459 
(b) filling the borrow pits and capping of the dredged material 
removes zones of anoxic ‘conditions resulting from lack of 
normal water circulation in the pits; 
(c) filling the pits reduces the effect these deep mining holes 
have on wave energy refraction, which can focus on a break- 
water or groin with damaging results. 
Usefulness of Borrow Pit Disposal 
In some places this can be an extremely useful technique that appears also 
to be economically as well as environmentally sound. The filling of pits 
permits additional sand mining to be accomplished without drastically al- 
tering ambient conditions in a harbor. Also, locating the pits near the 
area to be dredged makes them economically valuable. 
SPLIT-SITE DISPOSAL 
Description of the Technique 
The split-site may be useful when very large amounts of polluted material 
must be disposed. It involves both the dredging and the disposal proces- 
ses. It also requires a somewhat elongate dumpsite that is oriented at an 
angle across the longshore current (Figure 7). The dumpsite has, say, six 
release points tht are marked with a buoy for the precise dumping required 
by capping operations. The basic idea is to permit organisms in and down- 
stream of the dumpsite to depurate prior to capping operations. This tech- 
nique should permit the disposal of very large volumes of polluted material 
from a hopper dredge without serious environmental degradation. 
