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• Document and delineate the changes in bottom topography (accumulation and 

 consolidation) in the areas of concentrated disposal since August 1995. 



The large volume of capping material at the Seawolf Mound produced consolidation 

 of the underlying UDM through a process observed in other mounds (Poindexter-Rollings 

 1990; Silva et al. 1994). This combination of self-weight consolidation and overburden 

 from the cap sediments typically proceeds rapidly for the first nine months to a year after 

 capping is completed and then decreases to a very slow rate over subsequent years until 

 equilibrium is reached. In the case of the Seawolf Mound, consolidation of the entire mound 

 was as much as 2 m (about 50% by volume), equivalent to the initial thickness of the cap. 

 These volumetric changes were confirmed by long cores recovered from the center of the 

 mound. 



1998 



The follow-up monitoring in 1998 required by the Navy's Seawolf Program 

 Monitoring Plan achieved the following three main objectives: 



• Assess Further Consolidation of the Seawolf Mound Dredged Material 



The lack of significant topographic change between the 1997 and 1998 surveys 

 indicated that the Seawolf Mound completed the rapid phase of consolidation, and was in the 

 phase of limited, slow (secondary) consolidation. Tiered monitoring protocols, as well as 

 historical evidence from open- water disposal mounds, predict that the mound will remain 

 stable. Should a large storm occur in the eastern Sound, a follow-up, confirmatory 

 bathymetric survey should be conducted. Almost 2.5 years after capping was concluded, the 

 bathymetric configuration of the Seawolf Mound continued to depict a broad, flat 

 topography with a small central apex, large plateau, and surrounding apron. 



• Verify the Presence of at Least 50 cm of Capping Dredged Material (CDM) 



Core data again indicated that the top 50-cm of material had no elevated levels of 

 chemical contaminants that would indicate the presence of contaminated UDM. The long 

 core collected in the inner zone (Core 23 A) indicated approximately 1.1 m of CDM 

 overlying UDM, which was similar to the depth in the previous year near the same location 

 on the apex (Core 10A, 1.8 m of CDM). The PAH levels in the deepest samples of core 

 23 A, and the 0.5-0.75 m sample in 19 A, also suggested the possible presence of recovered 

 UDM, although PAH concentrations alone were not diagnostic of CDM/UDM materials. 

 Two cores clearly recovered ambient material: Core 17A in the outer zone below 2.2 m, and 

 short Core 21 A. Core 21 A was located near the outer edge of the cap and had physical 

 properties consistent with the reference area. There was no consistent difference in sediment 



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



