HARD TO COMPARE CAMBRIDGE VAPOUR INTRUSION DISASTER WITH GUELPH CONCERNS

There are a number of similarities including potentially multiple sources of the most dangerous contaminants released into the natural environment. In Cambridge the three most prevalent issues were trichloroethylene (TCE), trichloroethane (TCA) and Chromium VI. That said in Guelph TCE and TCA are also front and centre with notable concentrations of tetrachloroethylene (PCE) as well at the alleged source area of IMICO. Furthermore both sites also have the common breakdown products of both TCE and TCA present. For TCE this includes compounds of dichloroethylene (DCE) and vinyl chloride (VC). For TCA this includes compounds of dichloroethane (DCA).

Another similarity is the stratigraphy or sub-surface formations. Both sites have a shallow overburden of soils, gravels and silts with the Bedrock close to the surface. Whether this actually induces greater vapour production from the sub-surface solvents in both the groundwater and the soils, I am not certain. I do know that any attempts to lower the water table via pump and treat technology of the groundwater definitely can induce greater volatolization (i.e. liquid phase to a gas phase) of these toxic solvents.

A major difference so far is that while there are reports showing both soil and groundwater concentrations of TCE, TCA, PCE, DCE, DCA, and VC for both Cambridge and Guelph likely source locations, I have after considerable search been unable to find soil Vapour concentrations in and around the Cambridge Bishop St. sources and area. Recall that yesterday I mentioned that the Guelph resident had sent out a map showing soil vapor concentrations in his neighbourhood. That map and test results was produced by Geosyntec Consultants. Their map however while showing very high soil vapours of TCE, PCE, DCE, and VC does not show soil vapours for either trichloroethane (TCA) or its breakdown products such as DCA. What I view as the likely source, namely the former IMICO foundry does have soil and groundwater readings for TCA and DCA. Those reports were produced by Decommissioning Consulting Services.

In Cambridge at least at the moment it appears as if the MOE/MECP immediately understood the potential/probable consequences of TCE in the groundwater being able to volatolize and enter residential basements via vapour intrusion. Hence it appears as if they immediately began indoor air testing in those nearby homes. For some reason in Guelph it appears as if outdoor soil vapour testing was some kind of intermediate step. According to the e-mail I received from the local resident, indoor air testing will commence after the pandemic crisis has abated. I expect that decision was only made after the authorities (MOE/MECP ?) saw the results of the outdoor testing. Keep in mind the outdoor testing decision took place well prior to the extent of knowledge we now have regarding the spread of the coronavirus pandemic in Ontario.

I have not been able to determine any specific TCE groundwater concentration necessary in order to produce vapor intrusion. Also I have not been able to determine any measurement of quantity of free phase TCE in its form as a DNAPL (dense non aqueous phase liquid) that would be necessary to produce vapour intrusion into homes.