48 



(Figure 3-4). Depth difference calculations between SAIC's June 1991 and OSI's 

 December 1991 surveys showed the accumulation of dredged material to a thickness of 1.0 

 m around the D/S and NDA buoy locations (Figure 3-5; Appendix Al). 



According to the DAMOS disposal logs, the Gwen Mor Marina and Port Niantic 

 material was repeatedly deposited south and east of the NDA #1 and #2 buoy locations. 

 The majority of Dow Chemical Company and Stonington Harbor UDM was reportedly 

 disposed on the eastern side of the D/S buoy, consistent with the depth difference plot. 

 The smaller mounds (0.4 to 0.8 m high) to the east of the larger deposit probably represent 

 Gwen Mor Marina and Port Niantic dredged material released while the NDA #1 buoy was 

 off-station, due to contact with a U.S. Navy submarine. 



Comparisons were then made between the re-gridded August 1992 postcap 

 bathymetric survey performed by SAIC (Figure 3-6) and Ocean Survey Incorporated 's 

 December 1991 precap survey. The depth difference calculations showed the buildup of 

 CDM to a maximum thickness of 0.8 m approximately 350 m to the east of the D/S buoy, 

 with increases in depth of CDM up to 20-40 cm throughout the survey area (Figure 3-7). 

 It appears much of the CDM dredged from the Dow Chemical Company's Allyns Point 

 facility was actually released somewhat east of the UDM deposit (Figure 3-8). As a result, 

 the final, irregularly shaped bottom feature was formed by the coalescing of three sediment 

 deposits (NDA suitable material, D/S UDM, and D/S CDM; Figure 3-9). 



Detailed analysis of the 1995 and 1997 bathymetric surveys showed no significant 

 difference in the size or shape of the NL-91 and D/S mound complex since 1992. Given 

 the low profile of the capped mound as detected in August 1992, large-scale consolidation 

 of the sediment deposit was not anticipated. 



3.1.2 REMOTS® Sediment-Profile Photography 



In the August 1992 sediment-profile photography survey over the NL-91 and D/S 

 mound complex, 41 stations were occupied to examine surface sediment composition, 

 document benthic recolonization, and delineate the aerial extent of the disposal mound 

 apron. Follow-on surveys in August 1995, September 1997, and July 1998 consisted of a 

 truncated 13-station grid to facilitate long-term monitoring. A complete set of REMOTS® 

 image analysis results for these four surveys is presented in Appendix B; the survey results 

 are summarized below. 



Monitoring Cruise at the New London Disposal Site, 1992 - 1998 



