90 



are not positively correlated with increasing depth in the long cores (Table 3-8). The deep 

 section of 10A was not analyzed, but was re-sampled in 1998 (see below). 



3.1.4.2 July 1998 



1998 Visual Descriptions 



Cores were collected in the same areas using the same zonation scheme as in 1997 

 (Figure 2-6) and sampled for physical characteristics, geochemical analyses and cap 

 verification. Digital photographs of the cores were compiled and are presented in Appendix 

 D. 



The reference core (26 A), collected at WEST REF, was 103 cm in length. The top 5 

 cm consisted of olive gray-brown, silty fine sand, with an intact tube mat on the surface and 

 wood and plant fibers throughout this top section. Below the surface layer, there was gray, 

 sandy silt mottled with black. From 29 to 73 cm, the sediments contained gray clayey, fine 

 sand. Shell fragments were abundant throughout the core and a few intact shells were 

 identified at 60 cm and 85 cm. Below 73 cm, the clayey, shell-rich fine sand was mottled with 

 cohesive clay patches lacking shell fragments. 



The July 1998 short cores ranged in length from 84 to 183 cm, while the long cores 

 ranged from 288 to 300 cm (Table 2-7). Similar to the 1997 results, all cores were comprised 

 dominantly of olive gray silty clay, with common darker black olive gray sediment. Shell hash 

 and black marbling and streaks were common throughout many of the cores. Discrete gravel 

 and sand layers were present in a few short cores (14A and B and 21 A (18-36 cm), 25 A 

 (>175 cm), and in the deepest intervals of long cores 17A (100-1 35cm, >170 cm), 19A (>260 

 cm), and 23 A (>105 cm). The olive gray, clayey fine sand layers found deep in the other cores 

 (14A [>140 cm], 17A [>217 cm], 25A [>175 cm]) were similar to the ambient sediment 

 recovered in the reference core (26A) from WEST REF. The CDM/UDM boundary was not 

 easily identifiable based on visual analysis alone. Long Core 23 A (>1 10 cm) from the inner 

 zone contained black oily sandy material with some gravel, possibly indicative of UDM. 



During core processing, odors from the cores were noticeable and recorded. Almost all 

 of the cores collected from the mound emitted a hydrogen sulfide odor upon being split. In 

 contrast, the core at the reference area had only a faint marine smell. Core 14B had a stronger 

 marine odor, with a fishy smell. A hydrocarbon odor was apparent throughout long core 23A 

 and in the lower sections of 15 A, 17A (100-220 cm), and 20 A, which seemed to increase in 

 areas of black mottling and blackish sediments. These sulfide and hydrocarbon odors are 

 consistent with the interpretation that these sediments were dredged material and distinct from 

 ambient NLDS sediments. 



Monitoring Cruise at the New London Disposal Site, Seawolf Mound 1995 - 1998 



