170 
MOUNDING 
A circular mound about 4.8 ‘km is diameter and centered in the northwest corner 
of che Mud Dump has resulted from dumping dredged material during the past 37 
years (Freeland and Merrill, 1976). The geometry of the mound suggests that most 
dumping was controlled and restricted to the site. - + Ee Set eee 
Depths at the alternative sites are not sufficiently different that the 
amount of dredged material reaching the bottom as a cohesive mass will be 
variable. Thus the amount of sediment which will accumulate on the botton 
will be about the same. ‘However, the slightly greater depth at the 
Chsistiazensen Basin Site might reduce effects of mownding. Freeland et al. 
(1979) reported that the tate of accretion or erosion of the floor of the 
Caristiaensen Basin was so low between 1936 and 1973 that comsistent trends 
could not be determined. Only storms, particularly with northeast winds, 
create bottom currents fast enough to ‘erode muddy sediments in the 
Charistiaensen Basin and upper Hudson Shelf Valley. The greatest erosion (more 
tham 0.6m) is at the head of the 120-foot contour, which is near the southern 
boundary of the indicated site. 
The effects of mownding at the Outer Apex Site vesemble those at the End 
Dump. Impacts will be restricted to the site, unless short-dumping cccurs. 
t 
WATER COLUM 
TURBIDITY 
The duration of the turbid plume resulting from sediment disposal depends 
oa particle’ size, currents, and turbulent mixing (Wright, 1978). A turbid 
plume composed of fine particles will persist longer tham one made up of 
coarser particles. Water density is a factor. A plume which has disappeared 
irom the surface may persist near a pycnocline at intermediate depths nex 
the bottom because of sediment resuspension. As the.turdid piume moves; 
planktonic organisms may be carried with it, amd may be exposed longer than 
mobile animals which temporarily avoid the area. 
