EXECUTIVE SUMMARY 



Science Applications International Corporation (SAIC) conducted a monitoring 

 survey at the Central Long Island Sound Disposal Site (CLIS) from 27 August to 1 

 September 1995 as part of the Disposal Area Monitoring System (DAMOS) Program. The 

 field operations were concentrated over the New Haven 1993 (NHAV 93), CLIS 1994 

 (CLIS 94), and Field Verification Program (FVP) mounds and consisted of precision 

 bathymetric surveys, Remote Ecological Monitoring of the Seafloor (REMOTS®) 

 sediment-profile photography, and geotechnical coring. These surveying techniques were 

 employed to monitor the stability, cap thicknesses, consolidation rates, and benthic 

 recolonization of the NHAV 93, CLIS 94, and FVP mounds. 



The NHAV 93 mound represents the culmination of ten years of thoughtful 

 planning and controlled disposal at CLIS. This mound was developed during the 1993/94 

 disposal season as part of a large scale confined aquatic disposal (CAD) project. From 

 1984 through 1992, disposal operations at CLIS led to the construction of a ring of 

 disposal mounds. This ring formed an artificial containment cell that was capable of 

 accepting a large volume of unacceptably contaminated dredged material (UDM), limiting 

 the lateral spread of the deposit and, in turn, facilitating efficient capping operations. The 

 NHAV 93 mound was formed by the placement of approximately 590,000 m 3 of UDM 

 within the ring of seven historic disposal mounds. The UDM deposit was then covered to 

 a thickness of 0.5 m to 1.0 m by 569,000 m 3 of capping dredged material (CDM). 



SAIC has conducted a total of seven bathymetric, four REMOTS® sediment- 

 profiling, and five geotechnical coring surveys over the NHAV 93 mound since September 

 1993. The comprehensive time-series data set documents the formation of the mound 

 within the containment cell as well as its gradual consolidation and benthic recolonization. 

 In addition, the wealth of data has provided SAIC and the US Army Corps of Engineers, 

 New England Division (NED), with significant insight into the short- and long-term effects 

 of disposal and oceanographic processes on large dredged material mounds. 



The results of the September 1995 field effort indicate a moderate amount of 

 consolidation (0.25 m) over the majority of NHAV 93 with several pockets of 0.5 m 

 consolidation near the center of the mound. The heterogeneity of the material collected in 

 the five-member geotechnical coring data set makes tracking a single sediment horizon 

 throughout the project difficult. However, indicators such as shell fragments, gravel, and 

 detritus were useful in differentiating ambient, historic, UDM, and CDM sediment strata. 

 REMOTS® sediment profile-photography found the biota occupying the surface sediments 

 of the NHAV 93 mound to be recovering as anticipated. A seasonal reduction in dissolved 

 oxygen within the central Long Island Sound region appeared to be responsible for 



