The periods of deposition of Black Rock and New Haven Harbor material overlapped 

 to some extent (Figure 1-5). Clamshell dredging of Black Rock Harbor and subsequent 

 disposal at MQR began on 9 March 1983 and continued through 18 April 1983. Dredging of 

 New Haven Harbor began on 29 March 1983, and was completed on 17 May 1983 (Figure 

 1-5). Approximately 64,000 m 3 of Black Rock sediment was placed at the MQR mound and 

 capped with approximately 400,000 m 3 of additional New Haven material. The majority of 

 Black Rock material was disposed before New Haven. Subsequent to the final New Haven 

 cap deposition, however, two barge loads of Black Rock material (approximately 3,000 m 3 ) 

 were deposited at the MQR mound. This disposal sequence complicated evaluation of the 

 project, and may have resulted in a thin layer of Black Rock material at the surface. 



1.2 Biological Monitoring at MQR 



Biological monitoring at MQR has included several REMOTS® surveys since 

 deposition of the New Haven cap, body burden sampling and chemical analysis, and an 

 amphipod bioassay. This sequence of events followed closely the recently adopted tiered 

 approach to monitoring capped mounds (Germano et al. 1994). The observed amphipod 

 bioassay toxicity prompted the coring operation. 



A REMOTS® photographic survey of MQR in January 1983, following deposition of 

 both Mill and Quinnipiac River sediments and prior to Black Rock/New Haven sediments, 

 showed benthic conditions to be normal for a newly deposited disposal mound (Morton et al. 

 1984b). Stage I organisms dominated the surface area of the mound, and Organism- 

 Sediment Index (OSI) values ranged between 4 and 11. Successional stages and the 

 multiparameter OSI were used to characterize habitat disturbance. The parameters used to 

 calculate OSI included the apparent depth of the oxygenated layer (redox potential depth, or 

 RPD), the presence of methane, and the presence or absence of three successional stages of 

 benthic organisms (SAIC 1988). 



REMOTS® surveys at MQR in 1986, three years after deposition of the New Haven 

 cap, continued to show a dominance of Stage I species on the three-year-old cap with OSI 

 values ranging between 2 and 9 (SAIC 1990a). The 1987 survey indicated a continued 

 dominance of Stage I organisms with Stage in beginning to appear at depth. Associated OSI 

 values increased slightly but remained lower than those found concurrently at CLIS mounds 

 Cap Site 1 and 2 (CS-1 and CS-2), formed during the same 1983 disposal season of Black 

 Rock and New Haven Harbor sediments (SAIC 1990b). 



The causes of the evident differences in recolonization rates at the MQR disposal 

 mound were not clear. Because these differences were not apparent prior to the disposal of 

 the Black Rock/New Haven materials, it seemed likely that the recolonization difficulties 

 were related to this disposal operation. It also was hypothesized that seasonal hypoxic events 

 in Central Long Island Sound may have contributed to the slow recovery of MQR (SAIC 



Sediment Core Chemistry Data Summary from the MQR Mound, August and December 1991 



