A Structured Methodology for Objective Remedy Selection at Chlorinated Solvent Sites
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A remedy selection tool has been developed incorporating the principles introduced in ‘A Guide for Selecting Remedies for Subsurface Releases of Chlorinated Solvents’ (Sale and Newell, 2011). This tool has been demonstrated to aid in development of a priori evaluations and the benefits of a given remedial measure from the simple to the complex site.

A complex conceptual site model of a given chlorinated solvent release is simplified into fourteen environmental compartments. The source zone and plume zone include subzones of low and high permeability. Within these four zones the contamination can be present in multiple phases. Within source zones, chlorinated solvents can be present as a DNAPL, vapour, aqueous, or sorbed phase; whereas in plumes, they can be present as a vapour, aqueous, or sorbed phases. By definition, there is no DNAPL in a plume zone. A case study is presented where a pre-remediation fourteen compartment model is developed using existing data to populate each compartment with an order of magnitude (OoM) concentration value, and color to aid visual comparison. Arrows are used to show potential mass transfer between environmental compartments. The efficiency of specific remedial alternatives was evaluated based on the OoM concentration reduction in each environmental compartment for the pre-remediation scenario. An OoM approach is used because chlorinated solvent concentrations in groundwater often span several orders of magnitude, and are typically best represented by a lognormal statistical distribution (Sale and Newell, 2011). An overall ranking analysis for each remedial alternative is assessed, using the environmental compartment tool. This approach allows for conceptual designs that may include multiple remedial technologies to be compared quantitatively based on the remedial action objectives, Federal-, Provincial-, State-specific remedial selection, and site-owner specific criteria. Using the environmental compartment approach results in an objective and accelerated remedy selection process. The framework presented here guides the user to think holistically about contaminant distribution and the effect of the remedy on all zones and phases, which a traditional remedy selection process may overlook.

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Publication Summary

  • Geosyntec Authors: Derek Tomlinson
  • Title: A Structured Methodology for Objective Remedy Selection at Chlorinated Solvent Sites
  • Event or Publication: 39th Annual International Association of Hydrogeologists Congress
  • Practice Areas: Groundwater Assessment and Remediation
  • Date: 2012
  • Location: Niagara Falls, Ontario