Assessment of Environmental Contaminants Associated with the National Defense Reserve Fleet in Suisun Bay, California, February 2009

Executive Summary:

In response to requests from the U.S. Congress, the National Oceanic and Atmospheric Administration (NOAA) Office of Response and Restoration (OR&R) investigated environmental conditions related to the National Defense Reserve Fleet in Suisun Bay, California. These vessels are maintained by the U.S. Department of Transportation Maritime Administration and include more than 70 obsolete or decommissioned ships, sometimes referred to as the Reserve Fleet. A multidisciplinary team of scientists from OR&R initiated the study because of concerns regarding potential effects of peeling paint and hazardous materials that may have been released from these ships.

In July 2008, NOAA collected surface and subsurface sediment samples in the vicinity of the fleet, referred to as the Suisun Bay Reserve Fleet (SBRF) study area, and at reference and other locations within Suisun Bay and Carquinez Strait for contaminant analyses. NOAA also deployed mussels from June to September 2008 and collected resident clams to assess the bioavailability of contaminants. During the study, over 200 sediment samples from 72 stations and 42 tissue samples from 15 stations were analyzed for a suite of metals, some of which have been used in paint formulations applied to vessels. Polychlorinated biphenyls (PCBs), which may have been included in some paint formulations, and polycyclic aromatic hydrocarbons (PAHs) were also measured.

When developing the sampling plan, NOAA considered the dynamic nature of the San Francisco Bay system, which drains 40% of California and carries large amounts of sediment depending upon the time of year and water flow rates. In Suisun Bay and Carquinez Strait, locations of high and low water velocities exist, creating zones of sediment erosion or deposition. Major floods export large quantities of sediment and cause net erosion within Suisun Bay.

NOAA focused the sampling primarily within Suisun Bay and to a lesser extent into Carquinez Strait based on a hypothesis that fleet-related contaminants would tend to accumulate in areas of sediment deposition and that attribution to the fleet would be more feasible by examining sites closer to the SBRF rather than farther away. Although water currents and river flows move sediments downstream and away from the SBRF, factors such as dilution, sediment dispersion, and the presence of other contaminant sources were expected to confound interpretation of any contaminant inputs from the SBRF beyond Suisun Bay. Consequently, the sampling plan included more intensive sampling in the SBRF study area and suspected depositional areas near the fleet and less sampling farther away. Sampling locations were identified in part through analysis of available hydrodynamic information that revealed patterns of sediment erosion and deposition. Based on this hypothesis and approach, NOAA did not extend its sampling for this study into other parts of San Francisco Bay beyond Carquinez Strait.

NOAA recognizes that multiple industrial and municipal contaminant sources exist upstream of and in the vicinity of Suisun Bay and the greater San Francisco Bay area that could contribute environmental contaminants similar to those evaluated in this study. Characterization of other potential sources of contamination was not part of this study. However, NOAA did compare sediment contaminant concentrations identified in Suisun Bay to results from earlier studies and ongoing regional monitoring programs to provide a perspective on the magnitude and the distribution of specific contaminants in the greater bay area.

Based on a review of the literature and available data for the area, our discussions with scientists and stakeholder groups within the Suisun Bay and the greater San Francisco Bay areas, and evaluation of the data set generated by this study, NOAA concludes the following:

1. SEDIMENT ANALYSES:

According to NOAA’s statistical analyses, contaminant concentrations in sediments in the vicinity of the SBRF are not elevated relative to contaminant concentrations at reference locations. There are some instances in which concentrations of arsenic, copper, lead, and chromium observed across the project area are elevated relative to ambient values reported for other parts of San Francisco Bay. Generally, sediment metals concentrations from NOAA’s study are within a factor of two of the San Francisco estuary sediment ambient concentrations derived by the San Francisco Bay Regional Water Quality Control Board. NOAA did not find PCBs or PAHs in the project area at concentrations that exceeded sediment quality guidelines or ambient values.

2. PAINT CHIPS IN SEDIMENT:

Surface sediment samples from the vicinity of the SBRF were examined for visible metal debris and paint chips as well as various contaminants of potential ecological concern. In the project area, 18% of the surface sediment grab samples contained such debris or paint chips. In general, there did not appear to be elevated sediment contamination associated with those samples in which metal debris or paint chips were found. Finding paint chips in sediments is consistent with observations that paint continues to exfoliate from the vessels; this remains a matter of concern as an ongoing source of contamination to the bay.

3. TISSUE ANALYSES FOR TRANSPLANTED MUSSELS:

According to NOAA’s statistical analyses, concentrations of contaminants in mussels transplanted to the vicinity of the SBRF were not elevated relative to those at reference locations. However, the tissue concentration values should be considered preliminary and interpreted with caution. The transplanted mussels had low lipid levels, which could indicate stress caused by the low salinity regime encountered during the study. This might affect feeding rates and overall uptake of contaminants by the mussels.

4. TISSUE ANALYSES FOR RESIDENT CLAMS:

Concentrations of contaminants in clams collected from the vicinity of the SBRF were similar to concentrations found in resident clams from other parts of Suisun Bay and in other studies, although no statistical analyses were performed due to the limited number of tissue samples.

5. POTENTIAL FOR BIOLOGICAL EFFECTS:

Concentrations of contaminants in sediments were compared to literature guidelines to indicate the potential for toxicity to sediment dwelling organisms. Of the 18 metals that were analyzed for this study, nine have published sediment quality guideline concentrations for the effects range low (ERL) and the effects range median (ERM). Concentrations of some paint-related contaminants (for example, copper) in individual sediment samples in the vicinity of the SBRF exceeded the ERL, which is defined as a level below which adverse biological effects are rarely observed. Based on available data from previous studies, exceedances of the ERL are common for sediments throughout Suisun Bay and San Pablo Bay. Exceedances of the ERM values, defined as the concentration above which effects are observed in 50% of studies, occurred for nickel, mercury, and lead. Nickel concentrations throughout San Francisco Bay tend to be elevated and often exceed the ERM. Although all sediment samples in this study exceeded the ERM for nickel, previous studies revealed a poor relationship between observed toxicity and nickel concentrations, reducing the confidence in this ERM value. Nine percent of sediment samples in this study exceeded the guideline for mercury, and one sample exceeded the guideline for lead. Mercury is a known contaminant in San Francisco Bay due to historical use. None of the other metals analyzed exceeded the ERM.

Based on the points above, particularly comparison of the chemistry data collected for this study to sediment quality guidelines, NOAA concludes that sediments from the SBRF study area and the rest of Suisun Bay have a low to moderately low potential for toxicity to benthic invertebrates. The contaminant concentrations observed are largely comparable to values for the same metals and organics measured in other regions of the greater San Francisco Bay. Following this analysis, NOAA does not recommend specific sediment remedial actions in the vicinity of the Suisan Bay Reserve Fleet at this time.

Prepared by the:

National Oceanic and Atmospheric Administration, Office of Response and Restoration

Source Link:

http://response.restoration.noaa.gov/book_shelf/1845_ReportText_SuisunBayReportFinal.pdf