Fetters, K., G. Rosen, V. Kirtay, B. Chadwick, J. Conder, V.P. Sacks, M. Grover, and V. Magar.
Journal of Soils and Sediments [Published online 6 August 2019 ahead of print]

The demonstration study evaluated the effectiveness of a nominal 15-cm thin-layer sand cap (TLC) as an enhanced monitored natural recovery (EMNR) remedial strategy to address sediments moderately contaminated with dichlorodiphenyltrichloroethane and its derivatives (collectively DDX). Reductions observed were: surface sediment (84-97%), porewater (33-75%), and tissue concentrations (Lumbriculus variegatus deployed in situ) (72-82%). A 63-72% decrease in DDX depositional mass flux also was observed. Multiple lines of evidence indicated that the TLC material remained stable. The deposition of suspended material with low concentrations of DDX influenced concentrations in the surface sediments. No adverse effects were observed on the benthic invertebrate community after TLC placement, and ecological metrics indicated increases in benthic community health. The demonstration showed that EMNR can be effective at reducing biological exposure in surface sediments while minimizing short-term disturbances to benthic communities at sites where MNR is a remedy option, but natural deposition rates are inadequate to achieve cleanup goals within a reasonable timeframe. See additional information about this ESTCP-sponsored project at https://serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Sediments/In-place-Remediation/ER-201368/ER-201368.