Purpose:

Marine sediments serve as a repository for contaminants from a wide variety of sources. The environmental risks posed by these contaminants are determined largely by the degree to which they remobilize into the environment. This project demonstrates the organic contaminants application of an instrument recently certified by the California Environmental Protection Agency (EPA) for metal contaminants. Two demonstrations will be performed at the locations established for metals certification. One at San Diego Bay's regulatory "toxic hotspot" (Paleta Creek area of Naval Station San Diego) and another within the Super Fund site of Naval Complex Pearl Harbor's Bishop Point.

Description:

The Benthic Flux Sampling Device (BFSD) was adapted from benthic flux chamber technology developed for oceanographic studies of the cycles of major elements and nutrients on the seafloor. The BFSD is an autonomous instrument for in situ measurement of flux rates of sediment contaminants and is California EPA certified for heavy metals (e.g., lead, mercury, chromium, zinc, and copper). Extension of the certification to organics (e.g., polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and pesticides) is planned. The instrument can be configured to collect both metals and organics samples during a single test. As with metals, a flux out of, or into, sediment is measured by isolating a volume of water above the sediment, drawing off samples from this volume over time, and analyzing the samples for increase or decrease in toxicant concentration. Increasing concentrations indicate that the toxicant is fluxing out of the sediment. Decreasing concentrations indicate that the toxicant is fluxing into the sediment. The BFSD system performs autonomous collection of samples from a sealed volume at the sediment water interface during a period of 2 to 4 days. This can provide a basis for risk-based decision making and potential cost savings by measuring bioavailability of contaminated sediment, reducing cleanup requirements where contaminants are not remobilizing, evaluating the integrity of sediment caps, and documenting the actual contaminant contribution of sediments.

Benefits:

Where it can be demonstrated that remobilization of contaminants is limited because many contaminants are strongly sequestered within the sediment and not likely to leach out, significant cost avoidance may be achieved through reduction of cleanup costs. Estimated disposal costs for contaminated sediments range from $100 to $1,000 per cubic yard. A survey of U.S. Navy shoreside facilities (NRaD, 1995) indicated that of the 31 facilities that responded, 29 reported the presence of contaminated sediments. The actual volume of contaminated sediment at these sites is not well documented; however, even conservative estimates suggest that millions of cubic yards of material may exceed sediment quality guidelines. (Anticipated Project Completion - 2005)

Contact:

Mr. Tom Hampton
SPAWAR Systems Center
53475 Strothe Rd.
Division D-3604
San Diego, CA 92152-6310
Telephone: (619) 553-1172
Fax: (619) 553-6553
E-mail: thampton@nosc.mil