Conceptual Site Models

Conceptual Site Models
Conceptual site models (CSMs) are a valuable tool for understanding and communicating large data sets, and for making good decisions throughout the site remediation process. 

Our suc­cess as en­vi­ron­men­tal pro­fes­sion­als often re­quires mak­ing sense of com­plex sci­en­tific data sets at our sites to a diverse audience that may include risk assessors, earth scientists, remediation engineers, regulators and the public. The CSM provides a "picture" of the physical, chemical and biological processes that influence the transport, migration and potential impacts of contamination from its sources through environmental media to receptors within the environmental system. Conceptual site models help stakeholders visualize these complex interactions and create a common understanding for decisions and actions.

Conceptual site models help stakeholders visualize these complex interactions and create a common understanding for decisions and actions.

Dynamic Models Evolve with Re­me­di­a­tion Progress
CSMs are not static, and should never be con­sid­ered totally accurate or “complete”; instead, they should be viewed as dynamic and evolving as the re­me­di­a­tion process pro­gresses and new data are col­lected. They have a dif­fer­ent role in each phase of a re­me­di­a­tion project from pre­lim­i­nary in­ves­ti­ga­tion through remedial action (often over­looked) and post-cleanup mon­i­tor­ing:

  • Pre­lim­i­nary – Initiate an in­ves­ti­ga­tion.
  • Baseline – Guide the in­ves­ti­ga­tion based on sys­tem­atic planning.
  • Char­ac­ter­i­za­tion – Dictate any needed modifications to address important data gaps by incorporating new in­for­ma­tion through it­er­a­tive updates as the in­ves­ti­ga­tion proceeds.
  • Remedy se­lec­tion and design – Form the basis of the fea­si­bil­ity study and remedial design.
  • Re­me­di­a­tion and post-remedial action mon­i­tor­ing – Provide a means to optimize (or modify) the remedy through it­er­a­tive updates as per­for­mance mon­i­tor­ing data are col­lected.
Because we cannot “see” into the ground or char­ac­ter­ize every aspect of a site, CSMs will always be based on as­sump­tions and in­ter­pre­ta­tions. We must balance the degree of un­cer­tainty with current decision needs. A key decision point in the life of a re­me­di­a­tion project is deciding when the in­ves­ti­ga­tion phase is done and the CSM is sufficiently complete to identify and select appropriate remedies. From a risk as­sess­ment stand­point, this usually means po­ten­tial mi­gra­tion pathways are eval­u­ated and exposure point con­cen­tra­tions ad­e­quately quan­ti­fied. From a contaminant distribution stand­point, this usually means de­lin­eation of the nature (con­t­a­m­i­nants and con­cen­tra­tions) and extent. However, often over­looked until too late in the char­ac­ter­i­za­tion stage are many of the hy­dro­ge­o­log­i­cal and bio­geo­chem­i­cal at­trib­utes of a site that influence the selection of potential remedial tech­nolo­gies, cost es­ti­mat­ing and the remedial design. Ac­cord­ingly, a critical stage in the de­vel­op­ment of a robust CSM is the identification of data needs of all parties involved in the se­lec­tion and design of the remedial so­lu­tions.
GIS and Vi­su­al­iza­tion Tools Enhance CSMs
As sites and conceptual site models become more complex, CDM Smith has found that geographic information systems (GIS), effective data management and visualization tools greatly facilitate the functionality of the CSM. GIS-based CSMs are especially well suited for environmental site characterization and remediation because they are a means to compile, visualize, compare and analyze lots of spatially related data, bringing the many pieces of the puzzle together. This also facilitates nearly automated CSM updates through addition of newly collected data to the database. In addition, they enable remedy evaluations by allowing the environmental professional to quickly calculate numerical and area-weighted average concentrations, graphically select data sets to assess remediation volumes, evaluate residual concentrations, and target specific regions and geologic strata for potential remedies. Regulatory interactions regarding the adequacy of site characterization and realistic remedy selection are enhanced because all the data are visually integrated and at your fingertips for real-time manipulation. Finally, GIS-based CSMs greatly facilitate report preparation and enhance communications with stakeholders and the public.

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