Hot off the presses (or even not off the presses considering it was posted the day before the date on the document), the Proposed Plan for the Duwamish River Superfund Site is now available on EPA’s website.
I’ll provide a more complete analysis once I’ve reviewed, but it looks like EPA has gone with what was referred to as remedy option “5C+”. The Preferred Alternative, which addresses approximately 412 acres, includes the following elements:
•A total of 156 acres of active cleanup, consisting of:–84 acres of dredging or partial dredging and capping (an anticipated total volume of 790,000 cubic yards would be dredged and disposed in an upland landfill);–24 acres of capping, with possible amendment activated carbon or other contaminant-sequestering agents; and–48 acres of Enhanced Natural Recovery (ENR placing 6 to 9 inches of clean material over contaminated sediments) with possible amendment of activated carbon or other contaminant-sequestering agents, if these amendments are shown to be effective in pilot tests.• Further reduction of contaminant concentrations over time in the remaining 256 acres through Monitored Natural Recovery (MNR–relying on natural processes such as burial of contaminated sediments by cleaner sediments from upstream). Long-term monitoring data will determine whether additional cleanup actions will be necessary in MNR areas.•Institutional controls (ICs) and LDW-wide monitoring to enhance and measure protectiveness, and to protect the integrity of remedial action elements such as capping and ENR, while minimizing reliance on seafood consumption-related ICs to the extent practicable.