2.0 METHODS 



2.1 Bathymetry and Navigation 



The SAIC Integrated Navigation and Data Acquisition System (INDAS) 

 provided the precision navigation required for all field operations. This system uses 

 a Hewlett-Packard 9920 series computer to collect position, depth, and time data for 

 subsequent analysis, as well as providing real-time navigation. A Del Norte 

 Trisponder® system provided positioning to an accuracy of ±3 meters. Shore 

 stations were established in Connecticut at known benchmarks at Greenwich Point 

 and the Norwalk electric-generating facility. A detailed description of the navigation 

 system and its operation can be found in the DAMOS QA/QC Plan (SAIC, 1990c). 



An Odom DF3200 Echotrac® Survey Fathometer with a narrow-beam 208 kHz 

 transducer measured individual depths to a resolution of 3.0 cm (0.1 feet). Depth 

 values transmitted to the computer were adjusted for speed of sound and transducer 

 depth. Prior to starting the 1990 bathymetric survey, an Applied Microsystems 

 Model STD-12 CTD/DO probe was used to obtain a sound velocity profile. During 

 the analysis, correction for changes in tidal height standardized the raw bathymetric 

 data to Mean Low Water. A complete description of the bathymetric analysis 

 technique is also given in the DAMOS QA/QC Plan (SAIC, 1990c). 



A bathymetric survey of the entire site, conducted 14 and 15 July, 1990, 

 consisted of fifty-one lanes running east and west at a 50 meter lane spacing over a 

 3000 x 2500 m area centered at 40° 59.408'N and 73° 28.649'W (Figure 2-1). A 

 smaller, second bathymetric survey, conducted 15 July 1990, consisted of thirty-three 

 lanes running east and west at a 25 meter lane spacing over an 800 x 800 m area 

 centered approximately at the WLIS "A" mound (Figure 2-1). The previous two 

 bathymetric surveys of the WLIS site utilized this 800 x 800 m survey grid 

 (November 1987 and July 1988: SAIC, 1990a and 1990b, respectively). The volume of 

 accumulated material was calculated from comparison of the 1988 and 1990 surveys. 



12 REMOTS® Sediment-Profile Photography 



REMOTS® photography detected the distribution of thin (<20 cm) dredged 

 material layers, mapped benthic disturbance gradients, and monitored the progress 

 of infaunal recolonization on and adjacent to the disposal mounds. A detailed 

 description of REMOTS® image acquisition, analysis, and interpretative rationale is 

 given in the DAMOS QA/QC Plan (SAIC, 1990c). 



REMOTS® monitoring at WLIS utilized a 25 station star grid, with 100 m 

 spacing, centered at the buoy coordinates for the 1989 - 1990 disposal season (40° 

 59.254'N, 73° 29.095^ and a 13 station cross-shaped grid centered at the "B" mound 

 (Figure 2-2). Triplicate photographs were taken at each station. In addition, 

 sampling at three reference areas allowed comparison of ambient versus on-site 



Monitoring Cruise at the Western Long Island Sound Disposal Site 



