As Superfund practitioners know, federal NPL sites are generally settled on the basis that the PRPs will first attain interim cleanup levels, though final cleanup levels are not determined until EPA is actually ready to issue its certification of completion of the remedy. Moreover, EPA insists that, should any ARARs change during the course of the cleanup, whatever standards are in effect at the time of site closure will be applied.

We saw the impact of this on the ground in 2001, when EPA revised the Safe Drinking Water Act maximum contaminant level, or MCL, for arsenic from 50 ppb to 10 ppb. The new MCL became an ARAR for Superfund, and the expected date to attain cleanup standards suddenly got pushed back at a number of Superfund sites.

Even at the time, it was not clear that 10 ppb was the last word. EPA’s proposed rule had provided for a 5 ppb standard, but EPA eased off in response to public comment; small water suppliers can have great difficulty in attaining a 5 ppb standard.

Earlier this year, EPA announced the availability of a new toxicological review of arsenic. That review suggested greater cancer risks from arsenic. Yesterday, EPA’s Science Advisory Board issued a report generally supportive of the new toxicological review. If the result is a further tightening of the MCL, more stringent cleanups, through the ARARs process, will follow ineluctably.

I don’t normally post about developments this far from concrete regulatory changes. However, given the way the Superfund cleanup process works, PRPs negotiating cleanups of sites with arsenic groundwater contamination have to begin to factor this issue into their strategy now, because it’s not too early to starting thinking about cleanup cost estimates for alternative - meaning lower - arsenic MCLs.

Having put you on notice, I now have to tell one war story; if you don’t feel the need for a war story, you can stop reading here. In 1991, I was involved in negotiating the settlement for the cleanup of the Coakley Landfill Site, in southern New Hampshire. The federal government was a PRP. In Coakley, the government made a substantial (seven figure) contribution to the settlement. However, because the private PRPs had argued in negotiations with EPA that there was no need to treat groundwater – notwithstanding that the ROD remedy selected by EPA required groundwater treatment – the federal government as PRP insisted on getting a refund of the share of its payment attributable to the groundwater remedy, should EPA finally certify completion of the remedy without there ever having been an active groundwater treatment system in operation.

A few years later, the PRPs indeed persuaded EPA to eliminate active groundwater treatment. At the time, the expected date for certification of completion was 2007. In 2001, EPA changed the arsenic MCL from 50 ppb to 10 ppb. I don’t need to tell you that there is an arsenic issue at the Coakley Site. Now, the expected date for certification of completion is 2021. If, before then, EPA were to further lower the arsenic MCL, who knows what will happen to the expected date for certification of completion? The private PRPs may never have to reimburse the federal government!