3.0 RESULTS 



3.1 Bathymetry 



The CLIS 1990 bathymetric survey area was previously mapped in 1988 and 1986 

 (Figures 3-1, 3-2). Since July 1988, dredged material has been released at buoy locations 

 CLIS-88, CUS-89, and CS-90-1 (Figure 3-3). The July 1988 survey included the area west 

 of 72°53.500' W, and the July 1986 survey covered the area east of 72°53.500' W. The 

 disposal of dredged material at the CLIS-88 buoy (1988/89) formed a disposal mound 

 approximately 400 m long, 200 m wide, trending northeast/southwest, and encompassing 

 both the 1987 and 1988 disposal buoy locations. The mound height at CLIS-88 was 4.4 m 

 (minimum water depth of 14.2 m). Disposal mound CLIS-89 (1989/90) had a diameter of 

 approximately 200 m and a height of 3.0 m (minimum water depth of 15.6 m). At CS-90-1, 

 the dredged material and cap material formed a mound less than 1 m high (minimum water 

 depth of 17.7 m) and approximately 80 m across. 



A visual comparison of the 400 m x 1200 m area encompassing disposal mound 

 CLIS-88 in 1988 and 1990 showed a decrease in water depth from 18.5 m to 14 m near die 

 CLIS-88 buoy (Figure 3-4). The depth difference map for this area (Figure 3-5) indicated an 

 accumulation of 4.4 m of material at the CLIS-88 buoy location and smaller accumulations, 

 from 0.2 to 0.4 m, south of the CLIS-88 disposal mound. North of the CLIS-88 and CLIS- 

 87 disposal mounds there was an apparent loss of material ranging from 0.2 m to over 1.0 m 

 (Figure 3-5). The net volume of material calculated from the depth difference map (Figure 

 3-5) was 103,466 m^ (95% confidence limits: 92,176 m^ to 114,755 m^). For the same time 

 period, 1988 to 1990, barge logs recorded releasing 336,950 m^ in the area. 



A visual comparison of the 1986 and 1990 surveys for the areas surrounding disposal 

 mounds CLIS-89 and CS-90-1 showed disposal mound heights of approximately 3 m at 

 CLIS-89 and 1 m at CS-90-1 (Figures 3-2 and 3-3). The depth difference map comparing 

 the 1986 and 1990 depth matrices indicated an accumulation of material at CLIS-87 (4.6 m), 

 CLIS-89 (3.0 m), and CS-90-1 (0.8 m) (Figure 3-6). Smaller accumulations, 0.2 to 0.4 m, 

 occurred away from the disposal mounds. Volume calculations for the area north of 

 41°9.250' N showed approximately 153,000 m^ of dredged material deposited from July 

 1986 to July 1990 (95% confidence limits: 147,355 m^ to 158,644 m^). Barges recorded 

 releasing 152,166 m^ of material in the area between 1988 and 1990. These values do not 

 include material added to CLIS-87 between 1986 and 1988 or the 211,981 m^ of dredged 

 material released south of 41°9.250' N and east of 72°53.300' W between 1988 and 1990. 



3.2 REMOTS® Sediment-Profile Photography 



A REMOTS® survey around the active CLIS disposal points and three reference areas 

 detected the distribution of dredged material and assessed benthic recolonization status. 



Monitoring Cruise at the Central Long Island Sound Disposal Site, July 1990 



