52 



species on the three-year-old cap, with OSI 

 values ranging between 2 and 9 (Figure 3- 

 8). Hurricane Gloria had an impact on 

 biological communities at CLIS (especially 

 FVP). By the 1987 survey, Stage I 

 organisms still dominated, with Stage III 

 beginning to appear at depth. Associated 

 OSI values increased slightly but remained 

 lower than those found concurrently at Cap 

 Sites 1 and 2, formed at the same time and 

 with the same material as MQR (Figure 3- 

 8; SAIC 1990a,b). After the 1987 survey, 

 benthic conditions at MQR again 

 regressed, as will be discussed in more 

 detail below. 



The cause of the evident differences in 

 recolonization rates at MQR was not clear. 

 Because these differences were not 

 apparent prior to the disposal of the Black 

 Rock/New Haven material, it seems likely 

 that the recolonization difficulties were 

 related to this disposal operation. Seasonal 

 hypoxic events in Central Long Island 

 Sound may also have contributed to the 

 slow recovery of MQR (SAIC 1989). 



Black Rock material was also disposed 

 at the experimental Field Verification 

 Program mound (FVP) during the spring 

 of 1983. This mound was left uncapped 

 for comparison to the capped mound 

 projects. The apparently healthy response 

 of the uncapped FVP mound in 

 comparison to MQR is particularly 

 interesting. REMOTS® surveys conducted 

 prior to disposal at the FVP location in 

 August 1982 showed OSI values between 9 

 and 11, suggesting conditions essentially 

 similar to those at the established FVP 

 reference area (Figure 3-9). The 



placement of the Black Rock sediments in 

 May -June 1983 significantly reduced the 

 mean OSI value for the FVP stations in the 

 postdisposal June 1983 REMOTS® survey, 

 consistent with the anoxic, nearly azoic 

 nature of these sediments (Johnson et al. 

 1981). REMOTS® surveys from July 

 1983 to December 1984 showed a gradual 

 and significant increase in mean OSI 

 values for the aggregate of stations; values 

 approached those observed during the 

 predisposal survey for both the pooled 

 reference and FVP stations (Figure 3-9). 



Relatively healthy benthic conditions 

 continued, as indicated by later REMOTS® 

 surveys of FVP. August 1987 OSI values 

 at FVP stations ranged from 7.3 to 10, 

 with the exception of the center station, 

 which had an OSI value as low as 4.7. 

 Reference station OSI values were only 

 slightly higher, ranging from 8 to 11. 

 Successional stages at FVP were 

 dominated by Stage III organisms; Stage I 

 organisms, although present, were clearly 

 secondary in concentration. These latter 

 conditions were essentially similar to those 

 observed at the STNH capped mounds, 

 despite the evident differences in deposit 

 age, and suggested that habitat quality at 

 the FVP deposit, an uncapped mound, was 

 generally better than that at MQR. 

 Sediment chemistry results for FVP 

 sediments are within the lower contaminant 

 range of Black Rock material (Section 

 3.3). Diver observations, core 

 descriptions, and geotechnical 

 measurements (see below) indicated that 

 the surface material at FVP was coarse 

 black silt with much higher density than 

 typical Black Rock material. 



Sediment Capping of Subaqueous Dredged Material Disposal Mounds 



