PCB concentrations in the reference animals and those from the 

 on-site stations was not statistically significant, except at 

 station 1500NW where PCB body burdens were significantly lower 

 than the reference (Table 3-6) . 



4.0 DISCUSSION 



4 . 1 Bathymetry 



The results of the bathymetric survey at the New London 

 Disposal Site revealed a significant addition of dredged material 

 at the "NL-85" mound, centered approximately 60 meters 

 south-southeast of the disposal buoy. Scow logs verified that 

 approximately 82% of the material was disposed at this location in 

 the past year. No depth change was observed 530 m northwest of 

 the buoy on the southern flanks of the NL-RELIC mound, where an 

 estimated 12,400 cubic meters of material was disposed due to 

 miscommunications about the disposal location. 



The lack of an observable depth change at the northwest 

 location suggests that the material deposited there occurred in 

 layers less than 15 cm thick, which could not be detected reliably 

 by acoustic measurement. In addition, although some potentially 

 allochthonous sediment was observed in the REMOTS images from this 

 area, it is impossible to unequivocally classify this sediment as 

 dredged material due to the heterogeneity of the sediments 

 historically disposed within the New London site. Any disposed 

 material which might be present probably occurs in discontinuous, 

 thin coarse-grained layers, making it difficult to detect by 

 either bathymetry or REMOTS. 



A comparison of the dredged material volume estimated 

 from scow logs (67,500 m 3 ) with the volume calculated from depth 

 data (43,000 m 3 ) indicates a decrease in volume of 36%. If only 

 the area in the vicinity of the NL-85 mound is considered, a scow 

 estimate of 55,100 m 3 compares with a volume estimate of 33,951 

 m , representing a 38% decrease in volume. These decreases in 

 estimated volume compare well with the results of a study by the 

 New York District COE (Tavolaro, 1984), where it was determined 

 that the volume of material detected on the bottom by acoustic 

 techniques was approximately 40.7% less than the scow volume 

 estimates. Of this 40.7% volume decrease, 15.4% is attributed to 

 the loss of interstitial water during disposal and compaction of 

 the material after impacting the bottom. The remaining 25.3% 

 presumably occurs as thin layers of dredged material not detected 

 by the survey fathometer. 



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