66 



The penetration depth of the camera serves as a measure of sediment density or 

 compaction. At the three reference areas, (NLON REF, NE REF, and WEST REF), the 

 replicate-averaged mean camera penetration ranged from 5.6 to 11.7 cm (7.8 cm average; 

 Table 3-2) which was similar to that observed in 1997 (7.3 cm). Penetration was shallower 

 at the reference areas relative to the Seawolf Mound because of the presence of less compact, 

 finer grained sediments at the disposal mound. Penetration depths at the Seawolf Mound 

 varied from 8.45 to 15.78 cm, with an average of 13.06 cm. The average camera penetration 

 decreased by 0.39 cm since 1997. This change may be within the range of measurement 

 error and not significant, although the decreasing trend of camera penetration may suggest 

 increased compaction of the dredged material at the surface. 



The boundary roughness at the Seawolf Mound ranged from 0.4 to 2.1 cm, with an 

 average of 1.1 cm, which was higher than the average value measured at the reference areas 

 (0.9 cm). There was no obvious spatial pattern of boundary roughness values. Shell lag and 

 surface scour were predominant (Figure 3-4). Shell armoring of the surface was also 

 evident. It is expected that the sand and shell "lag" deposits (large sediment particles that 

 "lag" behind as the finer materials are washed away) would be resistant to further 

 winnowing on the scale experienced regularly. This process is called "textural armoring". 

 Several replicates were also identified as winnowed: 75SE (c), 150SE (a), 150NW (a and b), 

 300NW (c), and 450NW (c). The 1998 results have similar winnowed areas (which also 

 includes scour lag and surface scour) compared with those observed in 1997. Varieties of 

 surface types were observed across the mound (Figure 3-17). Surface scour and shell lags 

 also were apparent in some of the photographs of the reference areas. Further discussion of 

 the potential for physical disturbance of the Seawolf Mound material is provided in the 

 Discussion (Section 4.0). 



The replicate-averaged RPD for each station ranged from 0.30 to 3.75 cm (1.72 cm 

 average; Table 3-1). This value was less than the average calculated for the stations in 1997 

 (2.5 cm). The implications of the change between 1997 and 1998 are discussed further in 

 Section 4.0. The Seawolf Mound average RPD measured in 1998 also was below the 

 reference area average of 2.6 cm. No low dissolved oxygen (DO) conditions were observed 

 in 1998, compared to one replicate in 1997. Some stations had a visible redox rebound 

 varying in depth between 3 and 10 cm. The shallowest RPDs (<1.2 cm) were observed in 

 replicates on the plateau and apex of the mound, although the station average RPD values 

 had a high spatial variability (Figure 3-18). 



The successional status was advanced, with Stage n, Stage II to m, or Stage II on IE 

 communities inhabiting the sediments of the Seawolf Mound (Table 3-1). Only two of the 

 86 replicates were indeterminate, in contrast to the higher number classified as 



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



