3.4.2 Sediment Chemistry 



The sediment collected at BBDS contained low NERBC 

 concentrations of As, Cd, Cr, Cu, Pb, Hg, Ni, and Zn (Table 3-3) . 

 Metal concentrations tended to be higher in stations containing 

 greater percentages of clay and total organic carbon (Table 3-4) , 

 namely reference area 3, center and 200W, followed by stations 23, 

 22, 24 and 13. Stations 1, the disposal site center, and 20 had 

 the lowest concentrations of metals. 



The pesticides tested belong to the group of 

 organochlorines and fall within the general classification of 

 chlorinated hydrocarbons (Table 3-5) . Pesticide levels at BBDS 

 were very close to or below method blank values for all compounds 

 tested. Concentrations of all pesticides were slightly higher at 

 reference area 3 and station 13. Levels of DDT and dieldrin were 

 well below the high (NERBC) concentrations of >0.2 ppm and 0.1 ppm, 

 respectively. Concentrations of PCBs were below 0.5 ppm and met 

 the NERBC low limit of <0.5 ppm. 



The majority of high molecular weight PAHs were low in 

 comparison to concentrations measured for highly contaminated 

 estuarine sediments such as those at New Bedford Harbor (Table 3-6; 

 Pruell et al. , 1990) . No method blank results were reported for 

 this analysis, and NERBC criteria do not exist for PAHs. Detection 

 limits were higher for the lower molecular weight compounds 

 napthalene, acenaphthylene, and acenaphthene. Low concentrations 

 of the following higher molecular weight PAHs were detected at 

 reference area 3: phenanthrene, f louranthene, benzo(b)- 

 f louranthene, and benzo(a) pyrene. Pyrene was found in low levels 

 at stations 24, 13, and 20. 



4.0 DISCUSSION 



4 . 1 Bathymetry 



Based on results from the bathymetric survey and REMOTS® 

 photographs, two mounds were determined to originate from disposal 

 activity: the center mound, 1.2 m high and approximately 60 m wide, 

 and a 1.6 m high mound about 9 m in diameter to the southwest. 



4.2 REMOTS® Sediment-Profile Photography 



The distribution of the major modal grain size over the 

 surveyed area, as deduced from REMOTS® photographs, indicated a net 

 bedload sediment transport of fine-grained material to the 

 southeast. Stations containing a major mode of medium (2-1 phi) 

 and fine sand (3-2 phi) fractions were rippled, and the 

 superposition of sand over mud at stations not located on dredged 

 material suggests that the net bedload transport of fine-grained 

 material was from the north and west (source area) toward the 



