Microsoft Word - Final Draft

New Jersey

Department of Environmental Protection

Site Remediation and

Waste Management Program

Technical Guidance for Preparation and Submission

of a Conceptual Site Model

August 2019

Version 1.1

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TABLE OF CONTENTS

1.0 Intended Use of Guidance Document .......................................................................................... 4

2.0 Purpose ......................................................................................................................................... 5

3.0 Document Overview .................................................................................................................... 5

4.0 Definitions .................................................................................................................................... 6

5.0 Procedures .................................................................................................................................... 6

5.1 What is a Conceptual Site Model? .......................................................................................... 6

5.1.1 Description of Source, Pathways, and Receptors ............................................................ 7

5.1.2 Summary of Impacted Media........................................................................................... 7

5.1.3 A Tool for Remedial Decision Making............................................................................ 7

5.1.4 Form of the Model (diagram, text, and mapping) ............................................................ 8

5.2 Developing A Conceptual Site Model ................................................................................... 11

5.2.1 Description of Conceptual Site Model Scope – Site-wide or Area of Concern ............. 11

5.2.2 Summarizing Available Information ............................................................................. 11

5.2.3 Identification of Potential Sources ................................................................................. 12

5.2.4 Characterization of the Source(s) of Contamination ..................................................... 12

5.2.5 Migration Pathways ....................................................................................................... 13

5.2.6 Identification of Human and Ecological Receptors ....................................................... 18

5.2.7 Determination of the Extent of Investigative Area ........................................................ 19

5.2.8 Narrative Description ..................................................................................................... 19

5.3 Applying the Conceptual Site Model .................................................................................... 19

5.4 Data Gaps and Revising the Conceptual Site Model – Iterative Process .............................. 22

5.5 Examples of Development and Application of the Conceptual Site Model .......................... 22

6.0 References .................................................................................................................................. 24

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TABLE

Table 5-1: Applying the conceptual site model in the Remedial Process ............................21

LIST OF FIGURES

Figure 1: Conceptual Site Model – Exposure Pathway Schematic..............................................8

Figure 2: USEPA Generic Eco conceptual site model Illustration ..............................................9

Figure 3: Schematic illustration of conceptual site model for soil

exposure pathway evaluation .....................................................................................10

Figure 4: Importance of Proper Site Characterization ...............................................................16

APPENDICES

Appendix A: Conceptual Site Model Checklist .........................................................................25

Appendix B: Examples of Development and Application of a Conceptual Site Model. ...........31

Appendix C: Illustrations of Simple -Conceptual Site Model ...................................................39

Appendix D: Acronyms .............................................................................................................45

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1.0 Intended Use of Guidance Document

This technical guidance is designed to help the person responsible for conducting remediation to comply

with the New Jersey Department of Environmental Protection (NJDEP or Department) requirements

established by the Technical Requirements for Site Remediation (Technical Rules), N.J.A.C. 7:26E.

This guidance will be used by many different people involved in the remediation of a contaminated site;

such as Licensed Site Remediation Professionals (LSRPs), Non-LSRP environmental consultants and

other environmental professionals. Therefore, the generic term “investigator” will be used to refer to any

person that uses this technical guidance to remediate a contaminated site on behalf of a remediating

party, including the remediating party itself.

The procedures for a person to vary from the Technical Rules are at N.J.A.C. 7:26E-1.7. Variances from

a technical requirement or departure from guidance must be documented and adequately supported with

data or other information. In applying technical guidance, the Department recognizes that professional

judgment may result in a range of interpretations on the application of the technical guidance to site

conditions.

This guidance supersedes previous Department guidance issued on this topic. Technical guidance may be

used immediately upon issuance. However, the Department recognizes the challenge of using newly issued

technical guidance when a remediation affected by the guidance may have already been conducted or is

currently in progress. To provide for the reasonable implementation of new technical guidance, the

Department will allow a six-month “phase-in” period between the date the technical guidance is issued final

(or the revision date) and the time it should be used.

This guidance supersedes previous Department guidance issued on this topic and was prepared with

stakeholder input. The following people were on the committee who prepared this document:

Joseph Eaker, Chair, Bureau of Information Systems (BIS), NJDEP

Rob Lux, Bureau of Enforcement and Investigation (BEI), NJDEP

Kimberly McEvoy, Engineering and Construction Program, NJDEP

Nick DeRose, LSRPA, Langan Engineering and Environmental Services

Richard Britton, Matrix New World Engineering

Brendan Lazar, TRC Environmental Corp.

Jaime Wuelfing, Groundwater & Environmental Services

William Gottobrio, Golder Associates

Carrie McGowan, AECOM

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2.0 Purpose

This Conceptual Site Model Technical Guidance has been developed to provide a framework that can be

used to aid and document site characterization and remedial action decisions throughout the life of the

remedial process. A conceptual site model is a written and/or illustrative representation of the conditions

and the physical, chemical and biological processes that control the transport, migration and potential

impacts of contamination (in soil, air, ground water, surface water and/or sediments) to human and/or

ecological receptors.

This Conceptual Site Model Technical Guidance should be used in concert with the Administrative

Requirements for the Remediation of Contaminated Sites (N.J.A.C. 7:26C), Remediation Standards

(N.J.A.C. 7:26D), the Technical Requirements for Site Remediation (N.J.A.C. 7:26E), and the Heating

Oil Tank System Remediation Rules (N.J.A.C. 7:26F). While the CSM can greatly assist in explaining

results of an investigation, it is not a required deliverable for documents submitted to the Department.

The use of the conceptual site model does not replace the need for documenting procedures, or

methodologies for proper site investigation or remediation in accordance with the Department’s

regulatory requirements.

The conceptual site model is a critical tool that should be used to identify sources, receptors and

pathways associated with the area of concern and/or site. The conceptual site model should support

scientific and technical decisions for the site. The conceptual site model can also assist the investigator

to communicate effectively with interested parties about the critical issues, and/or processes identified at

the site, and support the remedial decision- making process. Development and refinement of the

conceptual site model will help identify data gaps in the characterization process and can ultimately

support remedial decision making. The Department accepts the conceptual site model as a valid

scientific approach to support professional judgment when applied in accordance with applicable

regulatory requirements, remediation standards and technical guidance documents.

3.0 Document Overview

This technical guidance, in conjunction with other Department technical guidance, reviews the

definition, procedures and application of a conceptual site model. A conceptual site model allows the

user to present a comprehensive and concise understanding of the site environmental system and the

potential risks to human health and the environment associated with identified contaminants of concern

(COCs). The conceptual site model can range from a simple illustration (see Figure C1-1) to a more

sophisticated comprehensive document (See Figure B1-1) depending on the complexity of the site and

the amount of data collected. The conceptual site model can be applied to all phases of the remedial

process to understand the relationship between sources, migration pathways and receptors associated

with the site or area of concern and identified COCs. The conceptual site model serves to identify

currently complete or potentially complete pathways to receptors and the potential for future risks.

The use of the conceptual site model does not replace the need for documenting procedures, or

methodologies for proper site investigation or remediation in accordance with the Department’s

regulatory requirements. The conceptual site model should be used to enable investigators to

communicate effectively with all interested parties, identify critical issues and/or processes and facilitate

the remedial decision-making process. The format and presentation of the conceptual site model may

also vary from a stand-alone document to being incorporated into the body of a submittal.

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Procedures for development of a conceptual site model are presented in this document

in three main sections:

Section 5.1 Describes the conceptual site model in detail and identifies the key components of a

conceptual site model. This section also provides a framework for the site characterization and

presents options for relaying the information to the end user.

Section 5.2 utilizes the site-specific information to describe the scope of the conceptual site model,

determine the extent of the investigative area and summarize all of the available information. This

section discusses the identification of all potential sources, pathways and receptors.

Section 5.3 describes how the conceptual site model should be continually revised to reflect the

current understanding of the site and how it can be used during all phases of the investigation,

remediation and support the remedial decision.

Specific examples are included in the document.

4.0 Definitions

Conceptual Site Model: The conceptual site model is a written and/or illustrative representation of the

physical, chemical and biological processes that control the transport, migration and actual/potential

impacts of contamination (in soil, air, ground water, surface water and/or sediments) to human and/or

ecological receptors. Development and refinement of the CSM will help identify investigative data gaps

in the characterization process and can ultimately support remedial decision making.

Complete Pathway: An exposure route with an impacted receptor that is associated with a confirmed

source and migration pathway. An incomplete pathway is missing one of these three components

Contaminant of Concern (COC): Site-specific compounds associated with a discharge(s) at or from a

site that are detected in environmental media (soil, ground water, surface water, sediment, air) above

regulatory criteria. It also includes the degradation byproducts from the COCs.

Migration pathway: The course through which contaminants in the environment may move away from

the source(s) to potential environmental receptors.

Smear Zone: Thickness of contaminant distribution that results from fluctuations of the water table that

is equal to or greater than the historical range of water table fluctuations.

Source – (ASTM 2008): The location from which a contaminant(s) has entered or may enter a physical

system. A primary source, such as a location at which drums have leaked onto surface soils, may

produce a secondary source, such as contaminated soils; sources, may hence be primary or secondary.

5.0 Procedures

5.1 What is a Conceptual Site Model?

The goal of a conceptual site model is to provide a description of relevant site features

and the surface and subsurface conditions to understand the extent of identified

contaminants of concern and the risk they pose to receptors. The conceptual site model is

an iterative tool that should be developed and refined as information is obtained during

review of the site history and continues throughout the site and/or remedial investigation.

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The level of detail of the conceptual site model should match the complexity of the site

and available data. Development and refinement of the conceptual site model will help

identify investigative data gaps in the characterization process and can ultimately support

remedial decision making.

5.1.1 Description of Source, Pathways, and Receptors

Potential sources of contaminants are identified and investigated as described in the Tech Regs

regulations and other Technical Guidance Documents. These sources may include tanks, material

transport areas, drainage conveyance areas, production areas, waste disposal areas, and other

areas of concern. Contaminants of Concern, as well as their concentrations in the various media

on site should be fully characterized to understand the extent and potential for migration.

Potential migration pathways for these contaminants to receptors are then identified and

evaluated to assess exposure risks. Identify incomplete pathways.

Preparation and use of the conceptual site model is an iterative process throughout the lifecycle

of the project. The conceptual site model should be modified to continually evaluate the

relationship between sources of contaminants, migration pathways, and receptors as new data

become available. Evaluation of these three components through the use of the conceptual site

model, in conjunction with initial preparation and subsequent revisions to the Receptor

Evaluation Form (N.J.A.C. 7:26E-1.12) will ensure receptors are identified and addressed.

5.1.2 Summary of Impacted Media

Investigate all environmental media (ground water, surface water, soils, sediment, and air) and

incorporate into the conceptual site model. The conceptual site model should be used to

document the presence or absence of contamination in a particular media. When data is

available, the CSM could include basic information for all potentially impacted media, such

as classification and applicable remediation standards, and summary tables and/or

other data summary methods for concisely describing data available for all media,

collected throughout the history of the site.

5.1.3 A Tool for Remedial Decision Making

The conceptual site model will evolve as information is gathered throughout the life of a project.

As the understanding of the source, nature and extent of contamination is realized, the

information should be used to evaluate fate and transport of the contaminants to the receptors. By

periodically evaluating the completeness of the conceptual site model, data gaps can be more

readily identified and addressed to ensure there is a complete understanding of contaminant

impacts. By developing the conceptual site model through this iterative process, remedial

decisions can be made to effectively address and protect the impacted and/or potentially

impacted receptors. Clearly identify uncertainties associated with the conceptual site model so

that efforts can be taken to reduce these uncertainties to acceptable levels. Early versions of the

conceptual site model, which are usually based on limited or incomplete information, will

identify the uncertainties that should be addressed. Perform an assessment of data usability/data

representativeness to ensure identification of data limitations affecting the use of the conceptual

site model.

Discussion of applying data usability/representativeness concepts to the conceptual site model is

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presented in Sections 2.4.3 and 2.4.4 of “Technical and Regulatory Guidance for the Triad

Approach: A New Paradigm for Environmental Project Management” (ITRC, December 2003).

5.1.4 Form of the Model (diagram, text, and mapping)

The conceptual site model can be presented in a number of forms. Often the forms will be

dictated by the complexity of the site or area of concern and the amount and type of available

data. The conceptual site model may be narrative, text, pictorial, presented as a computer model,

or some combination. It should represent the site or area of concern, contaminant sources, the

environmental media that have been impacted, and the processes that determine transport of

contaminants to potential receptors. Refine the CSM as information is collected throughout each

phase of a project until implementation of a remedy. A CSM is also useful after the remedy has

been implemented. For example, use post remediation monitoring data to validate the CSM and

confirm selection of a proper remedy for the site and/or AOC.

Figures 1 and 2 present illustrations of generic conceptual site models and potential human

health and ecological receptors, respectively. In addition, Figure 3 presents a generic U.S.

Environmental Protection Agency schematic diagram of a conceptual site model exposure

pathway evaluation. Examples of development and application of the conceptual site model are

also presented in Section 5.5 of this document.

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Figure 2: USEPA Generic ECO CSM Illustration

U.S. Environmental Protection Agency (USEPA) (2004)

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5.2 Developing A Conceptual Site Model

The following sections describe the components that should be included in development and

presentation of the conceptual site model in written submittals. The level of detail of the components

should be consistent with the complexity of the site and available data. The format and presentation

of the conceptual site model may also vary from a stand-alone document to being incorporated into

the body of a submittal.

To assist the investigator in developing the conceptual site model, an optional checklist is provided

in Appendix A to this guidance that identifies the types of information which could be collected

during the remedial process. All items on this checklist may not apply to each site and depending

upon the complexity of the site, there may be additional information required to complete the

development of the conceptual site model. The investigator is also encouraged to conduct a site visit

to assist in the development of a complete conceptual site model.

Components of the conceptual site model should clearly distinguish between background

contamination and contamination associated with an area of concern or site to understand the

receptor groups that may be associated with the exposure to contaminants of concern within a

pathway.

5.2.1 Description of Conceptual Site Model Scope – Site-wide or Area of Concern

The scope of the conceptual site model should include establishing the extent of the investigative

area to be characterized. Make clear if the conceptual site model will be limited to an area of

concern or the entire site, and if it will extend off site to include regional features. It is also

important to clarify if the conceptual site model is being developed to assess potential/actual

impacts to human or ecological receptors or both. The description of the conceptual site model

should include a complete site plan depicting the extent of the area addressed by the conceptual

site model, a depiction of identified area of concerns/source areas, potential COCs, pertinent

features affecting contaminant migration, identified potential receptors, and the applicable

remediation criteria.

5.2.2 Summarizing Available Information

The investigator should evaluate information collected throughout the remedial process

(Preliminary Assessment/Site Investigation (PA/SI), Remedial Investigation (RI), Remedial

Action) in developing and refining the conceptual site model. This should include providing a

summary of available site information and publications relevant to developing the conceptual site

model.

The following information should be included in the summary:

• general description of current uses of the property and surrounding properties

• current zoning status for the property and surrounding properties available historical

information on property use or activities that may be pertinent to its environmental status

• identification of the locations and depths of known subsurface utilities

• relevant off-site and regional information from aerial photographs, geographic information

system data, and historical and current tax maps, etc.

• photographs, topographic maps, and geologic quadrangle maps

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• historical discharges;

• historical contaminant concentrations in soil and ground water;

• aquifer classification and surface water body classification;

• applicable remediation standards for all potentially impacted media; and

• any applicable antidegradation policies.

5.2.3 Identification of Potential Sources

The investigator should conduct a diligent inquiry into the operational and ownership history of

the area of concern or site to determine source(s) which may have contributed to the

contamination. This may include information or data generated by a Preliminary Assessment

conducted in accordance with N.C.A.C 7:26E-3 and the current versions of the Department’s

Technical Guidance for Site Investigation of Soil, Remedial Investigation of Soil, and Remedial

Action Verification Sampling for Soil and the Ground Water Technical Guidance: Site

Investigation Remedial Investigation Remedial Action Performance Monitoring. The source is

then defined by specific area of concerns or may be a group of area of concerns. It is important to

consider individual contributions when grouping area of concerns into a single source area.

Source areas and plumes that overlap are encouraged to be investigated together and included in

the same CSM.

5.2.4 Characterization of the Source(s) of Contamination

The characterization of the source(s) provides the basis for completion of the site/remedial

investigation. The investigator should identify the discharge date, discharge point, discharged

material, and estimated volume of the discharge. Include a discussion of the affected media and

initial mitigation and/or remediation efforts.

Initially, the source should be characterized and the extent of contaminants of concern estimated.

As source characterization progresses, the conceptual site model should be refined using the site-

specific sampling data and additional historical information that is discovered during the

investigation/remediation.

The source characterization should discuss:

• location;

• content;

• dates of use;

• extent/volume/mass;

• maps; discharge maps;

• discharge information;

• prior remedial actions; and

• immediate environmental concerns conditions/mitigation.

Once significant contaminant data is available, summary tables, maps, graphs or other figures

should be used to describe the nature and extent of contamination in all media and/or to

concisely illustrate any temporal trends in the data. Historical monitoring/investigation data and

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past remedial actions taken should be included. Information that does, or may, explain any trends

in the data could also be discussed. In addition, any important implications for receptor exposure

that may be associated with changes in various contaminant levels over time in any media could

be noted.

During the review of available site and surrounding property information, it is important to

identify contamination in media on-site that may not be related to spills or site processes.

Specifically, it is important to determine if fill was placed on-site at any point in time and the

extent of the fill material. This material could meet the definition of historic fill and, if

contaminants are detected in the fill, may influence the choice of remedial action for part of the

site or area of concern. The presence of impacted fill does not preclude site investigation and

remediation of impacts that are associated with site operations.

It may also become apparent that contaminants detected on-site may be due to diffuse

anthropogenic contaminants, naturally occurring background concentrations, or impacts from

discharges at near-by sites. The existence of contaminants not related to the site operations is

important when determining site pathways and impacts to receptors. Source control or

remediation of these constituents may not be possible or necessary, but it is important to evaluate

the impact to receptors and consider this when ultimately making remedial decisions.

5.2.5 Migration Pathways

The conceptual site model can identify all potential and confirmed migration pathways of the

contaminants of concern for the area addressed by the conceptual site model. The purpose of this

section of the conceptual site model is to document all current and future migration pathways for

all contaminants of concern at the site. This section should also identify when the migration

pathway(s) are not complete and therefore will not be evaluated.

The media that should be evaluated in the development of a conceptual site model are soil,

ground water, surface water, sediment and air. The following sections provide information to

consider when evaluating migration pathways for each media. The investigator should then

evaluate which components are applicable based on the conditions and complexity of the site.

Soil

Soil sampling and characterization must be conducted in accordance with N.J.A.C. 7:26E- 3.4

and 4.2. The investigator should also follow the Department’s Technical Guidance for Site

Investigation of Soil, Remedial Investigation of Soil, and Remedial Action Verification

Sampling for Soil, and Department’s Field Sampling Procedures Manual. If the investigator

identifies constituents that exceed the appropriate Department remediation standards, the

investigator can develop a conceptual site model to characterize the nature and extent of

contamination. Include the evaluation of each potential exposure pathway and supporting fate

and transport analysis as appropriate. In this analysis, the investigator must identify the

boundaries that were used to define the site and/or area of concern, which should be supported

by the sampling locations. Based upon the complexity of the site and site conditions, the

conceptual site model should be able to provide the following information derived from field

investigations:

• contaminants of concern that are present, their concentrations, spatial variation in

concentration, and remediation standards;

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• physical characteristics of the soil in which contaminants of concern are present and

through which they may be moving

o examples include soil type, dry bulk density, permeability, organic carbon content,

porosity, field description from boring logs, and moisture content;

• heterogeneities within the soil column;

• existence of “smear zone”; and

• depth to ground water and/or bedrock.

Within the conceptual site model, identify site conditions that may represent potential exposure

risks and/or migration pathways. Examples of information to consider include:

• proximity to surface water and wetlands;

• surface and subsurface drainage features;

• subsurface storm water infiltration galleries;

• amount of soil cover;

• proximity to buildings;

• proximity to residential areas, schools, parks, etc.; and

• location of utilities/preferential migration pathways.

Documentation of above-mentioned properties and any significant variability over the site may

be very important later in developing a fate and transport analysis and in identifying any

potential secondary sources. Appendix C provides examples of conceptual site models for a

single discharge, where soil is one of the media of concern

Ground Water

If a release to ground water is suspected, ground water sampling must be conducted in

accordance with N.J.A.C. 7:26E- 3.5 and 4.3 and the current versions of the Department’s

Ground Water Technical Guidance: Site Investigation Remedial Investigation Remedial Action

Performance Monitoring and Department’s Field Sampling Procedures Manual. A ground

water conceptual site model can be used to aid in determining the extent of the migration of

contamination in each aquifer unit. The ground water conceptual site model is based on

knowledge of the site, ground water monitoring information, and the fate and transport

analysis. The investigator should evaluate and include the following in the conceptual site

model:

• types of contaminants of concern present, their concentrations and their

spatial variation in concentration;

• aquifer characteristics (e.g., porosity and permeability) of the material(s)

through which ground water moves;

• Geologic formations and Ground Water Classifications (Class I, II, or III) that has(have)

been impacted;

• direction of ground water flow;

• hydraulic gradient;

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• location of recharge and discharge areas including infiltration galleries;

• location of any present or historic pumping influence;

• water use area (potable, irrigation, industrial, etc.);

• heterogeneities within the saturated geologic matrix

• bedrock structure information that may control contaminant migration; and

• preferential pathways (e.g. location of subsurface utilities).

Organic contaminants can migrate into low permeability formations of clay or rock where they

remain at high concentrations. These may diffuse slowly into adjacent, aquifer formations.

Therefore, the nature and extent of organic COCs sorbed within low permeability soil and rock

matrices, both above and below the saturated zone, should also be characterized.

This information is not only necessary to describe and evaluate conditions at the site, but is

often vital to fate and transport analysis, especially when it requires a quantitative approach.

The conceptual site model should also identify if background contamination is migrating onto

the site and/or area of concern. If an off-site source of contamination is identified, then collect

the same information as if the ground water contamination was from the site and/or area of

concern. The presence of an off-site source does not preclude site investigation and remediation

of impacts that are associated with site operations.

The fate and transport evaluation of ground water in this section should identify the current and

historical extent of ground water contamination and the related receptors. The investigator

should also identify future receptors that may be impacted by the contamination stemming

from the site and/or area of concern.

The investigator will also need to determine when there may be a need for specialized

engineering and/or scientific expertise to support the characterization of the migration

pathway. Many situations may result in complex interactions between contaminants and the

environment. One common error that can invalidate the conceptual site model is the

installation of monitoring wells at a consistent pre-determined depth without evaluating

whether preferential pathways exist at the site. As illustrated by Figure 4, not accounting for a

dipping transmissive zone that acts as a preferential pathway could lead the investigator to

conclude that ground water contamination is delineated, when in fact contamination was

simply missed due to inadequate site characterization, resulting in the development of an

inaccurate conceptual site model.

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Surface Water

If a discharge is suspected to have occurred into surface water or there is a migration pathway

to surface water, then this pathway should be assessed as specified by N.J.A.C. 7:26E- 3.6 and

4.4 and the Department’s Ecological Evaluation Technical Guidance. A surface water and

sediment investigation is usually conducted if there is evidence of a direct discharge to surface

water, contaminated surface water runoff or ground water discharges into the surface water

body. This section will specifically address components that should be included when

assessing the surface water migration pathway.

Provide the following information in the conceptual site model when addressing the surface

water migration pathway:

• physical components associated with the surface water body such as identification of

stressed vegetation, sheens, seeps, discolored soil or sediment along the shoreline or on

the surface water body;

• documented historical discharges that may or may not be associated with the site and/or

area of concern including historical ecological studies documenting differences in

organism population density and diversity in areas potentially impacted by the site relative

to areas not impacted by the site;

• identification of ground water contaminants of concern that exceed the Surface Water

Quality Standards and migrate along the ground water path toward a surface water body;

• plume area, concentration and flow (Q) to estimate a mass loading to surface water;

• whether antidegradation policies apply,

• seasonal surface water flow.

Sediment

In accordance with N.J.A.C. 7:26E-3.6 and 4.8 and the Department’s Ecological Evaluation

Technical Guidance, the collection of sediment samples is required when it is evident that a

discharge to a surface water body has occurred and there is reason to believe that sediments

may have been impacted by contamination emanating from the site or area of concern. When

evaluating the sediment migration pathway, the investigator should determine if there is

potential exposure to human health and/or to the environment. Successful evaluation of

contaminated sediments requires knowledge of the nature, concentration and areal extent of

contamination, as well as site-specific variables that affect the expression of environmental

impacts. When trying to understand the relationship between contaminant concentrations and

exposure within the sediment migration pathway, the conceptual site model should identify:

• how site-related contaminants enter a system;

• how contaminants move in that system (including fate and partitioning); and

• mechanisms for exposure and uptake in human and/or ecological receptors.

Vapor and Air

If a vapor intrusion investigation is warranted in accordance with the VIG, the conceptual site

model should identify all potential vapor migration pathways and processes through which a

receptor can be exposed at a particular site. Vapor and liquid transport processes and their

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interactions with various geologic and physical site settings (i.e., variations in building

design/construction, soil texture/profile, temporal variation in atmospheric pressure,

precipitation/infiltration, soil moisture, and water table elevation) create a complex and

dynamic system. Consider as follows the main vapor transport mechanisms that should be

considered when evaluating vapor migration:

• diffusion of vapors from sources in the unsaturated zone;

• diffusion of vapors from sources in shallow ground water;

• advective/convective transport of vapors; and

• vapor migration through preferential pathways.

A vapor intrusion investigation must be initiated when any of the conditions outlined in

N.J.A.C. 7:26 E-1.15 are met. N.J.A.C. 7:26 E-3.7, 4.5 and the Department’s Vapor Intrusion

Guidance Document provides direction for such an investigation. The conceptual site model

can be used for the following:

• determining presence/absence of current conditions that would trigger a vapor

investigation;

• evaluating historical levels of ground water COCs which are not currently above screening

levels to assess potential VI concerns;

• assessing identified risks;

• identifying actions necessary to mitigate the risks;

• documenting effectiveness of mitigation activities; and

• identifying and evaluating airborne release mechanisms (emissions from stacks, roof

vents, dust collectors, fire and excavation/construction, etc.)

The conceptual site model should be used to document all sources, pathways, receptors and

associated investigative/corrective actions conducted in accordance with N.J.A.C. 7:26E-1.15,

3.7, 4.5 and the Vapor Intrusion Technical Guidance. A discussion of migration pathways for

the vapor pathway is included in Appendix B of this document.

5.2.6 Identification of Human and Ecological Receptors

The identification of potential receptors is the key function of the conceptual site model and

should take place upon the initial discovery of the discharge and continue to be refined as the

investigation proceeds. Human and ecological receptors include those that are impacted or

threatened by the contaminants of concern, located within the investigative area or present along

an identified migration pathway. Future use of the site may affect the exposure scenario;

therefore, the conceptual site model should identify, when possible, the future use of the site and

take into consideration future exposures to all receptors.

Include the following in the human receptor evaluation:

• contaminants or suite of contaminants that are evaluated;

• pathway of exposure to each contaminant of concern (via direct contact (i.e.,

ingestion, inhalation or dermal contact) or bioaccumulation along food chain);

and

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• populations that are currently or potentially exposed.

The ecological risk evaluation is often separate from the human risk evaluation since humans are

potentially exposed to contamination differently (e.g.., migration pathway or food source) than

ecological receptors. The information that is required to be evaluated in the Receptor Evaluation

Form, as required by N.J.A.C. 7:26E-1.12, will help with the identification of ecological

receptors. See the Department’s Ecological Evaluation Technical Guidance. Generally, the

ecological receptor evaluation should address the following components:

• contaminants of potential ecological concern (including co-occurrence of contaminants) for

soil, ground water, surface water and sediment;

• current and future exposed species: representative of major groups present at site, not

necessarily all species on or adjacent to site;

• contaminant migration pathways to environmentally sensitive areas;

• environmentally sensitive areas as described in N.J.A.C. 7:26E-3.6 and 4.8 and

• map of exposed population along each migration pathway.

Submit the presentation of the ecological and the human receptor evaluations as two separate

sections within the conceptual site model. As previously illustrated, Figures 1 and 2 present

generic conceptual site models to highlight potential human health and ecological receptors,

respectively.

5.2.7 Determination of the Extent of Investigative Area

The conceptual site model should not only characterize the source area and the extent of

contamination associated with the source area as described above, but the conceptual site model

should include a description of the extent of the investigative area. This would include

identification of human populations that may be impacted by the contamination (i.e., private or

public supply wells); any critical species that may live on or adjacent to the site, such as federally

or state threatened or endangered species; or any environmentally sensitive natural resources.

This should include identifying critical habitats within the area associated with identified

migration pathways. The investigator should present this information in map form and update as

the data is collected for all migration pathways related to the site.

5.2.8 Narrative Description

The narrative description puts all the pieces of the conceptual site model together in a summary

fashion for the site as it is understood at that time. For a simple scenario, the narrative

description may be notes or text boxes on a drawing. For a more complex site, it may be the

section of a report. It should clearly describe the site, contaminants, pathways, and receptors. It

also may include a discussion of data gaps or uncertainties.

5.3 Applying the Conceptual Site Model

The conceptual site model can be applied to all phases of the Remedial Process to understand the

relationship between sources (COCs), migration pathways and receptors associated with the Site or

area of concern. The use of the conceptual site model does not replace the need for documenting

procedures or methodologies for proper SI in accordance with the Technical Requirements for Site

Page 20 of 46

Remediation, N.J.AC. 7:26E. The conceptual site model allows the investigator to present a

comprehensive and concise understanding of all impacted media including soil, ground water, air,

surface water and sediment associated with the site or area of concern and the potential risks to

human health and the environment associated with the contaminants of concern. Use the conceptual

site model to enable the user to communicate effectively with all interested parties, identify critical

issues and/or processes and facilitate the remedial decision-making process.

Appendix C presents a series of graphical illustrations and schematic diagrams to illustrate the

application of basic conceptual site models for Preliminary Assessment and Remedial Investigation

phases.

A CSM is also useful after the remedy has been implemented. For example, post remediation

monitoring data can be used to validate the CSM and confirm that a proper remedy has been selected

for the site and/or AOC.

The conceptual site model can be applied in each phase of the remedial process as highlighted in the

table below.

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Table 5-1: Applying the conceptual site model in the Remedial Process

Preliminary

Assessment

• Allows the user to summarize collected information regarding area of

concerns as to its relationship to source, pathway and potential receptor.

• To eliminate need for further investigation (e.g., baseline ecological

evaluation; building interiors).

• Serves as basis for determining approach to the site investigation.

Site

Investigation /

Remedial

Investigation

• Characterize the physical, biological, and chemical systems existing at a site

or area of concern.

• Describe processes that affect discharges, contaminant migration, and

exposure to contaminants.

• Document non-site related contaminants (e.g., historic fill, naturally

occurring background, diffuse anthropogenic contamination).

Remedy

Selection

• Determine potential exposure routes (e.g., ingestion and inhalation) and

identify potential risks to human health and the environment.

• Identify potential remedial alternatives.

• Facilitate the selection of remedial alternatives to eliminate the

unacceptable exposure of environmental receptors to contaminants of

concern and thereby ensure protection of human health and the

environment.

• Identify data gaps that may preclude a definitive determination of the

remedial action selection and discussion of plans to address them.

• Summarize the data collection/evaluation and feasibility testing completed

to support the selected remedial approach (passive or active remediation).

• Identify interim or active remedial approaches that have been applied or are

planned for implementation at the site.

• Discuss selected remedial action as it relates to protection of human health

and the environment.

Post Remedial

Action

• Document the effectiveness of remedial actions selected to mitigate or

eliminate the exposure of all human and ecological receptors affected by

the chemicals of concern;

• Illustrate that sufficient investigative data were collected to support the

selected remedial action;

• Support that the appropriate engineering or institutional controls have been

implemented;

• Support a response action outcome

• Document the completion of all phases of remediation in accordance with

all applicable statutes, regulations, and guidance;

• Support the appropriateness of a variance or deviation from an applicable

regulation or guidance due to site-specific conditions; and

• Summarize the post remedial monitoring plan, as appropriate.

Page 22 of 46

5.4 Data Gaps and Revising the Conceptual Site Model – Iterative Process

It is recommended to develop a conceptual site model early in the investigative process (e.g., at the

preliminary assessment phase). The integration of available site history into an initial conceptual site

model assists in the identification of necessary information and/or data that may be required to be

collected during the investigation to ensure understanding of impacts associated with an area of

concern or site. The complexity of the conceptual site model should be consistent with the

complexity of the site. The conceptual site model will increase in detail as the characterization of the

site progresses. For example, a conceptual site model would be more complex when factoring in the

evaluation of both ecological and human health receptors. For larger, more complex sites, the Site

Investigation and Remedial Investigation phases will typically proceed in an iterative process, which

will act to incrementally refine the CSM expands and builds as the information is gathered.

It should be noted that the conceptual site model can change significantly as the investigation

proceeds and all data (soil, ground water, surface water, air, sediment) must be continually and

collectively evaluated over time. For example, changes in groundwater use, changes due to partial or

evolving remedial actions over time can affect the understanding of site conditions and in turn the

conceptual site model. New information should be utilized to modify or improve the conceptual site

model even if it changes a previously "established" conceptual site model.

During the early development of the conceptual site model, assumptions may be useful. The

conceptual site model should clearly identify the assumptions made about physical, chemical and

biological processes associated with the site and/or area of concern throughout all phases. The

assumptions employed in the conceptual site model are typically verified or adjusted based on

further information from subsequent phases of investigation. This iterative process is essential to the

development of a comprehensive conceptual site model.

When using the conceptual site model, the user should identify those components (e.g., source,

migration pathway, receptor) that may represent data gaps that may need to be expanded. As

previously identified in Section 5.1.3, development of the conceptual site model should also include

an evaluation to identify potential data gaps based on sources of data uncertainty as described in

“Technical and Regulatory Guidance for the Triad Approach: A New Paradigm for Environmental

Project Management” (ITRC, December 2003).

5.5 Examples of Development and Application of the Conceptual Site Model

Examples in Appendix B of this document will assist the investigator in understanding how to

develop, apply and describe the conceptual site model. These examples include:

• Example B1: conceptual site model for complex site underlain by fill with potential multi-media

pathways and receptors

• Example B2: Applying a Conceptual Site Model to Potential Indoor Air Migration

Examples in Appendix C of this document are illustrations of how to present case scenarios during

different phases of an investigation.

• Figure C1-1: Schematic of a site showing a single AOC and its proximity to a building during a

Preliminary Assessment.

• Figure C1-2: Flow chart showing the information known during the Preliminary Assessment.

Page 23 of 46

• Figure C2-1: Schematic of a site showing sampling conducted and the site-specific information

collected for a single AOC during the Site Investigation.

• Figure C2-2: Flow chart showing sampling data and evaluation of potential pathways for the

Site Investigation.

Page 24 of 46

6.0 References

ASTM CSM Guidance (ASTM E1689-95 (2008))

ATSDR, 2005. Public Health Assessment Guidance Manual (2005 Update). United States

Department of Health and Human Services, Agency for Toxic Substances and Disease Registry

(ATSDR). Atlanta, GA. January 2005.

Carr, D. B., L. C. Levy, and A. H. Horneman. 2011 "Stylistic Modeling of Vadose Zone Transport

Insight into Vapor Intrusion Processes" Presentation no. 08 at US EPA/AEHS Foundation West

Coast Conference on Soils Sediment, Water and Energy, San Diego, California, March 15, 2011.

DeVaull, G.E., R.A. Ettinger, J.P. Salanitro, and J.B. Gustafson. 1997. “Benzene, Toluene,

Ethylbenzene and Xylenes [BTEX] Degradation in Vadose Zone Soils during Vapor Transport:

First-Order Rate Constants.” In Proceedings of the Petroleum Hydrocarbons and Organic Chemicals

in Groundwater Conference: Prevention, Detection and Remediation, November 12-14, 1997,

Houston, TX. Ground Water Publishing Company, Westerville, Ohio, 365-379.

Rivett, M.O. 1995. “Soil-Gas Signatures from Volatile Chlorinated Solvents: Borden Field

Experiments,” GROUND WATER, 33(1).

“Technical and Regulatory Guidance for the Triad Approach: A New Paradigm for Environmental

Project Management” (ITRC, December 2003).

U.S. Environmental Protection Agency (USEPA). 2004. “Air Toxics Risk Assessment Reference

Library Volume 1, Technical Resource Manual,” ICF Consulting

Fairfax, Virginia, April 2004.

U.S. Environmental Protection Agency (USEPA). 2004a. “User’s Guide for Evaluating Subsurface

Vapor Intrusion into Buildings,” Office of Emergency and Remedial Response, Washington, DC

http://www.epa.gov/oswer/riskassessment/airmodel/ johnson_ettinger.htm.

Page 25 of 46

Appendix A

Conceptual Site Model

Checklist

Page 26 of 46

CONCEPTUAL SITE MODEL

This is an optional checklist that identifies the types of information which could be collected during

the remedial process. All items on this checklist may not apply to each site and depending upon the

complexity of the site, there may be additional information required to complete the development of

the conceptual site model.

Prepared By: _____________________________________

Site Name:

Site Address:

NJDEP Case #:

City, State:

NJDEP PI #:

Item Evaluation Criteria Comments/Discussion:

5.1

Release Point/Material/Estimated

Volume/Date of Discovery

Description of Sources, Pathways,

and Receptors

Initial Corrective Actions

Summary of Impacted Media

Soil:

Ground water:

Surface Water:

Sediment

Air:

IEC Conditions / Corrective Actions

Taken

Soil:

Ground water:

Surface Water:

Air:

At a minimum, a Site Map, depicting site features and areas of concern (AOCs), should be

included as part of Section 5.1.

5.2

Description of conceptual site model

Scope

DISCUSSION:

Site Wide / area of concern only / Offsite Impact:

Page 27 of 46

5.2

Contaminants of Concern (COC)

COC in Soil

COC in Ground water

COC Vapor Phase

Non-Aqueous Phase Liquid

Potential Migration Pathways and Regulatory Cleanup Goals (Human Health and

Ecological)

Soil

Ground water

Surface Water

Vapor (Soil Gas / Indoor Air)

Airborne

Other (if applicable)

Sensitive Receptors

Local Ground Water Designation or Use

# Residential Wells

(distance/direction from site)

# Municipal Wells

(distance/direction from site)

Surface Water Bodies

(distance/direction from site)

Public Community Water Supply -

surface water intakes.

Residential Buildings

Identify all Public Use Areas w/in 200

feet

Summarizing Available Information

Historical and Current Site Use/Status

Site & Adjacent Properties Usage / Zoning

Site

North Adjacent

East Adjacent

South Adjacent

West Adjacent

Subsurface Utilities / Depth to Invert

Soil

Lithology

Page 28 of 46

5.2

Depth to ground water

Smear zone

Depth to bedrock

Heterogeneities

Proximity to surface water wetlands

Soil cover

Proximity to buildings

Utilities / preferential pathways

Ground Water

Ground water flow

Depth to water trends

Hydraulic gradient

Porosity / Permeability

Hydraulic conductivity

Hydraulic radius of influence

Location of recharge and discharge

areas

Utilities / preferential pathways

Location of any pumping influence

Surface Water

Stressed vegetation/seeps/sheen

Discolored soil / sediment

Historic ecological study conclusions

Ground water flow

Ground water COCs in excess of surface

water Standards

Presence of background contamination

Note: Sediment sampling and assessment should be conducted when there is evidence

of a discharge to surface water pursuant to N.J.A.C. 7:26E-3.8 (b).

Air (Soil Gas/Indoor Air)

Ground water in excess of Screening

Levels within 30 feet from a building

Free product present within 100 feet from

a building (currently or historically)

Non-petroleum compounds present

within 100 feet from a building

Page 29 of 46

5.2

Could historical levels of ground water

COCs which are not currently above

screening levels result in a VI concern?

Presence of a basement / sump

Current usage of the building

Condition of basement floor/walls or slab

Presence of ground water or free

product in the basement or sump

Landfill located on or adjacent to the site

Soil gas or indoor air impact in excess of

applicable screening levels

Methanogenic conditions are present

Other identified risks (ex: odor)

Identification of Human and Ecological Receptors

within the complete extent of the investigation area

COCs in soil, surface water and sediment

Current and future exposed species

Environmentally Sensitive Areas (ESAs)

Exposed population along each migration pathway

Migration pathways leading to ESAs

Exposure Pathways (Human)

Human population currently or potentially exposed

All relevant photographs, topographic maps, geologic quadrangle maps, etc. should be included

as part of Section 5.2.

5.3

Remedial Selection

Remedial actions taken

Area(s) remediated

Remediation effectiveness

Remediation Action Outcome (RAO)

RAO justification

Post RAO monitoring plan

Classification exception area length / duration (if applicable)

Variances

Page 30 of 46

5.3

Attachments:

Site Location Map, Local Area Map, Site Map, Soil Data Maps, Potentiometric Surface Map,

Ground Water Chemical Data Maps, Soil Boring Logs, Well Construction schematics, Geologic

Cross-Sections, Potable Well Radius Map, Soil Data Tables, Historic Ground Water Conditions

Table, Hydrographs, and Ground Water Plume Model, and/or Remedial System Layout, and

Process and Instrumentation Diagram

Page 31 of 46

Appendix B

Examples of Development and Application

of a Conceptual Site Model

Page 32 of 46

Example B1: Conceptual Site Model for Complex Site

An initial conceptual site model was developed and presented to understand the potential sources of

contamination, contaminants of potential concern, potentially affected media (soil gas, soil, and ground

water), and transport and exposure pathways that could potentially impact human or ecological

receptors. The conceptual site model synthesizes what is known to date into a snapshot that

communicates the site physical setting and contaminants of potential concern discharge or exposure

mechanisms. Based on the findings of the SI, the initial conceptual site model was updated and the

current conceptual site model is presented as described below.

Description of Sources, Pathways and Receptors

Results obtained from previous investigations indicated that there are contaminants of potential concern

in soil in all parcels, and in ground water. Figure B1-1 illustrates their occurrence and associated

potential exposure pathways. As illustrated, metals, Extractable Petroleum, Polycyclic Aromatic

Hydrocarbons, and Polychlorinated Biphenyls have been detected in subsurface soil. Metals, Extractable

Petroleum Hydrocarbons, Polycyclic Aromatic Hydrocarbons, and Volatile Organic Compounds

(VOCs) have also been detected in ground water. Soil gas samples had not been collected previously.

The likely sources of these contaminants of potential concern are the historic fill material, former fuel

use and storage, and shipbuilding and other industrial operations located at the site. Chemicals may have

been placed during bay infilling, spilled on the ground surface or released in the subsurface soil and

leached into shallow ground water.

Some contaminants of potential concern including arsenic, cadmium, copper, chromium, nickel,

thallium, vanadium, and zinc are also naturally occurring in the native rock and soil. Ground water

contaminants may have spread following the direction of the shallow ground water gradient.

VOCs in soil and ground water also may have volatilized into the soil pore space above the ground

water table.

Based upon the types of chemicals present at the site and the media in which the chemicals are present,

the following mechanisms for chemical transport have been identified for the site (Figure B1-1):

• volatilization of VOCs from soil and ground water into soil pore space (soil gas);

• leaching of contaminants of potential concern from soil into ground water; and

• transport of contaminants of potential concern in ground water via ground water flow.

The following potential human exposure routes for chemicals have been identified for the

site (Figure B1-1):

• inhalation of VOCs volatized from soil gas;

• dermal contact inhalation and incidental ingestion of soil particulates; and

• dermal contact with ground water.

The site ground water is not currently used for or planned to be used for domestic purposes in the future.

The following ecological exposure routes for chemicals have been identified for the site (Figure B1-1):

Page 33 of 46

• inhalation of VOCs volatized from soil gas in burrow air;

• incidental ingestion and dermal contact of soil particulates;

• plants’ direct uptake of contaminated ground water and contaminated sediments; and

• ingestion and contact with contaminated surface water.

Exposure Assessment

In evaluating the potential human health risks posed by a site, it is necessary to identify the populations

that may potentially be exposed to the chemicals present, and to determine the pathways by which these

exposures may occur. Identification of the potentially exposed populations requires evaluating the

human activity and anticipated land use at the site.

Once the potentially exposed populations are identified, the complete exposure pathways by which

individuals in each of these potentially exposed populations may contact chemicals present in the soil

gas, ground water, and soil at the site are determined. A complete exposure pathway requires the

following three key elements:

• chemical contaminant source;

• migration route; and

• point for human exposure (e.g., soil, air, or water);

An exposure pathway is not complete unless all three elements are present.

Figure B1-2 is an example of a schematic diagram showing the relationship between a chemical source,

exposure pathway, and potential receptor at this site.

Page 34 of 46

Figure B1-1

Page 35 of 46

Figure B1-2

Page 36 of 46

Example B2: Applying a Conceptual Site Model

to Potential Indoor Air Migration

In order to construct a complete Conceptual Site Model (CSM) to assess potential impacts from volatile

organic compounds (VOCs) in” the subsurface, “the investigator must evaluate” the four main vapor

transport mechanisms; they are listed in section 5.2.5.5 and used as heading in the below discussion.

Diffusion of vapors from sources in the unsaturated zone

Diffusion occurs as a result of a concentration gradient between the source and the surrounding area; it

can result in the upward, lateral or downward migration of vapors through the vadose zone. The location

of the source is an important factor influencing the direction of vapor migration. Identifying soil gas

concentration gradients may help determine the location of unidentified vapor sources. For recalcitrant

VOCs that degrade slowly in the subsurface, limited case data and research studies suggest there may be

a significant time lag (e.g., months to years) between source removal and significant dispersion of

vapors that remain in the subsurface (Rivett 1995, Carr, et. al. 2011); variable mass storage capacity of

vapors in the vadose zone should be expected.

Diffusion of vapors from sources in shallow groundwater

Shallow ground water contamination and/or Non Aqueous Phase Liquid near the water table can act as a

source for diffusion resulting in the upward or lateral migration of vapors through the vadose zone.

Depending on the hydraulic conductivity, hydraulic gradient, aquifer heterogeneity, time since release of

chemicals and natural attenuation processes, the distribution of volatile chemicals in ground water may

extend considerable distances.

As discussed above, for recalcitrant VOCs investigators should consider whether ground water

concentrations and their distribution have, or could have, recently decrease/changed. Such changes

should impact the decision of whether a VI investigation is warranted for a potential receptor and

influence the overall scope of the area to be investigated. Those decisions should be based on an

accurate CSM and not solely on current ground water VOC concentrations because the vadose zone

could have considerable storage capacity; it may continue to be a source for VOCs for some period after

ground water concentrations have decreased significantly (Carr, et. al. 2011).

Diffusion of vapors in the vadose zone from shallow ground water contamination is illustrated below.

Advective/convective transport of vapors

The horizontal and vertical movement of vapors located near a building foundation is often affected

within an area referred to as the “zone of influence” (see Figure B2-1 below). Chemicals entering this

zone are drawn into the building via soil gas advection and convection resulting from building interiors

that exhibit a negative pressure relative to the outdoors and the surrounding soil. The reasons for this

pressure differential include: factors relating to operation of heating, ventilating and air conditioning

system including inadequate combustion or makeup air and unbalanced air supply and exhaust systems

• the use of fireplaces and other combustion sources, which results in venting of

exhaust gases to the exterior

Page 37 of 46

• the use of exhaust fans in bathrooms and kitchens

• higher temperatures indoors relative to outdoors during the heating season or as a

result of solar radiation on rooftops

• pressure exerted on the wall of a building caused by wind movement over the

building (Bernoulli’s principle).

The combination of these actions/conditions results in a net convective flow of soil gas from

the subsurface through the building foundation to the building interior. As would be expected

from the above list, indoor air volatile concentrations are generally higher during the heating

season in homes affected by vapor intrusion.

The CSM shown below suggests a permeable ground cover. If impermeable ground cover

exists on either or both sides of a structure that condition could result in higher soil vapor

concentrations near the building, a higher soil gas flow rate (Qsoil) and thus higher levels in

indoor air than in the scenario with permeable ground cover.

Figure B2-1

Advective and Convective Transport Near Buildings

Source: USEPA 2004b

Page 38 of 46

Vapor Migration Through Preferential Pathways

In preparation of each conceptual site model, investigators should look for the presence and locations of

natural and anthropogenic pathways in the subsurface with high gas permeability through which vapors

can rapidly migrate. Naturally occurring fractures and macropores may facilitate vertical or horizontal

vapor migration while anthropogenic features such as utility conduits would likely facilitate horizontal

vapor migration due to their shallow depth (USEPA 2002). Evaluate buildings that are, or may become,

inhabited if they are associated with a preferential pathway that is within some reasonable distance of a

source area (based on professional judgment).

Investigators should also evaluate the potential for vapor intrusion in situations where a preferential

pathway leading to a structure runs near or through a source area. For sources containing aerobically

degradable contaminants, however, it is unlikely that sufficient vapors will reach the structure to result

in a vapor intrusion problem unless the pathway and structure are both very close to the vapor source.

Biodegradation of benzene, toluene, ethylbenzene and xylene vapors in the vadose zone has been shown

to be a very efficient process as long as sufficient oxygen is available (DeVaull, et al. 1997). Thus, if a

preferential pathway is not close to a source area, biodegradable vapors would likely degrade before

reaching the pathway and/or within the pathway before reaching the structure.

Page 39 of 46

Appendix C

Illustrations of Simple Conceptual Site Model

Page 40 of 46

ILLUSTRATIONS OF SIMPLE CONCEPTUAL SITE MODEL

Examples in Appendix C of this document are illustrations of how to present case scenarios during

different phases of an investigation.

• Figure C1-1: Schematic of a site showing a single AOC and its proximity to a building during a

Preliminary Assessment.

• Figure C1-2: Flow chart showing the information known during the Preliminary Assessment.

• Figure C2-1: Schematic of a site showing sampling conducted and the site-specific information

collected for a single AOC during the Site Investigation.

• Figure C2-2: Flow chart showing sampling data and evaluation of potential pathways for the Site

Investigation.

Page 41 of 46

Page 42 of 46

Figure C1-2: Flow chart showing the information known during the Preliminary Assessment

Site Name: Vaste Warehousing Inc.

Address: 555 Vaste Lane

City/County: Forest City, Bergen County

NJDEP Case #: 000000

NJDEP PI #: G000000

Facility History: Facility was constructed in 1985 as

warehouse for paper products.

AOC 1 is an area of stained soil/gravel less than 25 sq ft. AOC

1 is the only AOC on-site. Review of Aerial photographs,

Sanborn maps, and Staff interviews indicate no other potential

Discharges. Surrounding properties are zoned

commercial/industrial

No IEC condition noted.

Actions Taken: Soil samples collected for Target Compound

List plus TICs/Target Analyte List (TCL + TICs/TAL). VOC

sample collected at 5 feet based on highest PID reading. All

other parameters collected at 0-6 inches

Impacted media: Based on staining, soil is expected to be

impacted. Ground water has a potential impact, while air (>

200 feet to structure) and surface water (> 200 feet to

closest feature) are unlikely to be impacted.

Ground Water

Pathway

Complete?

Unknown

Air Pathway

Complete?

Unknown

Surface Water

Pathway

Complete?

Unknown

Area of

Stained Soil

AOC 1

Soil Pathway

Complete?

Unknown

Soil sample

SB-1 collected

for TCL and

TAL @ 0-6”

VOC collected

at highest PID

500 PPB @ 5 ‘

Page 43 of 46

Page 44 of 46

Figure C2-2 Flow chart showing sampling data and evaluation of potential pathways for the Site Investigation.

Site Name: Vaste Warehousing Inc.

Address: 555 Vaste Lane

City/County: Forest City, Bergen Co.

NJDEP Case #: 000000

NJDEP PI #: G000000

Facility History: Facility was constructed in 1985 as warehouse

for paper products.

AOC 1 is an area of stained soil/gravel less than 25 sq ft. AOC 1 is

the only AOC on site. Review of Aerial photographs, Sanborn

maps, and Staff interviews indicate no other potential Discharges.

Surrounding properties are zoned commercial/industrial

No IEC condition noted.

Actions Taken: Soil sample SB-1 collected at 5’ for VOCs showed

8,000 ug/kg of xylene. All other parameters non-detect. Ground

water sample collected at 15’ for VOCs. Sample contained 200 ug/l

of xylene.

Impacted media/pathway:

Soil Direct Contact: All parameters below direct contact criteria.

Soil Impact to Ground Water: Xylene above Default Soil IGWC

therefore ground water investigated

Ground Water: Xylene detected below GWQC. Air: Pathway

incomplete

Surface Water: Pathway incomplete.

* As determined in accordance with applicable Technical Guidance

Soil sample SB-

1 shows Xylene

@ 8000 ug/kg

Soil Impact to Ground

Water Pathway?

(xylene > IGWC) All

other parameters

non-detect. Further

evaluation needed

Soil Direct Contact

Pathway?

(< residential direct

contact SRS) All other

parameters non-

detect. No further

evaluation

Ground Water

Pathway?

(< GWQC). All

other parameters

non-detect No

further evaluation

Air Pathway?

Incomplete *

Surface Water

Pathway?

Incomplete *

Area of Stained

Soil AOC 1

Ground Water

sample collected

from TWP-1 @ 15’.

Xylene @ 200 ug/l

Page 45 of 46

Appendix D

Acronyms

Page 46 of 46

ACRONYMS

AOC area of concern

COC contaminants of concern

CSM conceptual site model

ESA environmentally sensitive areas

IEC Immediate Environmental Concern

ITRC Interstate Technology and Regulatory Council

LSRP Licensed Site Remediation Professional

NAPL nonaqueous phase liquid

N.J.A.C. New Jersey Administrative Code

NJDEP New Jersey Department of Environmental Protection

PA/SI Preliminary Assessment/Site Investigation

RI Remedial Investigation

RAO Response Action Outcome

USEPA United States Environmental Protection Agency

VOC volatile organic compound