Richard Jackson delivered a very interesting presentation on the need for accurate and complete site conceptual models when dealing with contaminated sites. Richard used four unique case studies to illustrate how important it is to “get it right”. Getting the model right, allows the right decisions to be made - especially when it comes to determining the actual source of contamination.

First, he presented a case where two plumes of PCE (perchloroethylene) were found in the groundwater of an urban area. One plume was deep and much larger, the other was shallow, small, but had much higher concentrations of PCE. The smaller plume was attributed to a solvent recycling facility above the plume, and the larger plume was attributed to a nearby aerospace plant.

The recycling facility was ordered to pay $0.25 million and had to clean up their plume. The aerospace plant was sued for natural resources damages of $4.5 billion. A closer inspection of the field data with the help of a DNAPL flow model indicated that both plumes originated at the recycling facility. They had been split by infiltrating floodwaters from an unlined flood control channel (see figure below). The groundwater was found to be treatable and recoverable, as such, there was no actual loss of the resource.

This case study, and the three others presented, reinforced the need for detailed site characterizations. They provide a clearer picture of what is actually happening and what can and cannot be achieved at a contaminated site.

ABOUT THE SPEAKER - Richard E. Jackson, Ph.D., P.Eng.,
Intera Engineering Ltd.

Richard has worked as a hydrogeologist since 1970. He is currently a Principal with Intera Engineering of Ottawa, ON.