10 



2.0 METHODS 



2.1 Survey Area 



In order to fulfill the objectives of the 1996 WLIS monitoring survey, SAIC 

 conducted a comprehensive field effort consisting of precision bathymetry and REMOTS® 

 sediment-profile photography surveys. The bathymetric survey at WLIS was performed 

 over a 1400 m x 1000 m area centered at 40°59.555' N, 73°28.990' W. The July 1996 

 survey area extends 200 m east of the July 1992 (1200 m x 1000 m) survey boundary to 

 ensure adequate coverage of the flanks of the H mound. A total of 41 survey lanes at 25 m 

 lane spacing were required to delineate the topography of the active southwestern quadrant 

 of WLIS (Figure 2-1). Detailed bathymetric charts were generated for the 1.4 km^ area to 

 quantify mound height, lateral spread of dredged material, and position relative to other 

 disposal mounds. 



2.2 Navigation 



In an effort to provide strong comparisons with historic data sets, bathymetric data 

 were collected with the use of SAIC's Integrated Navigation and Data Acquisition System 

 (INDAS). 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 data to an accuracy of ±3 m in the 

 horizontal control of North American Datum of 1927 (NAD 27). Shore stations were 

 established along the Coimecticut coast at the known benchmarks of Norwalk Harbor 

 Power Plant (41°04.248' N, 73°24.501' W) and Greenwich Point (41°00.580' N, 

 73°34. 193' W). A detailed description of the navigation system and its operation can be 

 found in SAIC Report No. 290 (Murray and Selvitelli 1996). 



In order to maximize the efficiency of survey operations at WLIS, differential 

 Global Positioning System (DGPS) data in conjunction with SAIC's Portable Integrated 

 Navigation and Survey System (PINSS) were used to position the survey vessel over the 

 July 1996 REMOTS® camera stations. A Magnavox 4200D GPS receiver and a Magnavox 

 MX50R differential beacon receiver provided DGPS positioning data to PINSS in the 

 horizontal control of North American Datum of 1983 (NAD 83) to an accuracy of +5 m. 

 The Coast Guard differential beacon broadcasting from Sandy Hook, New Jersey, 

 (286 kHz) was utilized for satellite corrections due to its geographic position relative to 

 WLIS. 



The target REMOTS® station locations were calculated in NAD 27, then converted 

 to NAD 83 for real-time navigation with the use of the US Army Topographic Engineering 

 Center's CORPSCON version 3.01. The acmal positions of the REMOTS® replicate 



Monitoring Cruise at the Western Long Island Sound Disposal Site, July 1996 



