pipe basis, but there has not been any overall management or environmental assessment 
on the area. 
As previously stated, the major point sources include sewage treatment plants and 
sewage sludge discharges. These discharges contain high levels of PCBs, up to about 30 
parts per million (ppm) on a dry-weight basis, which is a very high level. 
Other toxic organic concentrations in sewage discharges have been studied and are 
available in a variety of unpublished reports. Generally, the amount of toxics in these 
discharges exceed water quality criteria even after initial dilution, but there are sources 
of PCBs in the area other than sewage. Some data on sediments indicate that high levels 
of PCBs are found in the Inner Harbor areas approaching the Charles River, a finding 
which may or may not be directly related to the sewage inputs. Combined sewage 
overflows and other industrial inputs probably are very important in defining organic 
pollutant distributions in the harbor. 
In recent studies, scientists at Battelle have sampled several stations in the Outer 
Harbor and Massachusetts Bay, focusing on sewage treatment plants inputs and the 
general distributions of PCBs and PAHs in the area (Figures 1 and 2). 
The Harbor contains the highest levels of PCBs (0.06 to 0.33 ppm), levels that are 
not exceptional according to all the information from other areas we have evaluated so 
far. What is really exceptional in the Harbor are the various pockets of very high levels 
of PAHs. A hot spot was discovered at Station BH-2, an area called Deer Island Flats and 
a site of potential deposition of sewage sludge discharged to the east. This area is a mud 
flat with high organic content (Figure 1). Station BH-2's sediments contain extremely 
high levels of PAHs (880 ppm), very much higher than areas such as New York Harbor and 
other highly polluted estuaries. PAH concentrations are highly variable in the Harbor. 
Our study is based on only seven stations with PAH concentrations ranging from 2.7 to 880 
ppm and a mean of 180 ppm (Table 1). Other PAH hotspots might exist in the Harbor. 
The ratio of these toxic organics to coprostanol, the sewage indicator, indicates that 
sewage or sewage overflows are prevalent inputs of chemicals to the sediments in the 
area. 
Looking at Massachusetts Bay, we see the topography is a basin-bank-type of 
system. Stellwagen Bank approaches a depth of 20 meters from the sea surface. The 
Bank is an area with a great deal of whale activity. There are other basin areas in the 
region such as Stellwagen Basin, westward of Stellwagen Bank. Other basins in the region 
represent potential "traps" for coastal sediments and for pollutants that are discharged 
from along the coast and from Boston Harbor. The relatively high percent of silt in the 
Bay characterizes the basin areas and suggests that these are potential deposition areas of 
pollutants. There are cobble or gravel areas closer to shore, but with increasing distance 
offshore, there are potential traps for pollutants that are discharged from along the coast 
and from Boston Harbor. 
63 
