Are the E2600 Critical Search Distances Inadequate?

The critical distances used in the ASTM E2600 Vapor Encroachment Standard to screen out sites for further investigation. The distances were supposed to based on data developed by VI experts to provide a 95% confidence certainty.
However, if one looks at the length of plumes in ever growing number of vapor intrusion lawsuits, the E2600 distances used to suggest the sites do not pose a risk of vapor encroachment to a target property seem extremely over-optimistic. Granted, the lawsuits are only a small universe of the total number of sites that are impacted by chlorinated solvents but but this random sampling would suggest that critical distances may not provide as much confidence as is claimed.

Developing data on plume lengths from lawsuits can be tricky since this information is usually not in the court opinios but buried in  pleadings and brief. Moreover, the focus is usually on whether the plaintiffs have been exposed, not how far they are located from the source of the contamination.  However, to advance the conversation, I have listed below some plume lengths I have been able to obtain from some of the more active vapor intrusin lawsuits.

The lawsuits seem to involve vapors migrating from shopping centers with dry cleaners, industrial facilities and landfills.

Maryland Square (Nv):  4,000 ft groundwater plume from shopping center (and crossed beneath major blvd)
White Swan Cleaner (NJ)- 2.5 mile groundwater plume from former dry cleaner (now bank branch office)
Bozeman Solvent Site (Mt)- plume from dry cleaner is several lengths of shopping center (appears to be at least mile long)

Raytheon (Fl)- at least 1,000 ft groundwater plume from industrial facility

Behr (Ohio)- at least 1500 plume from industrial facility

Ringwood (Ill)- plume "several thousand feet" from industrial lagoons
Pompton Lake (NJ)- neighborhood impacted from plume from industrial facility

There are many more sites that I will post as I get time to evaluate the pleadings and briefs. You will see that the sites above are evenly divided between industrial facilities and dry cleaners. Despite the fact that the latter are small businesses, they have used significant quantities of solvents. Studies have shown that between 75% to 90% of dry cleaners in operation before the turn of the century have suffered releases. Many of these are unreported and unremediated, thus able to continue to migrate. 

I would suggest that consultants who cling to the E2600 distance for screen out dry cleaners will underestimate the potential impacts of these facilities at their own risk.