1.0 INTRODUCTION 



A series of investigations at the Cornfield Shoals Disposal Site (CSDS) between July 

 1991 and May 1992 provided circumstantial evidence for active bed transport. These studies 

 included current meter data and survey data as part of a joint project between Dr. W. F. 

 Bohlen and staff at the University of Connecticut (UCONN) and the Newport, RI office of 

 Science Applications International Corporation (SAIC). Evidence for active bed transport 

 includes optical backscatter and transmissometer data, bedforms, sand over mud, and shifts 

 in sediment accumulation over time. In addition, current meter and survey results support 

 the predominantly E-W current flow described in the historical records (NUSC 1979). 

 Bathymetric and REMOTS® survey results show that dredged material can accumulate at the 

 site despite active bed transport. 



CSDS, located 3.3 nmi southeast of Cornfield Point in Old Saybrook, Connecticut, 

 has been under study by the New England Division (NED) of the US Army Corps of 

 Engineers since 1978 (Figure 1-1). It is the only dispersive dredged material disposal site 

 managed by NED as part of the Disposal Area Monitoring System (DAMOS) Program. At a 

 dispersive site, unlike a containment site, it is expected that the dredged material disposed at 

 the site will be transported out of the area. CSDS received low volumes of sandy dredged 

 material (29,000 m 3 annually) throughout the 1980s (SAIC 1991) although some fine-grained 

 dredged material (4,200 m 3 from North Cove) was released at the site in January 1988. 

 Before a disposal buoy was deployed at CSDS in 1991, barges released dredged material at 

 designated LORAN coordinates, usually at the center of the disposal site. 



Bathymetric surveys conducted in 1979, 1987, and 1990 did not detect a well-defined 

 dredged material mound. A REMOTS® survey in 1990 detected fine-grained dredged 

 material near the center of the site and showed evidence of active sediment transport in 

 bedforms, sand over mud stratigraphy, and possible winnowing of the finer portion of the 

 sediment (SAIC 1994). The National Marine Fisheries Service and the Connecticut 

 Department of Environmental Protection have expressed concern about possible sediment 

 transport towards, and impact on, shellfish beds located north of the site, north of Long Sand 

 Shoal (Figure 1-1). 



While it is unlikely that the dominant east-west tidal flow would transport suspended 

 sediment northward from the disposal site, these concerns warranted further investigation of 

 the dynamics of sediment transport at the site. A plan for monitoring this dispersive site was 

 developed (Figure 1-2), and the first phase of investigation was defined. The first phase was 

 based on the assumption that, if material were transported out of the disposal site, it would 

 mix with, and ultimately settle with, the larger volume of ambient sediment cycling within 

 the Sound. Since far-field tracking would be difficult due to the mixing with, and dilution 

 by, background sediments, the first goal was to determine if field-observed transport at the 

 disposal site is consistent with the predicted east-west transport. 



Synthesis of Monitoring Surveys at the Cornfield Shoals Disposal Site, July 1991 to May 1992 



