the southern half of the site. Depths range from about 65 meters 

 to 80 meters within the surveyed area. Comparison with the 

 bathymetric survey conducted in September 1984 (Figure 2-2b) 

 reveals no significant development of a disposal mound near the 

 buoy location. 



Figure 2-3 shows the results of the side scan survey at 

 the Rockland site conducted in May 1985. The outlined area 

 indicates the presence of intermediate acoustic reflectance that 

 could be caused by soft natural bottom or old dredged material. 

 The small dark areas show the location of higher acoustic 

 reflectance characteristic of dredged material. The central area 

 of the site is well covered by dredged material and is surrounded 

 by individual disposal events. Long narrow areas probably 

 indicate disposal that occurred underway or during a turn. 



Figure 2-4 is a photograph of the side scan record at 

 the center of the area showing this high acoustic reflectance. 

 Figure 2-5 shows a circular area, probably the result of a single 

 dump. Figure 2-6 shows the result of disposal occurring during a 

 turn. The side scan records did not detect any large 

 accumulation in the form of a mound. 



2.2 Sediment Characterization 



Figure 2-7 shows the location of sediment samples taken 

 at the Rockland Disposal Site to visually characterize the bottom 

 and detect the extent of dredged material. Table 2-1 describes 

 the sediment collected at each station with a 0.1 m^ Smith- 

 Maclntyre grab sampler. The pattern of stations sampled was 

 determined by visually identifying dredged material in the grab 

 and proceeding until natural bottom was encountered. The spatial 

 delineation of dredged material from the grab samples compared 

 well with the areas of high reflectance measured with side scan 

 sonar. Minor discrepancies resulted from the patchy nature of 

 single dump loads. The areas of intermediate reflectance could 

 indicate the presence of old dredged material. 



During the September 1984 survey, sediment samples were 

 collected at stations on North-South, East-West, Northwest- 

 Southeast, and Northeast-Southwest transects (Fig. 2-8) , as well 

 as at the Reference Site (2000m east) . Table 2-2 contains the 

 results of the chemical analyses of the sediment samples. 



The results of the chemical and physical analyses 

 indicate little variation throughout the site. The physical 

 tests indicate the similarity between locations with a pattern 

 common to most of the samples; olive in color, high percentage of 

 fines (average about 90% and predominantly clays) , low fine sand 

 percentages (around 10%) and very little medium and coarse 

 material (usually less than 1%). These values also occur at the 



