Contamination in fractured rock presents some of the most challenging conditions for successful remediation. This is especially true with DNAPL contamination in sedimentary rocks. In these dual porosity systems, transport takes place almost exclusively in the fractures.  At mature sites the vast majority of the contaminant mass likely resides in the rock matrix rather than in the fractures. In situ remedies that do not take this into account are unlikely to succeed.

Cascade’s COREDFN™ process is a high resolution approach to matrix diffusion assessments that determines mass distribution in the rock with very high quality data.  This approach provides a direct and definitive migration pathway determination, as well as mass distribution in dual porosity systems.

 

The sampling and processing methodologies were developed by Professor Beth Parker at the University of Waterloo (now at the University of Guelph) in Ontario, Canada. The extraction and analytical processes were developed by Prof Tadeusz Gorecki at the University of Waterloo in collaboration with Prof Parker. Cascade is the only authorized commercial provider of these methods under agreement with Professors Parker and Gorecki.

Sample extraction and analysis can either be done in a laboratory set up on site or in our laboratory in Montpelier, VT.  Extraction of VOCs is accomplished using a microwave assisted extraction process. The extract can then be analyzed in two ways:

1) A cool, on-column injection on a GC/uECD for low detection limits when the only analytes are chlorinated solvents.

2) By a modified EPA method 8260 using SPME and GC/MS when the analyte list is more complicated.

(photo credit Prof. Beth L. Parker; University of Guelph) 

“…instead of treating a more conventional rectangle, the density and quality of the COREDFN data allowed for us to isolate the contaminant zones to a smaller and more irregular shaped region of the site. We were able to confidently reduce the treatment area by about 40%. The result was a more focused and more efficient remediation strategy.”

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