Groundwater Completion Strategies for Complex Sites
Complex groundwater sites, such as those contaminated by dense non-aqueous phase liquids (DNAPLs), or those exhibiting challenging hydrogeologic conditions with highly variable hydraulic conductivities, continue to confound cleanup efforts, in some cases for decades. The conventional approach of selecting a remedial technology and applying it until contaminant concentrations meet maximum contaminant levels (MCLs) in groundwater are achieved has proven inefficient at best, and in many cases for complex sites, futile.
We need to set realistic remedial goals to reduce risk and establish a measureable path toward remedial action objectives.
Contaminant Mass Discharge as a Performance Metric
A key challenge for the environmental professional is to set realistic remedial goals that are necessary and appropriate to reduce risk and establish a measurable path toward remedial action objectives. Cleanup time frames are especially difficult to estimate, and contaminant mass in the subsurface is very difficult to quantify. However, contaminant mass is often not directly related to risk of exposure or harm. Rather, contaminant mass discharge is directly related to migration, potential exposure and risk. Contaminant discharge can be assessed and monitored in a variety of ways and can form the basis for realistic risk reduction and continued assessment of progress of the remedial systems. Accordingly, mass discharge and the associated dynamics of the plume (i.e., plume stabilization or reduction) make appropriate groundwater remedy performance metrics.