EXECUTIVE SUMMARY 



The objectives of the monitoring cruise at the New London Disposal Site (NLON) 

 were to 1) delineate the footprint and characterize the topography of the dredged sediment 

 deposited in the vicinity of the NL-TR mound during 1990-1991; 2) assess the benthic 

 recolonization rate at the active disposal site and monitor the successional status at the 

 inactive NL-88 mound; 3) measure near-bottom and surface dissolved oxygen (DO) 

 concentrations at the active disposal site and reference areas and; 4) collect sediment samples 

 at the three reference areas to provide information on percent total organic carbon (TOC), 

 grain size, and levels of polynuclear aromatic hydrocarbons (PAHs), cadmium, lead, and 

 zinc. 



The New London Disposal Site covers a one square nautical mile (nmi) area and is 

 centered at 41° 16. 100' N latitude and 72°04.600' W longitude. It is located approximately 

 3 nmi south of Eastern Point in Groton, CT. During the 1990-1991 disposal season, 

 31,475 m 3 of dredged material was disposed in the vicinity of the NL-TR mound at the 

 1990-1991 buoy location, 41°16.428' N and 72°04.333' W. From 24 to 27 June 1991, 

 Science Applications International Corporation (SAIC) conducted routine bathymetric and 

 Remote Ecological Monitoring of the Seafloor (REMOTS®) sediment-profile surveys, 

 sediment sampling, and measurements of near-bottom DO. 



A comparison of the June 1991 and July 1990 bathymetric surveys showed an 

 increase in height of 2.4 m at NL-TR. Also apparent was a smaller mound that developed 

 around the buoy and was adjacent to the NL-TR mound. This mound was 0.6 m in height 

 and approximately 100 m in diameter. The combined radii of these two mounds was about 

 150 m. Based on the 31,475 m 3 project volume, the DAMOS Capping Model predicted a 

 mound 2.0 m in height with a 150 m radius. 



The objective of the REMOTS® survey was to map that portion of the recently 

 deposited dredged material not detectable with bathymetry. Information obtained from the 

 REMOTS® survey indicated the presence of recently deposited dredged material within 

 200 m north, 400 m west, and 300 m south of the disposal site center. The REMOTS® 

 sediment-profile survey also provided information on the rate of benthic recolonization. The 

 majority of disposal site and reference area stations were dominated by Stage U, Stage JJ on 

 III, or Stage III assemblages. Stage II represents a transitional sere between Stages I and in 

 and is associated with recovery of a disturbed benthic habitat. Organism-Sediment Indices 

 for both the disposal site and reference area stations were variable and indicative of a patchy 

 benthic environment. 



Results of the metal and PAH analyses indicate relatively low concentrations for the 

 reference areas and no immediate need for further testing beyond the collection of baseline 

 information. Near-bottom dissolved oxygen concentrations were very similar at the reference 

 areas and disposal site, and results indicated a well-oxygenated water column throughout the 

 surveyed area. 



