1 . INTRODUCTION 



During the period 4 September to 14 October 1987, field 

 operations were conducted in selected areas of Rhode Island Sound 

 (RIS) and Narragansett Bay to gather information for a feasibility 

 assessment of offshore dredged material disposal sites. A total of 

 four discrete areas were studied; three in RIS (Brenton Reef, 

 Brenton-A, and Brenton-B) and one in Narragansett Bay (Prudence) . 

 Two of these areas (Brenton Reef and Prudence) are former disposal 

 sites. The Brenton Reef site, centered at 41° 23.470'N, 71° 

 18.126'W, is located in RIS approximately 6 nautical miles south of 

 Newport, RI (Figure 1-1) . This site was last used for disposal in 

 1971 and was last studied in 1981 under the DAMOS program (SAIC, 

 1981). Prudence, centered at 41° 23.470'N, 71° 18.126'W, is 

 located in the East Passage of Narragansett Bay southeast of 

 Prudence Island (Figure 1-2) ; disposal last occurred at this site 

 in 1966. The two remaining areas, named Brenton-A and Brenton-B, 

 are located in RIS approximately 10 nautical miles south-southeast 

 of Newport, RI (Figure 1-1). Brenton-A is centered at 41°16.673'N, 

 71° 15.633 'W, while Brenton-B is centered at 41° 19. 690 'N, 71° 

 12. 021 'W. These two areas were studied because preliminary 

 examination of bathymetric charts revealed topography indicative of 

 a depositional basin. 



Field operations included bathymetric, side scan and sub- 

 bottom surveys, sediment-profile photography (REMOTS®) , and 

 sediment sampling for physical and benthic community analyses. 

 Results from sub-bottom surveys performed by the University of 

 Rhode Island in the vicinity of Brenton-A and Brenton-B were 

 interpreted in conjunction with SAIC survey results; the seismic 

 stratigraphy and surficial seafloor texture in each of the four 

 study areas were characterized. Approximately 75 kilometers (47 

 miles) of high-resolution sub-bottom reflection (Uniboom) profiles 

 were examined to determine geologic structure. Surficial textural 

 characteristics were inferred from 100 kilometers (62 miles) of 

 side scan sonar observations. Grain size analyses of surface grab 

 samples, carried out by the Corps of Engineers, New England 

 Division, augmented the textural observations. 



The primary objectives of these investigations were to: 



■ Determine the areal extent of the historic mound formed 

 by dredged sediment within the Brenton Reef disposal 

 site. 



■ Determine the bottom elevations/ topography, physical 

 (including sub-bottom) characteristics, and sediment 

 types for all specified areas. 



■ Determine the benthic community structure at 

 stations inside and outside the historic Brenton 

 Reef Disposal Area. 



