A TALE OF TWO AQUIFERS: HOW QUATERNARY GEOLOGY AFFECTED THE HYDROGEOLOGY OF REMEDIATION AT TWO ONTARIO SITES

Ongoing research at the University of Kansas is aimed at the characterization of aquifers by direct groundwater velocity measurements. In two Ontario, Canada, aquifers composed of distinctly different Quaternary sediments, the direct velocity measurements detected changes in groundwater flow associated with attempts to remediate groundwater contaminants in situ. In the first case, the sediments comprised generally well-sorted beach sands, contaminated with petroleum hydrocarbons. The addition of dissolved oxygen to the groundwater caused subtle changes in flow direction and magnitude in the plume core, apparently due to microbial growth. In the second case, a heterogeneous outwash aquifer was treated with acetate to stimulate in situ denitrification. In that case, treatment efficiency was strongly tied to the sediment permeability, and once again the biostimulation caused flow redirection – much more pronounced in this case, which was also sensitive to the heterogeneity. These experiences illustrate the importance of gaining a good appreciation of a site’s Quaternary geology in advance of conducting hydrogeological investigations and remedial campaigns.