134 



below the CDM material, which was consistent with the bathymetric data (e.g., Core 2A; 

 Appendix D). Overall, the grain size of cores 3A and 3B was slightly sandier than the other 

 cores. 



The long core, Core 4A, was situated in the outer zone but in an area of recent 

 dredged material accumulation (Figure 2-6). The core consisted uniformly of dark olive- 

 gray silty clay that was similar in appearance and texture to the material collected in the 

 upper portion of cores from many of the other stations. This suggests that the material in 

 Core 4A was predominantly CDM. The three samples collected down-core were very 

 similar in both physical and chemical characteristics (Tables 3-5 and 3-6). Both metals and 

 PAH data were consistent with the samples collected from the cores representing CDM 

 (Appendix E). 



4.2.4.2 Middle Zone 1997 



Five cores were collected in 1997 in the middle zone, four short cores (1A, 5 A, 7A, 

 and 8 A), and one long core, 6 A. At the base of Core 1 A, located near the boundary of the 

 mound, there was an olive-gray gravelly sand and shell hash, similar to the ambient 

 sediments collected in Core 13A (Appendix D). This core also had relatively low metal 

 concentrations. In general, the middle zone cores consisted of sandy fine-grained sediment 

 (1 1-37% sand; 63-89% fine-sediment). The metals and PAH concentrations of the cores 

 collected in the middle zone were consistent with the CDM values measured at the dredging 

 area. The long core collected in the middle zone, Core 6A, again showed overall fine- 

 grained sediments relative to other middle zone cores, as with long Core 4A in the outer 

 zone. 



4.2.4.3 Inner Zone 1997 



Three short cores (9 A, 1 1 A, and 12A) and one long core (10A) were collected in the 

 inner zone as part of the 1997 survey. Core 9 A was located relatively close to middle zone 

 Core 8A and was similar in lithology and chemical concentrations to the cores in the middle 

 zone. The other two short cores collected in the inner zone showed overall higher fines 

 content (67-88%) and less sand. The PAH values were consistent with CDM, and metals 

 concentrations generally were within the range of those measured in the middle and outer 

 zones. The concentrations of Zn were on the higher side of the range measured in the CDM 

 material (101 mg/kg at Station 1 1A and 215 mg/kg at Station 12A), but evidence from the 

 PAH data support the determination that these were cap sediments. 



The long core collected in the inner zone (Core 10A) was the longest of the 1997 

 survey, and recovered the widest variety of lithologies. The upper two meters was similar to 

 CDM recovered in the other cores. Below this interval, patches of black oily sediment, 



Monitoring Cruise at the New London Disposal Site, Seawolf Mound 1995 - 1998 



