbon Ranges (Fractions), and Metabolites
4.3 Properties of Aliphatic and Aromatic Hydrocarbon Fractions
4.4 Alterations of Petroleum Mixtures in the Environment Through Weathering Processes
4.5 Definition of “TPH” in Environmental Media in Risk Assessment
5 Conceptual Site Models
5 Conceptual Site Models Overview
5.1 Source Identification (Qualitative CSM)
5.2 Source Area Characterization, Extent, Distribution (Source Definition)
5.3 Fate, Transport, and Attenuation Mechanisms (Pathway Definition)
5.4 Points of Exposure (Receptor Definition)
5.5 TPH Target Levels
5.6 Compiling a CSM
5.7 TPH Data Collection Plan
5.8 Field Sampling Methods and Handling Procedures
5.9 TPH Analytical Methods
5.10 Silica Gel Cleanup Method
5.11 Reporting, Data Qualification, and Chromatograms
5.12 Data Usability, Interpretation, and Implications
6 Human Health Risk
6 Human Health Risk Overview
6.1 Introduction
6.2 Exposure Assessment
6.3 Direct Contact with TPH
6.4 Soil to Ambient Air Exposure to TPH (Volatiles and Particulates)
6.5 Leaching from Soil to Groundwater
6.6 Exposure to Groundwater/Surface Water
6.7 Exposure to Air
6.8 Food Chain
6.9 Toxicity Assessment
6.10 Evaluating Toxicity of Polar Metabolites
6.11 Toxicity Considerations for Different Exposure Rates
6.12 Risk Characterization
7 Ecological Risk Assessment
7 Ecological Risk Assessment Overview
7.1 ERA Process for TPH
7.2 Current National and North American TPH ERA Practice
7.3 Exposure Assessment
7.4 Toxicity Assessment
7.5 Risk Characterization
8 Risk Calculators
8 Risk Calculators Overview
8.1 Calculating TPH Risk
8.2 Electronic TPH Risk Calculators
9 TPH Special Considerations
9 TPH Special Considerations Overview
9.1 Special Factors
9.2 Emergency Conditions
9.3 Worker Exposure and Safety
9.4 Managing Open and Reopened TPH-Contaminated Sites
9.5 Estimating TPH Fractions
9.6 Managing the Presence of TPH Breakdown Products/Metabolites
9.7 Remedial Action and Institutional Controls
9.8 Common Mistakes and Lessons Learned
10 Stakeholder Concerns
10 Stakeholder Concerns Overview
10.1 Community Engagement Plans
10.2 Tools for Effective Community Engagement
10.3 Risk Communication
10.4 Communicating Risk Associated with TPH
10.5 VOCs in Commonly Used Products
10.6 Public Notification of Sampling
10.7 TPH Concepts Explained
11 TPH Risk Case Studies
Additional Information
Appendix A. Fact Sheets
A.1 Definition of TPH—Don’t Let the Name Fool You
A.2 TPH Analytical Methods
A.3 Silica Gel Cleanup (SGC)
A.4 Chemistry of Weathering Processes
A.5 Chromatograms: A Wealth of Information
A.6 TPH Fractionation Methods
Appendix B. Risk Evaluation Reference Tool
Appendix C. States Survey
Appendix D. Field Screening Methods
Acronyms
Glossary
Acknowledgments
Team Contacts
Document Feedback

 

TPH Risk Evaluation at Petroleum-Contaminated Sites
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Appendix B. Risk Evaluation Reference Tool

Purpose: This risk evaluation reference tool serves as a summary of the primary elements/factors that could dramatically influence risk management decisions related to TPH either by significantly overestimating or underestimating exposure risks from TPH. This tool also includes links to the key discussions within the document for each of these primary issues.

Site Stage Decision/Issue Possible Impact Over- estimate Risk Under- estimate Risk Reference
Preliminary/ Initial Assessment (Project Scoping)

 

1. Does sufficient knowledge exist on the type and age of the petroleum product release?

2. Has the appropriate regulatory framework governing petroleum release sites been applied?

1. Incorrect technical approach encompassing sampling, laboratory analysis, CSM, data evaluation/interpretation, and risk assessment

2. Evaluation procedures that may be dated relative to scientific understanding or may be inconsistent among programs

✓ ✓ Conceptual Site Models, Sections 5–5.2
Site Characterization (Data Collection and Evaluation; Risk Assessment/ Characterization)

 

1. Does the contracting laboratory have the appropriate expertise (methods) and direction/ instruction to identify petroleum fractions?

1.b. Will the risk assessment use field data and will it be the only data used?

1.c. Has adequate consideration been given to the role of product weathering in selecting the analytical suite?

2. Is the characterization/ evaluation based on bulk TPH data (typically historic data)?

1.a. Additional uncertainty from use of less precise or unsuitable analytical techniques

1.b. Laboratory problems, e.g., separating aliphatics/cycloalkanes from aromatics

2.a. Increased level of effort necessary to evaluate bulk TPH results if using more recent risk assessment approaches

2.b. Inappropriate selection of analytes, e.g., BTEX compounds in a highly weathered release

2. Possible double-counting between bulk fractions and indicator compounds

✓ ✓ TPH Data Collection Plan

TPH Analytical Methods

Managing Open and Reopened TPH-Contaminated Sites

Site Characterization (Risk Assessment/ Characterization) 1. Are the selected toxicity values (those for indicator chemicals, fractions, or assigned based on percent composition of known mixtures) appropriate? 1. Incorrect conclusions from flawed assessment ✓ ✓ Toxicity Assessment

Toxicity Considerations for Different Exposure Routes

Remedy Selection 1. Do remedy and/or cleanup goals specifically target aromatic/light fractions and not consider residual TPH? 1. Inappropriate remedy selection when the residual TPH is more toxic or overly conservative remedy when the TPH is less toxic ✓ ✓ TPH-Specific Regulatory Challenges
Remedy Selection/Remedy Performance 1. Does performance data consider only light end indicator compounds (e.g., BTEX) and not consider residual TPH? 3.a. Inappropriate remedy selection when the residual TPH is more toxic

3.b. Inappropriate remedy monitoring to demonstrate effectiveness

✓ Managing Open and Reopened TPH-Contaminated Sites

Remedial Action and Institutional Controls

Remedy Complete/ Closure (Cleanup complete) 1. Are cleanup objectives based on light end indicator compounds (e.g., BTEX) only and not residual TPH? 1. Not meeting objectives if residual TPH was required to be addressed ✓ Remedial Action and Institutional Controls
Long-term Management (Subject to resource/

beneficial use)

1. Are only light end compounds (e.g., BTEX) identified as indicators? 1. Not meeting objectives if residual TPH was required to be addressed ✓ Document Objectives

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