Contours representing the "NL-RELIC", "NL-I", "NL-II" 

 and "NL-III" disposal points were identical to those determined in 

 1986. Minimum depths remain the same at 13.0, 15.5, 15.5 and 14.5 

 meters, respectively, indicating no loss or addition of material 

 at these mounds. 



According to the year's scow logs, of a total of 67,500 



! 3 



London disposal site, an estimated 12,400 m° (16,225 yds J ) of 



nr (88,240 yd J ) of dredged material was deposited at the New 



i jj i _ij *- 1 4-~j 10 Ann -».3 / i c o->c ir<3*-3\ _j 



material was deposited approximately 530 m northwest of the 

 disposal buoy on the extreme southern flank of the NL-RELIC 

 mound. No depth change, however, was apparent for this area in 

 the contour chart. The remaining 55,100 m 3 (72,000 yds 3 ) of 

 sediment, representing 82% of the year's disposed sediment as 

 estimated from the scow logs, were added to the NL-85 disposal 

 mound. The logs verify that almost all of this disposal occurred 

 in the immediate vicinity of the buoy. 



Volume calculations based on a comparison of the depth 

 data from the 1986 and 1987 surveys indicate a total of 43,000 

 m 3 (12,400 m 3 ) of material was added during the past year's 

 disposal activities. Because the majority of disposal operations 

 took place at NL-85, a volume was also calculated for the five 

 survey lanes passing directly over this mound. This volume, 

 33,951 m 3 (4615 m 3 ) , represents 79% of the total volume of 

 material disposed within the survey area. The remaining 21% 

 apparently consisted of relatively thin layers located farther out 

 on the flanks of the NL-85 mound and/ or in the area of inadvertent 

 disposal 530 m northwest of the buoy. 



3.2 REMOTS Sediment-Profile Photography 



Distinct dredged material layers with a thickness 

 exceeding the penetration of the REMOTS prism (> 16 cm) were 

 evident in the REMOTS images from stations in the immediate 

 vicinity of the disposal buoy (Figure 3-3). These stations were 

 CTR, 200E, 200W, 2-200SW, 200S, 2-200SE and 400SE. In general, 

 the dredged material was characterized by a distinct boundary 

 (i.e., RPD depth) between oxygenated sediment at the surface and 

 sediment with extremely low reflectance below (suggesting apparent 

 high sediment oxygen demand, Figure 3-4). Similar low-reflectance 

 dredged material exceeding the prism penetration depth was mapped 

 in this same area in the July 1986 REMOTS survey. This made it 

 difficult to distinguish between material deposited in the past 

 year versus that from previous years. Less sharply contrasting 

 layers of apparent dredged material were evident at stations 200N, 

 2-200NE, 2-400NE, 4-200NE and 4-400NE (Figure 3-5) . The deposits 

 at these stations, which occur in the vicinity of the NL-III and 

 NL-II mounds, were more readily distinguished as "relict" material 

 disposed in previous years (i.e., prior to the 1986-87 disposal 

 season) . 



