Some 126,000 U.S. sites have severe groundwater contamination, and 10% are so complex to address that they are unlikely to be cleaned up in the next 50 to 100 years, says a National Research Council report released last week. The costs of groundwater cleanup will likely exceed $127 billion, the report says, noting the Department of Defense has already spent $30 billion for groundwater remediation. The report stresses that for complex sites, no technology exists to complete a cleanup. Hence for many sites, there is a point at which contaminants will remain above legal limits for drinking water despite extensive cleanups. States and federal governments will shoulder most of the cost of groundwater remediation because at many sites the companies responsible for the pollution and its cleanup no longer exist, the report says. The report recommends a national R&D effort to develop innovative cleanup tools to ensure public health protection from residual contamination.