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6.8 MASSACHUSETTS BAY DISPOSAL SITE 



6.8.1 Summary of MBDS 



The Massachusetts Bay Disposal Site (MBDS) is a circular area with a diameter of 2 

 nmi. It is located in the northeast portion of Massachusetts Bay (42° 25. 700' N and 

 70°34.000' W) approximately 12 nmi south-southeast of Gales Point, Gloucester, 

 Massachusetts (Figure 6-51). (Note: in 1993, as part of the final designation by EPA, the site 

 boundary was shifted about 1 nmi to the southwest. The discussion here refers to the site 

 boundary from 1977 to 1993.) The topography of the site is divided into two areas: a shoal 

 region in the northeast quadrant of the area and a deep, relatively flat depression with an 

 average depth of approximately 85-90 m over the remainder of the site (Figure 6-52). 

 Depths within a smaller surveyed area in the southwestern quadrant ranged from 87.25 m in 

 the southwest to 92.25 m in the northwest (Figure 6-53). 



The oceanography of MBDS is influenced, in part, by the circulation of the Gulf of 

 Maine. The Gulf of Maine circulation patterns in the vicinity of MBDS are modified to a 

 large extent by the presence of Stellwagen Bank on the eastern margin. Bottom currents in 

 the vicinity of MBDS are less than 20 cm-s" 1 under nearly all conditions, whereas mid-depth 

 and surface currents may be higher (SAIC 1987d, 1988f). Bottom current velocities 

 measured during site designation studies in 1987 were less than 4 cm-s 1 over 85% of the 

 time, and historical current meter studies measured velocities less than 10 cm-s* 1 . These low 

 current conditions minimize the possibility of resuspension of deposited material at this site, 

 and the deep water tends to isolate the bottom from the effects of all but the severest of 

 storms. 



Vessels from the Massachusetts Bay area fish in the vicinity of the disposal site, 

 including Stellwagen Bank, throughout the year. Stellwagen Bank is a popular area for 

 fishing and whale watching and has been designated as a marine sanctuary. One major 

 concern raised by regulatory agencies and environmental groups is the proximity of marine 

 mammals (specifically, humpback and finback whales) on Stellwagen Bank to MBDS. These 

 mammals feed on the small plankton in the water column. While feeding they also may 

 ingest suspended particulates. There has been concern that there may be contaminants 

 associated with fine-grained particles released during disposal. However, the sediments 

 deposited at MBDS have been sands, silts, and clays which have met regulatory requirements 

 for open water dredged material disposal. All physical oceanographic information to date 

 has indicated that harmful effects are unlikely to occur (SAIC 19880- 



SAIC has conducted five monitoring surveys at MBDS, from 1985 to 1990 (SAIC 

 1988f, 19901, 1991b, Germano et al. 1994, Murray 1994). These studies were conducted to 

 assess MBDS for continued use as a disposal site, provide baseline information for 

 comparison with future monitoring surveys, determine the areal extent of dredged materials, 



DAM OS Summary Report, 1985-1990 



