calculation simply implies that the actual (and unknown) volume 

 difference will occur within these limits with a probability of 

 0.95. 



3 . 2 REMOTS® Sediment-Profile Photography 



As observed in previous REMOTS® surveys within the WLIS 

 disposal site, most of the survey area was dominated by silt-clay 

 (> 4 phi) sediments (Figure 3-3) . However, a cluster of 6 

 stations on and east of mound "C" consisted of very fine, fine, 

 and medium sands. Figure 3-4 shows the distribution of sandy 

 sediments across the survey area. Distinct sand layers, either 

 at the surface or buried, were evident throughout the northern 

 and eastern half of the region (Figure 3-5). Mounds "A" and "B", 

 composed predominately of silt-clay, also exhibited some near- 

 surface layers of sand. Based on this distribution, the sands 

 appear to represent dredged material deposited since the last 

 complete survey of this area in August 1985. This inference is 

 also supported by the lack of sand layers in images from the 

 western portion of the survey area and from the WLIS Reference 

 station. All replicates collected at the WLIS Reference station 

 exhibited a major mode of silt-clay (> 4 phi) . 



Dredged material layers (Figure 3-6) deposited since 

 1985 were readily detected when dredged material thickness was 

 less than the prism penetration depth (20 cm) . This was because 

 the relatively high-reflectance, pre-disposal interface was 

 evident below the low-reflectance dredged material (Figure 3-7) . 

 This high-reflectance material could be either natural bottom or 

 previously deposited dredged material that had developed a deep 

 RPD layer. The pre-disposal interface was not evident in many of 

 the images from the region around disposal mound "C" indicating 

 that dredged material layers were at least 2 cm or greater 

 throughout this area. Overall, dredged material was widespread 

 in the area surveyed. Only the southern portion of the site 

 lacked readily discernible dredged material layers. 



At the Reference station, thirty-five percent (7 of 20) 

 of the images showed subsurface low-reflectance layers overlying 

 high-reflectance sediments. These layers do not sharply contrast 

 with adjacent sediments and are generally discontinuous. They 

 are inferred to represent relict dredged material (i.e., material 

 disposed of a number of years ago) . Recently deposited dredged 

 material would be expected to contrast more sharply with the 

 buried pre-disposal interface. Similar dredged material layers 

 were observed at the Reference station in 1985 and 1984. At 

 those times, it was also concluded that this material represented 

 relict dredged material deposited in an historically-used 

 disposal site in that area (Eatons Neck) . REMOTS® images were 

 not obtained at the WLIS reference site prior to 1984. 



