United States
Environmental Protection Agency
Office of Solid Waste and
Emergency Response (5102G)
EPA542-F-11-011
July 2011
Environmental Cleanup Best Management Practices:
Effective Use of the Project Life Cycle Conceptual Site Model
Office of Superfund Remediation and Technology Innovation
Quick Reference Fact Sheet
The U.S. Environmental Protection Agency (EPA)
supports the use of best management practices
(BMPs)* as a mechanism for maximizing technical
effectiveness and resource efficiency in the
execution of site assessment and cleanup projects.
This fact sheet is the first in a series of documents
that address conceptual site models (CSMs). A more
comprehensive document is planned that will detail
techniques to develop and maintain an accurate CSM
as a primary planning and decision making tool used
to identify and manage site uncertainty that can
inhibit effective project decision making. This fact
sheet summarizes how environmental practitioners
can use CSMs to achieve, communicate, and
maintain stakeholder consensus on site
understanding, while satisfying the technical and
quality objectives required for each stage of a
cleanup project's life cycle. The focus is on defining
stages and products of CSMs along with potential
applications of CSMs at various stages of a project
life cycle. Content herein is presented in a Superfund
Program context; however, to the extent practical,
text has been written to maximize applicability in
other programs and regulatory frameworks. Other
agencies and programs may find these concepts
useful and environmental cleanup practitioners are
encouraged to explore the utility and integration of a
project life cycle CSM within their own program
requirements and deliverable schedules.
* Best Management Practices (BMPs) are, in general, methods or
techniques found to be the most effective and practical means in
achieving an objective while optimizing the use of resources.
BMPs, such as those described herein, however, are not
programmatic requirements.
Purpose and Audience
The Conceptual Site Model (CSM) is an iterative,
'living representation' of a site that summarizes and
helps project teams visualize and understand
available information. This fact sheet demonstrates
the utility of using the CSM to assist Superfund
project teams, hazardous waste site cleanup
managers, and decision makers throughout the life
cycle stages of investigation and cleanup. It also
encourages the creation and revision of a CSM as a
primary project planning and management tool.
The ability to efficiently access and interpret data is
essential to guiding project teams through the entire
cleanup process, from project planning to site
completion. Development and evolution of a CSM can
address the unique needs of each stage in a project's
life cycle, and provide a valuable tool for successful
environmental cleanup. The level of effort necessary
to develop specific CSM components should correlate
with the level of site maturity, site complexity, and
the magnitude of the characterization and cleanup
challenges project teams face.
The CSM uses a concise combination of written and
graphical work products to portray both known and
hypothesized site information. At more mature sites,
this information is often contained in a variety of
reports, data sets, and electronic or hard copy
formats where the construction and use of a CSM
synthesizes multiple independent data sets and
maximizes the value of historical information. A
range of tools, from simplified renderings to more
complex visualization tools, are used to capture and
communicate existing information and focus future
data collection to fill data gaps and reduce key site
uncertainties. The CSM serves as the framework for
incorporating new data as it becomes available
during characterization and remediation. A detailed,
up-to-date, and accurate CSM can be very beneficial in
supporting decisions related to key project elements,
such as cumulative risk, remedy selection, remedy
implementation, site completion, and site reuse.
Effective use of the CSM is also a critical BMP that
facilitates technical team decision making while
supporting stakeholder communication and
consensus building. By facilitating efficient real-time
evaluation of data, CSM elements provide a platform
to inform decision makers in a manner that can help
limit the number of field mobilizations necessary to
Effective Use of the Project Life Cycle Conceptual Site Model
-------
characterize a site, minimize the need to re-
characterize a site late in a project's life cycle, and
optimize elements of remedy implementation. A
comprehensive CSM synthesizes chemical data with
geologic, hydrogeologic, and other site information to
enhance a project team's ability to develop solutions
to ensure protectiveness, effectively manage
resources, and limit the environmental footprint of
site cleanup activities.
Conceptual Site Model Life Cycle
The life cycle of a CSM mirrors the common
progression of the environmental cleanup process
where available information is used, or new
information acquired, to support a change in focus for
a project. The focus of a CSM may shift from
characterization towards remedial technology
evaluation and selection, and later, remedy
optimization. As a project progresses, decisions, data
needs, and personnel shift as well to meet the needs
of a particular stage of a project and the associated
technical requirements.
Figure 1 shows the relationship of the CSM life cycle
stages to various environmental regulatory
programs and the applicability of other BMPs such
as comprehensive systematic planning, use of
dynamic work strategies, and real-time
measurement technologies. Note that CSMs become
increasingly quantitative and decreasingly
conceptual in nature as data are collected, data gaps
filled, and CSM elements that help depict site data
mature.
The project life cycle CSM presented in this technical
bulletin and summarized in the adjacent text box
consists of six stages. These are not six different
CSMs; rather, they are representations of the CSM as
it is evolved through defined states of maturity and
purposes over a project's life cycle. Whether early or
late in the project life cycle, development of the
preliminary and baseline CSMs necessitates an initial
compilation, synthesis, and presentation of the CSM
to the technical team and stakeholders to facilitate
systematic planning. Regardless of where in the
assessment and cleanup process a particular site
resides these earliest CSM versions can potentially
serve as milestone deliverables. These early stage
versions take advantage of text, figures, tables, and
potentially electronic 3-D data visualizations to
compile, interpret, and present the CSM. Project
teams are encouraged to consider existing schedules
and scope of programmatic deliverables to integrate
these CSM components early in the systematic
planning process. Project teams can initiate
development of a project life cycle CSM at any stage of
an active project to serve as a tool to help facilitate
site decision making. The phase of a project and the
adequacy of the existing CSM or project data will
indicate what stage of the CSM life cycle is most
appropriate.
Simple drawings and concepts are commonly used to
communicate early project stage CSMs. As the level of
information and complexity increases, the ability of a
CSM to capture and synthesize new data in support of
decision making can be significantly improved
through the use of visualization platforms,
appropriate data management strategies, and
decision support tools.1 These tools and strategies
enable the CSM to be revised as more site information
is collected and adapted to support the changing
decision making needs of a project.
Six Stages of the Project Life Cycle CSM
Key Points in the Development of a CSM
(1) Preliminary CSM Stage - Project milestone or
deliverable based on existing data; developed prior to
systematic planning to provide fundamental basis for
planning effort.
(2) Baseline CSM Stage - Project milestone or deliverable
used to document stakeholder consensus/divergence,
identify data gaps, uncertainties, and needs; an outcome
of systematic planning.
Key Points in the Evolution and Refinement of a CSM
(3) Characterization CSM Stage - Iterative improvement
of CSM as new data become available during
investigation efforts; supports technology selection and
remedy decision making.
(4) Design CSM Stage - Iterative improvement of CSM
during design of the remedy; supports development of
remedy design basis and technical detail.
(5) Remediation / Mitigation CSM Stage - Iterative
improvement of CSM during remedy implementation;
supports remedy implementation and optimization
efforts, provides documentation for attainment of
cleanup objectives.
(6) Post Remedy CSM Stage - Comprehensive site
physical, chemical, geologic, and hydrogeologic
information of CSM supports reuse planning; documents
institutional controls and waste left on site; and other
key site attributes.
Effective Use of the Project Life Cycle Conceptual Site Model
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Best
General Management VCUP
Environmental CSM Life Cycle Practices CERCLA-Superfund RCRA Brownfields UST Varies by IRP/ERP MMRP
Cleanup Steps SPP DWS/ state
RTMT
SITE ASSESSMENT
SITE INVESTIGATION
AND ALTERNATIVES
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Site inspection (SI) Assessment (ESA) r . B
National Priorities List (NPL) Initial Response ^RSte
No Further Remedial Action PrrSSjmwwPPl
Planned (NFRAP)
Remedial Investigation/ Facility Investigation Phase II ESA SI RI/FS RI/FS RI/FS
Feasibility Study JRI/FS) (RFI) Corrective Action NFRAP
Removal Actions - Emergency/ Corrective Measures Plan (CAP)
Time Critical/Non-Time-Critical Study (CMS)
Proposed Plan Statement of Basis Remedial Action Cleanup Selection ROD Proposed Plan Remedy Selection
Record of Decision (ROD) (SB* Plan (RAP) RQD
Final Decision
and Response to
Comments
Remedial Design (RD) Corrective Measure Cleanup and Corrective Action RD RD RD
Remedial Action (RA)- Implementation Development . Low-impact site RA RA-lnterim TimeCritical
Interim and Final cleanup and Final Removal Action
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- Risk-based Remedy in
remediation Place (RIP) RA
- Generic remedies RIP
- Soil matrix cleanup
Operational & Functional Period O&M Property LTM O&M Shakedown period Shakedown period
Operation & Maintenance (O&M) On-site inspections Management ^ Operating Properly Long Term
Long term monitoring (LTM) and oversight Long-term O&M and Successfully Management
P. ,- Redevelopment O&M
°Ptlmlzatlon Activities (Private- , TM
Long Term Response Action and Public-led)
(Fund-lead groundwater/surface
water restoration)
Construction Complete (CC) Certification of CC No Further Action CC Response RC
Preliminary or Final Close Out Completion property (NFA) Complete (RC) NFA
Report (PCOR/FCOR) Corrective Action Management NFA
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Site Deletion Controls
O&M as appropriate
Abbreviations:
SPP = Systematic Project Planning
DWS = Dynamic Work Strategies
RTMT = Real Time Measurement Technologies
CERCLA = Comprehensive Environmental Response.
Compensation and Liability Act
RCRA = Resource Conservation and Recovery Act
UST = Underground Storage Tanks
VCUP = Voluntarily Clean Up Programs
IRP/ERP = Installation Restoration Program/
Environmental Restoration Program
MMRP = Military Munitions Response Program
Figure 1. Crosswalk of Regulatory Program Stages and CSM Life Cycle Phases. Use of terminology from regulatory frameworks is not intended to supplement any specific
programmatic requirements or guidance; however, use of CSM components in a flexible and comprehensive framework can facilitate site decision making during the entire site-
cleanup process, irrespective of the environmental program driving site cleanup. Using SPP, evolving the CSM, and leveraging DWS and RTMT at each key project stage can
improve project efficiency and effectiveness.
Note: The width and gradation of the blue arrows demonstrating BMPs indicate the relative level of effort applied and the resulting impact and value of performing the BMPs at
the indicated project stages.
Effective Use of the Project Life Cycle Conceptual Site Model
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Where key stakeholders change, particularly project
managers, regulatory personnel, and contractors,
consistent use of a project life cycle CSM serves to
document and maintain the "state of knowledge"
about a site. Similarly, review of historical iterations
of the project life cycle CSM provides context for new
team members to understand previous site decisions
and can facilitate effective transition of supporting
data sets, data management strategies, and
visualization platforms.
Preliminary CSM
EPA requires that a systematic planning process be
employed to plan all environmental data operations.2
The Preliminary CSM, therefore, can act as a starting
point for compiling and synthesizing existing
information to support building stakeholder
consensus, identifying data gaps and uncertainties,
and determining subsequent data needs.
The Preliminary CSM provides a comprehensive
overview of the site, based on available site-related
documents, with information relevant to the
identified problems. Interviews with site owners and
other stakeholders, historical or regional
geologic/hydrogeologic information, and third-party
information such as historical aerial photographs,
electronic environmental databases, property tax
maps, and Sanborn Maps are also considered. The
evaluation and synthesis of this information forms
the basis for developing and presenting the
Preliminary CSM to systematic planning participants.
Figure 2 shows a pathway network receptor diagram,
which is commonly used as a CSM to support risk
assessment. A project life cycle CSM includes this
information, and to support investigation, design, and
remedy implementation project phases, it also
includes other elements, such as known and
suspected contaminants of potential concern
(CO PCs), locations of probable source areas, the
mechanisms and timing of historical and potential
releases, affected environmental media, contaminant
distribution data, potential migration pathways, and
potential receptors.
Visual elements of a Preliminary CSM can range from
simple sketches, to basic two-dimensional (2-D)
graphics such as maps and cross sections, to more
advanced three-dimensional (3-D) visualizations.
The complexity of the CSM at this stage depends on
the volume and state of data (electronic or hard copy)
along with any prior CSM component development.
A critical strategic output of a systematic planning
effort, the Baseline CSM is an improved, more
informative version of the Preliminary CSM used to
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Figure 2. Example Pathway Receptor Network Diagram. Commonly referred to as a CSM, the pathway receptor network
diagram is an important element of the project life cycle CSM, used to ensure the incorporation of human and ecological exposure
information in project planning and implementation.
Effective Use of the Project Life Cycle Conceptual Site Model
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help identify data gaps and information needed to
meet key project objectives. The Baseline CSM
documents stakeholder consensus (or divergence) on
known site conditions; uncertainty hypotheses; data
gaps, needs, and collection plans; and potential
remedial challenges. Armed with this knowledge,
project teams can leverage the Baseline CSM to
identify needs for data types, density, quality
objectives, and quality indicators such as precision
and accuracy.
At this point in the project planning process, the
project team can also consider the need for
collaborative data to support hypotheses testing and
uncertainty reduction, risk assessment, technology
evaluation and selection, and design for the most-
probable remedial technologies. The scale and
distribution of data gaps identified provides the basis
for designing a dynamic work strategy and
subsequent data collection efforts. The need to
perform a demonstration of methods applicability3 to
understand site and matrix specific analytical
performance or optimize sampling strategies, is
generally identified at this stage of the planning
process.
A 2-D diagram used to depict the Preliminary CSM for
the Cache La Poudre River Site4 project in Colorado is
shown in Figure 3. The diagram and supporting CSM
components effectively facilitated an agreement
between the project team to follow separate, but
related, paths to address questions posed by
stakeholder groups with differing views of site
conditions and processes. During systematic
planning, the project team did not reach consensus on
a single Baseline CSM; however, the team agreed to
use divergent CSM viewpoints to identify all data and
information needs necessary to resolve to one CSM
version and facilitate key project decision making.
Characterization CSM Stage
Using the Baseline CSM as its starting point, the
Characterization CSM is used to efficiently capture
and synthesize data generated during site
characterization efforts. This CSM is updated
continually at an agreed upon frequency or in relation
to key data collection efforts. When used effectively,
the Characterization CSM helps to identify and
manage stakeholder uncertainty associated with
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FORT COLLINS, COLORADO
PRELIMINARY
CONCEPTUAL SITE MODEL
U.S. EPA REGION VIII
IN COOPERATION WITH
BROWNFIELDS TECHNOLOGY SUPPORT CENTER
Figure 3. Preliminary CSM Representation. This Preliminary CSM summarizes general site information, including primary
site attributes, geologic stratigraphy, groundwaterpotentiometric surface and flow direction, groundwater-surface water
relationship, and presumed extent of soil and groundwater contamination. This representation of a CSM can be an effective
method of communicating site conditions to a diverse audience in an easy-to-understand format.
Effective Use of the Project Life Cycle Conceptual Site Model
-------
principle study questions like the nature and extent of
contamination, or identification of key
geologic/hydrogeologic features controlling fate and
transport processes.
Characterization CSM components capture and
synthesize data that can be used to support estimates
of cumulative risk and identification of immediate
risks to human health and the environment. The
Characterization CSM integrates key geologic,
hydrogeologic, and chemical data that can also be
used to support an effective screening of remedial
alternatives.
Figure 4 is a representation of the Characterization
CSM developed for the Poudre River Site project. The
CSM indicated that site contaminant type, sources,
and migration pathways were significantly more
complex than originally understood, affecting the
goals of subsequent characterization efforts. At this
stage of the project, the use of collaborative data sets,
comprised of field- and fixed-based laboratory
analyses, improved risk characterization and
facilitated collection of remedy design data during
site characterization efforts.
Characterization efforts are becoming more
comprehensive because of the availability of field-
based, high-density data collection methods. These
high-resolution tools effectively mature the CSM
more quickly, particularly when data management
strategies (such as use of electronic data deliverables
and relational databases) are employed in
conjunction with 3-D visualization platforms.
More than any other CSM life cycle stage, the use of
real-time technologies for dynamic data collection
efforts requires the Characterization CSM to be
flexible and easily modified in 'real-time.' This need
is driven by the fact that the nature and extent of
contamination and related cumulative risks typically
are not yet well defined at this stage, thus the
evolution of significant site knowledge tends to occur
rapidly as characterization data are collected. The
tools used to frame, document, or depict the CSM
must therefore be capable of quickly and efficiently
capturing high-density data streams and translating
those data streams into predetermined formats.
Once contamination and related risks have been
adequately defined, projects typically shift focus to
the collection of physical and chemical data needed to
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U.S. EPA REGION Vnr
IN COOPERATION WITH
BROWNFIELDS TECHNOLOGY SUPPORT CENTER
Figure 4. 2-D Component of Characterization CSM. The Characterization CSM serves as a repository for the integration of
site attributes with field observation and measurement data. Depictions of integrated data guide investigation effortsand
support technology selection and remedy decision-making.
Effective Use of the Project Life Cycle Conceptual Site Model
-------
support technology selection and remedy design.
These data may be of a different focus or density scale
than characterization efforts aimed solely at
delineation. For example, additional physical
property testing of the matrix or refinement of
treatment zones, source zones, residual phase, and
dissolved plume components is used support
feasibility studies and future design considerations.
Information from these efforts can be incorporated
into the Characterization CSM and used for
subsequent decision-making.
Collection, evaluation, and synthesis of data used to
refine the Characterization CSM also supports the
development of key remedial project support
documents such as the Record of Decision (ROD) or
intermediate decisions such as the need for
implementation of an interim remedy.
Design CSM Stage
CSM elements are used in the design stage to help
identify additional information requirements and
synthesize data supporting the implementation of a
selected remedy. The Design CSM directly supports
the design basis for implementation of both pilot and
full-scale remedies at a site. Physical property data,
geologic and hydrogeologic conditions, or
contaminant concentrations and distribution may
need to be refined to optimize remedy design. For
example, elements of the Design CSM might be used
to plan and incorporate the results of hydraulic
conductivity profiling or geochemical parameters
testing to support the design of an in situ treatment
strategy. Geologic and hydrogeologic Design CSM
components support evaluation of important design
considerations such as radius of influence, tracer
tests, or aquifer geochemical characteristics like pH,
oxidation/reduction potential, and dissolved oxygen.
For performance-based projects, the Design CSM can
support development of metrics for system
installation and performance. The Design CSM
typically can be developed using the same data
management and 3-D tools as those used during the
characterization effort. Elements of the Design CSM
such as concentration ranges, mass estimates,
location, and spatial dimensions of source materials
can be used to help establish initial benchmarks, as
well as short-, medium-, and long-term metrics, to
measure and evaluate remedy/system performance.
This capability has direct application to support
documentation and data analysis for Five Year
Review, remediation optimization efforts, or both.
For project managers, elements of the Design CSM
can be used to develop supporting documentation for
solicitation of final design and construction contracts.
Figure 5 depicts elements of the Design CSM
developed for the Cache La Poudre River Site project.
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Figure 5. 2-D Component of Design CSM. The Design CSM captures key design considerations, such as site attributes; geologic,
hydrogeologic, and chemical information; and fate and transport processes, in support of remedy design.
Effective Use of the Project Life Cycle Conceptual Site Model
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CSM Case Study: NASA Ames Research Center / Naval Air Station Moffett Field
NASA and the U.S. Navy (USN) undertook a joint effort at their adjacent installations in Mountain View,
California, to inhibit the migration of a trichloroethene (TCE) groundwater contamination plume from
NASA property onto the adjacent USN facility. The project involved designing an air sparging/soil
vapor extraction (AS/SVE) system across a buried sedimentary paleochannel to intercept the plume
and limit the spread of contamination. A Remediation/Mitigation CSM was used to visualize real-time
field data to verify site geology, optimize the remedy design, and ensure its successful implementation.
Initial characterization was completed using cone penetrometer testing (CPT) and 3-D visualization to
identify optimized sampling locations to verify the adequacy of remedy design. CPT data were used
collaboratively with soil cores and air sparging test results to optimize air sparging well construction.
Core recoveries were poor because of the consistency of sands within the paleochannel, making the
CPT data essential to the proper design of the sparging system.
The project team verified the CPT data to optimize the AS/SVE systems design in real-time. Data were
introduced into 3-D visualization software, and images of subsurface lithology developed from CPT
data at locations where air sparging wells were also installed. The 3-D visualizations, such as Figure 6,
provided the basis for optimizing the air sparging system through reduction in well point quantities
and provided assurance that the remedy would accomplish project goals.
Figure 6. 3-D Visualization Component of Remediation/Mitigation CSM. The Remediation/Mitigation CSM enhances a
project team's ability to evaluate and modify remedial designs during implementation to minimize resources and maximize
remedy effectiveness.
Data from 1-foot sparging screened intervals were correlated with geologic logs and CPT data to
identify the specific design modifications needed. The data were also used to optimize the long-term
monitoring program for groundwater. Project results confirmed that using a real-time evolving CSM
to manage and visualize collaborative data enabled the cost-effective development of a sound design
basis, design, and successful remedy implementation.
Effective Use of the Project Life Cycle Conceptual Site Model
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The updated CSM includes new information on water
levels, well locations, soil gas, and a critical dense
non-aqueous phase liquid (DNAPL) migration
pathway identified in fractured bedrock. Using the
Design CSM as a guide, remedial efforts were targeted
to address a variety of site concerns. Elements
included: defining spatial dimensions for source
areas to aid hydraulic isolation; identification of
DNAPL migration pathways and river discharge
locations to design a sheet pile wall barrier and
hydraulic control system to limit DNAPL migration to
the Poudre River; and supporting the design of vapor
intrusion mitigation systems at some site buildings.
Remediation/Mitigation
CSM Stage
The Remediation/Mitigation Stage CSM can be used
to guide remediation/mitigation efforts, such as:
(1) Directing and documenting excavation
activities;
(2) Managing phased remediation programs;
(3) Managing remediation at separate operable
units or subunits of a site;
(4) Responding to changed conditions encountered
in the field; and
(5) Optimizing in situ and ex situ treatment remedy
implementation
This stage also includes operation and maintenance
(O&M), and long-term monitoring activities.
Continuous updating of the CSM during this stage can
be used to maintain stakeholder consensus, identify
potential challenges as remediation/mitigation
progresses, and support future remediation
optimization efforts.
The same CSM platform and data management
system employed during the previous CSM stages
typically can be used as the basis for the
Remediation/Mitigation CSM. Consistent platform
use may help project teams realize significant cost
savings during remediation/mitigation. For example,
efforts could be limited to minor modifications to
data fields or the addition of new software for system
evaluations.
The Remediation/Mitigation CSM also can be used to
assess performance metrics to help ensure that
remedies are operating according to design or other
project parameters. For example, information about
changing concentrations in a monitoring well can be
indicative of source depletion, rebound, or other
important processes effecting assessment of remedy
performance. Similar to the Design CSM, the
Remediation/Mitigation CSM can be used to refine
further the scale of design to ensure remediation
approaches are sized appropriately to limit costly
over- or under-designed systems. The higher
resolution areas of the CSM also serve to identify
focus areas of sites that may warrant special design
considerations, such as source zones, NAPL areas,
dissolved phase contamination, and residual
contamination. When the Remediation/Mitigation
CSM is updated as a remedy is implemented or
optimized, system design specifications and operating
protocols can be modified in real-time to adapt to
small-scale variations in site conditions.
As a remedy begins to achieve performance goals
such as cleanup or action levels, components of the
Remediation/Mitigations CSM can be used to support
documentation of site completion activities, including
issuance of the final close-out report and site deletion
under the CERCLA program; or certifying completion
or making a No Further Action determination under
other regulatory programs.
Post Remedy CSM Stage
While use of the CSM in the Remediation/Mitigation
stage can help project teams document the
attainment of remediation goals, the utility of a life
cycle CSM does not end here. The Post Remedy CSM
provides integrated and synthesized information that
can assist project teams with a variety of
documentation and redevelopment planning needs.
When the Remediation/Mitigation CSM is
appropriately and fully evolved throughout the
performance of a remedial action project, its end state
will generally serve as a Post Remedy CSM.
Applications of the Post Remedy CSM can help:
(1) Provide a basis for using statistical methods to
programmatically evaluate remedy effectiveness
and performance for sites meeting cleanup
goals;
(2) Document and leverage identified best
management and technical practices associated
with a remedy success;
(3) Document site remediation activities including
locations, dimensions, and concentrations of
waste left on site; institutional/engineering
controls; and other important remedy features;
and
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(4) Facilitate reuse planning by providing detailed
understanding of geologic/hydrogeologic site
conditions and key site physical or chemical
features.
Figures 7a and 7b are 'during and after' photographs
of the investigation and river restoration effort at the
Poudre River Site, which served as components of the
Post Remedy CSM, visually documenting the
completed site remediation and restoration effort.
The project life cycle CSM is a versatile and powerful
tool than can be used to support project and site
decisions unique to each stage of a cleanup project. A
CSM developed and maintained on a single platform
is highly effective at integrating new information into
existing data sets. This enables project teams to
understand the significance of new data in the context
of existing site understanding. Environmental
cleanup practitioners can use CSMs to achieve,
communicate, and maintain stakeholder consensus
on site understanding, while satisfying the technical
and quality objectives required to perform the project
successfully.
This fact sheet highlights CSM life cycle stages and
provides examples of how CSM components can be
leveraged to answer principal study questions and
address key site challenges. From documenting and
spatially defining the nature and extent of
contamination and providing key system design and
optimization parameters, to facilitating reuse
planning, the project life cycle CSM provides a
platform to capture, synthesize, and readily use
important site data and information.
Direct References
1 Decision support tools are interactive software tools
used by decisions makers to help answer questions,
solve problems, and support or refute conclusions.
For examples of available tools, visit
www.frtr.gov/decisionsupport/index.htm
2 EPA Requirements for Quality Assurance Project
Plans, EPA QA/R5 March 2001, page 2. EPA/240/B-
01/003. www.epa.gov/quality/qs-docs/r5-final.pdf
3 Information on addressing site uncertainty,
developing DWS, and demonstrating methods
applicability can be found in the following resource:
U.S. EPA. 2008. Demonstrations of Method
Applicability under a Triad Approach for Site
Assessment and Cleanup Technology Bulletin;
August, www.clu-in.org/download/char/
demonstrations of methods applicability.pdf
4 A full case study of the Cache La Poudre River Site
project can be accessed at: Innovations in Site
Characterization Case Study: The Role of a Conceptual
Site Model for Expedited Site Characterization Using
the Triad Approach at the Poudre River Site, Fort
Collins, Colorado, www.cluin.org/download/char/
poudre river case study.pdf
Select EPA Superfund References
Pertaining to CSMs
"The CSM is a three-dimensional "picture" of site
conditions that illustrates contaminant distributions,
release mechanisms, exposure pathways and migration
routes, and potential receptors. The CSM documents
current site conditions and is supported by maps, cross
Figure 7a. Poudre River Site Restoration Effort
Photographs of active restoration efforts can be shared with
stakeholders, general public, and media to demonstrate
activities being conducted at sites.
Figures 7b. Poudre River Site Post-Restoration.
Photographs of the site after completion of restoration
efforts serve as partial documentation of this phase of
remedy completion.
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sections, and site diagrams that illustrate human and
environmental exposure through contaminant release
and migration to potential receptors. Developing an
accurate CSM is critical to the proper implementation
of the Soil Screening Guidance." (Section 2.1, p. 5)
Soil Screening Guidance: User's Guide, July 1996,
Publication 9355.4-23 (EPA 540-R-96-018).
www.epa.gov/superfund/resources/soil/
ssg496.pdf
"Analyses of the data collected should focus on the
development or refinement of the conceptual site
model by presenting and analyzing data on source
characteristics, the nature and extent of
contamination, the contaminated transport pathways
and fate, and the effects on human health and the
environment" (Ref 7, p. 3-19).
Guidance for Conducting Remedial Investigation and
Feasibility Studies Under CERCLA. October 1988.
OSWER Directive No. 9355.3-01.
www.epa.gov/superfund/policy/remedy/
pdfs/540g-89004-s.pdf
"A conceptual site model is a useful tool for selecting
sampling locations. It helps ensure that sources,
pathways, and receptors throughout the site have been
considered before sampling locations are chosen. The
conceptual model assists the Site Manager in
evaluating the interaction of different site features.
Risk assessors use conceptual models to help plan for
risk assessment activities. Frequently, a conceptual
model is created as a site map (see Figure 1) or it may
be developed as a flow diagram which describes
potential migration of contaminants to site receptors."
Superfund Program Representative Sampling
Guidance, OSWER Directive 9360.4-10 (EPA 540-R-
95-141). www.epa.gov/tio/download/char/
sf rep samp guid soil.pdf
"The site conceptual model synthesizes data acquired
from historical research, site characterization, and
remediation system operation. The conceptual model,
like any theory or hypothesis, is a dynamic tool that
should be tested and refined throughout the life of the
project. As illustrated in Figure 5, the model should
evolve in stages as information is gathered during the
various phases of site remediation. This iterative
process allows data collection efforts to be designed so
that key model hypotheses may be tested and revised to
reflect new information." (Section 4.4.3, p. 13)
"Conceptual Model Provides Basis for:
Early Action/Removal of Near Surface
Materials
Site Characterization Studies (RI/FS, RFI)
Removal of Subsurface Sources
Pilot Studies
Interim Ground-Water Actions
Evaluation of Restoration Potential (or TI)
Full-Scale Treatment System Design and
Implementation
Performance Monitoring and Evaluations
Enhancement or Augmentation of
Remediation System, if Required
Future Evaluation ofTI, if Required"
(Figure 5. Evolution of the Site Conceptual Model)
Guidance for Evaluating the Technical
Impracticability of the Ground-Water Restoration,
September 1993, publication 9234.2-25
www.clu-in.org/download/contaminantfocus/
dnapl/Policy and Guidance/TI guidance.pdf
"In addition to the items discussed in more detail
below, it is important to keep in mind that remedial
action costs are influenced, in general, by the quality of
the conceptual site model (CSM), which is a three-
dimensional 'picture' of site conditions that illustrates
contaminant distributions, release mechanisms,
exposure pathways and migration routes, and potential
receptors... It is initially developed during the scoping
phase of the RI/FS, and modified as additional
information becomes available. Careful evaluation of
site risks, incorporating reasonable assumptions about
exposure scenarios and expected future land use, and
the definition of principle threat waste generally
warranting treatment, help to prevent implementation
of costly remediation programs that may not be
warranted." (Section 1, p. 2)
The Role of Cost in the Superfund Remedy Selection
Process, Quick Reference Fact Sheet. Publication
9200.3-23FS (EPA 540-F-96-018). September 1996.
www.epa.gov/superfund/policy/cost dir/
cost dir.pdf
Additional CSM References:
Improving Sampling, Analysis, and Data Management
for Site Investigation and Cleanup (EPA 542-F-04-
001a)April2004.
www.triadcentral.org/ref/ref/documents/
2004triadfactsheeta.pdf
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Triad Issue Paper: Using Geophysical Tools to Develop
the Conceptual Site Model (EPA 542-F-08-007).
December 2008.
www.brownfieldstsc.org/pdfs/Geophysics Issue
Paper FINAL Dec 3 20081.pdf
Innovations in Site Characterization, Streamlining
Cleanup at Vapor Intrusion and Product Removal Sites
Using the Triad Approach: Hartford Plume Site,
Hartford, Illinois. (EPA542-R-10-006). September
2010. www.brownfieldstsc.org/pdfs/HartfordCase
Study FINAL 9-30-10.pdf
Streamlining Site Cleanup in New York City (EPA 542-
R-10-005) August 2010.
www.brownfieldstsc.org/pdfs/Streamlining Site
Cleanup in NYC Final.pdf
Best Management Practices: Use of Systematic Project
Planning Under a Triad Approach for Site Assessment
and Cleanup (EPA-542-F-10-010). September 2010.
www.clu-in.org/download/char/
epa-542-f-10-010.pdf
Improving Decision Quality: Making The Case For
Adopting Next-Generation Site Characterization
Practices (EPA-542-F-03-012). 2003.
http://nepis.epa.gov
tional Resources:
Triad Resource Center Web site
fwww.triadcentral.orgj
Contaminated Site Clean-Up Information
Network Web site [www.cluin.org]
The Brownfields and Land Revitalization
Technology Support Center
fwww.brownfieldstsc.orgl
EPA Super fund
fwww.epa.gov/superfund1
For technical inquiries regarding
this document, contact:
Stephen Dyment, EPA OSWER/OSRTI
dyment.stephen@epa.gov or 703.603.9903
Michael Adam, EPA OSWER/OSRTI
adam.michael@epa.gov or 703.603.9915
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