2.0 METHODS 



2.1 Survey Area 



From 10 July to 18 July 1994 SAIC conducted a comprehensive field effort at CLIS 

 consisting of precision bathymetry, surface sediment characterization, subbottom sediment 

 profiling. Remote Ecological Monitoring of the Seafloor (REMOTS®) sediment-profile 

 photography, grab sampling, and geotechnical coring. The bathymetric, surface sediment 

 characterization, and subbottom sediment profiling were conducted over a 2553 m x 

 2225 m survey area centered at 41°08.951' N, 72°53.413' W (Figure 2-1). This survey 

 required 89 lanes at 25 m lane spacing, and focused on the western two-thirds of CLIS. 

 Detailed bathymetric, surface, and subbottom charts were generated for this 5.68 km^ area. 



The REMOTS® sediment-profile photography and grab sampling were performed at 

 predetermined stations over both disposal mounds as well as the three reference areas 

 surrounding CLIS (2500W, 4500E, and CLIS-REF; Figure 2-1). The geotechnical cores 

 were collected over the NHAV 93 mound in a sampling pattern that provided a southwest- 

 northeast cross-section of the CAD mound. 



2.2 Bathymetry and Navigation 



The SAIC Integrated Navigation and Data Acquisition System (INDAS) provided 

 the precision navigation and data collection required for all SAIC field operations. This 

 system utilizes a Hewlett-Packard 9920® series computer to provide real-time navigation, 

 as well as collect position, depth, and time data for later analysis. A Del Norte 

 Trisponder® System provided positioning to an accuracy of ±3 m. Shore stations were 

 established along the Connecticut coast at the known benchmarks of Stratford Point 

 (41°09.112' N, 72°06.227' W) and Lighthouse Point (4ri4.931' N, 72°54.255' W). A 

 detailed description of the navigation system and its operation can be found in the DAMOS 

 Reference Report (Murray and Selvitelli 1996). 



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 ft) (Murray and 

 Selvitelli 1996). Depth values transmitted to INDAS were adjusted for the 1.0 m 

 transducer depth. The acoustic returns of the fathometer can reliably detect changes in 

 depth of 20 cm or greater due to the accumulation of errors introduced by the positioning 

 system, changes in sound velocity through the water column, the slope of the bottom, 

 vertical motion of the survey vessel, and tidal corrections. 



Monitoring Cruise at the Central Long Island Sound Disposal Site, July 1994 



