17 



3.2 REMOTS® Sediment-Profile Photography 



3.2.1 Grain Size Distribution 



The major modal grain size in the NL-TR survey area ranged from gravel (1-0 phi) 

 to silt/clay (>4 phi; Figure 3-6). The coarsest sediments, consisting of cobble, gravel, and 

 coarse sands, were located at stations 100SE, 100E, 200E, 300W, 400S, and 100N. This 

 coarse material may represent recent (100SE, 300W, and 100N) as well as relic (400S) 

 dredged material. Coarse sands were also present at some of the stations with active 

 bedforms (100SE, 100E, and 200E; Figure 3-7). The finest sediments (>4) were located at 

 NL-TR stations 400W and 400E and consisted of fine (3-2 phi) and medium (2-1 phi) sands 

 overlying mud (>4). Very fine sands (4-3 phi) were present to 400 m north, 300 m south, 

 and 200 m west, southwest, and northwest of the NL-TR survey center (Figure 3-6). In 

 general, these stations consisted of fine and medium sands (3-1 phi) overlying very fine sands 

 (4-3 phi) mixed with mud (>4 phi). Evidence of sand ripples were present at stations 100E 

 to 300E, 100NE and 200NE, 100SE, and 200W. 



Sediment grain size distributions at reference areas NE-REF and NLON-REF were 

 very similar with a major mode of 4-3 phi (very fine sands; Figures 3-6 and 3-8). Surface 

 characteristics at some of the NLON-REF stations included erosional shell lag deposits and 

 sand ripples. Mud clasts, possibly formed by bottom scour, were present at both reference 

 areas. The WREF reference area was characterized by fine sands (3-2 phi), scoured shell 

 lag deposits, and mussel beds (Figure 3-8). 



3.2.2 Boundary Roughness 



The frequency distribution of mean boundary roughness values for the NL-TR survey 

 area showed an equal distribution among classes 3-5 (Figure 3-9). Values over the area 

 ranged from 0.6 to 3.5 cm. Roughness values (calculated by measuring the vertical distance 

 between the highest and lowest points of the sediment-water interface) were highest at 

 stations located 100 m to 300 m from the NL-TR survey center and reflected surface physical 

 disturbance related to disposal operations and presence of sand ripples (Figure 3-10). The 

 majority of mean boundary roughness values for the reference area stations ranged from 0.6 

 to 1.4 cm (Figure 3-9). The mean boundary roughness of all stations on the disposal site 

 was significantly different from the mean for the pooled reference areas (p = 0.05, Mann- 

 Whitney U-test). 



3.2.3 Dredged Material Footprint 



Recently deposited (or "fresh") dredged material was indicated by the presence of 

 chaotic sedimentary fabrics, anomalous grain size distributions, and optical reflectance. The 

 distribution of fresh dredged material, as deduced from REMOTS® photographs, extended at 



Monitoring Cruise at the New London Disposal Site, June 1991 



