42 



6.3 NEW LONDON DISPOSAL SITE 



6.3.1 Summary of NLDS 



The New London Disposal Site (NLDS) is located 3.1 nmi south of Eastern Point in 

 Groton, Connecticut (Figure 6-19). The site, centered at 41° 16. 100' N and 72°04.600' W, 

 is 1 nmi 2 , with water depths ranging from 14 to 25 m. Currents in the region are primarily 

 tidal-induced, with a maximum tidal flow in a northwest-southeast direction ranging between 

 30 and 40 cm-s" 1 . Additional current flows are introduced by the Thames River. Since 

 disposal began at NLDS in 1977 with the dredging of the Thames River and Groton 

 Submarine Base, several disposal mounds have been formed (Figure 6-20). 



The location of NLDS, within commercial shipping lanes, is not conducive to 

 trawling activities or setting lobster pots. However, lobstering and trawling for fluke are 

 conducted in the general vicinity of the site. There is an active sport fishing industry at 

 NLDS, with catches of tautog, flounder, bluefish, and weakfish (SAIC 1988a). As with 

 other sites in Long Island Sound, disposal activity at NLDS is curtailed from June through 

 August. 



SAIC conducted 10 monitoring cruises at NLDS between 1985 and 1990 (SAIC 

 1988c, 1989b, 1990g, 1990h, 1990i, Germano et al. 1995). These surveys assessed the areal 

 extent of dredged material, the stability of existing disposal mounds, and the effectiveness of 

 capping operations. The cruises also were designed to monitor the benthic community, 

 sediment characteristics, and water column DO concentrations. Periodic monitoring allowed 

 evaluation of the response and subsequent recolonization of the benthic environment 

 following disposal operations. Assessment techniques have utilized precision bathymetry, 

 side-scan sonar, sediment sampling for chemical, physical, and biological analyses, current 

 meter and DAISY array deployments, SCUBA diver observations, and REMOTS® sediment- 

 profile photography (SAIC 1990f). 



Approximately 783,000 m 3 of dredged sediments has been deposited at NLDS (Figure 

 6-21). This dredged material either was added to a pre-existing disposal mound, formed a 

 new mound, or served as cap material to contain contaminated sediments. After disposal 

 was completed at a mound, most mound heights remained stable over time (Figure 6-22). 

 Side-scan sonar and REMOTS® surveys have shown thin layers (<15 cm) of dredged 

 material extending beyond the disposal mounds and outside of the disposal site boundaries 

 (Figure 6-23). This broad distribution of dredged material has resulted primarily from barge 

 release points away from the disposal buoy and the proximity of designated disposal points to 

 the site boundary (Figure 6-24). Although strong, intermittent currents occur in the region, 

 the limited fetch at the NLDS site reduces the incidence of storm-driven currents and the 

 possibility of redistribution of sediments. The precision bathymetric survey following the 

 passage of Hurricane Gloria did not reveal any evidence of mound erosion (SAIC 1989b). 



DAM OS Summary Report, 1985-1990 



