for unconfined open water disposal. One 

 alternative the New England Division of 

 the Army Corps of Engineers (NED) has 

 proposed is that the unsuitable sediments be 

 disposed at MBDS and then capped with 

 the remaining suitable dredged materials. 



MBDS is a 2 nmi diameter circular area 

 located 17 nmi east-northeast of Boston 

 Harbor and 12 nmi southeast of Gales Point 

 in Gloucester (Figure 1-1). The site was 

 given final designation status in 1993 by 

 the Environmental Protection Agency 

 (EPA) as an Ocean Dredged Material 

 Disposal Site (ODMDS). As part of this 

 designation, the site boundary was shifted 

 0.95 nmi to the southwest. Water depths at 

 the existing site are a maximum of 92 m 

 (Figure 1-2). The MBDS boundary 

 overlaps a portion of the old Industrial 

 Waste Site which had been in use since the 

 1940s for the disposal of dredged material 

 as well as other waste. EPA records show 

 no permitted use of the Industrial Waste 

 Site after 1976, and it was formally de- 

 designated on February 2, 1990. The 

 MBDS has been used exclusively for the 

 disposal of dredged material since 1977. 

 The successful use of MBDS for the 

 disposal of contaminated dredged material 

 requires the formation of a stable disposal 

 mound that can be capped and monitored. 



Initial capping attempts at MBDS 

 (formerly known as the Boston Foul 

 Ground, BFG, and the Foul Area Disposal 

 Site, FADS) in the summer/winter of 

 1982/1983 were problematic. Positioning 

 problems during the disposal operation may 

 have caused inaccurate and widely spaced 

 placement of dredged material, hindering 

 the formation of a dredged material mound. 



The project design called for sediment 

 from Boston Harbor to be dredged 

 mechanically using a clamshell dredge and 

 transported to MBDS where it was to be 

 point dumped at a taut-wired buoy during 

 the summer of 1982 (SAIC 1984a). 

 However, a bathymetry survey conducted 

 after the disposal operation did not detect a 

 mound of dredged material below the 

 location of the buoy. A side-scan survey of 

 the area did detect scattered patches of 

 highly reflective sediment, usually 

 indicative of dredged material. Sediment 

 samples containing the contaminated 

 dredged material were collected at locations 

 500 m south and 700 m north and west of 

 the disposal location. After these surveys 

 were concluded, it was suggested that 

 increased disposal accuracy would occur by 

 shortening the hawser, slowing the tug, and 

 opening the barge doors only when close 

 aboard the buoy. 



In January 1983, cleaner cap material 

 was placed at the site by a hopper dredge 

 using LORAN-C coordinates. Because the 

 contaminated dredged material did not form 

 a mound, the capping sediment released by 

 the hopper dredge was effective in capping 

 only that portion of the contaminated 

 dredged material that was deposited at the 

 correct disposal location. Where patches of 

 contaminated dredged material were found 

 at the buoy location, contaminant levels in 

 that sediment decreased after the cap 

 material was released (SAIC 1984a). 



Deep Water Capping 



