Important changes to Michigan's Part 201 cleanup criteria
became effective September 28, 2012. Among other revisions,
inhalation pathway criteria for both soil and groundwater were made
more stringent for several constituents or have been developed for
some hazardous substances where previously insufficient data was
available to develop criteria.
For example, the TCE criteria have decreased substantially,
including the concentration in groundwater criterion for
volatilization to indoor air, which decreased from 15,000 ppb to
2,200 ppb for residential closures and from 97,000 ppb to 4,900 ppb
for nonresidential closures. These changes potentially could affect
cleanups at many sites throughout Michigan (particularly vapor
intrusion sites), and potentially result in reopeners at sites
where the investigation or even the remedy had been completed.
These more stringent values will be more difficult (and probably
more costly) to achieve.
