94 



1.8, 0.04, and 7.6 mg/kg, respectively (for data below detection, Vz the detection limit was 

 used for statistical calculations). 



Concentrations of Cu, Pb, and Ni also were consistent in the short core samples, except 

 for Core 14B in the outer zone. Excluding 14B, Cu ranged from 1 1 to 29 mg/kg 

 (14B was 120 mg/kg), Pb ranged from 17 to 29 mg/kg (14B was 88 mg/kg), and Ni ranged 

 from 12 to 23 mg/kg (14B was 71 mg/kg). Of the measured metals, the zone-averaged 

 concentrations were highest in the outer 400-600 m for all metals except Cd and Hg, primarily 

 due to Core 14B. Core 21 A generally had the lowest concentrations of measured metals. 



Similarly, Zn, which was measured both in the short and long cores, was relatively 

 consistent with depth and across the mound in both short and long cores. Zinc ranged from 40 

 to 95 mg/kg, with the exception of Core 14B (340 mg/kg) and the deepest sample from Core 

 23 A (1.0-2.0m, 130 mg/kg). The range of Zn in the long cores was variable (62-130 mg/kg) 

 and did not appear to correlate with the depth of the sample. 



The difference in metals concentrations, primarily for Core 21 A, was in part a function 

 of grain size. After normalizing the metals data to the percent of fine-grained sediments, the 

 outer cores still had the highest concentrations of Pb, Ni, Zn, and Cr, although the inner and 

 middle zones had similar normalized concentrations of Ni, As, and Cd (Table 3-11). Core 

 14B contained the maximum normalized values for Cr, Cu, Pb, Ni, and Zn. 



The mean values of the trace metals detected at the mound were consistently higher 

 than at the reference area, WEST REF 26A (Table 3-10; Figure 3-27). For raw metal values, 

 the data for Core 21 A tended to be closer to WEST REF than the mean for the Sea wolf Mound 

 cores. The normalized data (Table 3-11; Figure 3-28) indicated that the Seawolf Mound metal 

 values were similar to WEST REF. The 1997 short and long core data were very similar to 

 the data collected in 1998 (Figures 3-27 and 3-28). 



The metals data from the sediment cores were also compared to samples taken from 

 the dredging site prior to dredging operations (Tables 3-10 and 3-11; Figures 3-27 and 3-28). 

 Because of the difference in sampling methods of the pre-dredge samples, the average of 1990 

 and 1994 data, representing the entire depth of the channel to be dredged, was reported 

 separately from the 1992 data (Maguire Group 1995). The 1992 data were more influenced by 

 the concentrated contaminants in the upper 3 feet (see above). In addition, the grain size data 

 were not consistent for the 1990 and 1994 data sets and not available for the 1992 data set. 

 The 1990 and 1994 data did not show significant differences in metals concentrations for the 

 UDM and CDM designated areas. The 1992 UDM metals values were more representative of 

 the most contaminated sediments. 



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



