I’ve been looking at EPA studies on the safety of hydrofracturing.  The chief concern is contamination of groundwater by the fluids that are injected.  (More about the nature of these fluids in upcoming posts.)

One 2004 study is  called  ”Evaluation of Impacts to Underground Sources of Drinking Water by Hydraulic Fracturing of Coalbed Methane Reservoirs.” Here is a link the EPA web page with links to the full  study.   This study concludes that the practice is safe, at least insofar as coal bed methane is concerned.  As stated in the fact sheet:

The Agency has concluded that the injection of hydraulic fracturing fluids into CBM wells poses minimal threat to USDWs (Underground Sources of Drinking Water).

If the practice is as safe as advertised, then it would seem to be a slam dunk to get the suppliers of  hydrofracturing and propping (as in propping open the fractures) to add tracer compounds to the fluids the drillers inject.   That way, years hence, if there are groundwater problems, they could be assigned to the appropriate parties for clean-up.

One  can hypothesize about the  properties of such tracers.  They should be water soluble,  refractory (non-reactive), and ought not be retained in the subsurface by association with subsurface minerals and other substances.  It would be useful to have a way of varying the tracers so that they could be made specific to each well and/or firm doing the injecting.  That said, there are a number of tracers that hydrogeologists use to determine the age and origins of groundwater, and there are surely good methods that could be developed  for this purpose.