Abstract
A preliminary environmental investigation conducted by the current private owners of a former US Navy facility, NAS Green Cove Springs, found evidence of historic releases of polychlorinated biphenyls (PCBs) and other hazardous substances from the facility to the St. Johns River in Green Cove Springs, Florida. The current owners subsequently entered the voluntary cleanup program with the Florida Department of Environmental Protection to understand the origin, nature, and extent of contamination caused by the suspected releases.
Beginning in the 1940s until 1960, the Naval Station berthed up to 500 ships of the Atlantic Reserve Fleet. Fourteen piers, up to a quarter mile long, were constructed to dock and maintain these ships. Ships were kept in a state of near-readiness and maintenance was ongoing. Each pier contained one or more electrical transformers containing 100 to 150 gallons of Askeral di-electric fluid. Askeral, a mixture of PCBs and chlorinated benzenes, was directly released to the river during maintenance activities based on witness testimony. Based on this information and other historical records, it was concluded that releases of hazardous substances to the river likely occurred in connection with the Navy’s activities. However, in the subsequent five decades of private ownership, the site has been operated as a private port facility, with several tenants engaged in marine services, which may have contributed to conditions in the river and confound interpretation of the Navy’s historical releases.
The primary goal of the study was to determine if releases to the St. Johns River related to historical Navy activities contributed to sediment contamination. To achieve this goal, a multiple line of evidence approach was used. Extensive sampling of Site sediments adjacent to the piers was performed. This sampling included the collection of surface and subsurface sediment samples from 32 locations within the pier area. Locations adjacent to former transformer locations were targeted during this sampling. PCBs demonstrated a significant increase with sediment depth at most locations. To estimate the timeframe in which the higher PCBs observed at depth in the sediment were deposited, a geochronology evaluation was conducted using sediment cores collected at five locations. Cesium-137 in sediment was used to construct a time history of sediments at various depths. Associated with atmospheric testing of thermonuclear weapons, the location in the sediment column where Cesium-137 first appears and where it is measured in its highest concentration can be used as time markers within the sediments representing 1954 and 1963, respectively. Using these markers, sediment intervals corresponding to the Navy’s occupation of the site were identified. From this interval, a reference sample was analyzed for PCB congeners to facilitate forensic analysis. The PCB congener profile of this sample revealed a relatively unweathered profile consistent with Aroclor-1260, a known Aroclor used in the manufacture of Askeral. The PCB composition of the
remaining sediment samples was compared to the composition of the reference sample to determine if they are similar (and therefore consistent with PCBs associated with historical Navy releases). This analysis demonstrated that the PCB congener signature found in sediments throughout the site is consistent with a known Aroclor mixture used by the Navy during its operations at the site. Finally, metals and PAHs are frequently observed together in deeper sediment intervals, supporting their common historical origin and contemporaneous release. In addition, elevated levels of these metals and PAHs are within the sediment horizons identified as representing the Navy’s presence at the site.
Multiple lines of evidence indicate that the sources of contamination in Site sediment are related to Navy releases and that several sources of uncontrolled releases of contaminants existed during that time. These contaminants, including PCBs, are primarily found at depth but have mixed throughout the sediment column and are present at low levels in surface sediments. Overall, this approach conclusively demonstrated for the current owners that site contaminants, particularly PCBs, were historical in origin and related to legacy releases during the Navy’s presence at the site. Subsequent investigations defined the full nature and extent of those historical releases. These investigations confirmed that elevated PCBs are confined to deeper sediments near known historical Navy releases.