During the period of July to November 1986, 

 approximately 30,000 m 3 of maintenance material from two permit 

 projects (Blue Circle Atlantic, 25,800 m 3 ; and General Electric, 

 4,000 m 3 ) were disposed at FADS which had elevated levels of PCBs 

 and heavy metals (Table 1-1) . An additional objective of this 

 survey was to determine if these disposed materials had a unique 

 chemical signature for specific identification so that the 

 effectiveness of any future capping exercise could be evaluated. 



2 . METHODS 



2 . 1 Bathymetry 



The precise navigation required for all field 

 operations was provided by the Science Applications International 

 Corporation (SAIC) Integrated Navigation and Data Acquisition 

 System (INDAS) . This system uses a Hewlett-Packard 9920 Series 

 computer to collect position, depth, and time data as well as to 

 provide real-time navigation. During a bathymetric survey, a 

 display is provided to the helmsman of the research vessel with 

 the survey lanes and the real-time position of the vessel 

 indicated. The positional information is recorded on magnetic 

 disk every second along with depth and time. The computer system 

 calculates accurate positions from the range data provided by the 

 positioning system and is capable of converting from state plane 

 coordinates in the Transverse Mercator system to Lambert or 

 Mercator coordinates. 



Positions were determined to an accuracy of ±3 meters 

 from ranges provided by a Del Norte Trisponder System. Shore 

 stations are established over known benchmarks used in previous 

 surveys to allow accurate comparisons of seasonal surveys. For 

 the present survey, shore stations were established at Marblehead 

 Light and Eastern Point Light. 



The individual depth measurements were determined using 

 a Raytheon DE-719 Precision Survey Fathometer with a 208 kHz 

 transducer. The fathometer was calibrated with a bar check at 

 fixed depths below the transducer before the survey began. 

 Survey lanes were run east and west at a 25 meter lane spacing 

 over a 1200 X 1200 m area centered at the disposal buoy (42°25.1' 

 N, 70°34.4' W; Figure 2-1). This lane spacing provides good 

 resolution for subsequent data analysis and the production of 

 detailed depth contour charts. 



Analysis of the bathymetric data corrects the raw depth 

 values to Mean Low Water by adjusting for ship draft and for 

 tidal changes for the duration of the survey. All data points in 

 terms of depth and position are checked for unreasonable values 

 so that the final contour plots will not contain errors. 



