81 



Some differences were apparent for Nephtys trace metal data between stations (Figure 

 6-50). Copper concentrations were significantly higher at the reference station at either the 

 south or north CADS stations. Conversely, the concentrations of iron in the reference 

 Nephtys samples were significantly lower than the south or north Nephtys samples. DDT and 

 PCBs were not detected in any body burden samples. The metal concentrations measured in 

 Nephtys from all of the CADS locations are equal to or lower than concentrations reported 

 for the MBDS and CLIS reference locations (SAIC 1987c and 1988f). Although Central 

 Long Island Sound and Massachusetts Bay are not pristine, the reference locations in these 

 areas are not considered to be seriously affected by anthropogenic activity. 



6.7.2 CADS: 1990 Monitoring Results 



The precision bathymetric survey conducted at CADS in May 1990 was used to 

 position a permanent buoy and to determine the remaining site capacity. It was predicted 

 that the central portion of the trough would have a maximum decrease in depth of 2 m with 

 only 10 to 30% of the disposed material detected by comparing the sequential bathymetric 

 plots. This relatively low detection was expected because of the extremely rough topography 

 at the site. 



A temporary buoy had been deployed at CADS in April 1990 at 43° 17.775 ' N, 

 70° 27. 194' W. The results of the bathymetric survey in May indicated that the buoy did not 

 need to be repositioned. The new buoy was deployed in the same location. 



The initial site capacity at CADS, based on a 36 m minimum depth, was 

 approximately 600,000 m 3 within the disposal site boundaries (SAIC 1990m). The area of 

 the disposal site > 36 m depth was confined mostly to a 300 x 300 m area around the 

 disposal buoy location. The volume of dredged material measured for the 300 x 300 m area 

 disposed between 1987 and 1990 was 129,260 m 3 . Considering the percentage of material 

 accumulating in the disposal site and compaction after disposal, the amount of dredged 

 material necessary to fill the site would be 462,580 m 3 . 



6.7.3 References for Section 6.7 



Larsen, P. F.; Zdanowicz, V.; Johnson, A. C. 1983. Trace metal distributions in the 

 surficial sediments of Penobscot Bay, Maine. Bull. Environ. Contain. Toxicol. 

 31:566-573. 



Larsen, P. F.; Gadbois, D. F.; Johnson, A. C. 1985. Observations on the distribution of 



PCBs in the deep water sediments of the Gulf of Maine. Mar. Poll. Bull. 16:439-442. 



DAMOS Summary Report, 1985-1990 



