2.0 METHODS 



The study team used bathymetric surveys, REMOTS® sediment-profile photography, 

 and current meter moorings with transmissometers and optical backscatter sensors to 

 ascertain whether material was accumulating and/or eroding, and likely directions of 

 sediment transport (Table 2-1). By conducting a series of four bathymetric surveys over the 

 study area - one before, two during, and one after dredged material disposal - SAIC was 

 able to determine where material had collected during the disposal operation and where 

 material had been lost. SAIC also used REMOTS® sediment-profile photography to help 

 delineate the presence of dredged material and small scale ( < 20 cm thickness) sediment 

 structures that may indicate sediment transport. Current strength and direction were 

 measured near the bottom and at mid-depth using moorings supporting a single current meter 

 deployed by UCONN's team. Suspended sediment concentration was measured by 

 UCONN's DAISY (Disposal Area In Situ System), comprised of a transmissometer and 

 optical backscatter sensor mounted on the bottom structure supporting the current meter. 



Dredged materials were released at two different locations at CSDS in 1991-92 to 

 permit observations of distinct disposal projects. The current meter mooring that housed the 

 near-bottom current meter was located in conjunction with the disposal buoy. The 

 chronology of buoy and mooring deployments and their location are shown in Table 2-1 and 

 in Figure 2-1. 



2.1 Bathymetry 



The four bathymetric surveys were conducted between August 1991 and May 1992 at 

 the following times: 



1. Before the disposal season (8 August 1991), 



2. After disposal of sandy dredged material from Connecticut River bars at buoy 

 location A (18 and 19 October 1991), 



3. During disposal of fine-grained North Cove sediments at buoy location B (10 

 December 1991), and 



4. After disposal was completed (May 1992). 



The bathymetric surveys were set up over a 1200 X 1200 m grid (49 lanes at 25 m lane 

 spacing) centered on the first disposal buoy (location A, Figure 2-1). The August, October, 

 and May surveys were completed over the whole grid. The December bathymetric survey 

 included only the northern 30 lanes due to bad weather. During analysis of the August, 

 October, and December surveys, the grid area was reduced to 1000 x 1000 m to correspond 

 with the 1987 survey and correct for irregularities in the tidal estimations and roll of the 

 ship. The May 1992 survey data were processed by the SAIC Hydrographic Data Analysis 

 System (HDAS) and did not require comparison to the 1987 data. 



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



