94 



At ten out of thirteen REMOTS® stations, the dredged material thickness exceeded 

 the camera prism penetration depth in all of the replicate photographs (Table 3-5). Along 

 the southeast stations, dredged material thickness either exceeded prism penetration depth 

 or reached a maximum of 13.24 cm (100SE) and 9.23 cm (50SE). At Station 150E, 

 dredged material thickness was less than penetration depth and averaged 12.8 cm. 



The mean prism penetration depths ranged from 12.2 cm to 15.9 cm and averaged 

 14.0 cm. These values are consistent with the presence of fine-grained material at most of 

 the stations. Most REMOTS® photographs taken at the USCGA mound showed 

 homogeneous silt-clay (>4 phi). Very fine sand (4 to 3 phi) was noted in two replicates at 

 100S, and at one replicate each at 100W, 50N, 50S, and CTR. Sand-over-mud layering was 

 noted at all stations. 



The boundary roughness values for the USCGA mound sediment-profile photographs 

 were low (ranging from 0.6 to 1.6 cm with an average of 1.0 cm), indicating relatively little 

 surface disturbance. Boundary roughness was due to biogenic activity in all but one 

 photograph. In one of the replicate photographs at Station 100E, the boundary roughness 

 was due to the presence of shell lag at the sediment surface. 



Station-averaged apparent RPD depths ranged from 0.8 cm to 7.6 cm at the 

 USCGA mound (Figure 3-37; Table 3-5). The average RPD value for the mound was 

 2.69 cm, with no geographic pattern to the distribution of values. The RPD values for two 

 out of three replicate photographs taken at the center station (CTR) were unmeasurable due 

 to camera artifacts. These two photographs were noted as being potentially hypoxic, along 

 with one replicate image at Station 50S and one replicate at Station 100S. 



A Stage II biological assemblage dominated the USCGA mound. The presence of 

 Stage III organisms (primarily Stage II on III) was noted in three of the replicate images at 

 Station 50W, two replicates at Stations 50E and 100E, and one replicate at Stations 100SE 

 and 100W (Figure 3-38). Many of the photographs showed dense aggregations of 

 amphipod tubes, or disturbed and decaying tube mats. Due to the presence of Stage II or 

 Stage II on III communities, the USCGA mound at the time of the August 1995 survey 

 appeared to be recovering more rapidly than predicted for recently deposited dredged 

 material (Germano et al. 1994). 



Median OSI values at USCGA mound REMOTS® stations ranged from +3 to +9, 

 with an overall average of +6.4 (Table 3-5). The lowest OSI was at the CTR station 

 (+3), primarily due to low dissolved oxygen conditions and lack of Stage III organisms, 

 although only one CTR photograph had a measurable OSI due to camera artifacts on the 



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



