conceptual site model training

Conceptual Site Models

Purpose, Development, Content and Application

CP Annual TrainingOctober 27, 2015

Conceptual Site Model (CSM) Purpose

• Typical environmental remediation project– Particular program and rules (Remedial, VAP,

RCRA) that directs a set of tasks:• Site assessment and investigation

• Evaluation of remedial alternatives

• Remedy selection and implementation

• Post-construction activities, monitoring, O&M

– Generate volumes of information about the site

CSM Purpose

• Typical environmental remediation project– What’s missing?

– What’s the common understanding of the project information with respect to site-specific project objectives?

– The CSM, which exists to provide common understanding among project stakeholders

CSM Purpose

• Conceptual understanding (example):

Board game – 2 to 4 players. Each starts with $1,500. Players move around the game board by rolling dice, and land on properties or reward or penalty squares. Properties may be purchased, traded, mortgaged, developed with houses or hotels, and rent is collected from opponents landing on the property. Players are eliminated by going bankrupt; the last player left wins. The game takes hours to complete.

CSM Purpose• Board game example (conceptual understanding):– Don’t need to know every rule to understand the concept

(could grasp the concept by observation)

– The concept prepares you to play the game through its various stages

• CSM– Provides a conceptual understanding of the information

associated with remediation project under a particular program at a specific site that prepares you to work through the project stages

CSM Purpose

• Remediation project, three aspects:

1. Regulatory framework +

2. Information/data +

3. CSM(The CSM Provides direction on how to best utilize information within a regulatory framework to achieve project objectives, i.e., identify data gaps)

CSM Purpose

MODEL Qualitative Quantitative

Simple CSM

Detailed

CSM Purpose

• A model is a description of a system with the objective of making predictions

• A model is based on data, but is not data

• A good model is one that achieves its objectives

• What are the objectives of a CSM?

CSM Objectives

1. Provide an iterative representation of a contaminated site in a simple, concise manner (evolves with new data and project stages)

2. Describe the site environmental system:• Contamination sources, pathways, receptors• Processes controlling contaminant transport

3. Facilitate a basic and common understanding of site contamination and potential exposure scenarios among all stakeholders

CSM Development• CSM is essentially a hypothesis for making site-specific

predictions about:

– The occurrence of contamination

– The potential for adverse impacts to receptors

• Initially developed during the determination of project objectives, DQOs, RAOs…

• Continuously tested and revised (as necessary) during subsequent project stages, e.g., site investigation, remedial alternative development, etc.

CSM Development• Every hypothesis (and every CSM) is speculative to some

degree• Development and subsequent revision?– “Bottom up” approach works best: base CSM on

assumptions that provide the simplest explanation of the observed data (Occam’s razor: maximize certainty, minimize speculation)

– Don’t try to eliminate data gaps by increasing the complexity of the assumptions underlying the CSM! (Instead collect the data needed to fill the gap indicated by the CSM; complexity ≠ accuracy or certainty)

CSM Development

• Development and use of a formal (written) CSM is a critical step in the site remediation process

• Helps ensure that all project stakeholders are working with a similar understanding of the site

• Without a formal CSM, each stakeholder will develop their own “informal CSM”

• Multiple informal CSMs lead to misunderstanding and disagreement, delays and increased costs

CSM Development

• Criteria for CSM development, maintenance and use:

1. The CSM should be applied as a systematic planning tool through all stages of a remediation project

2. The CSM should be iteratively updated (as data gaps are progressively filled, the CSM becomes more accurate)

3. The CSM should be maintained as a stand-alone document accessible to all stakeholders during the course of the project

CSM Components & Presentation

• The CSM

–Consists of a concise combination of graphical and written information that

–Describes (and clearly distinguishes) known and hypothesized site conditions in a manner that is

–Readily understandable to all project stakeholders


• DERR recommends that the CSM include the following components– A pictorial model of site conditions (2-d or 3-d)

– A pathway receptor network diagram

– A brief written description

– Additional information (maps, tables, figures) if necessary


• Pictorial model of site conditions, including but not necessarily limited to– Topography and surface hydrology

– Locations of contaminant sources

– Structures and utilities

– Geology and hydrogeology


• Pathway network receptor (PNR) diagram

– Support risk assessment, remedy development

– Often used as stand-alone CSMs; however, PNRs

• Do not provide sufficient information concerning the site hydrogeologic system

• May not identify all CSM data gaps


• Brief narrative, including:

– Current site conditions and site history

– Contaminant source characterization

– Migration pathway descriptions

– Identification of data gaps

• No need to include supporting data – this is provided by of the reports (e.g., RI/FS)

CSM Project Life Cycle Utilization

• The CSM should be used through all stages (life cycle) of a remediation project– Dynamic systematic planning tool

– Basic framework for evaluating new data

– Should evolve as project progresses (increase in detail and accuracy)

• CSM project life cycle includes six stages or successive versions of the same CSM (U.S. EPA)


• CSM will need to be updated and revised during this process– Changes in project scope or regulatory

requirements

– Recognition of a previously unknown contaminant, pathway or receptor

– Changes in the planned end use of the site


• Changes to the CSM should increase its accuracy, but not to the detriment of its simplicity (complexity ≠ accuracy)

• All project stakeholders should be provided the opportunity to review, understand and provide input into CSM revisions

• Final revisions and supporting information should be documented for later reference

Common CSM Problems

• Treating the CSM as an administrative task rather than a planning tool

• Dispersing CSM components throughout multiple project documents

• Using an overly generic CSM that is not sufficiently site-specific to be useful

• Using an overly detailed CSM that presents data rather than a concise synopsis of site conditions

CSM References(Available Upon Request)

• DERR Conceptual Site Model Guidance (Draft)

• U.S. EPA, July 2011, Environmental Cleanup Best Management Practices: Effective Use of the Project Life Cycle Conceptual Model, EPA 542 F–11– 011

• ASTM E1689–95, Standard Guide for Developing Conceptual Site Models for Contaminated Sites (Reapproved 2014)

Questions?

Thanks for your time and attention!

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