hazardous substances to the environment, particularly when a groundwater resource is threatened.

Although some of the success stories described above were challenging in terms of contaminants present and underlying hydrogeology, the majority of sites that have been closed were relatively simple (e.g., shallow, localized petroleum contamination from USTs) compared to the remaining caseload. Indeed, hundreds of thousands of sites across both state and federal programs are thought to still have contamination remaining in place at levels above those allowing for unlimited land and groundwater use and unrestricted exposure (see Chapter 2).1 According to its most recent assessment, EPA estimates that more than $209 billion dollars (in constant 2004 dollars) will be needed over the next 30 years to mitigate hazards at between 235,000 to 355,000 sites (EPA, 2004). This cost estimate, however, does not include continued expenditures at sites where remediation is already in progress, or where remediation has transitioned to long-term management.2 It is widely agreed that long-term management will be needed at many sites for the foreseeable future, particularly for the more complex sites that have recalcitrant contaminants, large amounts of contamination, and/or subsurface conditions known to be difficult to remediate (e.g., low-permeability strata, fractured media, deep contamination). Box 1-1 describes the characteristics of complex sites, where long-term management is a likely outcome given the difficulty of remediating the groundwater to conditions allowing for unlimited use and unrestricted exposure.

The Department of Defense (DoD) exemplifies a responsible party that has made large financial investments to address past legacies of their industrial operations. According to the most recent annual report to Congress (OUSD, 2011), the DoD currently has almost 26,000 active sites under its Installation Restoration Program where soil and groundwater remediation is either planned or under way. Of these, approximately 13,000 sites are the responsibility of the Army, the sponsor of this report. The estimated cost to complete cleanup at all DoD sites is approximately $12.8 billion. (Note that these estimates do not include sites containing unexploded ordnance.)

DoD has set a procedural goal for each of the Services stating that all sites will reach the response-complete or remedy-in-place milestone by 2014. Remedy in place means that a remedial strategy has been implemented and is in the performance assessment stage of the site’s life cycle, while response complete means that remedial actions have been completed,


1 “Contamination remaining in place,” as used in this report, is consistent with the interagency definition of hazardous substances, pollutants, or contaminants remaining at the site above levels that allow for unlimited use and unrestricted exposure (UU/UE) (EPA, 2001; DoD, 2012).

2 Long-term management is defined as requiring decades to centuries, well beyond the typical 30 years used to discount remedial costs.

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