Conceptual Site Models Don t Start a Project Without One

Transcription

1 Conceptual Site Models Don t Start a Project Without One Travis Shaw USACE, Seattle District Joint Services Environmental Management Conference & Exposition Denver, CO March 2006

2 What Is He Talking About? Conceptual Site Model definition Types of CSMs Elements of CSM development Importance of using CSMs as a project planning and decision tool

3 Background Scientific Inquiry Scientific Inquiry begins with problem conceptualization. This leads to development of a hypothesis to be tested. Successful resolution normally requires an iterative process of data collection and analysis.

4 What is a Model? Dictionary: tentative description of a theory or system that accounts for all of its known properties physical, mathematical, chemical

5 Definition of Conceptual Conceptual thought, the act of conceiving in the mind So Conceptual Model - a tentative description of a theory or system that accounts for all of its known properties, conceived in the mind.

6 CSM Definition Definitions developed by - EPA, ASTM, Corps of Engineers and others Generic definition A method to describe what is known or can be inferred about a site for the purpose of making a decision. Physical, chemical and biological systems Contaminant release and transport Societal issues policy, land use, exposures

7 Type 1 Comprehensive CSM Integrate all site information scientific societal Linked to project objectives and the specific decisions necessary to meet those objectives.

8 Type 2 Limited Scope CSM Focused conceptualization Discipline or task specific Naming convention might link to purpose, for example conceptual hydrogeologic model Ideally create from within the context of a comprehensive CSM

9 Type 2 Hydrogeology Geology Limited Scope CSM Discipline or Task Based Risk assessment / exposed receptors Environmental engineering (remedial design) UXO / ordnance clearance Contaminant transport

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11 CSM of DNAPL Treatment Ref: Technology News & Trends, 2004

12 Conceptual Site Exposure Model Used by risk assessment community Variant of limited scope CSM Flow chart depicting contaminant interaction with receptors Intended to convey information on completed receptor pathways Type 3

13 The CSM is Key to Successful Projects THE Basis for Cost-Effective, Confident Decisions Decision-maker s mental picture of what s happening to contamination so decisions can be made about risk & cleanup A CSM is a tool that represents contaminant populations to make predictions about Nature & extent of contamination Exposure to contamination Strategies to reduce risks from contamination

14 CSM According to the Corps (EM ) CSM serves as a planning instrument A modeling and data interpretation aid A communication device for the project team Aids communication with the public and project stakeholders Provides a standard means to summarize what is known about the site and identify data gaps

15 Conceptual Site Model: Evolving Throughout Project Preliminary CSM describes initial site understanding CSM guides development of decision process/work plans Information confirms or modifies CSM as it gradually matures Mature CSM is considered complete when closure is achieved

16 The Preliminary CSM Highlights the Physical Features of Site Man-made Structures / Historically Disturbed Areas Potential release and physical transport mechanisms Evaluate hypotheses w/ actual site data (not just chemical data!) or professional judgment Incorporates known Societal Considerations Future Land Use / Community Goals Potential Exposure Pathways Risk Management Scenarios

17 Kinds of Data Relevant to CSM Development Chemical Hydrogeological Biological Geochemical Geophysical Hydrology Preferential paths Historical activities Source areas Land use Receptors Exposure pathways Community plans

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19 How Might a CSM Appear? Text? Computer Model? 2-d Cross Section? Receptor Flow Chart? 3-d Physical Model? How can we organize this information?

20 Other Possibilities

21 Correct CSM = Better Decisions March Air Reserve Base

22 Why were regulators so concerned about nature and extent of contaminated groundwater?

23 Inaccurate Geologic CSM

24 Unrealistically Simple Worldview

25 Can You Say Heterogeneity"?

26 A More Realistic Worldview Still frame from a 3D Video of Plume vs. GW Wells Adapted from Columbia Technologies, Inc., 2003

27 Wells Have Issues when it comes to characterization Screen elevation and length need to be carefully selected Possible low bias due to mixing Adapted from Columbia Technologies

28 Contamination Then

29 Contamination Now

30 Updated CSM generated by increased data density will have a profound impact on selecting remedial alternatives

31 Take-Aways Your CSM, the key to project success Basis for cost-effective, confident decisions Decision-maker s mental picture of what s happening to contamination so decisions can be made about risk & cleanup Maturing the CSM will keep the project focused and provides a basis for communicating with stakeholders