Exhibit_D_Appendix_D-16_NMED_SSG.pdf

NEW MEXICO ENVIRONMENT

DEPARTMENT

Risk Assessment Guidance for Site Investigations and Remediation

Volume I

Soil Screening Guidance for Human Health Risk

Assessments

February 2019

RFP-0000297

Risk Assessment Guidance for Investigations and Remediation

Volume I

ES-1

EXECUTIVE SUMMARY

This guidance document is being developed in coordination with the New Mexico Environment

Department’s (NMED) Hazardous Waste Bureau (HWB) and the Ground Water Quality Bureau.

This guidance document sets forth recommended approaches based on current State and Federal practices and intended for used as guidance for employees of NMED and for facilities within the

State of New Mexico.

In the past, the material contained within this document existed in multiple guidance and/or position papers. In order to streamline the risk assessment process and ensure consistency between guidance/position papers, these documents have been combined into one document:

Risk Assessment Guidance for Site Investigations and Remediation.

The Risk Assessment Guidance for Site Investigations and Remediation dated December 2018 replaces and supersedes previous versions of this document as well as the following documents:

• Technical Background Document for Development of Soil Screening Levels, Revision

6.0, 2012,

• New Mexico Environment Department TPH Screening Guidelines, October 2006, and

• Risk-Based Remediation of Polychlorinated Biphenyls at RCRA Corrective Action Sites, NMED Position Paper, March 2000.

• Guidance for Assessing Ecological Risks Posed by Chemicals: Screening-Level

Ecological Risk Assessment, March 2000 and 2008.

This Risk Assessment Guidance for Site Investigations and Remediation is organized into two volumes.

• Volume I –Soil Screening Guidance for Human Health Risk Assessments

• Volume II - Soil Screening Guidance for Ecological Risk Assessments

Volume I presents information related to conducting screening level human health risk assessments. Previously, the soil screening levels (SSLs) were available in the Technical

Background Document for Development of Soil Screening Levels while the screening levels for total petroleum hydrocarbons (TPH) were found in the New Mexico Environment Department

TPH Screening Guidelines. Now both are contained in Volume I. Volume I also includes SSLs for select Aroclors, congeners of polychlorinated biphenyls (PCBs), total petroleum hydrocarbons (TPH), and chemicals of emerging concern.

February 2019

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Volume II provides guidance for conducting ecological risk assessments and contains guidance that was previously contained in the Guidance for Assessing Ecological Risks Posed by

Chemicals: Screening-Level Ecological Risk Assessment, March 2008.

February 2019

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SUMMARY OF CHANGES

The following table summarizes changes to the “Risk Assessment Guidance for Investigations and Remediation,” Volume I. Specific changes are as follows:

VOLUME I

SOIL SCREENING GUIDANCE FOR HUMAN HEALTH RISK ASSESSMENTS

Item Section Change

November 2014

1 Global Update default exposure parameters; includes changes to text, tables, equations, and soil screening levels in Appendix A

2 Global General edits and clarifications

3 Table of Acronyms Updated

4 Table of Contents Updated

5 Summary of

Changes

Added new section summarizing changes to document by revision number and date

6 Section 1.2.1 and

Table 1-1

Addition of tap-water exposure, vapor intrusion and beef ingestion pathways

7 Section 2.1 Additional chemical-specific information added for clarification.

Includes changes or additions to dioxin/furans, polychlorinated biphenyls (PCBs), hexavalent and total chromium, vanadium, xylene, phenanthrene, and polycyclic aromatic hydrocarbons

(PAHs).

8 Section 2.1.7 Section added addressing emerging contaminants

9 Section 2.2.1 and

Equations 12-17

Incorporated carcinogenic and mutagenic effects to calculation of trichloroethylene (TCE) specific soil screening levels

10 Section 2.4 Modified to include dermal exposure

11 Equations 24-26 Equations were modified and added to include dermal contact with tap water pathway

12 Equation 27 Changed noncarcinogenic exposure parameters from adult exposure to child exposure (tap water)

13 Equations 29-30 and Equations 31-

Added dermal pathway to equations for vinyl chloride and mutagens

14 Section 2.5 Section added addressing the vapor intrusion pathway and derivation of vapor screening levels

15 Section 2.6 Section added describing the evaluation of the beef ingestion pathway

16 Section 2.7.2 Section added describing background threshold values

17 Section 2.7.3 Clarification added on determination of constituents of potential concern

18 Section 2.7.7 Section added providing guidance for calculation of exposure-point concentrations

19 Section 3.4 Added list of sources used for deriving chemical property information

February 2019

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20 Section 5.0 Clarification added to text on the use of the SSLs

21 Section 5.1 Section added describing chromium speciation and tiered approach to using chromium screening levels

22 Section 5.2 Section added describing derivation of screening levels for essential nutrients

23 Section 6.0 Updated Total Petroleum Hydrocarbon (TPH) methodology;

removed groundwater screening levels.

24 Section 7.0 Updated references

25 Table A-1 Updated NMED screening levels

26 Table A-2 Updated default exposure parameters

27 Table A-3 Table added displaying vapor intrusion screening levels

28 Tables B-1 and B-2 Updated chemical property information with references added

29 Table B-3 Table added showing input parameters and chemical properties for dermal tap-water pathway

30 Table C-1 Updated toxicity data

April 2015

31 Section 2.7.7 Update preferred method for handling non-detects

January 2017

1 Global Updated toxicity data; includes changes to text, tables, equations, and soil screening levels in Appendix A

2 Section 1.3 New section addressing use of the guidance and screening levels

3 Section 2.1 Added information of application of a relative bioavailability correction factor in the calculation of soil ingestion screening levels for arsenic.

4 Section 2.1 Added equation for calculation of toxicity equivalents for dioxin/furan congeners

5 Section 2.1 Added discussion on essential nutrients

6 Section 2.1 Added discussion on perfluorinated compounds

7 Equation 27 Updated age-adjusted dermal exposure factor

8 Equation 36 Updated age-adjusted tap water dermal exposure factor, mutagens

9 Section 2.3.3 Clarification on use of lead screening levels

10 Section 2.5.1 Updated attenuation factors

11 Section 2.5.2 Added discussion on use of the Johnson and Ettinger (J&E) bulk soil model

12 Section 2.5.2.3 Clarified steps for analysis of the vapor intrusion pathway.

13 Section 2.6 Due to issues with the preliminary remediation goal calculator for the beef ingestion pathway, requirement for a quantitative assessment removed; only a qualitative analysis is required.

14 Section 2.7 Section re-written to address only site assessment and provide guidance on data quality objectives and background threshold values (BTVs).

15 Section 2.8 New section addressing site characterization, conceptual site models, and exposure intervals.

16 Section 2.8.3.1 New section on determining constituents of potential concern

(COPCs) for organics and chemicals without background data.

February 2019

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17 Section 2.8.3.2 New section on comparison to BTVs using discrete data.

18 Section 2.8.3.3 New section on comparison to BTVs using incremental sample methodology (ISM) data.

19 Section 2.8.5.2 Added section for determination of UCLs for ISM data.

20 Section 4.9 Added allowance of additional lines of evidence for migration to groundwater.

21 Section 5.0 Clarification of how to assess risks/hazard to chemicals with both forms of toxicity.

22 Section 5.2 Added text and new equation to clarify how to assess risk from essential nutrients.

23 Section 6.1 New screening levels for TPH fractions

24 Appendix A, Table

A-1

Screening levels for both carcinogenic and noncarcinogenic toxicity provided for all chemicals (previous versions only listed more conservative level).

Added soil-to-groundwater migration screening levels based on

New Mexico Water Quality Standards and/or Federal Maximum

Contaminant Levels.

Updated toxicity data; also added information of application of a relative bioavailability correction factor in the calculation of soil ingestion screening levels for arsenic.

25 Appendices A -C, New Chemicals

Screening levels have been added for the following chemicals:

alachlor, atrazine, carbofuran, cobalt, dimethyl phthalate, glyphosate, 1-methylnaphthalene, 2-methylnaphthalene, nitrophenol, perfluorinated chemicals, perfluorohexane sulfonic acid, perfluorooctane sulfonate, perfluorooctanoic acid, simazine, and p-xylene.

February 2019

1 Section 1.3 Clarified text for Step 1, determining COPCs.

2 Table 2-6 Added the soil-to-groundwater pathway

3 Section 2.8.3 Added clarification on handling duplicates.

4 Section 2.8.3.2 Updated to reflect organics and chemicals with background data.

Includes new Sections 2.8.3.2.1 and 2.8.3.2.2 and additional clarifications on how to conduct site attribution analyses.

5 Section 2.8.4 Modified Section to address initial and refined exposure point concentrations

6 Section 4 Revised terminology for SSLs for the soil-to-groundwater pathway to reflect target leachate concentrations. Included addition of Equation 58 to address how to use target leachate concentrations compared to site data.

7 Section 5 Added clarification that overall risk and hazard calculations exclude the soil-to-groundwater pathway.

8 Table 5-1 Updated essential nutrient levels

9 Section 5.3 New section on PFAS, including preliminary screening levels for

PFOA, PFOS, and PFHxS.

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10 Table 6-1 Added gasoline

11 Table 6-2 Added a SSL for gasoline

12 Table 6-4 Updated terminology to reflect target leachate concentrations.

Updated groundwater SSLs and SL-SSLs and added values for gasoline

13 Appendix A, Table

A-1

Revised table to only list target leachate concentration to be used in initial screening assessments.

14 Appendix A, Table

A-3

Added table showing calculation of all target leachate concentrations.

15 Updated toxicity RDX

16 Appendix E Added supporting information on PFHxS

SOIL SCREENING GUIDANCE FOR HUMAN HEALTH

RISK ASSESSMENTS

February 2019 i

TABLE OF CONTENTS

Contents Page

Executive Summary ................................................................................................................ ES-1

Summary of Changes .............................................................................................................. ES-2

List of Acronymns ........................................................................................................................ iv

1.0 Introduction

1.1 Organization of the Document

1.2 Scope of the Soil Screening Guidance

1.2.1 Exposure Pathways

1.2.2 Exposure Assumptions

1.2.3 Target Risk and Hazard

1.2.4 SSL Model Assumptions

1.3 How to Use the Guidance in Volume I

2.0 Development of Pathway Specific Soil Screening Levels

2.1 Human Health Basis

2.1.1 Additive Risk

2.1.2 Acute Exposures

2.1.3 Early-Life Exposures to Carcinogens

2.1.4 Direct Ingestion

2.1.5 Dermal Absorption

2.1.6 Inhalation

2.1.7 Contaminants of Emerging Concern

2.2 Soil Screening Levels for Residential Land Uses

2.2.1 Residential Receptors

2.3 Soil Screening Levels for Non-residential Land Uses

2.3.1 Commercial/Industrial Worker

2.3.2 Construction Worker

2.3.3 Alternative Evaluation for Lead

2.4 Tap Water Screening Levels

2.5 Vapor Intrusion Screening Levels

2.5.1 Calculation of Vapor Intrusion Screening Levels

2.5.2 Evaluation of the Vapor Intrusion Pathway

2.6 Beef Ingestion Soil Screening Levels

2.7 Site Characterization

2.7.1 Development of Data Quality Objectives

2.7.2 Determination of Background Threshold Values

2.8 Site Assessment

2.8.1 Development of a Refined Conceptual Site Model

2.8.2 Determine Exposure Intervals

2.8.3 Identification of COPCs

2.8.4 Initial and Refined Exposure Point Concentrations

February 2019 ii

TABLE OF CONTENTS, Cont.

3.0 Chemical-Specific and Physical-Chemical Parameters

3.1 Volatilization Factor for Soil

3.2 Soil Saturation Limit

3.3 Particulate Emission Factor

3.4 Physical-Chemical Parameters

3.4.1 Solubility, Kow, and Henry’s Law Constant

3.4.2 Soil Organic Carbon/Water Partition Coefficients (Koc)

3.4.3 Soil/Water Partition Coefficients (Kd)

4.0 Migration of Contaminants to Groundwater

4.1 Overview of the SSL Model Approach

4.2 Model Assumptions

4.3 Soil Water Partition Equation

4.4 Dilution Attenuation Factor

4.5 Limitations on the Use of the Dilution Attenuation Factor

4.6 Generic SL-SSLs for Protection of Groundwater

4.7 Development of Site-Specific SL-SSLs for Protection of Groundwater

4.8 Detailed Model Analysis for SL-SSLs Development

4.9 Summary of the Migration to Groundwater Pathway SL-SSLs

5.0 Use of the SSLs

5.1 Use of Chromium Screening Levels

5.2 Essential Nutrients

5.3 Perfluoroalkyl Compounds (PFOA, PFOS, PFHxS)

6.0 Total Petroleum hydrocabons (TPH)

6.1 TPH Fraction and Indicator Approach

6.2 Total Petroleum Hydrocarbons in Soil

6.3 Determination of Groundwater and Soil-to-Groundwater Screening Criteria for

Petroleum Hydrocarbon Releases

6.4 Application of the Groundwater and SL-SSLs at Facilities Potentially Impacted by

Petroleum Hydrocarbon Releases

7.0 References

February 2019 iii

TABLE OF CONTENTS, Cont.

Tables

Table 1-1. Exposure Pathways Evaluated in Soil Screening Guidance Table 2-1. Dioxin and Furan Toxicity Equivalency Factors Table 2-2. PCB TEFs Table 2-3. Polycyclic Aromatic Hydrocarbon Toxicity Equivalency Factors

Table 2-4. Summary of the Residential Land Use Receptors Table 2-5. Summary of Non-Residential Land Use Receptors Table 2-6. Soil Exposure Intervals Table 4-1. Input Parameters and Resulting SSLs for the Sensitivity Analysis of the Soil-Water

Partition Equation - Migration to Groundwater Pathway Model

Table 4-2. Input Parameters and Resulting DAFs for the Sensitivity Analysis of the Dilution

Attenuation Factor-Migration to Groundwater Pathway Model Table 5-1. Soil Screening Levels for Essential Nutrients

Table 5-2. PFAS Analyte List

Table 5-3. Preliminary Screening Levels for Perfluoroalkyl CompoundsSelect PFAS (PFOA, PFOS, PFHxS)

Table 6-1. TPH Compositional Assumptions Used in Deriving Screening Levels

Table 6-2. TPH Soil Screening Levels

Table 6-3. Indicator Compounds Associated with TPH Mixtures in New Mexico

Table 6-4. Groundwater and Soil-to-Groundwater Screening Levels for TPH Mixtures

Figures

Figure 3-1 Mean Value - Fraction Organic Carbon (foc)-All counties in New Mexico Figure 5-1. Eh-pH Diagram for Chromium

Appendices

Appendix A: NMED Soil Screening Levels (SSLs)

Appendix B: Chemical and Physical Properties

Appendix C: Toxicity Data

Appendix D: Guidance for Risk-Based Remediation of Polychlorinated Biphenyls

Appendix E: Recommendations for Addressing Perfluorohexane Sulfonic Acid (PFHxS) in New

Mexico

February 2019 iv

LIST OF ACRONYMS

AI Adequate Intake

ALM Adult Lead Methodology

ASTDR Agency for Toxic Substances and Disease Registry

BGS Below Ground Surface

BTEX Benzene, Toluene, Ethylbenzene and Xylenes

BTV Background Threshold Value

C Celsius

CalEPA California Environmental Protection Agency

CMTP Composite Model for Leachate Migration with Transformation Products

COPC Contaminants of Potential Concern

CSM Conceptual Site Model

DAF Dilution Attenuation Factor

DQO Data Quality Objectives

EPA/ORD Environmental Protection Agency Office of Research and Development

EPC Exposure Point Concentration

EPH Extractable Petroleum Hydrocarbons

EPI Estimation Program Interface

GWQB Groundwater Quality Bureau

HEAST Health Effects Assessment Summary Tables

HWB Hazardous Waste Bureau

IEUBK Integrated Exposure Uptake Biokinetic

IRIS Integrated Risk Information System

IUPAC International Union of Pure and Applied Chemistry

IUR Inhalation Unit Risk

J&E Johnson and Ettinger

MADEP Massachusetts Department of Environmental Protection

MCL Maximum Contaminant Level

MDL Minimum Detection Limit

MRL Minimum Risk Level

MTBE Methyl Tertiary Butyl Ether

NAPL Non-aqueous Phase Liquid

NHL Non-Hodgkin’s Lymphoma

NJDEP New Jersey Department of Environmental Protection

NMAC New Mexico Administrative Code

NMED New Mexico Environment Department

NRCS National Resource Conservation Service

PAH Polycyclic Aromatic Hydrocarbon

PCB Polychlorinated Biphenyl

PEF Particulate Emission Factor

PFAS Polyfluoroalkyl and Perfluoroalkyl Compounds

PFOA Perfluorooctanoic acid

PFOS Perfluorooctane Sulfonate

PPRTV Provisional Peer-reviewed Toxicity Value

PRG Preliminary Remediation Goal

February 2019 v

LIST OF ACRONYMS, Cont.

RAGS Risk Assessment Guidance for Superfund

RAIS Risk Assessment Information System

RCRA Resource Conservation and Recovery Act

RDA Recommended Daily Allowance

RfC Reference Concentration

RfD Reference Dose

RSL Regional Screening Level

SCEM Site Conceptual Exposure Model

SL Screening Level

SQL Sample Quantitation Level

SSG Soil Screening Guidance

SSL Soil Screening Level

SVOC Semi-volatile Organic Compound

TCDD Tetrachlorodibenzo-p-dioxin

TCE Trichloroethylene

TEF Toxicity Equivalency Factor

TEQ Toxicity Equivalent

TPH Total Petroleum Hydrocarbon

TPHCWG Total Petroleum Hydrocarbon Criteria Work Group

UCL Upper Confidence Limit

UL Upper Intake Limit

US EPA United States Environmental Protection Agency

USGS United States Geologic Survey

UTL Upper Tolerance Limit

VF Volatilization Factor

VISL Vapor Intrusion Screening Level

VOC Volatile Organic Compound

VPH Volatile Petroleum Hydrocarbons

WHO World Health Organization

WQCC Water Quality Control Commission

February 2019

1.0 INTRODUCTION

The New Mexico Environment Department (NMED) Hazardous Waste Bureau (HWB) and the

Ground Water Quality Bureau (GWQB) have developed this soil screening guidance (SSG) for internal department use within corrective action programs. The SSG discusses the methodology used to derive chemical-specific soil screening levels (SSLs), tap water screening levels, and vapor intrusion screening levels (VISLs). In addition, guidance is provided to assist in identifying and evaluating appropriate exposure pathways and receptors. Finally, this document provides generic SSLs, tap water SLs, and VISLs for chemicals commonly found at contaminated sites based on default exposure parameters under residential and non-residential land-use scenarios.

The SSG provides site managers with a framework for developing and applying the SSLs and is likely to be most useful for determining whether areas or entire sites are contaminated to an extent that warrants further investigation. It is intended to assist and streamline the site investigation and corrective action process by focusing resources on those sites or areas that pose the greatest risk to human health and the environment. Implementation of the methodologies outlined within this SSG may significantly reduce the time necessary to complete site investigations and cleanup actions at certain sites, as well as improve the consistency of these investigations.

Between various sites there can exist a wide spectrum of contaminant types and concentrations.

The level of concern associated with those concentrations depends on several factors, including the likelihood of exposure to concentrations that could impact human health or ecological receptors. At one end of the spectrum are levels that clearly warrant a response action; at the other end are levels that are below regulatory concern. Appropriate cleanup goals for a site may fall anywhere within this range depending on site-specific conditions. Screening levels such as

SSLs identify the lower end of this spectrum – levels below which there is generally no need for further concern—provided the conditions associated with the development of the SSLs are consistent with the site being evaluated. It is important to note that SSLs do not in themselves represent cleanup standards, and the SSLs alone do not trigger the need for a response action or define “unacceptable” levels of contamination in soil.

1.1 Organization of the Document

The NMED SSG is organized into five major sections with supporting appendices. The remainder of Section 1 addresses the purpose of the NMED SSLs and outlines the scope of the document. Section 2 outlines the receptors, exposure pathways, and exposure assumptions used in calculating the NMED SSLs. It also discusses the risk levels on which the SSLs are predicated and presents the SSL model assumptions. Finally, Section 2 discusses site assessment/characterization activities that should be completed prior to comparing site contaminant concentrations with SSLs. These activities include development of data quality objectives, conducting site sampling, preparation of a preliminary conceptual site model (CSM), and identification of contaminants of potential concern (COPCs). Section 3 provides a detailed description of the process used to develop pathway-specific SSLs. Included in this section is a discussion of the human health basis for the SSLs, additive risk, and acute exposures. Additional

February 2019 topics discussed in Section 3 include chemical specific parameters used to develop the SSLs and calculation of volatilization factors, particulate emission factors and soil saturation limits.

Section 4 presents methodologies for assessing the potential for migration of contaminants to groundwater from contaminated soil in concert with generic and site-specific leaching models.

Section 5 addresses special use considerations for addressing contaminant concentrations in soil and notes specific problems that can arise when applying the SSLs to specific sites. Finally, Section 6 addresses the screening criteria that should be applied at sites with potential petroleum releases. Soil and tap water screening levels for contaminants are presented in Table A-1 of

Appendix A. Table A-2 of Appendix A presents the default exposure factor values used in the generation of the NMED SSLs. Table A-3 presents all derived target soil leachate concentrations. Screening levels for the vapor intrusion pathway are presented in Table A-4 of

Appendix A. Physical-chemical values used in the calculation of the SSLs are presented in

Tables B-1, B-2, and B-3 of Appendix B. Toxicity criteria are presented in Table C-1 of

Appendix C. Additional discussion of polychlorinated biphenyls (PCBs) is provided in

Appendix D. Appendix E provides recommendations for evaluating potential risk and hazard from perfluoroalkyl compounds.

1.2 Scope of the Soil Screening Guidance

The SSG incorporates readily obtainable site data and utilizes methods from various United

States Environmental Protection Agency (US EPA) risk assessment guidance and derives site-specific screening levels for selected contaminants and exposure pathways. Key attributes of the

SSG include default values for generic SSLs where site-specific information is unavailable, and the identification of parameters for which site-specific information is needed for the development of site-specific SSLs. The goal of the SSG is to provide a consistent approach for developing site-specific SSLs for evaluating facilities under the auspices of the corrective action process within NMED.

The NMED SSLs are based on a 1E-05 target risk for carcinogens, or a hazard quotient of 1.0 for noncarcinogens. In instances where an individual contaminant has the capacity to elicit both types of responses, both SSLs are provided. SSLs for migration to groundwater are based on

NMED-specific tap water SSLs. As such, the NMED SSLs serve as a generic benchmark for screening level comparisons of contaminant concentrations in soil. NMED anticipates that the

SSLs will be used as a tool to facilitate prompt identification of those contaminants and areas that represent the greatest risks to human health and the environment. While concentrations above the NMED SSLs presented in this document do not automatically designate a site as

“contaminated” or trigger the need for a response action, detected concentrations in site soils exceeding screening levels suggest that further evaluation is appropriate. Further evaluation may include additional sampling to better characterize the nature and extent of contamination, consideration of background levels, reevaluation of COPCs or associated risk and hazard using site-specific parameters, and/or a reassessment of the assumptions associated with the generic

SSLs (e.g., appropriateness of route-to-route extrapolations, use of chronic toxicity values to evaluate childhood and construction-worker exposures).

Prior to calculating site-specific SSLs, each relevant chemical specific parameter value and toxicological datum should be checked against the most recent version of its source to

February 2019 determine if updated data are available.

If a NMED SSL is not listed for a given chemical, other sources of screening levels should be consulted, such as the US EPA Regional Screening Levels (RSLs) (US EPA, 2018a or most current), or a review of toxicological data should be conducted and if available, a screening level calculated for that given chemical. Care should be used when other sources of screening levels are used to ensure that target risk/levels used in development of the levels are consistent with those applied by NMED. For example, the US EPA carcinogenic RSLs are based on a 1E-06 risk level and must be adjusted to a 1E-05 risk level for use. RSLs for noncarcinogens are provided for hazards of 1.0 and 0.1; the RSLs based on a hazard quotient of 1.0 should be applied.

1.2.1 Exposure Pathways

A complete exposure pathway consists of (1) a source, (2) a mechanism of contaminant release,

(3) a receiving or contact medium, (4) a potential receptor population, and (5) an exposure route.

All five elements must be present for the exposure pathway to be considered complete.

SSLs have been developed for use in evaluating several exposure scenarios representing a variety of potential land uses: residential, commercial/industrial, and construction. The SSG presents lists of potential pathways for each scenario, though these lists are not intended to be exhaustive. Instead, each list represents a set of typical exposure pathways likely to account for the majority of exposure to contaminants in soil or other media at a given site. These include:

• Direct (and incidental) ingestion of soil,

• Dermal contact with soil,

• Inhalation of volatiles and fugitive dusts from contaminated soil,

• Migration of chemicals through soil to an underlying potable aquifer or water-bearing unit,

• Ingestion of tap water during domestic use,

• Dermal contact with tap water during domestic use,

• Inhalation of volatile organic compounds (VOCs) volatilized from tap water into indoor air during domestic use,

• Inhalation of volatiles in indoor air via the subsurface vapor intrusion pathway, and

• Ingestion of potentially contaminated beef.

Under some site-specific situations, additional complete exposure pathways may be identified.

In these cases, a site-specific evaluation of risk is warranted under which additional exposure pathways can be considered. If other land uses and exposure scenarios are determined to be more appropriate for a site (e.g., home gardening, recreational land use, hunting, and/or Native

American land use), the exposure pathways addressed in this document should be modified or augmented accordingly or a site-specific risk assessment should be conducted. Early identification of the need for additional information is important because it facilitates development of a defensible sampling and analysis strategy.

The exposure pathways addressed in this guidance are presented by land-use scenario in Table 1-

1.

Table 1-1. Exposure Pathways Evaluated in Soil Screening Guidance

Potential Exposure Pathway Residential Commercial

/Industrial

Construction

Direct ingestion of soil

Dermal contact with soil

Inhalation of dust and volatiles from soil

Inhalation of VOCs from vapor intrusion --

Ingestion of tap water -- --

Dermal contact with tap water -- --

Inhalation of VOCs volatilized from tap water during domestic use

Ingestion of beef -- --

1.2.2 Exposure Assumptions

SSLs represent risk-based concentrations in soil derived from equations combining exposure assumptions with toxicity criteria following the US EPA’s preferred tiered hierarchy of toxicological data. The models and assumptions used were developed to be consistent with the

Superfund concept of “reasonable maximum exposure” (US EPA 1989 and 2009). This is intended to provide an upper-bound estimate of chronic exposure by combining both average and conservative (i.e., 90th to 95th percentile) values in the calculations. The default intake and duration assumptions presented here are intended to be protective of all potentially exposed populations for each land use consideration. Exposure point concentrations in soil should reflect either directly measured or estimated values using fate and transport models. When assessing chronic, long-term exposures, the maximum detected site concentration should be used for an initial screen against the SSLs. A more refined assessment may include use of an estimate of the average [95 percent upper confidence level (UCL) of the mean] concentration if sufficient site data are available to allow for an accurate estimation of the UCL. Where the potential for acute toxicity may be of concern, estimates based on the maximum exposure may be more appropriate.

The resulting estimate of exposure is then compared with chemical-specific toxicity criteria. To calculate the SSLs, the exposure equations and pathway models are rearranged to back calculate an “acceptable level” of a contaminant in soil corresponding to a specific level of target risk or hazard.

1.2.3 Target Risk and Hazard

Target risk and hazard levels for human health are risk management-based criteria for carcinogenic and noncarcinogenic responses, respectively, to determine: (1) whether site-related contamination poses an unacceptable risk to human health and requires corrective action or (2) whether implemented corrective action(s) sufficiently protects human health. If an estimated risk or hazard falls within the target range, the risk manager must decide whether or not the site

February 2019 poses an unacceptable risk. This decision should consider the degree of inherent conservatism or level of uncertainty associated with the site-specific estimates of risk and hazard. An estimated risk that exceeds these targets, however, does not necessarily indicate that current conditions are not safe or that they present an unacceptable risk. Rather, a site risk calculation that exceeds a target value may simply indicate the need for further evaluation or refinement of the exposure model.

For cumulative exposure via the ingestion, inhalation, and dermal pathways, toxicity criteria are used to calculate an acceptable level of contamination in soil. SSLs are based on a carcinogenic risk level of one-in-one-hundred thousand (1E-05) and a noncarcinogenic hazard quotient of 1.0.

A carcinogenic risk level is defined as the incremental probability of an individual developing cancer over a lifetime as a result of exposure to a potential carcinogen. The noncarcinogenic hazard quotient assumes that there is a level of exposure below which it is unlikely for even sensitive populations to experience adverse health effects.

1.2.4 SSL Model Assumptions

The models used to calculate inhalation exposure and protection of groundwater based on potential migration of contaminants in soil are intended to be utilized at an early stage in the site investigation process when information regarding the site may be limited. For this reason, the models incorporate a number of simplifying assumptions. For instance, the models assume an infinite contaminant source, i.e. a constant concentration is maintained for the duration of the exposure period. Although this is a highly conservative assumption, finite source models require accurate data regarding source size and volume. Such data are unlikely to be available from limited sampling efforts. The models also assume that contamination is homogeneous throughout the source and that no biological or chemical degradation occurs. Where sufficient site-specific data are available, more detailed finite-source models may be used in place of the default model assumptions presented in this SSG.

1.3 How to Use the Guidance in Volume I

The intent of this guidance is to streamline the risk assessment process using a step-wise approach. The human health screening level risk assessment should be performed after nature and extent of contamination has been fully defined. The general steps for conducting the human health screening risk assessment are:

Step 1: Determine constituents of potential concern (COPCs). This includes conducting a site attribution analysis and elimination of some constituents through comparison of site concentrations to background levels.

Step 2: Compare maximum detected site concentrations for COPCs to appropriate SSLs for each receptor. Note that a review of Table A-1 is required, as a chemical may present both carcinogenic and noncarcinogenic heath toxicity. Comparison to both screening levels, if available, is required.

• If the resulting Hazard Index (HI) (sum of all hazard quotients, HQs) is less than

1.0, stop; no additional assessment for noncarcinogens is needed. Move to Step

5.

February 2019

• If resulting cancer risk (sum of all cancer risks) is less than 1E-05, stop; no additional assessment for carcinogens is required. Move to Step 5.

Note: risks/hazards across all appropriate pathways must be included in the comparison to NMED target levels of 1 and 1E-05. Any risk/hazard from vapor intrusion or other site-specific pathway must be added to the summed risk/hazard calculated using the

SSLs. The beef ingestion pathway should be addressed in the Uncertainty Section.

Step 3: If Step 2 results in adverse risk/hazard, calculate refined exposure point concentrations

(EPCs).

Step 4: Compare EPCs to the appropriate SSLs for each receptor:

• If the resulting Hazard Index (HI) is less than 1.0, stop; no additional assessment for noncarcinogens is needed. Move to Step 5.

• If resulting cancer risk is less than 1E-05, stop; no additional assessment for carcinogens is required. Move to Step 5.

Step 5: Compare the site concentrations to the soil-to-groundwater target soil leachate concentrations (based on a dilution attenuation factor of 20). Maximum detected concentrations should be applied first, followed by use of a refined EPC and/or site-specific data, if the initial comparison results in an exceedance of the applicable soil-to-groundwater target soil leachate concentrations.

Step 6: Discuss Uncertainties

Step 7: If Step 4 and/or Step 5 results in excess risk/hazard or potential to impact groundwater, conduct additional site-specific refinements of the assessment and/or implement corrective actions.

Volume II contains guidance for conducting the ecological screening assessment.

2.0 DEVELOPMENT OF PATHWAY SPECIFIC SOIL SCREENING LEVELS

The following sections present the technical basis and limitations used to calculate SSLs, tap water screening levels (SLs), and VISLs for residential, commercial/industrial, and construction land use scenarios. The equations used to evaluate inhalation and migration to groundwater include a number of easily obtainable site-specific input parameters. Where site-specific data are not available, conservative default values are presented. The equations used are presented in

Sections 2.2 through 2.6. Generic SSLs and tap water screening levels are calculated using these default values and are presented in Table A-1 of Appendix A. Vapor intrusion screening levels were calculated for chemicals considered toxic and volatile and are presented in Table A-4.

2.1 Human Health Basis

The toxicity criteria used for calculating the SSLs are presented in Table C-1 of Appendix C.

The selected toxicity values were based on chronic exposure. The primary sources for the

February 2019 human health benchmarks follow the US EPA Superfund programs tiered hierarchy of human health toxicity values (US EPA 2003). Although the US EPA 2003 identified several Tier 3 sources, a hierarchy among the Tier 3 sources was not assigned by the US EPA. For the calculation of NMED SSLs, the following hierarchy of sources was applied in the order listed, and is similar to the hierarchy utilized in the calculation of US EPA’s RSLs (US EPA, 2016a):

1) Integrated Risk Information System (IRIS) (US EPA, 2018b) (www.epa.gov/iris),

2) Provisional peer reviewed toxicity values (PPRTVs) (http://hhpprtv.ornl.gov/) and appendices,

3) Agency for Toxic Substances and Disease Registry (ATSDR) (http://www.atsdr.cdc.gov/) and minimal risk levels (MRLs) (http://www.atsdr.cdc.gov/mrls/index.asp),

4) California EPA’s Office of Environmental and Health Hazard Assessment values

(CalEPA) (http://www.oehha.ca.gov/air/allrels.html and http://www.oehha.ca.gov/risk/pdf/tcdb072109alpha.pdf), and

5) Health Effects Assessment Summary Tables (HEAST) (US EPA 1997a).

Special assumptions were also applied in determining appropriate toxicological data for certain chemicals.

Dioxins/Furans. Toxicity data for the dioxin and furan congeners were assessed using the

2005 World Health Organization’s (WHO) toxicity equivalency factors (TEF) (Van den berg, et al 2006) and are summarized in Table 2-1. When screening risk assessments are performed for dioxins/furans at a site, the TEFs in Table 2-1 should be applied to the analytical results and summed for each sample location; the sum, or toxicity equivalent

(TEQ) as calculated using Equation 1, should be compared to the NMED SSL for 2,3,7,8-

Tetrachlorodibenzo-p-dioxin (TCDD).

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Equation 1

Calculation of Toxicity Equivalents for Dioxin and Furan

Congeners

𝑇𝐸𝐹𝑖 × 𝐶𝑖 = 𝑇𝐸𝐶𝑖

∑ 𝑇𝐸𝐶𝑖 = 𝑇𝐸𝑄

TEFi Congener-specific toxicity equivalency factor

(Table 2-1)

Ci Congener-specific concentration

TEQ Toxicity Equivalent

Table 2-1. Dioxin and Furan Toxicity Equivalency Factors

Dioxin and Furan Congeners TEF

Chlorinated dibenzo-p-dioxins

2,3,7,8-TCDD 1

1,2,3,7,8-PeCDD 1

1,2,3,4,7,8-HxCDD 0.1

1,2,3,6,7,8-HxCDD 0.1

1,2,3,7,8,9-HxCDD 0.1

1,2,3,4,6,7,8-HpCDD 0.01

OCDD 0.0003

Chlorinated dibenzofurans

2,3,7,8-TCDF 0.1

1,2,3,7,8-PeCDF 0.03

2,3,4,7,8-PeCDF 0.3

1,2,3,4,7,8-HxCDF 0.1

1,2,3,6,7,8-HxCDF 0.1

1,2,3,7,8,9-HxCDF 0.1

2,3,4,6,7,8-HxCDF 0.1

1,2,3,4,6,7,8-HpCDF 0.01

1,2,3,4,7,8,9-HpCDF 0.01

OCDF 0.0003

Polychlorinated biphenyls (PCBs). Toxicity data for Aroclors were taken from the IRIS database. Aroclor 1016 is considered low risk; therefore, toxicity values deemed as

“lowest risk” were applied. It was assumed that all the other Aroclors are high risk; as such, toxicity values deemed as “highest risk” were applied.

Toxicity data for the dioxin-like PCBs were calculated relative to 2,3,7,8-TCDD toxicity.

TEFs for non-ortho [International Union of Pure and Applied Chemistry (IUPAC) numbers 77, 81, 126, and 169)] and mono-ortho congeners (IUPAC numbers 105, 114, 118, 123, 156, 157, 167, and 189) were assessed using the 2005 WHO TEFs (Van den

Berg, et al 2006) while TEFs for di-ortho congeners (IUPAC numbers 170 and 180) are

February 2019 taken from Ahlborg, et al, 1993 (see Table 2-2).

Table 2-2. PCB TEFs

IUPAC No. Structure TEF

77 3,3',4,4'-TetraCB 0.0001

81 3,4,4',5-TetraCB 0.0003

105 2,3,3',4,4'-PeCB 0.00003

114 2,3,4,4',5-PeCB 0.00003

118 2,3',4,4',5-PeCB 0.00003

123 2',3,4,4',5-PeCB 0.00003

126 3,3',4,4',5-PeCB 0.1

156 2,3,3',4,4',5-HxCB 0.00003

157 2,3,3',4,4',5'-HxCB 0.00003

167 2,3',4,4',5,5'-HxCB 0.00003

169 3,3',4,4',5,5'-HxCB 0.03

189 2,3,3',4,4',5,5'-HpCB 0.00003

170 2,2',3,3',4,4',5-HpCB 0.0001

180 2,2',3,4,4',5,5'-HpCB 0.00001

Arsenic. The SFo and RfDo for arsenic were multiplied by a relative bioavailability correction factor of 0.6 in the calculation of the SSLs for ingestion of soil. Relative bioavailability accounts for differences in the bioavailability of a contaminant between the medium of exposure (soil) and the media associated with the toxicity value. The factor is applied in the derivation of soil ingestion screening levels because the arsenic

RfD and CSF are derived from drinking water studies (US EPA, 2016a).

Cadmium. IRIS provides an oral reference dose (RfD) for both water and food. For deriving the tap water SSL, the RfD for water was applied and for the soil-based SSL, the

RfD for food was applied.

Vanadium. The oral reference dose (RfD) for vanadium was calculated based on the

RfDo for vanadium pentoxide and factoring out the molecular weight of the oxide ion.

Lead. An SSL was not calculated for lead. Rather, the US EPA recommended levels for lead, based on blood-lead modeling (Integrated Exposure Uptake Biokinetic Model, IEUBK) were applied for the residential scenarios and industrial/construction workers

(Adult Lead Methodology).

Total Chromium. Toxicity data for total chromium were adjusted based on a ratio of 1:6

(hexavalent chromium to trivalent chromium). If there is reason to believe that this ratio for total chromium is not representative of site conditions, then valence-specific site concentrations and SSLs for trivalent chromium (chromium (III)) and hexavalent chromium (chromium (VI)) should be applied. See Section 5.1 for further information on the use of chromium screening levels.

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Chromium (VI). The oral cancer slope factor selected for chromium (VI) is based on a publication by the New Jersey Department of Environmental Protection (NJDEP) entitled

Derivation of Ingestion-Based Soil Remediation Criterion for Cr+6 Based on the NTP

Chronic Bioassay Data for Sodium Dichromate Dihydrate (April 8, 2009). This publication presents cancer potency values derived from a two-year dose-response study conducted by the National Toxicology Program (2008). NJDEP derived an oral cancer potency value of 0.5 mg/kg-day for chromium (VI). See Section 5.1 for further information on the use of chromium screening levels.

The inhalation unit risk (IUR) factor for chromium (VI) was derived by multiplying the total chromium IUR by seven (7) to account for a chrome speciation ratio of 1:6

(chromium (VI) to chromium (III)). See Section 5.1 for further information on the use of chromium screening levels.

Xylenes. Toxicity criteria for xylenes (mixture) from US EPA’s IRIS were used as surrogate values for the three isomers of xylenes (o-xylene, m-xylene, and p-xylene) based on structural similarity.

Essential Nutrients. Toxicity for the essential nutrients (calcium, chloride, magnesium, phosphorus, potassium, and sodium) was based on dietary guidelines. See Section 5.2 for further information on how the essential nutrient screening levels were developed and how to use these levels.

Phenanthrene. Based on structural similarity, toxicity data for pyrene were used as surrogate values for phenanthrene.

Polycyclic aromatic hydrocarbons (PAHs). Toxicity data for PAHs were calculated by applying TEFs relative to benzo(a)pyrene. The selected TEFs presented in US EPA

(1993) were applied in the calculation of NMED SSLs and are listed in Table 2-3.

Table 2-3. Polycyclic Aromatic Hydrocarbon Toxicity Equivalency Factors

Polycyclic Aromatic

Hydrocarbon

TEF

Benzo(a)pyrene 1.0

Benzo(a)anthracene 0.1

Benzo(b)fluoranthene 0.1

Benzo(k)fluoranthene 0.01

Chrysene 0.001

Dibenz(a,h)anthracene 1.0

Indeno(1,2,3-cd)pyrene 0.1

Perfluorinated Compounds. Perfluorinated compounds are considered an emerging contaminant. These include perfluorohexane sulfonic acid (PFHxS), perfluorooctane sulfonate (PFOS), and perfluorooctanoic acid (PFOA). Additional discussion of perfluorinated compounds and recommendations on assessing them in risk assessments is provided in Section 5.3.

February 2019

2.1.1 Additive Risk

It is important to note that no consideration is provided in the calculation of individual NMED

SSLs for additive risk when exposures to multiple chemicals occur. The SSG addresses this issue in Section 5. Because the NMED SSLs for carcinogenic effects correspond to a 1E-05 risk level individually, exposure to multiple contaminants may result in a cumulative site risk that is above the anticipated risk management range. While carcinogenic risks of multiple chemicals are simply added together, the issue of additive hazard is more complex for noncarcinogens because of the theory that a threshold exists for noncarcinogenic effects. This threshold is defined as the level below which adverse effects are not expected to occur and represents the basis for the RfD and reference concentration (RfC). Since adverse effects are not expected to occur at the RfD or RfC and the SSLs are derived by setting the potential exposure dose to the

RfD or RfC, the SSLs do not address the risk of exposure to multiple chemicals at levels where the individual chemicals alone would not be expected to cause any adverse effects. In such cases, the SSLs may not provide an accurate indicator for the likelihood of harmful effects. As a first-tier screening approach, noncarcinogenic effects should be considered additive. If the hazard index results in a value above the target level of 1, noncarcinogenic effects may be evaluated for those chemicals with the same toxic endpoint and/or mechanism of action. The sources provided in Section 2.1 should be consulted to determine the endpoint and/or target organ system prior to attempting to evaluate the additive health effects resulting from simultaneous exposure to multiple noncarcinogenic contaminants.

2.1.2 Acute Exposures

The exposure assumptions used to develop the SSLs are based on a chronic exposure scenario and do not account for situations where high-level exposures may result in acute toxic effects.

Such situations may arise when contaminant concentrations are very high or may result from specific site-related conditions and/or behavioral patterns (e.g., pica behavior in children). Such exposures may be of concern for those contaminants that primarily exhibit acute health effects.

For example, toxicological information regarding cyanide and phenol indicate that acute effects may be of concern for children exhibiting pica behavior. Pica is typically described as a compulsive craving to ingest non-food items (such as clay or paint). Although it can be exhibited by adults as well, it is typically of greatest concern in children because they often exhibit behavior (e.g., outdoor play activities and greater hand-to-mouth contact) that results in greater exposure to soil than for a typical adult. In addition, children also have a lower overall body weight relative to the predicted intake.

2.1.3 Early-Life Exposures to Carcinogens

US EPA’s (2005a) Supplemental Guidance states that early life exposures (i.e., neonatal and early life) to certain carcinogens can result in an increase in cancer risk later in life. US EPA’s

(2005a) suggests that age-specific factors be applied to the estimated cancer risks. These factors should address four life stages: 1) children under 2 years of age; 2) children aged 2 to 6 years; 3) children 6 years to 16 years of age; and 4) children over 16 years of age. Effects of mutagenicity have been incorporated into the SSLs for those contaminants which are considered carcinogenic by a mutagenic mode of action.

February 2019

2.1.4 Direct Ingestion

Exposure to contaminants through incidental ingestion of soil can result from the inadvertent consumption of soils adhering to the hands, food items, or objects that are placed into the mouth.

It can also result from swallowing dust particles that have been inhaled and deposited in the mouth. Commercial/industrial, construction workers, and residential receptors may inadvertently ingest soil that adheres to their hands while involved in work- or recreation-related activities.

Calculation of SSLs for direct ingestion are based on the methodology presented in US EPA’s

Risk Assessment Guidance for Superfund (RAGS): Volume I - Human Health Evaluation Manual

(Part B, Development of Risk-Based Preliminary Remediation Goals), Interim (US EPA 1991), Soil Screening Guidance: Technical Background Document (US EPA 1996a), and Supplemental

Guidance for Developing Soil Screening Levels for Superfund Sites (US EPA 2002a).

2.1.5 Dermal Absorption

Exposure to soil contaminants may result from dermal contact with contaminated soil and the subsequent absorption of contaminants through the skin. Contact with soil is most likely to occur as a result of digging, gardening, landscaping, or outdoor recreation activities. Excavation activities may also be a potential source of exposure to contaminants, particularly for construction workers. Calculation of the SSLs for dermal contact with soil under the residential exposure scenario is based on the methodology presented in US EPA’s Risk Assessment

Guidance for Superfund: Volume I - Human Health Evaluation Manual (Part B, Development of

Risk-Based Preliminary Remediation Goals), Interim (1991), and Soil Screening Guidance:

Technical Background Document (US EPA 1996a). The suggested default input values used to develop the NMED SSLs are consistent with US EPA’s interim RAGS, Part E, Supplemental

Guidance for Dermal Risk Assessment (US EPA 2004a).

2.1.6 Inhalation

US EPA toxicity data indicate that risks from exposure to some chemicals via the inhalation pathway far outweigh the risk via ingestion or dermal contact; therefore, the NMED SSLs have been designed to address inhalation of volatiles and fugitive dusts. To address the soil/sediment-to-air pathways, the SSL calculations incorporate a volatilization factor (VF) for volatile contaminants (See Section 3.1) and a particulate emission factor (PEF) (See Section 3.3) for semi-volatile and inorganic contaminants. The SSLs follow the procedures for evaluating inhalation soil, VOCs, and fugitive dust particles presented in US EPA’s Risk Assessment

Guidance for Superfund: Volume I - Human Health Evaluation Manual (Part F, Supplemental

Guidance for Inhalation Risk Assessment), Final (US EPA 2009), Risk Assessment Guidance for

Superfund: Volume I - Human Health Evaluation Manual (Part B, Development of Risk-Based

Preliminary Remediation Goals), Interim (US EPA 1991), Soil Screening Guidance: Technical

Background Document (US EPA 1996a), Human Health Risk Assessment Protocol for

Hazardous Waste Combustion Facilities (US EPA…