Vapor barriers are great for buildings above contamination, but what if the contamination happens on top of the barrier?  I recently did a Phase I on a strip shopping center that has had a vapor barrier and passive venting system in place for 12 years.  The vapor barrier was originally installed to mitigate the effects of naturally occurring methane.   One of the tenants is a dry cleaner that uses PCE.  Clearly, the potential for releases from a 12-year dry cleaner is sufficient to justify a Phase II, but does the presence of the vapor barrier change things?

Doing a traditional Phase II with soil borings would be infeasible as borings would penetrate the vapor barrier.  Also, the vapor barrier would likely prevent PCE from getting into the native soil; thus, greatly reducing the threat of groundwater contamination.   Does this eliminate the REC?  What do you think?