11 



3.0 RESULTS 



3.1 Bathymetry 



The July 1990 bathymetric results indicated that minimum water depths at the "A", 

 "B", "C", and "D" mounds were 29.75, 30.75, 28.25, and 28.00 m, respectively (Figure 3- 

 1). In comparison to the June 1991 survey (1200 x 800 m), the heights of the "A", "B", 

 and "C" mounds remained relatively unchanged (minimum water depths of 29.75, 31.00, and 

 28. (X) m, respectively) while the height of the "D" mound decreased approximately 0.5 m 

 (minimum water depth of 28.50 m;Figure 3-2). 



The 1990-1991 disposal operations resulted in the formation of the WLIS "E" mound. 

 Based on acoustically detected changes in depth, WLIS "E" had a diameter of approximately 

 175 m. The minimum water depth at the WLIS "E" mound was 29.75 m, with a 

 surrounding ambient bottom depth of approximately 32.75 m. This represented a mound 

 height of approximately 3.0 m. WLIS "E" is located beyond the eastern boundary of the 

 area surveyed prior to the 1991 field effort; therefore, the height and volume of material 

 comprising this mound could not be calculated by depth difference analysis (comparing the 

 1990 and 1991 depth data). 



3.2 REMOTS® Sediment-Profile Photography 



3.2.1 Dredged Material Footprint 



Due to the magnimde of historic disposal operations at the WLIS Disposal Site and 

 the proximity of the five disposal mounds, virtually all stations in the WLIS "E" and "D" 

 REMOTS® grids, except 400N (Figure 3-3), provided evidence of dredged material. The 

 most recent disposal took place near the center of the WLIS "E" grid where approximately 

 86,462 m^ was disposed between November 7, 1990 and May 31, 1991 (Figure 3-4). The 

 footprint of this material is a NW-SE trending ellipsoid centered on the WLIS "E" grid with 

 a maximum diameter of approximately 400 m and a minimum width of 275 m. This 

 footprint is adjacent to, and overlaps some sections of, the dredged material footprint 

 developed during the 1989-1990 disposal season (Figure 3-5). 



Within the area covered by dredged material, recently deposited dredged material 

 exceeded the penetration of the camera prism at several stations adjacent to the disposal 

 point. Criteria used to differentiate fresh (1991) from old (pre-1991) dredged material 

 included the presence of a thin (1 cm deep or less) or patchy Redox Potential Discontinuity 

 (RPD), a chaotic fabric or physical layering (i.e., relic/buried RPD or sand/mud layering) 

 near the sediment surface, high physical boundary roughness, and/or unconsolidated, high 

 water content sediments (Figure 3-6). 



Monitoring Cruise at the Western Long Island Sound Disposal Site, June 1991 



