a 150 m grid spacing was used for these background surveys. Such a wide spac- 

 ing increases the coverage, but greatly restricts the ability of the bathymetric 

 system to define small features. The purpose of these surveys was to describe 

 the major features of the disposal sites and define any specific locations where 

 spoils might be present and detectable with acoustic methods. 



On the Boston Foul Ground the only major features are Stellwagon Bank in 

 the northeast corner of the site and a circular mound in the north central 

 portion of the site. Sampling of this mound indicated it was composed of 

 glacial material and is probably related to the same forces that created Stell- 

 wagon Bank. The remainder of the site is extremely flat, although a small de- 

 pression exists near the center of the site. This depression contains fine black 

 spoil material, probably from the Charles River Dam project, however, there is 

 no topographic indication of spoil material . 



At the Boston Lightship Dumping Ground a similar situation exists. The 

 bottom in most of the surveyed area has a smooth, gentle slope to the north- 

 east, and the only major feature in the disposal area is a bank rising toward 

 Scituate, Mass. in the southwestern corner of the site. There are possible 

 indications of spoil material in the vicinity of the disposal buoy that can be 



seen as spikes on transects 13 and 14 (Fig. n-6e) of the May survey. During 

 the December survey, the weather was rough and problems were experienced utili- 

 zing the Bathymetric system for the first time under these conditions. Much of 

 the northeast corner of the disposal site was lost due to bad data (Fig. D-5 

 (a-d)) and comparison of transects between surveys is probably not possible. 

 The indications of spoil found in the Hay survey were not ievident in December, 



