62 



Stations CTR, 150N, and 150NW could not be calculated because of an indeterminate 

 successional stage, partially due to smears of gray-black clay from the REMOTS® camera 

 wiper blade obscuring the sediment surface. Outside the central area, stations with average 

 OSI values of <+6 (indicating disturbance) were randomly located (Figure 3-14). 



CDM was not detected acoustically at Station 300E (Figures 3-6 and 3-13), but CDM 

 was detected in all three REMOTS® replicates. Figures 3-15 and 3-16 show the sediment 

 profile photographs taken at this station as well as a replicate from the center station for 

 comparison. Glacial gray clay was detected in two of the replicates, 300E B and C, similar 

 to the center station (Figure 3-16). Minor surface scour and Stage II tube mats were 

 apparent at 300E and not at the center station, due to the stations' respective locations on the 

 mound. The color mottling in replicate 300E A (Figure 3-15) indicates multiple source 

 areas of the CDM deposited there. The brown sand and silt is consistent with characteristics 

 of CDM placed in other areas of the mound. 



3.1.2.2 July 1998 Survey 



In July 1998, dredged material was again present in all of the photographs collected 

 within 300 m of the center station (Table 3-1). For all replicate stations with dredged 

 material, the observed thickness was greater than penetration (Table 3-1, see Appendix B for 

 replicate values). This means that the camera penetration depth did not exceed the thickness 

 of the dredged material layer, and no ambient sediments were visible except in two replicate 

 photographs on the mound apron, where dredged material was not detected. 



A mix of silt and clay (>4 phi), which was more common at the inner stations (within 

 150 m of center), and very fine (4 to 3 phi) sand characterized the near surface sediments of 

 the Seawolf Mound (Table 3-1). The grain size at the inner stations was finer than at the 

 reference areas, which were characterized as very fine sand (Table 3-2). Stations 150N, 150S 

 and 300S each had one replicate with a coarser grain size of fine sand (3 to 2 phi). Surface 

 sand overlying fine-grained sediment (sand-over-mud stratigraphy) was noted for many 

 photographs (Appendix B). The dominant grain size was similar to that measured at the 

 reference areas (major mode primarily 4 to 3 phi), except for the inner stations dominated by 

 silt/clay. Eight stations had a finer major mode size (>4 phi) in 1998 than observed in 1997 

 (4 to 3 phi). 



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



