prior disposal operations. At the time of the study, it rose to 

 within seven meters of the sea surface. The cratered bottom 

 consisted of circular depressions surrounded by an elevated rim. 

 The authors suggested that these may have been formed by the 

 disposal of sand onto a mud bottom. The rubble field, which 

 occupies most of the region surveyed, represents numerous small 

 topographic highs apparently associated with the wider disposal of 

 dredged material. The "wave field", evident in the sidescan sonar 

 records, is located just north of the disposal mound. The authors 

 could not determine whether it was related to bottom forces (i.e., 

 bedforms) -or to disposal operations. If the "wave field" does 

 represent bedforms, a localized high energy region may be present, 

 and fine-grained material deposited in this region may be 

 dispersed. The sand waves may be due to recent storm activity, 

 however sidescan sonar records indicate that this is an isolated 

 area and evidence of sand waves is not seen elsewhere in the Bay. 



3.3 Hydrography of Buzzards Bay 



Tidal currents are the dominant circulation forces in 

 Buzzards Bay (Figure 6) . The dominance of tidal flow results from 

 the island complex to the southeast that protects the Bay from 

 large, long period open ocean waves. Tidal current strength is low 

 (20 cm/sec; 0.4 knots) in the region of the disposal site, when 

 compared to much of the Bay. 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 2 2°C 

 to 0°C in winter. During colder winters, the upper reaches of the 

 Bay often freeze over. Because there are no large streams bringing 

 fresh water into the Bay, the salinity is essentially the same as 

 that of Block Island and Vineyard Sounds, ranging from 29.5 to 32.5 

 ppt. (Sanders, 1958) . Groundwater seepage may represent a 

 significant portion of freshwater inflow (Rosenfeld et al. . 1984). 

 A weak and transient thermocline (Figure 7) was present from April 

 to October (Anraku, 1962; Rosenfeld et al. , 1984). However, the 

 shallowness of the Bay, combined with surface wave mixing and 

 turbulent tidal flow prevents strong thermal stratification. An 

 extensive hydrographic study of Buzzards Bay was carried out in 

 1982 and 1983 (Rosenfeld et a 1 . . 1984). Overall, the Bay is a 

 tide-dominated, well-mixed estuarine system. 



Detailed, seasonal changes in near-bottom hydrographic 

 conditions at four stations located northwest of the Cleveland 

 Ledge channel have been described by Driscoll (1975) . Two of these 

 stations were located in nearshore, sandy facies, while two were 

 located in deeper, silt-clay dominated regions (Figure 8) . Driscoll 

 concluded that bottom-water dissolved oxygen and pH levels were 

 largely a function of sediment type. Lower dissolved oxygen and 

 pH levels occur over finer-grained, more organic-rich sediments 

 presumably due to higher biochemical and chemical oxygen demand. 



