U.S. EPA Region 10, 70 pp, 2019

A pilot program is underway on the Lower Duwamish Waterway to test the use of activated carbon (AC) to augment enhanced natural recovery (ENR) using sand or gravelly sand materials and reduce the bioavailability of PCBs in sediment. Parallel ENR and ENR+AC subplots were successfully placed in three separate 1-acre plots: one in the deeper navigation channel, one in a berthing area subject to prop scour and one in an intertidal location subject to waves and wakes. Construction occurred from November 2016-February 2017. Monitoring is scheduled for three years to evaluate and compare ENR and ENR+AC performance in reducing the bioavailability of PCBs in the uppermost 10-cm surface layer. Monitoring events already completed include baseline sampling before construction, post-construction monitoring in February-March 2017, and the Year 1 monitoring event completed May-June 2018. Monitoring metrics are used to evaluate ENR and ENR+AC stability, including the stability of carbon in the ENR+AC layers, and chemical bioavailability using whole sediment and porewater analyses. https://ldwg.org/wp-content/uploads/2019/04/Final-ENR-AC-Year-1-Monitoring-Report_04032019.pdf Also see poster by V.S. Magar, et al.: https://www.battelle.org/docs/default-source/conference-proceedings/2019-sediments-conference-proceedings/b3.-mnr-and-enhanced-mnr/b3_-329_poster_magar.pdf?sfvrsn=c90c5782_2