If the State brings a remedial action -- that is, measures to permanently remediate hazardous wastes -- under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 ("CERCLA"), the statute of limitations begins to run by the commencement of cleanup construction. If a State brings a removal action -- that is, measures taken to address immediate threats to public health -- the statute of limitations begins to run at the completion of the removal action.
In State of New York v. Next Millenium Realty, LLC, a case involving pollution emanating from the New Cassel Industrial Area in the Town of Hempstead, the District Court had held that the action was a remedial action, and granted summary judgment to the defendants, claiming that the limitations period had run. The Second Circuit disagreed, holding that it was a removal action and that because the removal action was not complete, the statute had not even begun to run. The Court found that the actions taken by the state were taken to address an immediate threat to public health and did not permanently remediate the environmental problem at issue. Hence, the case was not time barred.
The decision in this case can be found here.