region to the southeast. This oxygen stress may have been 
inhibiting benthic recolonization in the southeast portion of the 
disposal mound. At the New London Disposal Site, overall, the 
highest OSI values were to be associated with NL-I; this mound has 
not received dredged material since 1977 and (according to the July 
1985 REMOTS® survey) this area did not experience late summer 
hypoxic conditions. The OSI map of the southwest grid (Figure 
3-52) provides only a few values from the northern and southern 
edges of the surveyed area because of the shallow prism penetration 
and dense shell aggregations at the sediment surface. All of the 
mapped values were below the threshold value of +6; this apparently 
reflected local physical disturbance factors. 
The distribution of OSI values for all stations combined 
(Figure 3-53a) was not significantly different from the Reference 
station (Figure 3-53c, Mann-Whitney U-test; p = 0.2973). 
Similarly, OSI values at the NL-85 mound (Figure 3-53b) did not 
significantly differ from the Reference station (p = 0.6753). The 
NL-85 mound had significantly higher indices than recorded in the 
January 1986 post-disposal survey (p = 0.006). This indicates that 
the NL-85 mound was experiencing successful colonization, 
particularly at its northern and western flanks. The slower 
colonization rate in the SE quadrant most likely was related to the 
presence of hypoxic bottom water in this area. 
3.4 Sediment Characteristics 
All of the sediment samples collected in the area 
southwest of the New London Disposal Site during the August 1985 
survey were composed of a large number of disarticulated mussel 
shells on the surface of a 2-4 cm layer of medium to fine sand 
(Table 3-1). Samples taken from stations C-13 and E-14 contained 
small amounts of black anoxic sediment. Past experience at 
locations within the central portion of the disposal site has shown 
that the ambient bottom normally is composed of a thin (2-3cm) 
layer of fine sand laying over a cohesive layer of clayey silt, 
(several vibracores taken at the site in December 1983 confirmed 
this interpretation and indicated that the clay layer typically 
extends down to a depth in excess of 4 meters). The higher 
concentrations of all the metals and oil and grease found at 
stations C-13 and E-14 (Table 3-2) suggest the presence of dredged 
material. 
During the July 1986 survey, sediment samples were 
collected at the five disposal mounds and at the Reference station. 
The sediment on the disposal mounds was either organic silt or 
silty sand (Table 3-3) while the Reference station contained only 
silty sand. Some variability can be seen in the size class data 
for replicate samples from the same mound and between the top and 
bottom samples. Where detectable levels were reported for the 
chemical composition of the replicates (Table 3-4), a mean and 
27 
