Topics explored at the recent “Partners in Environmental Technology Technical Symposium” sponsored by SERDP and ESTCP of the Department of Defense (DoD) include the remediation of contaminated sediments and environmental impacts on Navy sea ranges.

Contaminated Sediments:

We need to transform our thinking about remediating contaminated sediments, says Dr. Victor S. Magar of Environ International Corporation of Chicago. He argues that we should focus on in situ methods for remediating contaminated sediments, as opposed to dredging, for example, which should be used only for hotspots or in places that cannot be treated otherwise. Monitored natural recovery (MNR) can reduce the negative impacts of the more aggressive remedies and it can be integrated with other remedies. Monitoring can reduce the uncertainties of MNR. Magar says that he prefers MNR to dredging for the Hudson River PCB cleanup. The cost of MNR is one-tenth that of dredging, and one can afford to wait a few years to see if MNR is working. He says that MNR should be a component of every selected remedy for contaminated sediments. Current trends, such as increased urbanization, more drivers on the road, declining wetlands and legacy contaminants reflect changes in contaminant concentrations in sediments. Lead and DDT concentrations are declining, because the incineration of waste and the use of non-leaded gas are falling. PAHs, on the contrary, are increasing, due in part to the rise in vehicle use.

Dr. Richard G. Luthy of Stanford University is conducting a three-year field study at the Hunters Point South Basin in the San Francisco Bay to evaluate and demonstrate an in-situ treatment applying activated carbon amendment to sediments contaminated with PCBs. Hunters Point is one of several PCB hotspots in San Francisco Bay. It is a former naval shipyard and has been designated a Superfund site. A landfill at Hunters Point site is the source of PCBs. Dr. Luthy points out that PCBs are persistent, and they bioaccumulate. Fish in the area have been found to have unhealthful levels of PCBs. One could dredge for mass removal of PCB-contaminated sediments. However, with environmental dredging, one must avoid overdredging into clean material. As a result, some residuals remain. He and his team are using activated carbon to sequester PCBs. They mixed activated carbon into the biologically active zone in the first six inches of sediment. The South Basin area of Hunters Point is a tidal basin, where sediments are cohesive. When activated carbon is mixed into this sediment, it stays put, says Dr. Luthy. Results to date indicate that the activated carbon amendment is proving to be a cost effective, in situ non-removal solution that reduces the bioavailability of PCBs in sediments at the site. Dr. Luthy may be contacted by e-mail: luthy@stanford.edu

Assessing and Managing Environmental Impacts on Navy Sea Ranges:

Barbara Sugiyama of the Naval Facilities Engineering Service Center Marine says that marine resource science is still evolving. She reports that the munitions constituents RDX and MDX are biodegrading in the marine environment at navy sea training ranges. RDX and HMX are not toxic at expected marine concentrations. There is little or no potential for TNT, RDX or HMX to bioaccumulate in marine life, because it is excreted quickly. Studies are underway to determine how fast explosives residues from unexploded ordnance (UXO) are being released into the sea. Also under study are the corrosion rates of underwater UXO. A new topic of research for the Navy is the environmental effects of abandoned equipment (not ordnance) in the marine environment.

In a poster presentation at the DoD Environmental Technologies Symposium, Jim Barton of Underwater Ordnance Recovery, Inc. described the robotic device he has developed to recover hazardous materials from the sea floor. It can operate down to 1,000 feet and could be used to recover military munitions, for example, from numerous testing and dumping sites in the U.S., Canada, Japan, Brazil, Belgium, Sweden and the Baltic Sea.