EXECUTIVE SUMMARY 



During January and May 2000, an estimated total of 14,200 m^ of sediment dredged 

 from the U.S. Coast Guard Base in New Haven, CT was placed in a small, man-made 

 depression (borrow pit) in Morris Cove, located in outer New Haven Harbor. A monitoring 

 survey was conducted over the Morris Cove borrow pit in late September 2000 to document 

 the distribution of the dredged material on the seafloor, verify the stability of the sediment 

 deposit, and evaluate recolonization of the deposit by benthic organisms. 



The monitoring involved the use of REMOTS® sediment-profile imaging, side-scan 

 sonar, single-beam bathymetry, and towed video to evaluate benthic conditions within and 

 adjacent to the borrow pit. Sediment-profile images also were obtained at a reference area 

 located approximately 800 m west of the borrow pit to provide a comparison with ambient 

 seafloor conditions. 



The side-scan sonar data showed a clear differentiation between softer sediments 

 within the borrow pit and coarser, more compact sediments comprising the outer walls of the 

 pit. Multiple bottom features with increased vertical relief and surface roughness detected 

 within a 50 m radius of the central disposal point and to the east of this point were attributed 

 to dredged material deposition. Both the side-scan sonar and towed video data suggested 

 that the impacts associated with the deposition of dredged material were contained largely 

 within the southern portion of the Morris Cove borrow pit. The controlled placement of 

 small barge loads of dredged material had facilitated the creation of a small-scale sediment 

 deposit within the confines of the pit. 



The REMOTS® sediment-profile images served to confirm the presence of dredged 

 material at stations located within the borrow pit. The dredged material was observed at 

 stations in close proximity to the disposal buoy position and extending out 100 to 150 m 

 from this central disposal point. The measured thickness of the dredged material layer 

 typically exceeded the penetration depth of the sediment-profile camera (i.e., greater than 

 about 10 or 15 cm). The dredged material was predominantly fine-grained, consisting of 

 soft, sandy silt. 



The presence of methane gas bubbles in the sediment at three stations within the 

 borrow pit suggested that some of the dredged material continues to contain a high inventory 

 of organic matter. Fine-grained sediments having relatively high surface boundary 

 roughness, shell lag deposits, and shallow depth of aeration characterized the reference area. 

 It was hypothesized that the shallow reference area may experience periodic physical 

 disturbance from fishing activities or the scouring action of waves and currents during high 

 wind events. 



At the time of the survey (5 months post disposal), it appeared that benthic 

 recolonization of the dredged material deposit was progressing as expected. The sediment- 

 profile images showed that the benthic infauna included primarily Stage I opportunistic 



