Preparing a Site Conceptual Model

1
Preparing a Site Conceptual Model
2
Typical Site Management Problems

• Site complexities
• Complicated hydrogeology
• Multiple contaminants of concern (COCs)
• Multiple receptors/pathways
• Multiple phases of investigation and remediation
• Deliverables that are not stand-alone documents
• Changes in consultants
• Changes in regulatory oversight
• Case load

3
Common Outcome

• An abundance of data
• Lack of clarity concerning the major site issues
  and how to move the site toward closure

4
Suggestion

• Direct the Responsible Party (RP) to complete a
  Site Conceptual Model

5
Site Conceptual Model (SCM)

• EPA A representation of site conditions
  developed using readily available (existing) data
  that illustrates the relationship between
  contaminants, retention/transport media, and
  receptors.

EPA. November 2000. Using the Conceptual Site
Model to Select Performance Standards and Develop
Data Quality Objectives in the CAS.
6
Purpose

• Organize information already known about the site
• Help identify additional information that must be
  obtained
• Suggest when site characterization is
  completei.e., if the SCM is not likely to
  significantly change upon collection of
  additional information, the existing data are
  adequate

7
SCM Presentation

• The SCM is generally documented by written
  descriptions and supported by maps, geological
  cross-sections, tables, diagrams and other
  illustrations.

EPA. November 2000. Using the Conceptual Site
Model to Select Performance Standards and Develop
Data Quality Objectives in the CAS.
8
SCM Support

• Local and regional plan view maps showing
  location of sources, extent of contamination
  (i.e., an interpretive drawingnot a plot of
  laboratory results), direction and rate of
  groundwater flow, and locations of receptors.
  Receptors include, but are not limited to, all
  supply wells within 2000 feet of the source area.

Arulanantham, R. December 2000. Assessment and
Management of MtBE Impacted Sites.
9
(No Transcript)
10
SCM Support

• Cross-section maps showing subsurface geologic
  features, depth to groundwater, man-made
  conduits, monitoring well construction, and an
  interpretive drawing of the vertical extent of
  soil contamination (i.e., an interpretive
  drawingnot a plot of laboratory results)

Arulanantham, R. December 2000. Assessment and
Management of MtBE Impacted Sites.
11
(No Transcript)
12
(No Transcript)
13
SCM Support

• Exposure evaluation flowchart (similar to Figure
  2 in ASTMs Standard Guide for Risk-Based
  Corrective Action Applied at Petroleum Release
  Sites)

Arulanantham, R. December 2000. Assessment and
Management of MtBE Impacted Sites.
14
(No Transcript)
15
SCM Support

• Plots of chemical concentrations vs. time (e.g.,
  if groundwater monitoring is being conducted,
  plots should be shown for each monitoring well
  which has had detectable levels of contaminants)

Arulanantham, R. December 2000. Assessment and
Management of MtBE Impacted Sites.
16
(No Transcript)
17
SCM Support

• Plots of chemical concentrations vs. distance
  from the source

Arulanantham, R. December 2000. Assessment and
Management of MtBE Impacted Sites.
18
(No Transcript)
19
SCM Support

• Summary tables of chemical concentrations in
  different media

Arulanantham, R. December 2000. Assessment and
Management of MtBE Impacted Sites.
20
SCM Support

• Boring and well logs (including
  construction/screening)

Arulanantham, R. December 2000. Assessment and
Management of MtBE Impacted Sites.
21
Summary

• SCMs are a big picture look at a site
  contamination problem
• SCMs may help you through some common site
  management problems and clarify major site issues