field. The reference stations selected for the 1990 survey fall 

 outside the area studied in 1981. 



Tidal currents within the disposal site average 20 cm/sec 

 or 0.4 knots (SAIC, 1989a) . Complete tidal mixing of Bay water 

 with ocean water is estimated to occur approximately every 10 days. 

 Water temperatures in the Bay range from a summer maximum of 22 °C 

 to 0°C in winter. Salinity levels are essentially the same as 

 those of Block Island and Vineyard Sounds, ranging from 29.5 to 

 32.5 ppt, due to a minimal amount of freshwater inflow (primarily 

 groundwater seepage) (SAIC, 1989a) . 



From 27 to 29 March 1990, field operations were conducted 

 at BBDS to provide information on the effects of past disposal 

 operations. Field operations included a precision bathymetric 

 survey, REMOTS® sediment profile photography, and sediment sampling 

 for benthic, chemical, and physical analyses. The overall 

 objective of the cruise was to characterize existing bathymetric, 

 sediment grain size, sediment chemistry, and benthic conditions at 

 and around the disposal site. Based on results of the 1981 survey, 

 the disposal site was predicted to contain a low relief disposal 

 mound, and the bottom sediment in and around the site was expected 

 to be heterogeneous. The benthic community at the site was 

 believed to consist of small pioneering polychaetes (Stage I) and 

 larger burrowing deposit feeders (Stage III) as would be typical of 

 a shallow fishery-rich embayment. Stage III was expected to 

 predominate at most stations due to infrequent use of the disposal 

 site. Stage III taxa represent high-order successional stages 

 typically found in low disturbance regimes. 



2 . METHODS 



2.1 Navigation and Bathymetry 



The precise navigation required for all field operations 

 was provided by the SAIC Integrated Navigation and Data Acquisition 

 System (INDAS) . A complete description of this system is provided 

 in DAMOS contribution #48 (SAIC, 1985) . Shore stations used in the 

 1990 field operations were established at the Falmouth fire tower 

 (41° 35.876'N and 70° 37.093'W) and Wings Neck Lighthouse (41° 

 40.809'N and 70° 39.699'W). 



Depth was determined to a resolution of 3.0 cm (0.1 feet) 

 using an Odom DF3200 Echotrac® Survey Recorder with a narrow-beam 

 2 08 kHz transducer. The speed of sound was determined from the 

 water temperature and salinity data measured by an Applied 

 Microsystems CTD probe. 



The bathymetric survey conducted on 27 March encompassed 

 an 800 x 800 m grid centered around BBDS at coordinates 41°36.000'N 

 and 70°41.000'W. Thirty-three lanes were run south to north at 25 



