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3.0 RESULTS 



3.1 Bathymetry and Navigation 



The most recent bathymetric surveys of WLIS were conducted in 1988, 1990, and 

 1991 (Figures 3-1, 3-2, and 3-3). The June 1991 bathymetric survey (33 lanes) covered a 

 1200 x 800 m area which incorporated the five WLIS disposal mounds (WLIS "A," "B," 

 "C," "D," and "E"). The July 1992 bathymetric survey consisted of 41 lanes and covered a 

 1200 x 1000 m area (Figure 3-4). Lanes 1-33 duplicated the 1991 survey grid. This 

 portion of the 1992 survey incorporated the five WLIS mounds in addition to the newly 

 formed WLIS "F" mound. Lanes 34-41 of the 1992 survey provided bathymetric detail of 

 the 1200 x 200 m region southward. This southern region shoals gradually from 35 to 32 

 m. A shallow ridge extends approximately 200 m into the surveyed region and terminates 

 100 m southeast of the WLIS "F" mound. 



The minimum water depths of the disposal mounds in the 1991 survey were "A," 

 29.75 m; "B," 31.00 m; "C," 28.00 m; "D," 28.50 m; and "E," 29.75 m. Prior to detailed 

 analyses, the 1992 depth data was standardized to the 1991 survey. This procedure allowed 

 the comparison of the 1991 and 1992 depth data, including the assessment of changes in 

 mound heights and depth difference analysis. Only the 1200 x 800 m area common to the 

 1991 and 1992 surveys could be standardized in the 1992 survey (Figure 3-5). The data 

 reported in Figure 3-5 showed that the 1992 minimum water depths of the WLIS "B," "C," 

 "D," and "E" mounds remained unchanged since the 1991 bathymetric survey; however, the 

 measured minimum water depth of the WLIS "A" mound increased from 29.75 to 30.25 m, 

 a decrease of 0.5 m in mound height. 



Acoustically detected changes in water depth showed that WLIS "F" was an 

 elliptically shaped mound with an approximate diameter of 200 m and a height of 1.9 m 

 (minimum water depth 32.25 m; Figure 3-6). Based on the depth difference analysis 

 (comparing the 1991 and 1992 surveys), approximately 23,320 m 3 of sediment accumulated 

 at the disposal point to form the WLIS "F" mound. Barge volumes reported for the 

 November to May disposal period totaled approximately 39,705 m 3 (Table 1-1). 



3.2 REMOTS® Sediment-Profile Photography 



3.2.1 Dredged Material Footprint 



The WLIS "F" mound was located approximately 300 m south of the WLIS "E" 

 mound and 350 m southeast of the WLIS "D" mound. The dredged material footprints 

 developed during the formation of WLIS "D" and "E" (the 1988-1990 and 1990-1991 

 disposal seasons, respectively) fell within 100 m of the center of WLIS "F" (Figure 3-7). 

 The persistence of features associated with dredged material within these older footprints 



Monitoring Cruise at the Western Long Island Sound Disposal Site, July 1992 



