Demonstration & Validation of Enhanced Monitored Natural Recovery at DoD Sediment Sites

Cleanup costs of contaminated sediments at Navy and US Marine Corps (USMC) sites are estimated to exceed $1 billion. For contaminated sediment sites, risk reduction and ecological recovery are achieved primarily by reducing chemical bioavailability in surface sediments, thereby mitigating contaminant exposure pathways. Cost effective remedies for sediment remediation at moderately contaminated Navy/USMC sites are lacking. Currently, the primary remedial options for Navy/USMC are dredging, isolation capping, and monitored natural recovery (MNR - see also: Development of DoD Guidance for Monitored Natural Recovery at Contaminated Sediment Sites). Dredging is expensive, can have adverse short-term effects, severely impacts the benthic community, and can negatively impact surface water hydrology and aquatic habitat. Conventional isolation capping, though less expensive than dredging, also severely impacts the benthic community, and can disrupt surface water hydrology and aquatic and near shore habitat by changing bathymetric elevations. MNR is cost effective, but is difficult to ensure performance and can take decades to be effective.

MNR combined with thin-layer capping (TLC), referred to as Enhanced Monitored Natural Recovery (EMNR or ENR), has the potential to accelerate and improve the effectiveness of MNR. TLC augments natural recovery processes by placing a thin layer (e.g., 15-30 cm) of clean material over contaminated surface sediments. Initially, the TLC isolates sediment contaminants and creates a relatively clean surficial sediment layer. This layer provides an initial foothold for benthic biota that facilitates recovery, creating a positive chain reaction where surface sediment concentration reductions promote additional colonization and recovery.

The objective of this project is to foster broader understanding and acceptance of the EMNR remedy through demonstration and validation of performance and cost-effectiveness at DoD contaminated sediment sites. This project will pursue this objective by reviewing and documenting cost and performance data from sites where EMNR has been previously implemented, and through a full-scale field demonstration and validation of EMNR at a DoD contaminated sediment site. Together, this information will provide DoD site managers and regulatory agencies with well-documented cost, performance, and risk-of-remedy data with which to evaluate EMNR during the remedy selection phase, and to gauge remedy effectiveness during the monitoring phase.

Capabilities:

• Sediment assessment and remediation expertise

Applications:

• Improve DoD’s ability to effectively assess and manage contaminated sediment sites

More Information:

• Merritt, K., J. Conder, V. Magar, V.J. Kirtay, and D.B. Chadwick. 2009. Enhanced Monitored Natural Recovery (EMNR) Case Studies Review. Technical Report 1983. SSC Pacific, San Diego, CA. 39 pp. [2.53 MB PDF file]
• McMeechan M., J. Conder, J. Germano, V. Kirtay, and B. Chadwick. 2010. Baseline Benthic Community Characterization in Advance of Thin-layer Placement at Quantico Embayment, Virginia, USA. Proceedings of SETAC North America 2010 Annual Meeting, Portland, Oregon, November 2010. [5.29 MB PDF file]