43 



Due to contaminant levels measured in some project material prior to disposal, 

 capping has been conducted at NLDS. Approximately 13,700 m 3 of contaminated sediments 

 from the Thames River were capped at NLDS. SAIC monitored the coverage of the capping 

 operation since October 1988 with bathymetric and REMOTS® surveys (SAIC 1988c, 1990h, 

 Germano et al. 1995). Monitoring has indicated that the cap thickness at this capping 

 disposal point varied considerably, primarily due to multiple point dumping of capping 

 material. Additional cap material continued to be directed to this point through ongoing site 

 management to augment the cap. 



Sediment chemistry and body burden analyses were conducted at NLDS in 1986 and 

 1987. In 1986, sediment chemistry samples were collected at the center of each of the five 

 disposal mounds (NL-85, NL-I, NL-II, NL-III, and NL-Relic) and at the reference area. 

 Sampling stations in 1987 transected the disposal site along the axis of predominant water 

 movement (Figure 6-25). 



Results for both years indicated that the levels of As, Cd, Cr, Cu, Hg, Ni, Pb, Zn, 

 oil and grease, and PCBs were well within the low limits for contaminant levels of dredged 

 material relative to the NERBC classification system (Figure 6-26). No significant 

 contamination was observed when data were normalized to Fe or percent total carbon. 

 Concentrations of organochlorine pesticides measured in sediments in 1987 were, in general, 

 below the analytical detection limits at all stations. In most cases, the concentrations of 

 sediment contaminants in 1985 were higher at the five disposal mounds than at the reference 

 area and were higher in recent dredged material than in relic (Figure 6-26). The percent 

 fines and percent total organic carbon were also elevated for these areas in comparison with 

 the reference area. Results of the 1987 study did not detect contaminant deposition outside 

 of the site. 



Test organisms for body burden analysis in 1986 (the bivalve Pitar) were collected at 

 the reference area and the NL-II disposal mound (Figure 6-25). Results of statistical tests 

 (Mann-Whitney U-test) indicated that there were no significant differences, at the p<0.05 

 level, in the tissue levels of any of the trace metals measured between the two stations 

 (Figure 6-27). This information and comparisons of the trace metal data to literature values 

 from relatively clean sites suggested that trace metals were not bioaccumulating in the 

 bivalve (SAIC 1989b). In 1987, Pitar was not present in sufficient abundance for body 

 burden collection. Contaminant levels in tissues of the suspension-feeding amphipod 

 Leptocheirus were measured in 1987 and were either below detection limits, less than, or not 

 different from levels obtained at the reference station (Figure 6-27). 



REMOTS® sediment-profile surveys have revealed a typical, progressive 

 recolonization of dredged material by the benthic infauna. Similar to that of other Long 

 Island Sound disposal sites (i.e., WLIS, CLIS, and CSDS), the response of the NLDS 

 benthic community to disposal operations reflects the physical, relatively time-dependent 



DAMOS Summary Report, 1985-1990 



