67_ 



200 m, 300 m, and 400 m southeast of the survey center were inhabited solely by Stage II 

 assemblages. One station (300 W) produced no benthic infauna data due to shallow camera 

 penetration depths. Because of the diversity in benthic infaunal recolonization status of the 

 disposal mound and the widespread presence of Stage II organisms, the overall 

 successional stage of the disposal mound can be characterized as a solid Stage II population 

 advancing to Stage III. 



Based in part on the relatively advanced successional status and moderate RPD 

 depths, the median OSI values over the disposal site ranged from +2.0 to +8.0 (Figure 3- 

 19; Table 3-1). The higher OSI values were found on the perimeter of the REMOTS® 

 sampling grid and were randomly distributed. No methane or low DO conditions were 

 observed in any of the replicate images. 



3.1.2.2 August 1995 Survey 



The August 1995 REMOTS® sediment-profile survey at the NL-91 and D/S mound 

 complex was used to map the aerial extent of dredged material and determine benthic 

 recolonization levels relative to the 1992 findings. The REMOTS® sampling grid occupied 

 in 1995 was reduced to a modified 13-station cross grid and shifted south-southeast relative 

 to the 1992 grid (Figures 2-4 A and 2-4B). The center point was based on the D/S buoy 

 position, and station placement was designed to cover the two lobate sections of the NL-91 

 and D/S mound complex. 



Recently deposited dredged material was detected in nine of the thirteen REMOTS® 

 sediment-profile stations across the NL-91 and D/S mound complex. Dredged material 

 thickness was greater than camera penetration along the east-west transect, as well as at 

 stations 100S and 100N (Figure 3-20). The surface sediments at Stations 300N, 200N, 

 100W, and 200S appear to have been reworked significantly since 1992, losing the typical 

 characteristics of recently deposited sediments. As a result, these stations were classified 

 as being composed of historic dredged material. The average penetration depths ranged 

 from 4.5 cm to 15. 1 cm. The stations with the shallowest camera penetration ( < 10 cm) 

 displayed sediment with a higher sand component. Most of the stations with camera 

 penetration greater than 10 cm had dredged material greater than penetration. 



The major modal grain size at eight of thirteen stations over the NL-91 and D/S mound 

 complex was classified as 4 to 3 phi (very fine sand; Table 3-2). Three stations (100E, 400E, 

 and 300N) were composed entirely of fine-grained sediments (>4 phi; silt/clay). The two 

 stations with coarser grained sediment were 200W (3 to 2 phi, fine sand) and 200S (<-l phi, 

 granules and pebbles; Figure 3-21). A stratigraphic pattern consisting of a surface layer of 

 very fine sand overlaying mud at depth was observed at all stations except 100W, 100N, 



Monitoring Cruise at the New London Disposal Site, 1992 - 1998 



