458 
(e) After disposal of about, two-thirds of the capping material 
at the buoy, the rest should be dumped in a circle with a 
radius equal to that of the initial mound (as determined by 
bathymetry) in order to insure that its flanks are covered. 
BORROW PIT DISPOSAL: ANOTHER CMC TECHNIQUE 
Description of the Technique 
Another recent innovative approach to capping operations utilizes existing 
submarine borrow pits which have been made during sand mining in an outer 
harbor or on the continental shelf adjacent to the harbor. Because sand is 
becoming an important item of commerce in many regions, it is likely to 
become a very important technique. Where possible the final cappng is done 
with clean sediment of similar lithology to the surrounding area. Because 
these pits have acted as traps for very fine material it is suggested that, 
where possible, dense sands not be used as the capping material since 
collapse of the sand cap could occur. 
Example of the Borrow Pit Technique 
Sand mining operations in New York Harbor have left several large pits on 
the Harbor floor (Bokuniewicz, 1980). The largest pit has a volume of 
about 25 x 10°m3. It is about 7m deeper than the surrounding floor and 
has side slopes of about 10°. The Corps of Engineers, New York District 
has developed plans to use the borrow pits for the disposal of polluted 
dredged material taken from the upper Harbor pit. 
Environmental Soundness 
Borrow pit capping operations have several environmental advantages, viz., 
(a) they isolate the “hot material"; 
