2.0 METHODS 



2.1 Navigation 



The 4 August 1992 survey was performed onboard the research vessel R/V UCONN 

 owned and operated by the University of Connecticut. Positioning and navigation were 

 accomplished using Northstar 800 LORAN-C and Differential Global Positioning System 

 (DGPS) MX4200 receivers interfaced to an integrated navigation system. Positional data were 

 serially routed from the receivers to SAIC's Portable Integrated Navigation and Survey System 

 (PINSS). PINSS consists of an IBM-compatible 386 computer capable of processing data 

 from multiple sensors. A video display of the vessel's position aids the helmsman in 

 navigating to a particular station location or maintaining a specific course. Positional data are 

 recorded on diskette and may be redundantly charted on a plotter. Navigational procedures are 

 discussed in greater detail in SAIC's QA/QC Manual (SAIC 1990a). 



2.2 Side-scan Sonar Survey 



Side-scan sonar data were acquired using a Klein Model 400 Graphic Sonar Recorder 

 and a Model 422 dual frequency towfish capable of detecting bottom features to a resolution of 

 less than 1 m. The survey was performed using a single 100 kHz frequency transducer. The 

 side-scan recorder was configured to produce an 85 m instrument sweep to optimize the 

 resolution. A 1600 m by 3800 m survey grid centered about the midpoint of the disposal site 

 was established to characterize the entire disposal site. Eight tracklines 200 m apart were 

 situated in an east-west trend to parallel the depth contours in the vicinity of the disposal site. 



The speed of the vessel was maintained at 3 knots while the sonar (i.e., towfish) was 

 towed approximately 11m from the seafloor. During the survey, the navigation system 

 generated a plot of the ship's position with respect to the target survey lanes (Figure 2-1). 

 Time was automatically annotated on the plot every 5 minutes. At the same time, the sonar 

 record was annotated with time so that targets present on the sonar record could be transferred 

 (compensating for cable layback) to the real-time navigation plots following the survey. The 

 resulting mosaic of acoustic targets was used to establish the locations of the REMOTS® 

 stations (Figure 2-2). 



2.3 REMOTS® Sediment-Profile Photography 



Thirteen REMOTS® stations were visited during the 4 August 1992 survey (Figure 2- 

 1). Twelve of the thirteen stations were clustered in the northeast quadrant of the site where 

 the presence of dredged material was suspected. Two other stations were situated in the 

 western half of the site to characterize areas of suspected dredged material deposits there. 

 Film from the REMOTS® camera was developed on the research vessel to verify that the 

 photographs collected during the one-day sampling effort were usable. Three replicate 



Reconnaissance Survey of the Historical Bridgeport Disposal Site, August J 992 



