Over the past 25 plus years of conducting peer reviews, Dragun has seen poorly designed CSMs or the lack of a CSM again and again. In fact, this is such an important issue that, over the past year, we have been providing a series of Environmental Minutes “Eight Keys to Successful Environmental Remediation.” In these minutes, we go into detail regarding CSMs, but in very general terms, here is a nickel tour of what it takes to develop a CSM.
Conceptual Site Model
A Conceptual Site Model is an integration of everything we know about a site including (1) site history, (2) geologic/hydrogeologic information, (3) history of chemical-release source(s) and timing, (4) physical and chemical properties of the release, (5) contaminant fate and transport, (6) distribution of chemicals, and (7) risks, exposure pathways, & receptors. A CSM is, ultimately, a multi-dimensional picture that tells the story about the site. Why is all of this information so important? If you miss one key bit of data, you can end up chasing phantom issues, overlooking the real issue, or unknowingly remediating someone else’s release.
Preliminary Conceptual Site Model
This is the starting point to developing a CSM, and it is far too often overlooked because this step can be viewed as mundane. The Preliminary CSM is typically comprised of information such as the following:
- Reference literature regarding the local or regional soils & geologic conditions
- Environmental database information that should include records regarding companies in the area and types of manufacturing/chemical usage
- Historical aerial photos
- Current and historical information regarding registration of tanks and spills
Also, interviews should be conducted with people familiar with the site and previous environmental practices. Requesting the purchase of records may provide clues to chemical usage and quantity of chemicals. The Preliminary CSM can also include site-specific data regarding the subsurface conditions if there were historical environmental investigations conducted on the site.
Revised Conceptual Site Model
The preliminary CSM provides a framework of the site conditions. To “fill in” the framework, you need to look for corroborating evidence. With site history in hand, the questions become more focused, more refined, and more specific about the site. Where was the underground storage tank and when was it removed? Where were the previous generations of tank farms installed on the site? Where was the burn pit, and how long did these activities take place? With this more specific information, you can narrow the focus your soil and groundwater investigation.
Robust Conceptual Site Model
This is the step where too many are hasty to begin. However, it’s only after you have done all the hard work necessary to put this site into proper context that you are in a position to use these more advanced tools.
Why a robust conceptual site model? Because environmental remediation, environmental enforcement, and/or environmental litigation can be very costly (Image Credit: Dragun Corporation).
If you have taken the proper steps and have gathered relevant site-specific data, then a CSM can be significantly enhanced by integrating these more advanced tools, such as groundwater modeling, chemical fingerprinting, and isotope testing. If the CSM is accurate, site-specific data can be used to “ground truth” the CSM and the conclusions drawn about chemical fate and transport. Ultimately, does the “feedback” fit the rest of the picture?
As stated earlier, this is just a very quick nickel tour of a CSM process. If you would like copies of any the Environmental Minutes previously mentioned, drop me a note, and I will be happy to send you a copy.
As always, you can reach me at 519-979-7300, ext. 114, or by email cpare@dragun.com.