3.4 Physical Implications for Dredged Material Disposal 



Overall, the Buzzards Bay Disposal Site appears to lie 

 within a relatively low kinetic energy portion of Buzzards Bay. 

 Tidal currents, which represent the strongest physical forces in 

 the Bay, are generally low in the area. Large storm waves are 

 precluded due to the region's physiography and limited fetch. The 

 disposal site is dominated by fine-grained sediments; much of the 

 coarse material (sand and gravel) present apparently represents 

 deposited dredged materials. However, observations indicate some 

 dispersion of disposed materials is possible. The presence of 

 coarse-grained sediments atop the existing disposal mound at 

 Buzzards Bay suggests that scour of fine-grained sediments may 

 occur on shallow topographic features. Bathymetric monitoring of 

 future disposal operations may aid in documenting changes in these 

 topographic features. 



4.0 CHEMICAL CHARACTERISTICS 



4 . 1 Water Column 



Sanders (1958) noted that dissolved nutrient and 

 chlorophyll levels in Buzzards Bay were significantly lower than 

 levels observed in Long Island Sound. This contrast apparently 

 reflects the relatively small drainage basin which feeds Buzzards 

 Bay. Gilbert et al. (1973) measured nutrients, chlorophyll, and 

 coliform bacteria levels in surface and bottom waters at 14 

 stations in the Bay during May 1973 (Table 1, Figure 8) . Surface 

 water N0 3 levels ranged from 2.24 to 20.45 micrograms/liter with 

 the highest values occurring at the mouth of the Bay northwest of 

 Cuttyhunk Island. Near-bottom N0 3 levels ranged from 0.3 to 25.33 

 micrograms/liter. Again, relatively high levels were observed at 

 the mouth of the Bay. This pattern may illustrate the influence of 

 organic inputs from the Acushnet River/New Bedford Harbor region. 

 The highest bottom N0 3 concentration was observed in the Fairhaven 

 Disposal Area located near the mouth of the Acushnet River. 

 Chlorophyll levels, both surface and bottom, were generally uniform 

 throughout the Bay, ranging from 1.4 to 4.6 micrograms/liter. 

 Highest levels occurred over the Fairhaven Disposal Area and at the 

 mouth of the Bay. Coliform counts were low (less than 4 counts/100 

 ml) throughout the Bay, except for the Fairhaven Disposal Area 

 where 14 and 19 coliform counts/100 ml were measured in surface and 

 bottom waters, respectively. The high levels of nutrients and 

 coliform bacteria in waters above the Fairhaven Disposal Area 

 suggest that either disposal operations were taking place around 

 the time of the Gilbert study or other factors such as sewage 

 outfalls or ground seepage may have played a role. Excluding the 

 mouth of the Bay and the Fairhaven site, the distribution of 

 dissolved nutrients and chlorophyll did not show any distinct 

 spatial pattern. In particular, at the two stations (2 and 3, 

 Figure 8) located in and just to the west of the Buzzards Bay 



