A402 
centrations of contaminants, most conventional treatment processes are infeasible, 
particularly when considered for use in the dredging operation itself. Some process- 
es are feasible for confined disposal facilities and are discussed later. However, with 
regard to open-water disposal, only in-line oxygenation to reduce the dissolved 
oxygen sag accompanying disposal of certain kinds of material being moved by a 
pipeline dredge appears operationally and economically practical. The use of floccu- 
lents to reduce turbidity in an open-water disposal situation is not.effective or prac- 
tical in most situations. 
No studies directly addressed the issue of hopper dredge overflow as this is not a 
disposal problem per se. Nevertheless, program results do shed some light on this 
matter since turbidity from overflow is no different from that resulting from other 
dredging-related causes. In many, in not most, cases, this practice should result in 
no significant impact; however, there is an element of risk involved since the fine- 
grained materials overflowed are the ones that contain the relatively highest con- 
taminant loads. The negative public image of this practice is widespread and there 
can be situations where aesthetic impacts are more important than biological im- 
pacts. A study of foreign dredging practices and technology showed that there is a 
simple and inexpensive technique developed in Japan that shows promise for signifi- 
cantly reducing the amount of surface turbidity associated with hopper dredge over- 
flow. 
Confined or diked containment of dredged material as a conventional alternative 
was also extensively investigated. Confining contaminated material on land or in 
shallow water next to land can be an environmentally sound and preferred alterna- 
tive, but not inherently better than open-water disposal for several reasons. There 
are technical reasons why confined disposal could be less effective in protecting 
water quality or organisms. These include the change in the geochemical environ- 
ment that could lead to an enhanced release of contaminants and the difficulty in 
retaining the finer grained particles in environmental settings where they are likely 
to have greater impact when released (e.g., wetlands or small streams). Also, it 
should not be overlooked that confined facilities are expensive, of finite life, and 
result in a permanent change in the physical landscape, often in conflict with land- 
use and management plans. : 
Irrespective of the alternative decision, if a confined disposal area is to be con- 
structed, it must be designed, built, and operated in such a way as to achieve maxi- 
mum effective capacity and satisfactory effluent quality. Unfortunately, historically, 
neither of these basic objectives has been met by most of the facilities that have 
been built. These objectives are by no means mutually incompatible and the reasons 
they have not been met involve lack of technical knowledge as well as policy and 
institutional factors such as cost, funding sources, and diffused construction and 
management responsibilities. 
The DMRP developed and issued in report and manual form a variety of guidance 
and information that should largely alleviate the technical knowledge limitation. 
No longer is it necessary to rely primarily on “rules of thumb” and personal experi- 
ence. Specific guidelines were prepared for designing containment areas with appro- 
priate storage capacities, surface areas, and shapes; designing and building dikes; 
designing and placing inflow pipes and weirs; selecting equipment for operating in 
disposal areas; landscaping containment areas; and controlling problems such as 
mosquito breeding and noxious odors. 
If a confined disposal site is to be effective from an environmental protection 
standpoint, it must be efficient in retaining a high percentage of the finer soil parti- 
cles, for it is the clays and silts that carry the contaminants. These are admittedly 
the materials most difficult to retain in an area, but if they can be, the effluents 
should be essentially nontoxic except for occasional situations where nutrient levels 
and oxygen depletion may be excessive. 
e guidance mentioned above contains specific information on how disposal site 
retention times can be maximized; however, there are cases where sites are simply 
incapable of providing adequate retention. Addressing these situations, studies 
found that coagulants and flocculents can be quite effective for effluent treatment, 
and treatment system design and operation guidelines were developed based on 
actual field tests. Studies also considered the principles involved in the land treat- 
ment of wastewater and concluded from a limited field test that the regulated dis- 
charge of disposal area effluents through a natural marsh can be effective in remov- 
ing nutrients. 
With time, the soil physicochemical environment in a confined disposal site can 
become appreciably different from that of sediments before dredging or sediments 
deposited in open water. The upland drained situation can lead to an oxidizing 
acidic environment that was shown in laboratory studies to be conducive to the 
