104 



Fine to very fine sands (4 to 3 phi) characterized most of the sediment at the reference 

 areas (Table 3-2). Two stations within NE REF were composed primarily of fine-grained 

 sediments (>4 phi) while WEST REF displayed several stations with a significant fine sand 

 component (3 to 2 phi). 



Boundary roughness values were generally low (<1 cm), except at WEST REF 

 Station W13 (STA 08), which had a replicate average value of 1.7 cm. Disturbances within 

 the surface sediments at the reference areas were primarily attributed to physical forces. 

 However, evidence of biological activity causing the surface disturbance was present in 

 approximately 33% of the reference area photographs. 



The RPD depths ranged from 1.55 cm to 3.98 cm, with an overall average of 2.55 cm 

 (Table 3-2). In general, the RPD depths at both NLON REF and WEST REF tended to be 

 deeper than those at NE REF. Redox rebound layers were apparent roughly 4 cm below the 

 sediment- water interface at two stations within NE REF (Stations 10 and 12). 



Amphipod tube mats were common at the reference areas; some of these mats 

 appeared to be disturbed at NE REF and WEST REF. Stage II was considered the dominant 

 successional stage. Stage I was found at multiple stations in all three reference areas, but 

 only seven replicates had active feeding voids at depth to indicate the presence of Stage III 

 individuals. 



The OSI median values ranged from +5 to +10, with an overall average of +6.7. 

 These were very similar to values observed in 1997 (+6.8). No replicates had low dissolved 

 oxygen conditions, although a few replicates from NE REF did portray dark, sulfidic 

 sediments. No methane gas pockets were detected in the images obtained from the reference 

 areas in July 1998. 



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



